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Difference between revisions of "EDT:Tutorial: RUI With DataBase Lesson 8"

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[[EDT:Tutorial: Access a database with EGL Rich UI|Access a database with EGL Rich UI]]
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[[EDT:Tutorial: Access a database with EGL Rich UI|Access a database with EGL Rich UI]]  
  
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<br>
  
{| style="float: right"
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{| style="float: right" class="FCK__ShowTableBorders"
|[[EDT:Tutorial: RUI With DataBase Lesson 7|&lt; Previous]] | [[EDT:Tutorial: RUI With DataBase Lesson 9|Next >]]
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|-
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| [[EDT:Tutorial: RUI With DataBase Lesson 7|&lt; Previous]] &#124; [[EDT:Tutorial: RUI With DataBase Lesson 9|Next &gt;]]
 
|}
 
|}
= Lesson 8: Add variables and functions to the Rich UI handler =
 
  
Add source code that supports the user interface.In lessons 8 and 9, you update the EGL source code directly
+
= Lesson 8: Add variables and functions to the Rich UI handler  =
and review changes in the Preview tab.
+
  
== Add code to support the data grid ==
+
Add source code that supports the user interface.In lessons 8 and 9, you update the EGL source code directly and review changes in the Preview tab.
  
Change the declaration of the data grid for two purposes: to
+
== Add code to support the data grid ==
cause the web page to react when the user selects a cell and to ensure
+
that the grid output is formatted correctly.
+
  
<ol><li>In Project Explorer, open '''PaymentClient''' &gt; '''EGLSource''' &gt; '''handlers''' and double-click '''PaymentFileMaintenance.egl'''.
+
Change the declaration of the data grid for two purposes:&nbsp;to cause the web page to react when the user selects a cell and to ensure that the grid output is formatted correctly.
<li>Click on the Source tab.
+
 
</ol>
+
#In Project Explorer, open '''PaymentClient''' &gt; '''EGLSource''' &gt; '''handlers''' and double-click '''PaymentFileMaintenance.egl'''.  
 +
#Click on the Source tab.
  
 
Make the following changes, ignoring the error marks:  
 
Make the following changes, ignoring the error marks:  
  
In the '''allPayments_ui''' DataGrid declaration,
+
In the '''allPayments_ui''' DataGrid declaration, add the following code immediately before the '''columns''' property:  
add the following code immediately before the '''columns''' property:  
+
 
   selectionListeners ::= cellClicked,  
+
   selectionListeners&nbsp;::= cellClicked,  
The '''selectionListeners''' property
+
 
specifies one or more functions that are called whenever the user
+
The '''selectionListeners''' property specifies one or more functions that are called whenever the user selects a cell in the grid. In this case, you are appending a function name to a pre-existing array. You will write the '''cellClicked''' function later in this lesson.  
selects a cell in the grid. In this case, you are appending a function
+
 
name to a pre-existing array. You will write the '''cellClicked''' function
+
Formatters are functions that change the appearance of the values in DataGrid columns. To demonstrate the feature, find the DataGridColumn declaration for category. To ensure that the user sees a category description rather than an integer, add this code after '''width=90''':
later in this lesson.
+
  
Formatters are functions that change the appearance of
 
the values in DataGrid columns. To demonstrate the feature, find the
 
DataGridColumn declaration for category. To ensure that the user sees
 
a category description rather than an integer, add this code after '''width=90''':
 
 
   , formatters = [ formatCategory ]
 
   , formatters = [ formatCategory ]
When you display dollar amounts in a column, you typically
+
 
right-align the values. You do not need to code a function to cause
+
When you display dollar amounts in a column, you typically right-align the values. You do not need to code a function to cause right-alignment. Instead, add this code after the '''width''' entry for amount:  
right-alignment. Instead, add this code after the '''width''' entry
+
 
for amount:
+
 
   , alignment = DataGridLib.ALIGN_RIGHT
 
   , alignment = DataGridLib.ALIGN_RIGHT
The '''allPayments_ui''' declaration
+
 
is now as follows, with error marks for '''cellClicked''' and '''formatCategory''':  
+
The '''allPayments_ui''' declaration is now as follows, with error marks for '''cellClicked''' and '''formatCategory''':  
 +
 
 
       allPayments_ui DataGrid{
 
       allPayments_ui DataGrid{
 
         layoutData = new GridLayoutData{
 
         layoutData = new GridLayoutData{
 
                           row = 2, column = 1,
 
                           row = 2, column = 1,
 
                           verticalAlignment = GridLayoutLib.VALIGN_TOP},
 
                           verticalAlignment = GridLayoutLib.VALIGN_TOP},
         selectionListeners ::= cellClicked,
+
         selectionListeners&nbsp;::= cellClicked,
 
         columns =[
 
         columns =[
 
             new DataGridColumn{name = "category", displayName = "Type",  
 
             new DataGridColumn{name = "category", displayName = "Type",  
Line 59: Line 53:
 
         selectionMode = DataGridLib.SINGLE_SELECTION};
 
         selectionMode = DataGridLib.SINGLE_SELECTION};
  
Save the file before going on to the next step.
+
Save the file before going on to the next step.  
  
 
== Code the function that responds when the user clicks the data grid  ==
 
== Code the function that responds when the user clicks the data grid  ==
Line 95: Line 89:
 
   allPayments_ui.getSelection()[1] as paymentRec  
 
   allPayments_ui.getSelection()[1] as paymentRec  
  
In each case, the '''as''' clause provides the necessary cast.
+
In each case, the '''as''' clause provides the necessary cast.  
  
== Format column values in the grid ==
+
== Format column values in the grid ==
  
To add the formatter function:
+
To add the formatter function:
 +
 
 +
*Add the following code before the final '''end''' statement in the file:
  
*Add the following code before the final '''end''' statement in the file:
 
 
   function formatCategory(class string, value string, rowData any in)
 
   function formatCategory(class string, value string, rowData any in)
 
       value = PaymentLib.getCategoryDesc(value as INT);
 
       value = PaymentLib.getCategoryDesc(value as INT);
 
   end
 
   end
 +
 
:Formatters have the parameters shown. In this case, the formatter wraps a library function you created earlier.
 
:Formatters have the parameters shown. In this case, the formatter wraps a library function you created earlier.
 +
 
*Press Ctrl-Shift-O to organize the required import statements and save the file. All the error marks disappear.
 
*Press Ctrl-Shift-O to organize the required import statements and save the file. All the error marks disappear.
  
== Test the formatting of the data grid and the transfer of data to the single-record layout ==
+
== Test the formatting of the data grid and the transfer of data to the single-record layout ==
  
You can test your recent changes even before you gain
+
You can test your recent changes even before you gain access to the database.  
access to the database.
+
 
 +
*Click the Preview tab and note that&nbsp;the categories are now descriptions (for example, '''Rent''' rather than '''1'''). [[Image:EDT Tutorial edt richui sql08 formatted grid.jpg|The formatted data grid]]
 +
*Click one or another row in the data grid and note that the single-row layout is updated appropriately. However, the formatter affected only the data grid, and the description field in the single-row layout contains a numeric. The tutorial will address that issue later.
 +
*Click the Source tab and change the '''start''' function so that the first record in the prototype data includes a value for '''payeeName''', which is a '''paymentRec''' record field that is not displayed by the data grid:
  
*Click the Preview tab and note that the categories are now descriptions (for example, '''Rent''' rather than '''1'''). [[Image:EDT_Tutorial_edt_richui_sql08_formatted_grid.jpg|The formatted data grid]]
 
*Click one or another row in the data grid and note that the single-row layout is updated appropriately. However, the formatter affected only the data grid, and the description field in the single-row layout contains a numeric. The tutorial will address that issue later.
 
*Click the Source tab and change the '''start''' function so that the first record in the prototype data includes a value for '''payeeName''', which is a '''paymentRec''' record field that is not displayed by the data grid: 
 
 
   function start()
 
   function start()
 
       allPayments_ui.data =[
 
       allPayments_ui.data =[
Line 124: Line 121:
 
       new paymentRec{category = 3, description = "test03", amount = 300.00}];
 
       new paymentRec{category = 3, description = "test03", amount = 300.00}];
 
   end
 
   end
*Click the Preview tab and click the first row in the data grid. [[Image:EDT_Tutorial_edt_richui_sql08_prototype_and_all_plus.jpg|The data transferred from data grid to the single-record layout]]
 
  
As shown, you can switch quickly from one tab in the Rich
+
*Click the Preview tab and click the first row in the data grid. [[Image:EDT Tutorial edt richui sql08 prototype and all plus.jpg|The data transferred from data grid to the single-record layout]]
UI editor to another, to test even a small change.
+
 
 +
As shown, you can switch quickly from one tab in the Rich UI editor to another, to test even a small change.  
 +
 
 +
== Comment the prototype data  ==
  
== Comment the prototype data ==
+
You can comment or uncomment code quickly, as shown in this step.
  
You can comment or uncomment code quickly, as shown in this
+
*Click the Source tab.
step.
+
*In the '''start''' function, select the complete assignment statement, right-click the area selected, and click '''EGLSource &gt; Toggle Comment'''. [[Image:EDT Tutorial edt richui sql08 toggle comments.jpg|The selection of code and the Comment menu item]]
 +
*Comment marks (//) are now at the start of each line. You could remove the comments by selecting the commented statements and repeating the task. However, leave the comments in place. EGL also supports the use of slash asterisk (/*) and asterisk slash (*/) delimiters, as shown here:
  
*Click the Source tab.
 
*In the '''start''' function, select the complete assignment statement, right-click the area selected, and click '''EGLSource > Toggle Comment'''. [[Image:EDT_Tutorial_edt_richui_sql08_toggle_comments.jpg|The selection of code and the Comment menu item]]
 
*Comment marks (//) are now at the start of each line. You could remove the comments by selecting the commented statements and repeating the task. However, leave the comments in place.  EGL also supports the use of slash asterisk (/*) and asterisk slash (*/) delimiters, as shown here:
 
 
   /*  
 
   /*  
 
       You can add comments in either of two ways.  
 
       You can add comments in either of two ways.  
Line 202: Line 199:
 
#*'''updateAll'''  
 
#*'''updateAll'''  
 
#*'''serviceExceptionHandler'''
 
#*'''serviceExceptionHandler'''
 +
 
The two are ''callback functions'', which are invoked by the EGL runtime code after the service responds or fails. If the service returns a value successfully, the '''updateAll''' function is invoked. If the call fails, the EGL runtime code invokes the function named '''serviceExceptionHandler'''.  
 
The two are ''callback functions'', which are invoked by the EGL runtime code after the service responds or fails. If the service returns a value successfully, the '''updateAll''' function is invoked. If the call fails, the EGL runtime code invokes the function named '''serviceExceptionHandler'''.  
  
Our example exception handler function just displays the exception messages in the display of error information in the at the bottom of the web page (at run time). However, you would typically an error handler of your own that might log the error information, but display a message to the user saying something like "Your request cannot be completed at this time."
+
Our example exception handler function just displays the exception messages in the display of error information in the at the bottom of the web page (at run time). However, you would typically an error handler of your own that might log the error information, but display a message to the user saying something like "Your request cannot be completed at this time."  
  
Now, to create the '''updateAll''' callback function, click anywhere in the '''call''' statement, right-click, hold down the Ctrl key, and press 1.<br>[[Image:EDT Tutorial edt richui sql08 ctl-1 callback.jpg|The Create Callback Functions option]]<br>EGL offers you an empty '''updateAll''' function. Click on '''Create function''' in the pop-up window to have the empty function inserted into your program. An error handler would have been created as well if you had not already included a function named '''serviceExceptionHandler''' in the program.  
+
Now, to create the '''updateAll''' callback function, click anywhere in the '''call''' statement, hold down the Ctrl key, and press 1.<br>[[Image:EDT Tutorial edt richui sql08 ctl-1 callback.jpg|The Create Callback Functions option]]<br>EGL offers you an empty '''updateAll''' function. Click on '''Create function''' in the pop-up window to have the empty function inserted into your program. An error handler would have been created as well if you had not already included a function named '''serviceExceptionHandler''' in the program.  
  
 
The parameter list in the created '''updateAll''' function is equivalent to the type of return value that is expected from the service. Here are the relationships that explain the behavior of the Rich UI editor:  
 
The parameter list in the created '''updateAll''' function is equivalent to the type of return value that is expected from the service. Here are the relationships that explain the behavior of the Rich UI editor:  
Line 260: Line 258:
 
*Help topic: Invoking a service asynchronously from a Rich UI application<br>
 
*Help topic: Invoking a service asynchronously from a Rich UI application<br>
  
== Update the start function to initialize the data grid with database rows ==
+
== Update the start function to initialize the data grid with database rows ==
 +
 
 +
To initialize the data grid, add the following code before the '''end''' statement of the '''start''' function:
  
To initialize the data grid, add the following code before
 
the '''end''' statement of the '''start''' function:
 
 
   readFromTable();
 
   readFromTable();
Although
 
you could have assigned the '''readFromTable''' function
 
directly to the '''onConstructionFunction''' property,
 
you are advised to retain the '''start''' function as a
 
separate unit of logic in case you later decide to add other code
 
that runs before the web page is rendered.
 
  
Retain the commented
+
Although you could have assigned the '''readFromTable''' function directly to the '''onConstructionFunction''' property, you are advised to retain the '''start''' function as a separate unit of logic in case you later decide to add other code that runs before the web page is rendered.  
code in the '''start''' function in case you need to test
+
the web page without accessing the database. You can use the comment
+
and uncomment capability of the Rich UI editor to quickly switch from
+
the function call to the prototype data and back again.
+
  
== Complete the callback functions ==
+
Retain the commented code in the '''start''' function in case you need to test the web page without accessing the database. You can use the comment and uncomment capability of the Rich UI editor to quickly switch from the function call to the prototype data and back again.
  
You now complete the callback functions that were created
+
== Complete the callback functions ==
automatically:
+
  
<ul><li>'''updateAll'''
+
You now complete the callback functions that were created automatically:
<li>'''recordAdded'''
+
<li>'''recordRevised'''
+
</ul>
+
  
The '''updateAll''' function receives an array
+
*'''updateAll'''  
of '''paymentRec''' records from the dedicated service.
+
*'''recordAdded'''  
The function is called in the following ways:
+
*'''recordRevised'''
  
<ul><li>As a callback function at startup, after the '''readFromTable''' function
+
The '''updateAll''' function receives an array of '''paymentRec''' records from the dedicated service. The function is called in the following ways:
calls the service.
+
 
<li>As a callback function whenever the user clicks the '''Sample''' button
+
*As a callback function at startup, after the '''readFromTable''' function calls the service.  
to invoke the '''sampleData''' function.
+
*As a callback function whenever the user clicks the '''Sample''' button to invoke the '''sampleData''' function.
</ul>
+
 
 +
Update the '''updateAll''' function so that the code is as follows:
  
Update the '''updateAll''' function so that
 
the code is as follows:
 
 
   function updateAll(retResult paymentRec[] in)
 
   function updateAll(retResult paymentRec[] in)
 
       allPayments = retResult;
 
       allPayments = retResult;
 
       allPayments_ui.data = allPayments as any[];
 
       allPayments_ui.data = allPayments as any[];
 
   end
 
   end
The function updates the global
 
array of payment records with the data received from the service and
 
then refreshes the data grid.
 
  
The '''recordAdded''' function receives the
+
The function updates the global array of payment records with the data received from the service and then refreshes the data grid.
record that was sent to and returned by the service function '''addPayment'''. Update the '''recordAdded''' function so that
+
 
the code is as follows:  
+
The '''recordAdded''' function receives the record that was sent to and returned by the service function '''addPayment'''. Update the '''recordAdded''' function so that the code is as follows:  
 +
 
 
   function recordAdded()
 
   function recordAdded()
 
       readFromTable();
 
       readFromTable();
 
   end
 
   end
The function '''readFromTable''' reads
 
all the rows from the database. The data stored by the grid can then
 
contain the new row, including the '''paymentID''' value
 
that was automatically generated by the database and that is otherwise
 
unavailable to the grid.
 
  
The '''recordRevised''' function receives
+
The function '''readFromTable''' reads all the rows from the database. The data stored by the grid can then contain the new row, including the '''paymentID''' value that was automatically generated by the database and that is otherwise unavailable to the grid.
the record that was sent to and returned by the service function '''addPayment'''.Update the '''recordRevised''' function so that
+
 
the code is as follows:  
+
The '''recordRevised''' function receives the record that was sent to and returned by the service function '''addPayment'''.Update the '''recordRevised''' function so that the code is as follows:  
 +
 
 
   function recordRevised()
 
   function recordRevised()
 
       allPayments_ui.data = allPayments as any[];
 
       allPayments_ui.data = allPayments as any[];
 
   end
 
   end
The function refreshes the data grid.
 
 
Clean up this step by formatting your code and saving the file.
 
If you see errors
 
in your source file, compare your code to the file contents in [[EDT:Tutorial: RUI With DataBase Lesson 8 Code|Code for PaymentLib.egl after lesson 8]].
 
  
== Test the interface ==
+
The function refreshes the data grid.
  
Preview your work now that you are accessing a database.
+
Clean up this step by formatting your code and saving the file. If you see errors in your source file, compare your code to the file contents in [[EDT:Tutorial: RUI With DataBase Lesson 8 Code|Code for PaymentLib.egl after lesson 8]].  
  
<ol><li>Click the Preview tab. The data grid has
+
== Test the interface  ==
no content because you commented out the prototype data, and the database
+
has no rows.<br />[[Image:EDT_Tutorial_edt_richui_sql08_initial_ui.jpg|The initial data grid]]
+
  
<li>Click '''Sample''' to create sample data.
+
Preview your work now that you are accessing a database.  
<li>If EGL requests a password, enter '''admin''' for
+
both the '''User ID''' and '''Password''' fields.
+
Select '''Remember my user ID...''' and click '''OK'''.<br /> [[Image:EDT_Tutorial_edt_richui_sql08_pwd.jpg|The ID and password window]]
+
  
If you exit and restart the workbench
+
#Click the Preview tab. The data grid has no content because you commented out the prototype data, and the database has no rows.<br>[[Image:EDT Tutorial edt richui sql08 initial ui.jpg|The initial data grid]]
before you complete this tutorial, this window might be re-displayed
+
#Click '''Sample''' to create sample data.
the next time you attempt to access the database.
+
#If EGL requests a password, enter '''admin''' for both the '''User ID''' and '''Password''' fields. Select '''Remember my user ID...''' and click '''OK'''.<br>[[Image:EDT Tutorial edt richui sql08 pwd.jpg|The ID and password window]] If you exit and restart the workbench before you complete this tutorial, this window might be re-displayed the next time you attempt to access the database. Eventually the grid is re-displayed with rows of sample data.<br>[[Image:EDT Tutorial edt richui sql08 sample data.jpg|Three payment entries, "œApartment,"? "œGroceries,"? and "œISP"? are displayed]]  
Eventually
+
#Click the '''Add''' button. A new row with a single default value is displayed at the bottom of the grid.<br>[[Image:EDT Tutorial edt richui sql08 added.jpg|A new row is added]]  
the grid is re-displayed with rows of sample data.<br /> [[Image:EDT_Tutorial_edt_richui_sql08_sample_data.jpg|Three payment entries, &quot;œApartment,&quot;? &quot;œGroceries,&quot;? and &quot;œISP&quot;? are displayed]]
+
#Select the Apartment row and click '''Delete'''. The row is deleted from both the display and the database.<br>[[Image:EDT Tutorial edt richui sql08 deleted.jpg|The "Apartment" row is now gone.]]  
<li>Click the '''Add''' button. A new row with a single default value is displayed at
+
#Click the first row of the data grid.<br>[[Image:EDT Tutorial edt richui sql08 transfer database.jpg|The data grid and single-record layout both contain data from the database.]] Data from the database was transferred from the data grid to the single-record layout. Note that the value of the '''Key''' field reflects how many rows were added to the database and will probably not match the value on your web page.
the bottom of the grid.<br />[[Image:EDT_Tutorial_edt_richui_sql08_added.jpg|A new row is added]]
+
<li>Select the Apartment row and click '''Delete'''. The row is deleted from both the display and the database.<br /> [[Image:EDT_Tutorial_edt_richui_sql08_deleted.jpg|The &#34;Apartment&#34; row is now gone.]]
+
<li>Click the first row of the data grid.<br /> [[Image:EDT_Tutorial_edt_richui_sql08_transfer_database.jpg|The data grid and single-record layout both contain data from the database.]]
+
Data from the database was transferred
+
from the data grid to the single-record layout. Note that the value
+
of the '''Key''' field reflects how many rows were
+
added to the database and will probably not match the value on your
+
web page.
+
</ol>
+
  
== Lesson checkpoint ==
+
== Lesson checkpoint ==
  
You learned how to complete the following tasks:
+
You learned how to complete the following tasks:  
  
<ul><li>To create formatters.
+
*To create formatters.  
<li>To respond to the user's selection in a data grid.
+
*To respond to the user's selection in a data grid.  
<li>To transfer data from the data grid to a grid layout.
+
*To transfer data from the data grid to a grid layout.  
<li>To comment and uncomment code.
+
*To comment and uncomment code.  
<li>To access services from a Rich UI application.
+
*To access services from a Rich UI application.
</ul>
+
  
In the next lesson, you will complete the code for the Rich
+
In the next lesson, you will complete the code for the Rich UI handler.  
UI handler.
+
  
{| style="float: right"
+
{| style="float: right" class="FCK__ShowTableBorders"
|[[EDT:Tutorial: RUI With DataBase Lesson 7|&lt; Previous]] | [[EDT:Tutorial: RUI With DataBase Lesson 9|Next >]]
+
|-
 +
| [[EDT:Tutorial: RUI With DataBase Lesson 7|&lt; Previous]] &#124; [[EDT:Tutorial: RUI With DataBase Lesson 9|Next &gt;]]
 
|}
 
|}
  
 
[[Category:EDT]]
 
[[Category:EDT]]

Revision as of 20:59, 18 December 2011

Access a database with EGL Rich UI


< Previous | Next >

Lesson 8: Add variables and functions to the Rich UI handler

Add source code that supports the user interface.In lessons 8 and 9, you update the EGL source code directly and review changes in the Preview tab.

Add code to support the data grid

Change the declaration of the data grid for two purposes: to cause the web page to react when the user selects a cell and to ensure that the grid output is formatted correctly.

  1. In Project Explorer, open PaymentClient > EGLSource > handlers and double-click PaymentFileMaintenance.egl.
  2. Click on the Source tab.

Make the following changes, ignoring the error marks:

In the allPayments_ui DataGrid declaration, add the following code immediately before the columns property:

  selectionListeners ::= cellClicked, 

The selectionListeners property specifies one or more functions that are called whenever the user selects a cell in the grid. In this case, you are appending a function name to a pre-existing array. You will write the cellClicked function later in this lesson.

Formatters are functions that change the appearance of the values in DataGrid columns. To demonstrate the feature, find the DataGridColumn declaration for category. To ensure that the user sees a category description rather than an integer, add this code after width=90:

  , formatters = [ formatCategory ]

When you display dollar amounts in a column, you typically right-align the values. You do not need to code a function to cause right-alignment. Instead, add this code after the width entry for amount:

  , alignment = DataGridLib.ALIGN_RIGHT

The allPayments_ui declaration is now as follows, with error marks for cellClicked and formatCategory:

     allPayments_ui DataGrid{
        layoutData = new GridLayoutData{
                         row = 2, column = 1,
                         verticalAlignment = GridLayoutLib.VALIGN_TOP},
        selectionListeners ::= cellClicked,
        columns =[
           new DataGridColumn{name = "category", displayName = "Type", 
                              width = 90, formatters = [ formatCategory ]},
           new DataGridColumn{name = "description", displayName = "Description", 
                              width = 120},
           new DataGridColumn{name = "amount", displayName = "Amount due", 
                              width = 90, alignment = DataGridLib.ALIGN_RIGHT}
        ], 
        data = allPayments as any[],
        selectionMode = DataGridLib.SINGLE_SELECTION};

Save the file before going on to the next step.

Code the function that responds when the user clicks the data grid

The cellClicked function is invoked when the user clicks a cell in the data grid.

Immediately below the start function, add the following lines:

  function cellClicked(myGrid DataGrid in)
     selectedPayment = allPayments_ui.getSelection()[1] as paymentRec;
     selectedPayment_form.publish();
  end

First, the cellClicked function updates the selectedPayment record with data from a single data-grid row. That row can include more fields than are displayed to the user. In this application, the single row in the data grid will have come from a single row in the database.

Second, the publish function causes the transfer of data from the selectedPayment record to the selectedPayment_ui layout. That transfer is made possible by code that was provided for you when you created the selectedPayment_ui layout, which is the single-record layout at the right of your web page. If you review the code, you can trace the relationships: 

  • A Form Manager declaration includes form fields.
  • Each form field references a controller declaration.
  • The controller declaration relates a model to a view; in this case, a field of the selectedPayment record to a child of the selectedPayment_ui layout.

The Form Manager provides various benefits but is essentially a collection of controllers.

Here is an explanation of two other issues"”the use of the bracketed array index ([1]), and the use of the as operator:

  1. The getSelection function always returns a subset of the rows in the data array of the data grid. However, when you declared the data grid, you specified the following setting to indicate that the user can select only one row at a time: selectionMode = DataGridLib.SINGLE_SELECTION. When the user can select only one row, only one element is available.
  2. Every element in the array returned by a getSelection function is of type ANY. You typically use the same Record type to process input to the grid and to process output from the grid, and in this tutorial, the Record type is paymentRec. The Record type has the following uses:
  • To be the basis of the array elements that you assign to the data property of the data grid, as shown in the following setting:
  data = allPayments as any[]
  • To cast the array element that is returned by the getSelection function of the data grid, as shown here:
  allPayments_ui.getSelection()[1] as paymentRec 

In each case, the as clause provides the necessary cast.

Format column values in the grid

To add the formatter function:

  • Add the following code before the final end statement in the file:
  function formatCategory(class string, value string, rowData any in)
     value = PaymentLib.getCategoryDesc(value as INT);
  end
Formatters have the parameters shown. In this case, the formatter wraps a library function you created earlier.
  • Press Ctrl-Shift-O to organize the required import statements and save the file. All the error marks disappear.

Test the formatting of the data grid and the transfer of data to the single-record layout

You can test your recent changes even before you gain access to the database.

  • Click the Preview tab and note that the categories are now descriptions (for example, Rent rather than 1). The formatted data grid
  • Click one or another row in the data grid and note that the single-row layout is updated appropriately. However, the formatter affected only the data grid, and the description field in the single-row layout contains a numeric. The tutorial will address that issue later.
  • Click the Source tab and change the start function so that the first record in the prototype data includes a value for payeeName, which is a paymentRec record field that is not displayed by the data grid:
  function start()
     allPayments_ui.data =[
     new paymentRec{
        category = 1, description = "test01", amount = 100.00
         , payeeName = "Someone" },
     new paymentRec{category = 2, description = "test02", amount = 200.00},
     new paymentRec{category = 3, description = "test03", amount = 300.00}];
  end
  • Click the Preview tab and click the first row in the data grid. The data transferred from data grid to the single-record layout

As shown, you can switch quickly from one tab in the Rich UI editor to another, to test even a small change.

Comment the prototype data

You can comment or uncomment code quickly, as shown in this step.

  • Click the Source tab.
  • In the start function, select the complete assignment statement, right-click the area selected, and click EGLSource > Toggle Comment. The selection of code and the Comment menu item
  • Comment marks (//) are now at the start of each line. You could remove the comments by selecting the commented statements and repeating the task. However, leave the comments in place. EGL also supports the use of slash asterisk (/*) and asterisk slash (*/) delimiters, as shown here:
  /* 
      You can add comments in either of two ways. 
  */

Declare a service-access variable

You now declare a service-access variable, which will let you communicate with the service that you defined earlier.

To create the variable:

  • Near the top of the EGL source code, find the handler declaration for PaymentFileMaintenance. Add a blank line, and immediately before the ui GridLayout declaration, add the following statement:
  dbService SQLService?{@dedicatedService};
The @dedicatedService property indicates that the service being referenced is a dedicated service, which will be deployed with the Rich UI handler.
In the following display, the red X in the margin indicates a problem in the code: The declaration of the service-access variable, in code
To see the error message, move the cursor over the X.
  • Fix the unresolved type error by pressing Ctrl+Shift+O. The new import statement provides access to the services package, SQLService type, which is in the PaymentService project. The reference to SQLService is resolved because that project is on the EGL build path of the PaymentClient project.
  • Save the file.

Create functions that use the service-access variable to invoke the service

You now create several functions to invoke different functions in the dedicated service. Once you understand how to set up one invocation, the others are straightforward.

First add a service exception handler and logging functions prior to the final end statement. Include the following code:

  function serviceExceptionHandler(ex anyException)
       try
           throw ex;
       onException(serviceEx ServiceInvocationException)
           log("Failure:  service invocation, exception = " +
                           serviceEx.message);
           log("Detail 1:  " + serviceEx.detail1);
           log("Detail 2:  " + serviceEx.detail2);
           log("Detail 3:  " + serviceEx.detail3);
       onException(anyex anyException)
           log("Failure:  service invocation, exception = " + anyex.message);
       end
       throw ex;
  end
  
  logActive boolean = true;
  
  function log(text string in)
       if(logActive)
           sysLib.writeStderr(text);
       end
  end

Then include the function that reads all data from the table. Leave a blank line after the cellClicked' function and add the following code:

  function readFromTable()
     call dbService.getAllPayments() returning to updateAll
        onException serviceExceptionHandler;
  end

Notes:

  1. The call statement in Rich UI is a variation used only to access services. The runtime communication in this case is asynchronous, which means that the user can continue to interact with the handler while the service is responding.
  2. The asynchronous call statement includes two function names:
    • updateAll
    • serviceExceptionHandler

The two are callback functions, which are invoked by the EGL runtime code after the service responds or fails. If the service returns a value successfully, the updateAll function is invoked. If the call fails, the EGL runtime code invokes the function named serviceExceptionHandler.

Our example exception handler function just displays the exception messages in the display of error information in the at the bottom of the web page (at run time). However, you would typically an error handler of your own that might log the error information, but display a message to the user saying something like "Your request cannot be completed at this time."

Now, to create the updateAll callback function, click anywhere in the call statement, hold down the Ctrl key, and press 1.
The Create Callback Functions option
EGL offers you an empty updateAll function. Click on Create function in the pop-up window to have the empty function inserted into your program. An error handler would have been created as well if you had not already included a function named serviceExceptionHandler in the program.

The parameter list in the created updateAll function is equivalent to the type of return value that is expected from the service. Here are the relationships that explain the behavior of the Rich UI editor:

  • The parameter list in the callback function is correct because the getAllPayments function in the Service type is available to the editor.
  • The function is available because you resolved the reference to the SQLService type in a previous step.

Next, create the function that adds sample data. Click Ctrl-F to gain access to the Find/Replace dialog, type SampleData, and click Find. Update the sampleData function so that the code is as follows:

  function sampleData(event Event in)
     call dbService.createDefaultTable() returning to updateAll
        onException serviceExceptionHandler;
  end

You do not use the feature to create the callback function because the callback functions already exist.

Next, create the function that adds data. Update the addRow function so that the code is as follows:

  function addRow(event Event in)
     call dbService.addPayment(new paymentRec) returning to recordAdded
        onException serviceLib.serviceExceptionHandler;
  end

Now click anywhere in the call statement and press Ctrl-1 to create an empty call back function. Click on Create function in the pop-up window to included the recordAdded function in your program.

Now create the function that deletes data. Update the deleteRow function so that the code is as follows:

  function deleteRow(event Event in)
     for(i INT from 1 to allPayments.getSize()) 
        if (allPayments[i].paymentID == selectedPayment.paymentID)
           allPayments.removeElement(i);
           exit for;
        end
     end
     call dbService.deletePayment(selectedPayment) returning to recordRevised
        onException  serviceExceptionHandler;
  end

The function acts as follows:

  • Deletes the selected row from the local array of records
  • Calls the database service to delete the row from the database itself

Now click anywhere in the call statement and press Ctrl-1 to create an empty call back function. Click on Create function in the pop-up window to included the recordRevised function in your program.

To complete this step,

  • Press Ctrl-Shift-F to format the code.
  • Save the file.

Related information

  • Help topic: Invoking a service asynchronously from a Rich UI application

Update the start function to initialize the data grid with database rows

To initialize the data grid, add the following code before the end statement of the start function:

 readFromTable();

Although you could have assigned the readFromTable function directly to the onConstructionFunction property, you are advised to retain the start function as a separate unit of logic in case you later decide to add other code that runs before the web page is rendered.

Retain the commented code in the start function in case you need to test the web page without accessing the database. You can use the comment and uncomment capability of the Rich UI editor to quickly switch from the function call to the prototype data and back again.

Complete the callback functions

You now complete the callback functions that were created automatically:

  • updateAll
  • recordAdded
  • recordRevised

The updateAll function receives an array of paymentRec records from the dedicated service. The function is called in the following ways:

  • As a callback function at startup, after the readFromTable function calls the service.
  • As a callback function whenever the user clicks the Sample button to invoke the sampleData function.

Update the updateAll function so that the code is as follows:

  function updateAll(retResult paymentRec[] in)
     allPayments = retResult;
     allPayments_ui.data = allPayments as any[];
  end

The function updates the global array of payment records with the data received from the service and then refreshes the data grid.

The recordAdded function receives the record that was sent to and returned by the service function addPayment. Update the recordAdded function so that the code is as follows:

  function recordAdded()
     readFromTable();
  end

The function readFromTable reads all the rows from the database. The data stored by the grid can then contain the new row, including the paymentID value that was automatically generated by the database and that is otherwise unavailable to the grid.

The recordRevised function receives the record that was sent to and returned by the service function addPayment.Update the recordRevised function so that the code is as follows:

  function recordRevised()
     allPayments_ui.data = allPayments as any[];
  end

The function refreshes the data grid.

Clean up this step by formatting your code and saving the file. If you see errors in your source file, compare your code to the file contents in Code for PaymentLib.egl after lesson 8.

Test the interface

Preview your work now that you are accessing a database.

  1. Click the Preview tab. The data grid has no content because you commented out the prototype data, and the database has no rows.
    The initial data grid
  2. Click Sample to create sample data.
  3. If EGL requests a password, enter admin for both the User ID and Password fields. Select Remember my user ID... and click OK.
    The ID and password window If you exit and restart the workbench before you complete this tutorial, this window might be re-displayed the next time you attempt to access the database. Eventually the grid is re-displayed with rows of sample data.
    Three payment entries, "œApartment,"? "œGroceries,"? and "œISP"? are displayed
  4. Click the Add button. A new row with a single default value is displayed at the bottom of the grid.
    A new row is added
  5. Select the Apartment row and click Delete. The row is deleted from both the display and the database.
    The "Apartment" row is now gone.
  6. Click the first row of the data grid.
    The data grid and single-record layout both contain data from the database. Data from the database was transferred from the data grid to the single-record layout. Note that the value of the Key field reflects how many rows were added to the database and will probably not match the value on your web page.

Lesson checkpoint

You learned how to complete the following tasks:

  • To create formatters.
  • To respond to the user's selection in a data grid.
  • To transfer data from the data grid to a grid layout.
  • To comment and uncomment code.
  • To access services from a Rich UI application.

In the next lesson, you will complete the code for the Rich UI handler.

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