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Difference between revisions of "ATL/Design Patterns"
< ATL
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This page describes various [http://en.wikipedia.org/wiki/Software_design_pattern design patterns] that are specific to the use of ATL. | This page describes various [http://en.wikipedia.org/wiki/Software_design_pattern design patterns] that are specific to the use of ATL. | ||
| − | + | == Mapped-By == | |
If you find yourself executing the following code many times, the Mapped-By pattern may be useful to you: | If you find yourself executing the following code many times, the Mapped-By pattern may be useful to you: | ||
Revision as of 05:17, 28 February 2015
This page describes various design patterns that are specific to the use of ATL.
Mapped-By
If you find yourself executing the following code many times, the Mapped-By pattern may be useful to you:
METAMODEL!MetaClass.allInstances()->any(e | e.property = variable.property)
This code is expensive if executed more than once, because it has to iterate over all instances of METAMODEL!MetaClass every time (O(n)). Instead, you can create a Map that indexes all instanced by their requested property:
helper def : metaClassByProperty : Map(OclAny, METAMODEL!MetaClass) =
METAMODEL!MetaClass.allInstances()->iterate(e; acc : Map(OclAny, METAMODEL!MetaClass) = Map{} |
acc->including(e.property, e)
);
Building the Map still runs in O(n), but after that, you can write the initial code as follows:
thisModule.metaClassByProperty.get(variable.property)
Because this is a hash map lookup, it runs in O(1).