Derivation expressions
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Consider this model: | Consider this model: | ||
[[File:2020-08-25 15h13 44.png|none|thumb|615x615px]] | [[File:2020-08-25 15h13 44.png|none|thumb|615x615px]] | ||
The Green-side subclasses 2,3 match the pink-side subclasses 5,6. It would be good to have a derived association that matches 1 and 4 whatever the subclass is. | The Green-side subclasses <code>2,3</code> match the pink-side subclasses <code>5,6</code>. It would be good to have a derived association that matches <code>1</code> and <code>4</code> whatever the subclass is. | ||
# Implement the derived link and set the OCL implementation to Class4.nullvalue - it will not be used if your Class1 is abstract. | # Implement the derived link and set the OCL implementation to Class4.nullvalue - it will not be used if your Class1 is abstract. | ||
# On class3, click on DerivationExpressions - find the Class4Derived expression - replace it with ocl: self.Class5 (valid since Class5 is a Class4) | # On class3, click on DerivationExpressions - find the Class4Derived expression - replace it with ocl: self.Class5 (valid since Class5 is a Class4) | ||
Revision as of 06:35, 1 November 2023
You can derive both attributes and association ends.
When it comes to sub-classes that inherit classes that have anything derived, you may want to override the existing derivations.
You can do this in the Derivation Expressions tool:
Consider this model:
The Green-side subclasses 2,3 match the pink-side subclasses 5,6. It would be good to have a derived association that matches 1 and 4 whatever the subclass is.
- Implement the derived link and set the OCL implementation to Class4.nullvalue - it will not be used if your Class1 is abstract.
- On class3, click on DerivationExpressions - find the Class4Derived expression - replace it with ocl: self.Class5 (valid since Class5 is a Class4)
- On class2, click on DerivationExpressions - find the Class4Derived expression - replace it with ocl: self.Class6 (valid since Class5 is a Class4)
You have now overridden the dummy default implementation ( Class4.nullvalue) to something valid in the context of the subclass.
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