Boolean
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A boolean in OCL can be both Non-nullable and Nullable. | A boolean in OCL can be both Non-nullable and Nullable. | ||
Revision as of 07:38, 17 June 2024
This page was created by Lars.olofsson on 2021-09-12. Last edited by Edgar on 2025-01-20.
Definition
A boolean in OCL can be both Non-nullable and Nullable.
NonNullableBoolean : Boolean
NullableBoolean : Boolean?
As an attribute on a class that is saved to the database, almost always use non-nullable. Why? Because otherwise, it will default to null, and it's easy to handle False and Null mistakenly and incorrectly.
Evaluating
Remember to evaluate booleans like this:
class.BooleanAttribute not class.BooleanAttribute
Not like this:
class.BooleanAttribute = True class.BooleanAttribute = False
i.e. without an equal sign and True, False.
Mistakes We Have Seen Happen
class.BooleanAttribute->notEmpty
The expression will always return True because it will be converted to a list with one Boolean and that list will never be empty.
See also Initial values and Default Database values for more information on adding Boolean values and evolving the database