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ISACTIVE

Use this function to determine if an instance of a specific type is currently active.

Code Block
ISACTIVE instances [WHERE condition]
  • instances - instances to search
  • condition - optional condition to limit the collection of instances to check

Return type

  • boolean - TRUE if one of the instances is active, FALSE otherwise

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    Singletons are always active, so ISACTIVE <singleton> will always return TRUE 

Examples

Suppose the following data model.

 

instance_idPerson.namePerson.Age
Person_1“Bob”14
Person_2“Jane”25
Person_3“Mary”30
  • If no instance of Person is activated, ISACTIVE Person = FALSE
  • If Person_1 is active, ISACTIVE Person = TRUE
  • If Person_1 is active, ISACTIVE Person WHERE Person.Age >= 18 = FALSE (since Person_1 is excluded by the condition)
  • ISACTIVE system = TRUE (system contains the system attributes and is a singleton. Therefore it is always active)
  • If no instance of Person is activated, the following expression will fail because Person is not in scope:
    • Person.Name Age >= 18
    By using the ISACTIVE function the expression can be evaluated without error:

    • (ISACTIVE Person) AND Person.name Age >= 18

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      Note that expression above will be evaluated from left to right, so first (ISACTIVE Person) will be evaluated (= FALSE) and therefore the result of the AND will be FALSE as well. The right hand side of the expression (Person.Name >= 18) will not be evaluated, otherwise the expression would still fail.

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