+= statement

The += statement adds an implementation to an abstract property.

Syntax

abstractProperty(param1, ..., paramN) +=
    [WHEN conditionExpr THEN]
    implementationExpr;

Description

The += statement does not create a new property. It adds another implementation to an already declared abstract property.

For an abstract property of type CASE, the WHEN conditionExpr THEN block is required. For abstract properties of types MULTI and VALUE, the WHEN ... THEN block is not used and the implementation expression appears directly after +=.

The position of the added implementation in the abstract property's implementation list is determined by the abstract property's OVERRIDE FIRST / OVERRIDE LAST setting; see the ABSTRACT operator for the available modes.

Parameters

• abstractProperty

  ID of the abstract property being extended.

• param1, ..., paramN

  List of typed parameters of the implementation being added; defines its signature. The list may be empty. The number of parameters and their classes must be compatible with the signature of the abstract property. These parameters can be used in implementationExpr and, for the CASE form, in conditionExpr.

• conditionExpr

  Expression for the selection condition of this implementation. Used only for an abstract property of type CASE.

• implementationExpr

  Expression for the implementation. Its result class must be compatible with the result class of the abstract property.

Examples

CLASS ABSTRACT AClass;
CLASS BClass : AClass;
CLASS CClass : AClass;
CLASS DClass : AClass;

name(AClass a) = ABSTRACT BPSTRING[50] (AClass);
innerName(BClass b) = DATA BPSTRING[50] (BClass);
innerName(CClass c) = DATA BPSTRING[50] (CClass);
innerName(DClass d) = DATA BPSTRING[50] (DClass);

name(BClass b) = 'B' + innerName(b);
name(CClass c) = 'C' + innerName(c);

name[AClass](BClass b) += name(b);
name(CClass c) += name(c);
name(DClass d) += 'DClass' + innerName(d) IF d IS DClass;

CLASS Person;
CLASS PersonDocumentType;
name = DATA ISTRING[64] (PersonDocumentType);

caption = ABSTRACT CASE ISTRING[100] (Person, PersonDocumentType);

caption(Person p, PersonDocumentType t) +=
    WHEN p IS Person AND name(t) == 'Passport' THEN 'Passport';