BASE (initializer)


Specifies an initializer for the base UDT in derived UDT constructors

Syntax:
base ( constructor-parameters... )
or:
base UDT-initializer

Description:
The Base initializer can be used at the top of constructors of derived UDTs. It allows to specify an explicit constructor call or UDT initializer to be used to initialize the base object. It will replace the implicit default initialization, and must appear above any other statements in the constructor it is used in.

Note: Unlike "Base( )", a "Base.Constructor( )" statement does not replace the implicit default initialization done by the constructor of a derived UDT, and can usually not be used legally, because it would result in two constructor calls for the base object (for an inheritance structure extending the built-in Object type, this second base constructor call may also corrupt the vtable pointer to point to the base-type vtable instead of to the type vtable).

Examples:
Type SimpleParent
    As Integer a, b, c
End Type

Type Child extends SimpleParent
    Declare Constructor( )
End Type

Constructor Child( )
    '' Simple UDT initializer
    Base( 1, 2, 3 )
End Constructor


Type ComplexParent
    As Integer i
    Declare Constructor( ByVal As Integer = 0 )
End Type

Constructor ComplexParent( ByVal i As Integer = 0 )
    This.i = i
End Constructor

Type Child extends ComplexParent
    Declare Constructor( )
    Declare Constructor( ByRef As Child )
End Type

Constructor Child( )
    '' Base UDT constructor call
    Base( 1 )
End Constructor

Constructor Child( ByRef rhs As Child )
    '' Base UDT constructor call
    Base( rhs.i )
End Constructor

Dialect Differences:
Differences from QB:
See also:
Back to User Defined Types
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