Base (Initializer)keyword

Specifies an initializer for the base UDT in derived Udt constructors

Syntax

Base ( constructor-parameters... )

or:

Base ( UDT-initializers... )

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 initializers 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 (Member Access).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).

Remarks

Dialect Differences

Methods are only supported in the -lang fb dialect, hence Base has no function in other dialects.

Differences from QB

New to FreeBASIC

Example

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

Reference

Documented in KeyPgBaseInit.html