Union typename

fieldname as datatype
Declare member function declaration ...
...

End Union

typename
fieldname
member function declaration

Unions are similar to a Type structure, except that the elements of a union occupy the same space in memory. The size of the Union is the size of the largest data item. A data item can be an unnamed Type . Since they occupy the same space, only a single element can be used.

Unnamed unions can be nested inside a type structure and unnamed types can be nested inside an union . See Example.

Unions support member functions including Constructor, Destructor, Function, Operator, Property and Sub. All members of a union are public and access control is not supported.

A Union can be passed as a user defined type to overloaded operator functions.

'define our union
Union AUnion
    a As UByte
    b As Integer
End Union
'define a composite type
Type CompType
    s As String * 20
    ui As Byte 'Flag to tell us what to use in union.
    Union 
        au As UByte
        bu As Integer
    End Union
End Type

'Flags to let us know what to use in union.
'You can only use a single element of a union.
Const IsInteger = 1
Const IsUByte = 2

Dim MyUnion As AUnion
Dim MyComposite As CompType

'Can only set one value in union
MyUnion.a = 128

MyComposite.s = "Type + Union"
MyComposite.ui = IsInteger 'Tells us this is an integer union
MyComposite.bu = 1500

Print "Union: ";MyUnion.a

Print "Composite: ";
If MyComposite.ui = IsInteger Then
    Print MyComposite.bu
ElseIf MyComposite.ui = IsUByte Then
    Print MyComposite.au
Else
    Print "Unknown type."
End If

Sleep

• Object-related features as functions defined inside the Union block are supported only in the -lang fb dialect.
  
• Not available in the -lang qb dialect unless referenced with the alias __Union.
  
  

• New to FreeBASIC
  
  

• Type