Static (Member)
Declare a static member procedure or variable
Syntax
`
Type typename
Static variablename As DataType [, ...]
Declare Static Sub|Function procedurename ...
...
End Type
Dim typename.variablename As DataType [= initializer] [, ...]
[Static] Sub|Function typename.procedurename ...
...
End Sub|Function
`
Description

- Static member procedures

`Static` methods do not have an implicit `This` instance argument passed to them. This allows them to be used like normal non-member procedures (for example with callback procedure pointers). An advantage of `Static` methods are that they are encapsulated in the `typename` namespace, and therefore have the ability to access the `Private` or `Protected` members or methods of instances of `typename`.
`Static` methods can be called directly anywhere in code, like normal non-member procedures, or on objects of type `typename`, similar to non-static methods, however either way there is no implicit or explicit `This` (or explicit `Base`) access possible from within a static method.
For member procedures with a `Static` declaration, `Static` may also be specified on the corresponding procedure bodies, for improved code readability.

- Static member variables

`Static` member variables are created and initialized only once independently of any object construction, in contrast to non-static ("instance") member variables which are created again and again for each separate object. `Static` members are always `Shared`, even if `Shared` was not specified in the declaration. Thus, `Static` member variables are similar to global variables, except that they are declared in a `Type` namespace.
Each `Static` member variable declared in a Type must be explicitly allocated somewhere outside the type by using a `Dim` statement. The declaration inside the Type is the prototype that is visible to every module seeing the Type declaration. The definition outside the Type allocates and optionally initializes the `Static` member variable. There can only be one definition per `Static` member variable: it can only be allocated in a single module, not in multiple ones. This is the same as for `Extern` variables.
A `Static` member variable is subject to member access control except for its definition outside the Type. If a private `Static` member variable is to be explicitly initialized outside the Type's member procedures, an initializer must be provided with the definition.
Example
`
'' Example showing how the actual procedure invoked by a member can be set at runtime.
'' using static member procedures.
Type _Object
Enum handlertype
ht_default
ht_A
ht_B
End Enum
Declare Constructor( ByVal ht As handlertype = ht_default)
Declare Sub handler()
Private:
Declare Static Sub handler_default( ByRef obj As _Object )
Declare Static Sub handler_A( ByRef obj As _Object )
Declare Static Sub handler_B( ByRef obj As _Object )
handler_func As Sub( ByRef obj As _Object )
End Type
Constructor _Object( ByVal ht As handlertype )
Select Case ht
Case ht_A
handler_func = @_Object.handler_A
Case ht_B
handler_func = @_Object.handler_B
Case Else
handler_func = @_Object.handler_default
End Select
End Constructor
Sub _Object.handler()
handler_func(This)
End Sub
Sub _Object.handler_default( ByRef obj As _Object )
Print "Handling using default method"
End Sub
Sub _Object.handler_A( ByRef obj As _Object )
Print "Handling using method A"
End Sub
Sub _Object.handler_B( ByRef obj As _Object )
Print "Handling using method B"
End Sub
Dim objects(1 To 4) As _Object => _
{ _
_Object.handlertype.ht_B, _
_Object.handlertype.ht_default, _
_Object.handlertype.ht_A _
}
'' 4th array item will be _Object.handlertype.ht_default
For i As Integer = 1 To 4
Print i,
objects(i).handler()
Next i
`
`
'' Assign an unique ID to every instance of a Type (ID incremented in order of creation)
Type UDT
Public:
Declare Property getID () As Integer
Declare Constructor ()
Private:
Dim As Integer ID
Static As Integer countID
End Type
Dim As Integer UDT.countID = 0
Property UDT.getID () As Integer
Property = This.ID
End Property
Constructor UDT ()
This.ID = UDT.countID
UDT.countID += 1
End Constructor
Dim As UDT uFirst
Dim As UDT uSecond
Dim As UDT uThird
Print uFirst.getID
Print uSecond.getID
Print uThird.getID
`
Differences from QB

- New to FreeBASIC

See also

- `Class`
- `Declare`
- `Type`
- `Static`