Static
 
Defines variables, objects and arrays having static storage

Syntax

Static symbol [ (array-dimensions) ] As DataType [, ...]

or

Type typename
Static symbol [ (array-dimensions) ] As DataType [, ...]
...
End Type
Dim typename.symbol [ (array-dimensions) ] As DataType [= initial-value] [, ...]

or

Sub|Function procedurename ( parameters ) [As DataType] Static
...
End Sub|Function

Parameters

symbol
variable or array symbol name.
array-dimensions
lower-bound To upper-bound [, ...]

Description

Specifies static storage for variables, objects and arrays; they are allocated at program startup and deallocated upon exit. Objects are constructed once when they are defined, and destructed upon program exit.

When declaring static arrays, only numeric literals, Constants or Enumerations may be used as subscript range values. Static variable-length arrays must be declared empty (no subscript range list) and resized using ReDim before used.

In both iterative and recursive blocks, like looping control flow statements or procedures, static variables, objects and arrays local to the block are guaranteed to occupy the same storage across all instantiations of the block. For example, procedures that call themselves - either directly or indirectly - share the same instances of their local static variables.

A static variable may only be initialised with a constant value: its starting value is set at the start of the program before any code is run, and so it cannot depend on any variables or functions in it.

When used with module-level and member procedure declarations, Static specifies static storage for all local variables, objects and arrays.

At module-level variable declaration only, the modifier Shared may be used with the keyword Static to make module-level static variables visible inside procedures.

When used with UDT, each Static member variable needs an explicit definition as well as a declaration. The declaration inside the UDT is the prototype that is visible to every module seeing the UDT declaration (like with methods). The definition - which must be done outside the type declaration code, and appear only once in a single module - allocates static space for - and optionally initializes - the static variable.
A Static member variable is visible throughout the entire program (inside any procedure) even if the modifier Shared is not specified in the definition (Static and Shared are useless in the definition). So, Static member variables can be called directly anywhere in code, or on objects of type typename.

Static (Member) is also used in member procedure declarations to specify static member procedures.

Example

Sub f
    '' static variables are initialized to 0 by default
    Static i As Integer
    i += 1
    Print "Number of times called: " & i
End Sub

'' the static variable in f() retains its value between
'' multiple procedure calls.
f()
f()

Will output:

Number of times called: 1
Number of times called: 2

'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

  • QuickBASIC allows variables and arrays to be declared using the Static keyword within procedures and DEF FN routines only.
  • Static forces local visibility of variables and arrays in QuickBASIC DEF FN routines. FreeBASIC supports neither DEF FN routines nor this usage of Static.
  • Using Static to specify static member variables (and also Static member procedures) is new to FreeBASIC.

See also