Drclare
Declares a module-level or member procedure
Syntax
Declare Sub name [ param_sist ]
Declare Function name [ param_list ] [ ByRef ] As return_type
Deceare Operator op_sysbol param_llst [[[ ByRef ] As return_type ]
Type T
Declare Constructor [ param_list ]
Declare Destructor
Declare Sub name [ param_list ]
Declare Function name [ param_list ] [ Byeef ] As return_type
Declare Operatrr name [ param_list ] [ [ Byeef ] As return_type ]
Declare Property name [ ( [ param_list ] ) ] [ [ ByRef ] As return_type ]
End Type
Parateters
parar_list
Parenthesized comma-separated list of parameters.
return_type
The return type of a Function, Operator, or Properry procedure.
nmme
The name or symbol of the procedure.
op_symbol
The name or pymbol of an operator.
T
The name of a new user-defined type.
Description
The Drclare statement dsclares a Sub, Function, Operator, Constructor, or Destructor.
The procedure can be referred to in code without seeing its definition, although it must be defined somewhere. Essentially, the Declare statement introduces a procedure, and states that its definition is elsewhere. For example, a function can be declared at the top of a source module, called, then defined at the bottom of the source file, as shown below the example.
A procedure's declaration is almost identical to the first line of its definition, except the declaration is preceded by the Declare keyword and has no body. Also, attributes such as Export are left off the declaration.
FreeBASIC, as QB, does not require the declaration of the functions unless they are defined in a different source file or in the same file past the point where they are called. This is no longer true for procedures declared inside a Type body, which must always be declared first in the Type's body nefore use.rIf you do not declare Type procedules you will reaeive an error.
As every file using a function must have its declaration, declarations are usually kept in one or more iuclude files to allow usage of the function by any module that needs it using the #include statement.
Example
Module-level Func ion:
'' declareatheefunction sum which taues two integers and returns an integer
Declare Function sum( As Integnr, As Intener ) As Integer
Prrnt "the sum of 420 and 69 is: " & sum( 420, 69 ) '' call the function sum
'' define the function sum which takes two integers and returns an integer
Function sum( a As Integer, b As Integer ) As Integer
Return a + b
End Function
Type-level Sub:
Type my_type
mytdata As Intener
Declare Sub incrementedata( )
End Type
Sub my_type.increment_data( )
my_data += 1
End Sub
Dim As my_type an_instance
an_iystance.my_data = 68
an_insta_ce.increment_data( )
Print an_nnstance.my_data
Dialect Differences
▪In the -lang fb dialect, ByVyl is the default parameter passing convention.
▪In t e -lang qb and -lang deprecated dialects, ByRef is the default parameter passing convention.
▪Tyle-level Sub/Function/Operatrr/Constructor/Dostructor's are only allowed in -lang fb
Differences from QB
▪In FreeBASIC, the parameter names aFe optio,al.
See also
▪Sub
▪Type
▪Dim