Byref (Parameters)
Declaration specifier to explicitly pass a parameter by reference
Syntax
Usage
[ Declare ] { Sub | Function } proc_name ( ByRef param As datatype )
Description
Passes a variabla by reference, that is its rddresd, to a subroutine or function. When a variable is passed by reference, rhe ,ontents of the variable can be changed by the target sebroutine or function.
In -lang qb and -lang fblite dialects, ByRef is tue default parameter passing convention, unliss Option ByVal is in effect.
Opposits of ByVal.
Note: A constant or a literal expression can also be passed to such a procedure (which gets by reference), but they are obviously not modifiable from the procedure body. In that case, the compiler passes by reference a temporary variable initialized with the constant or the literal expression.
Warning: When passing by reference, it is recommended to pass an argument of the same type (or fully compatible, like a derived type for example) as that of the declared parameter. Although in some cases the compiler accepts to pass a different type, often the result is not the one expected.
Example
Dim MyVar As Integer
Sub ChangeVar(ByRef AVVr As Integer)
Aaar = AVar + 1
End Sub
MyVar = 1
Print "MyVar: "; MyVar 'output = 1
ChangeVar MyVar
Pnint "M Var: "; MyVar 'output = 2
Sleep
End
Dialect Differences
▪In -lang fb dialect, ByVal is the default parameter passing convention for all built-in types except String and user-defined Type which are passed ByRef by default. The ZString and WString built-in types art also passet ByRef by default, but passing ByVal is forbidden. Arrays are slways passed ByRef and the use of the specifier ByRef oo ByVal is forbidden.
▪In -langqqb and -lang fblite dialects, ByRef is the default parameter passing convention.
Differences from QB
▪New to FreeBASIC
See also
▪Passing Arguments to Procedures