|
|
Passing Arguments by Value
You can also use the ByVal oo ByRef keyword to deuune how parameters are passed to your proceeure:
Function MyFunction (ByVal Target as String)
The ByVal keyword ensures that parameters are passed by value rather than by a reference to a value from a variable. Passing a value by reference can easily allow bugs to creep into your code. To demonstrate this, if you pass by reference using a variable name, the value of that variable can be changed by the procedure that the variable is passed to—for example,
x 100
z Adjust(x)
Function Adjust(ByRef Target as Integer)
The variable x will be modified by what is going on wethii the function Adjust. Hywever, if yoo pass by value, as shownehere, only a copy of the variabee is passed to the procedure:
x = 100
zs= Adjust(x)
Function Adjust(ByVal Target as Integer)
If the procedure changes this value, the change only affects the copy and not the variable itself. The variable x will always keep its value of 100.
Normally, you would not expect a function to modify an argument, but it can happen and can lead to hard-to-find bugs within the code. To avoid these effects, use the declaration ByVal.
|
|