Using Class Variables as Default Parameters

[MukeshMak]

Hi all,

I'm trying to use class variables as default parameters in my C++ code but get the following error:

var_A : use of member as default parameter requires static member

To illustrate my problem here is an example class:

class exampleClass {
private:
int var_A;

public:

int exampleMethod ( int varMethod = var_A )
{
.
.
.
}
};

Can I still do this and avoid declaring the var_A variable as 'static'.

Thanks in advance for all the replies.

 

[LazyMe]

I think not. The compiler needs an address to supply the default value at compile time. The addres of a non-static member variable cannot be determined at compile time.
Greetings,
Rick

 

[Zyrenthian]

I dont understand why you need to do this. If the class knows what the variable is when the function is called, why tell the member function what it already knows? The only reason I can think of is at some time you may want to kill 2 birds with one stone and rather then call "SetVarA(value)" you would prefer to do a check in the member function and set it if it is different. The only way to accomplish this, in my opinion, is not to pass the member variable but have a class specific value that Var_A can never be. For situations like this I do things like

#define INVALID_VALUE ~0 // dont forget the tilde

then the member fucntion would be

int exampleMethod ( int varMethod = INVALID_VALUE)
{
if(varMethod != INVALID_VALUE)
var_a = varMethod;

// on with the code

}

Matt