Thread: Very easy function call question

Code:

class IOField
{
	private:
			int row,
				col;
	protected:
			void *data;
			IOScreen *owner;
			bool Ok;
			void (*help)(IOScreen *scrPtr); 
			bool (*isValid)(void *data, IOScreen *scrPtr);
			int Row();
			int Col();

	public:
			IOField(int row, int col, 
				    void (*help)(IOScreen *) = NULL,
					bool (*isValid)(void *, IOScreen *) = NULL)
			        { this->row = row;
					  this->col = col;
						help(IOScreen);
		
					}
};

In the public constructor, how do I pass to help the pointer that is coming into the constructor which I defaulted to NULL?

The error is on help(IOScreen) with the message

Code:

error C2275: 'IOScreen' : illegal use of this type as an expression

Edit: The same with isValid, how would I pass it whatever comes in

You're passing a pointer to a function to the constructor. You need an IOScreen object to pass to the help function. Possibly, you could pass this to the constructor (although I'm not sure this is what you want to do):

Code:

IOField(int row, int col, void (*help)(IOScreen *) = NULL, bool (*isValid)(void *, IOScreen *) = NULL, IOScreen* ioscrObj)
{ 
  this->row = row;
  this->col = col;
  if(help)
    help(ioscrObj);
}

It's also a bad idea to default that function pointer to NULL unless you also check that it isn't null before calling it.