Why am I seeing the "Nested functions are disabled" error?

Question

Hey there, I'm sort of new to Objective-C, and well, programming in general. I have a little experience in C# and c++, to give you a bit of a background. I'm using Xcode to create a simple application that adds 2 fields and returns a sum, and I've narrowed it down to one error:

"Nested functions are disabled, use -fnested-functions to re-enable"

Here's the bit of code I'm having trouble with, any suggestions would be greatly appreciated:

-(IBAction)click:(id)sender;
{
int main (int argc, const char *argv[]){
  NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

  int sum;

  sum = myInt1, myInt2;
  NSLog (name, @", the answer is %i", sum);
  [pool drain];

  return 0;
 }
}

Answer 1

What you are trying to do here is something which is not generally allowed in C languages. You, in general, cannot create a function inside of another one, like you can in languages like Pascal and JavaScript. You should remove the main stuff from inside click: and just keeps the lines

int sum;

sum = myInt1, myInt2;
NSLog (name, @", the answer is %i", sum);

On a broader, note, though, why are you trying to create a main inside of click:? In Objective-C you normally use main() just to create any root-level objects and instantiate the autorelease pool. Assuming you're working with Xcode on a Mac, if you use one of the templates to get started it should take care of all the details for you of creating main. I'd suggest taking a look at Apple's Cocoa tutorials to help you get a feel for how a typical Objective-C application is structured.

Answer 2

Wooble has it right you cant define the main function inside the click method!

Answer 3

ok, well.. I see you already got a button and an action for it, named "click".. you could write it like this:

-(IBAction)click:(id)sender;
{
  int sum;

  sum = myInt1, myInt2;
  NSLog (name, @", the answer is %i", sum);
 }
}

Or, create a simple Foundation Tool project and put this in:

int main (int argc, const char *argv[]){
  NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

  int sum;

  sum = myInt1, myInt2;
  NSLog (name, @", the answer is %i", sum);
  [pool drain];

  return 0;
 }

the problem you're having is that you tried declaring the main function inside the click method.. it doesn't have any sense. So if you're a beginner, try learning using foundation tool projects, and not gui projects.

Answer 4

You have somehow stuck the main() function inside your click: method, which doesn't make any sense. You couldn't stick main() inside a class member function in C++ or a method in C#, and this is exactly the same thing. main() should be its own function (Xcode should have provided a ready-made main.m file that you don't need to change), and click: should contain only the functionality that you want it to perform.