CODEWITHSUNDEEP
cobjective-cfunctionscope
Roja Buck
Roja Buck

Reputation: 2354

Whats the scope of a c function defined within objective-c class?

I was reading up about bypassing objective-c's messaging to gain performance (irrelevant to this specific question) when i found an interesting bit of code:

#import <Cocoa/Cocoa.h>

@interface Fib : NSObject { }

- (long long) cFib: (NSUInteger) number;

@end

@implementation Fib

// c implementation of fib
long long cFibIMP(NSUInteger number)
{
  return (number < 3) ? 1 : cFib(number - 1) + cFib(number - 2);
}

// method wrapper for c implementation of fib
- (long long) cFib: (NSUInteger) number
{
  return cFibIMP(number);
}

@end

My question is; when using c function, within an objective-c object, what scope is the c function (cFibIMP in this particular case) placed in? Does the objective-c class encapsulate the c function removing change of name-clash or is the c function simply dumped into the global scope of the whole objective-c program?

Upvotes: 5

Views: 839

Answers (2)

Stephen Canon
Stephen Canon

Reputation: 106187

The C function has global scope.

If you want to have something like "class" scope, your best bet is probably to use the static keyword, which limits the scope of the function to the source file in which it is contained. For the sort of usage you're illustrating here, that's usually close enough.

Upvotes: 1

diciu
diciu

Reputation: 29333

The functions are dumped in the "global" scope.

You can check this by adding a new class at the end of your sample code:

@interface Gib : NSObject {}
@end
@implementation Gib
- (void) t
{
    NSLog(@"%d", cFibIMP(10));
}
@end

Upvotes: 4

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