CODEWITHSUNDEEP
objective-c
codenamepenryn
codenamepenryn

Reputation: 461

From another class, how do I call a method that's declared in the implementation file but not interface?

In this tutorial here: http://www.raywenderlich.com/62989/introduction-c-ios-developers-part-1

It mentions that for Objective-C:

Even if you only declare a method inside the implementation of a class, and don’t expose it in the interface, you technically could still call that method externally.

How is this done?

Upvotes: 1

Views: 43

Answers (2)

Chuck
Chuck

Reputation: 237080

There are a lot of ways.

For example, as long as a compatible method is declared somewhere, you can call it normally with dynamic typing. Here's a demonstration:

// MyClass.h
@interface MyClass : NSObject
@end

// MyClass.m
@interface MyClass()
- (void)addObject;
@end
@implementation MyClass
- (void)addObject:(id)object {
    NSLog(@"Whoa, I got called!");
}
@end

// main.m
#import <Foundation/Foundation.h>
#import "MyClass.h"

int main() {
    id something = [[MyClass alloc] init];
    [something addObject:@"Look ma, no errors!"];
    return 0;
}

Since there is a known method named addObject: that takes an object, and id variables are dynamically typed, this is 100% valid and will call MyClass's addObject: method.

They could even get it with a statically typed variable and a method that isn't known by declaring the method in a category. A few other options:

  • using performSelector: as @michaels showed in his answer
  • going straight to objc_msgSend()
  • getting the method IMP and calling it directly.

Upvotes: 2

mspensieri
mspensieri

Reputation: 3521

You can use the performSelector: method of NSObject, though the compiler will give you a warning if the selector is not publicly declared anywhere

[someObject performSelector:@selector(someMethod)];

Upvotes: 0

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