Objective-C - Access method from other controller

Question

i have a little question about getting access to a method in another controller, nu i am trying this. So for example i have the controller A and B. In the controller A i have programmed a method, now i want to get access this through controller B.

What i have done in class A in the header file:

+(void)goBack;

and in the implementation file:

+(void)goBack {
NSLog(@"go back");
}

in the controller B i do this to get access to the method in controller A:

+(void)goPreviousArticle:(id)sender {
ViewProductInformation_ViewController *theInstance = [[ViewProductInformation_ViewController alloc] init];
[theInstance goBack];
}

However when i execute the program, then it does not work, the program just shuts down, when i do command click on the function goBack in controller B i get referred to the method in controller A.

Does anybody have an idea what the problem could be?

thanks in advance,

snowy

Xcode is just the IDE - the language is Objective-C. (As such, I've re-tagged your question.) — John Parker, May 02 '11 at 14:05

score 3 · Accepted Answer · edited May 23 '17 at 12:06

3

It's quite easy ... you just mixed the class and instance-method declaration: The "+" sign indicates that the method is a class method. In your case it should be a "-" so

-(void)goBack; // a instance method declaration!

Hope this helps.

Class vs instance method declaration ... see also What is the difference between class and instance methods?

edited May 23 '17 at 12:06

Community

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answered May 02 '11 at 14:09

crosscode

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this surely helps ! i am glad after many hours of searching that you could give me a solution. also thank you for the explanation, it has cleared out a lot for me ! – Snowy May 02 '11 at 14:45

score 0 · Answer 2 · answered May 02 '11 at 14:10

0

You are declaring goBack as a CLASS method (with the preceding "+"). Change the + to a -.

answered May 02 '11 at 14:10

Rayfleck

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score 0 · Answer 3 · answered May 02 '11 at 14:11

0

Since goBack is a static method of Class A, you don't need an instance of A to call it's method, you can just call it like so:

[ClassA goBack];

answered May 02 '11 at 14:11

Todd Hopkinson

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I tried this, but does not worked out for me, the solution above works fine for me. – Snowy May 02 '11 at 14:47

score 0 · Answer 4 · answered May 02 '11 at 14:15

You don'y need to declare static functions you can writ like this:

-(void)goBack {
NSLog(@"go back");
}

In the class A and same in the class B:

-(void)goPreviousArticle:(id)sender {
ViewProductInformation_ViewController *theInstance = [[ViewProductInformation_ViewController alloc] init];
[theInstance goBack];
}

Then use them. I think in that case application will not crashed.

Objective-C - Access method from other controller

4 Answers4