Objective-C - 来自其他 controller 的访问方法

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

Answer 1

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?

Answer 2

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

Answer 3

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];

Answer 4

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.