我可以使用类方法作为委托回调吗

Question

In a class method method I declare the following:

    UIAlertView *alert = [[UIAlertView alloc]initWithTitle:@"Hello" 
                                                   message:@"World"
                                                  delegate:self
                                         cancelButtonTitle:@"Cancel" 
                                         otherButtonTitles:@"Done", nil];

Now even though the containing method is a class method, the compiler does not complain about the delegate:self . Now to be the delegate I have to implement the method in UIAlertViewDelegate protocol.

Does it now matter, if the method is a class method or not, in order to be called when the user interacts with my AlertView?

I am asking this question, because my class does not have any instance variables so I would prefer it to contain class methods only.

Answer 1

I would like to share some of my findings:

1. It does not matter whether I declare the delegate like this delegate:self or delegate:[MyClass class]

2. However, it does matter how I declare the method:

   This works

   +(void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex{ // Some Actions here }

   Although the following "syntax" is the declaration in the UIAlertViewDelegate protocol, it does not work :

    // Mind the `-` sign at the start of the line. -(void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex{ // Some Actions here }

Answer 2

First, I assume by "static" methods, you mean class methods (declared with + instead of - ).

"The compiler does not complain" about Objective-C doesn't always tell you much. All it really means is that you have convinced the compiler that everything should (or at least could ) work at runtime.

In the end, if the object you provide as a delegate responds to the right messages, the compiler won't care that it's a class (and neither will the runtime). In this case, you are providing self from a class method. It is as though you typed [MyClass class] .

I think it's probably questionable whether this is what you should do--but that's probably outside the bounds of your question.

Answer 3

Yes you can !!! A class is also an object.