How to add (id) sender to the following -(IBAction)?

How do you add a (id) sender to the following code?

- (IBAction) gobutton: (UIButton *) button5 {

Everything I try开发者_如何学C fails, any help would be appreciated. Thanks.

EDIT: I need to keep the (UIButton *) button 5 reference in the (IBAction)

If I recall correctly, and if you are using this in the way I think you are,

- (IBAction) gobutton: (id) sender {
if(sender == button5)
   //do something...
else
   //do something else...
}

Assuming that you specified button5 as a parameter to indicate that this executes in response to button5 being pressed.

Ok, first.... IBAction doesn't really mean anything special except to Interface Builder. Basically:

#define IBAction void

So whenever you see IBAction, think "void". The only reason it's there is as a flag to tell Interface Builder that a method is a valid method to connect control actions to. The Objective-C compiler doesn't need to know about it and so it's defined to void since all "action" methods return void.

Second, action methods also have one argument which could be an object of any number of types. Because of this, action methods are supposed to use type id as the type for their argument. That way they can be passed a pointer to any Objective-C object without causing the compiler to generate a type checking error.

So usually actions should work something like this:

- (IBAction)myAction:(id)sender {
    if (sender == self.someButton) {
        UIButton *button = (UIButton *)sender;
        ...
        return;
    } else if (sender == self.someControl) {
        UIControl *control = (UIControl *)sender;
        ...
        return;
    }
}

In other words, an id is almost like an untyped pointer like a void * is routinely used in C when some function needs to take a pointer to something of unknown type. sender could be different types of control, so something generic like id is used then sender is cast to something more specific once the code knows what it is.

Anyway, there is absolutely no reason to define something as having a return type of IBAction unless you are going to use that method as a target action in Interface Builder. Having an IBAction in your app delegate seems kind of unusual....

It's not clear what you are trying to do but most actions look like:

- (IBAction) gobutton: (id)sender;

The first parameter to an action is always the sender (you can specify the type and name as appropriate).

If a method is the action for a button, then the first parameter will be the button. If that method is the action for several buttons, then the first parameter will allow you to determine which button was tapped (as Leper describes).

What problem are you actually trying to solve?
There are techniques for passing information to the action method. For example, if you have a button that appears on a table view cell and performs the same action for every cell, then in the action method, you would want to be able to determine which cell's button was tapped.

How can I get the id of the sender before the user touches the control?

Found it! Set a tag and the use viewWithTag.

Can you create a simple structure that contains both the UIButton and the sender and use that?

struct myObject { UIButton* button5; id sender; }

...or, you could create your own NSObject (probably more cocoa-y):

@instance myObject : NSObject { ... }