Simple Inheritance Question.

[willmeister]

The SDK tells me that UIBarButtonItem inherits from UIBarItem. That should mean that a UIBarButtonItem should have an associated tag property.

The problem for me is that Xcode is telling me that tag, title and other properties are *NOT* available for UIBarButtonItem.

I even ran the program with

NSLog(@"class: %@", [item class]);

to make sure I was actually using the correct class. It outputs:

class: UIBarButtonItem

I don't understand why I'm getting the compile error "Request for member "tag" ... et cetera."

What simple mistake am I doing/missing please? I'm about to go insane.

-- Edit --

Believe I figured out a workaround, I set my method to (IBAction) selection: (UIBarButtonItem *) sender. I always thought you could compile anything with any message to id and would only crash at runtime.

[Duncan C]

Originally Posted by willmeister

The SDK tells me that UIBarButtonItem inherits from UIBarItem. That should mean that a UIBarButtonItem should have an associated tag property.

The problem for me is that Xcode is telling me that tag, title and other properties are *NOT* available for UIBarButtonItem.

I even ran the program with

NSLog(@"class: %@", [item class]);

to make sure I was actually using the correct class. It outputs:

class: UIBarButtonItem

I don't understand why I'm getting the compile error "Request for member "tag" ... et cetera."

What simple mistake am I doing/missing please? I'm about to go insane.

-- Edit --

Believe I figured out a workaround, I set my method to (IBAction) selection: (UIBarButtonItem *) sender. I always thought you could compile anything with any message to id and would only crash at runtime.

You are right about inheritance and UIBarButtonItem. A UIBarButtonItem should indeed have all the properties and methods that a UIBarItem does, because it is a subclass.

Can you post the offending code (before your work-around) along with the exact error you are getting from XCode?

[Kalimba]

Before your workaround, your code probably looked something like this:

(IBAction) selection: (id) sender
{
    ...
    <blah blah> sender.tag <blah>
    ...
}

Because the parameter 'sender' is of type 'id', the compiler essentially knows nothing about it. It certainly isn't aware that it might have a 'tag' property, and so it emits a warning or error. When you change the 'sender' parameter type to 'UIBarButtonItem', the compiler now knows everything you can and can't do with 'sender'.

An alternative to your workaround is to simply cast 'sender' to the data type you know it is, like this:

(IBAction) selection: (id) sender
{
    UIBarButtonItem * myBBI = (UIBarButtonItem *)sender;

    ...
    <blah blah> myBBI.tag <blah>
    ...
}