CODEWITHSUNDEEP
objective-cprotocolsnsobject
user3251270
user3251270

Reputation: 107

confusion with some objective-c protocols

I downloaded the source code for an application called adium, because I wanted to learn cocoa better by scrutinizing other people's code, but there is something very confusing to me in this interface:

@interface AIAdium : NSObject <AIAdium, SUVersionComparison> {
@private
IBOutlet    NSObject <AIMenuController>         *menuController;
IBOutlet    NSObject <AIInterfaceController>        *interfaceController;
IBOutlet    SUUpdater                                   *updater;

NSObject <AIAccountController>                  *accountController;
NSObject <AIChatController>                     *chatController;
NSObject <AIContactController>                  *contactController;
NSObject <AIContentController>                  *contentController;...

It goes on like this. What I don't understand is how NSObjects are conforming to protocols like AIAccountController. I thought you had to implement the methods defined in the interface of a protocol to conform to it, but how could NSObject be doing that?

Upvotes: 0

Views: 48

Answers (1)

rmaddy
rmaddy

Reputation: 318794

That's not what those lines mean. Example:

NSObject <AIAccountController> *accountController;

What this means is that the accountController ivar is a pointer to any NSObject derived class that also conforms to the AIAccountController protocol.

Since NSObject is the root class of most other classes, this basically means any custom class that conforms to the protocol can be assigned to the ivar.

Nothing about the line has any bearing on NSObject itself.

What the author of this code should have used was:

id<AIAccountController> accountController;

Upvotes: 3

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