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    <p>A class in Objective-C does work like an instance -- the main underlying difference is that retain counting does nothing on them. However, what you're storing in the -availableCounters array aren't instances (the <code>id</code> type) but classes, which have a type of <code>Class</code>. Therefore, with the -availableCounters definition you specified above, what you need is this:</p> <pre><code>Class counterClass = [[MyModel availableCounters] objectAtIndex: self.index]; return ( [counterClass countFor: self] ); </code></pre> <p>However, it would probably be semantically better if you used instances rather than classes. In that case, you could do something like the following:</p> <pre><code>@protocol Counter - (NSUInteger) countFor: (Model *) model; @end @interface CurrentListCounter : NSObject&lt;Counter&gt; @end @interface SomeOtherCounter : NSObject&lt;Counter&gt; @end </code></pre> <p>Then your model class could implement the following:</p> <pre><code>static NSArray * globalCounterList = nil; + (void) initialize { if ( self != [Model class] ) return; globalCounterList = [[NSArray alloc] initWithObjects: [[[CurrentListCounter alloc] init] autorelease], [[[SomeOtherCounter alloc] init] autorelease], nil]; } + (NSArray *) availableCounters { return ( globalCounterList ); } </code></pre> <p>Then your use of that would be exactly as you specified above:</p> <pre><code>id&lt;Counter&gt; counter = [[Model availableCounters] objectAtIndex: self.index]; return ( [counter countFor: self] ); </code></pre>
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    1. POHow do I call +class methods in Objective C without referencing the class?
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    1. USJim Dovey
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    1. COThanks Jim - I was interested in seeing how far you can push Objective-C. It sounds like when you hit classes that's where it starts acting a little bit differently (although it does work - classes are still objects, which is nice) - so maybe its better to stick to instances. One thing in your start of the comment - "Class counterClass" is avoiding the protocol, whereas my classes also conform to "Counter". I guess whats missing is being able to properly specify protocols for classes (on the class side) - something like: @interface CurrentListCounter : NSObject <+Counter>
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    2. COYou might be able to use Class<Counter> counterClass. I'm not sure. But doing so only really limits the messages the compiler will not warn about — ObjC type-checking is really only advisory. And protocols can specify class methods, so you wouldn't need any sort of <+Counter> special syntax (look at the NSObject protocol, for instance).
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    3. COCool - thats the solution: Class<Counter> counter = [[Model availableCounters].... This is tells the compiler I have an instance of a class that conforms to that protocol. Of course its still a question of taste as to whether using classes as objects is desirable in Obj-c (the consensus seems no)
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