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    <p>Do you cast the returned object to your object type (<code>MyObject</code>)?</p> <p>You should do something like:</p> <pre><code>((MyObject*)[mutableArray objectAtIndex:0]).age = 20; </code></pre> <p>The reason you're not getting any errors when using <code>[[mutableArray objectAtIndex:0] name]</code> syntax is that you're calling a method on the returned object (which is of type <code>id</code>), and <code>id</code> s tend to not choke in the compile-time if you call a (yet) non-existant method on them. At the run-time, <code>[mutableArray objectAtIndex:0]</code> <em>might</em> resolve to type <code>MyObject</code> an in that case, the message <code>[obj name]</code> has a proper implementation (<code>IMP</code>). If it doesn't resolve to <code>MyObject</code>, your app will crash.</p> <p>And note that the reason you're not even getting a compile-time warning is that Xcode knows that there is at least 1 class in your codebase that implements the method <code>name</code>, and it trusts you with calling this method <em>only</em> on instances of that class. if you do something like <code>((MyObject*)[mutableArray objectAtIndex:0]).ageeeeee = 20;</code>, it'll give you a warning as there's a very good chance that it'll crash (no class in your app implements the method <code>ageeeeee</code> <em>statically</em>). </p> <p>The type <code>id</code> does not have a property <code>name</code>, and that's why you can't use dot syntax.</p> <p>Actually, this incident shows perfectly why ObjC is called a dynamic language!</p>
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    1. POWhy does calling a property on NSObject pointer gives build errors?
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    1. USPooria Azimi
    1. USPooria Azimi
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    1. COThats fine. but the dot syntax is suppose to represent a call to setter or getter method. so shouldn't it work the way as a method call whether or not it existed ? anyways.. thanks for the clarification :)
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      1. USAmogh Talpallikar
    2. COWhat if the property is supposed to be read only? Unless the compiler knows exactly which class/property you are talking about, it can't know whether you should be allowed to use it (at least in the case where you want to set the value).
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      1. USUIAdam
    3. CO@UIAdam: Nice point but if the property is readonly then, setter wont be generated, and i should get an "unrecognized selector sent to object exception" at runtime.
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      1. USAmogh Talpallikar
 

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