StackOverflow2013

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copied!<h1>Pass by reference in Objective-C is almost never the right way.</h1> <p>There are a number of problems with that code.</p> <ul> <li><p><code>(id**)</code> is a <em>pointer to a pointer to a pointer to an object</em>. Probably not at all what you want.</p></li> <li><p><code>YES</code> and <code>NO</code> are <code>BOOL</code> return types; not <code>TRUE</code></p></li> <li><p>there is no reason in that code to be returning something by reference.</p></li> <li><p>method names start with lower case letters. Arguments do, too.</p></li> <li><p>There will never be an instance of <code>NSMutableArray</code> in an application; just subclasses</p></li> <li><p>You can't tell the difference between a mutable and immutable array in the first place; check for <code>isKindOfClass:</code> or <code>isMemberOfClass:</code> for an <code>NSMutableArray</code> won't do you <em>much</em> good (it is useful, but misleading).</p></li> </ul> <p>This is better:</p> <pre><code>-(BOOL)remoteCall: (id) dataThing { if([dataThing isKindOfClass:[NSMutableArray class]] == YES) { NSMutableArray *swArray = dataThing; // not strictly necessary, but good defensive practice //do something with swArray return YES; } return NO; } </code></pre> <p>To be called like:</p> <pre><code>NSMutableArray * channelArray = [[NSMutableArray alloc]init]; // you'll need to release this somewhere Services * serv = [[Services alloc] init]; return [serv remoteCall:channelArray]; </code></pre> <p>Since you don't return a different array in <code>remoteCall:</code>, <code>channelArray</code>'s contents will be manipulated by the method and the YES/NO return value.</p> <p>If there is some reason why the above seemingly won't work for you, please explain why.</p> <p><b>Note:</b> The code obviously requires an <code>NSMutableArray</code> if you are going to muck with the contents. The <code>isKindOfClass:</code> could be checking for <code>NSMutableArray</code> or <code>NSArray</code> and it wouldn't matter either way. When using arrays in your code and requiring a mutable array, it is up to you to make sure the data flow is correct such that you don't end up w/an immutable array where you need a mutable array.</p>

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