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POObjective-C - iVar Scoped Method Variables?
 

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  1. POObjective-C - iVar Scoped Method Variables?
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    <p>I was messing around in Objective-C earlier, and I ran into a quite common situation:</p> <p>I had a class, which was not a singleton, that needed a variable shared between method calls, like <code>static</code>, but each instance needed it's own variable. However, this variable only needed to be used in one particular method, we'll call it <code>-foo</code>.</p> <p>What I'd love to do, is have a macro, let's call it <code>ivar</code>, which lets me do the following:</p> <pre><code>@implementation MyClass -(foo) { ivar int someVal = 10; // default value, ivar scoped variable. } -(bar) { someVal = 5; // error, outside of `foo`'s scope. } @end </code></pre> <p>How the variable is defined does not matter to me (either a macro like <code>OBJC_IVAR(Type, Name, Default)</code> or <code>ivar someType someName = value</code>), as long as it meets the following requirements:</p> <ul> <li>Has thread safety</li> <li>Can have variable of same name (but different value) in another method</li> <li>Type-less (doesn't matter what type the variable is)</li> <li>Default Value support</li> <li>Variable can be declared in one line (I shouldn't have to write 15 lines of code just to put a variable in my code)</li> </ul> <p>I am currently working on an Objective-C++ implementation myself, I was just wondering if anyone else had any thoughts (or existing tools) on how to do this.</p> <p>Obviously, this doesn't have to be done with a true iVar. More likely, this should be done with associated objects at run-time, which also manages deallocation for us.</p>
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    1. USRichard J. Ross III
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    1. COI'm puzzled -- why can't it be a regular ivar that you only use in the one method? And then use code inspection to assure it's only used where intended? If you feel it necessary you can name it by the method -- eg, "foo_someVal".
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    2. CO@HotLicks because that clutters up the iVar declaration of the object. Plus, adding an iVar for a method that may or may not be called is a bit overkill, don't you think? This is also useful for categories, where you CAN'T add an iVar to the class.
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    3. COThere are lots of things that clutter up things. Objective-C is more clutter than code. And how is adding the ivar for the method somehow more "overkill" than adding the method?
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