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POAdding values to two different NSMutableArray without increasing the retain count
 

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  1. POAdding values to two different NSMutableArray without increasing the retain count
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    <p>I have two simple NSMutableArray that consists of few objects. Some of these objects can be common but need to be stored in both of the arrays as uses of both arrays are defined for totally different purpose. </p> <p>However, the problem is that after adding same objects to both array, on changing the value of one of the common object, does not reflect in 2nd array.</p> <p>For example,</p> <p>Let's say we have two mutable NSArray:</p> <pre><code>NSMutableArray *mutableArrayOne; NSMutableArray *mutableArrayTwo; </code></pre> <p>Now let's create the object definition that these array needs to contain.</p> <pre><code>@interface: DummyObject : NSObject { int objectValue; } @property (nonatomic) int objectValue; -(void) printObjectValue; @end </code></pre> <p>Now let's create the base class to store the arrays. </p> <p><strong>Base Class Definition</strong> </p> <pre><code>@interface: BaseClass : NSObject { NSMutableArray *mutableArrayOne; NSMutableArray *mutableArrayTwo; } -(void) init; -(void) printBothArrays; @end </code></pre> <p><strong>Base Class Implementation</strong> </p> <pre><code>@implementation BaseClass -(void) init { // initialize the mutable array. mutableArrayOne = [[NSMutableArray alloc] initWithCapicity:5]; mutableArrayTwo = [[NSMutableArray alloc] initWithCapicity:5]; DummyObject *dummyObject = [DummyObject alloc]; [dummyObject setObjectValue:5]; DummyObject *dummyObjectTwo = [DummyObject alloc]; [dummyObjectTwo setObjectValue:2]; [mutableArrayOne addObject:dummyObject]; [mutableArrayOne addObject:dummyObjectTwo]; [mutableArrayTwo addObject:dummyObjectTwo]; } @end </code></pre> <p>Now let me the modify the DummyObject in array One:</p> <pre><code>for (DummyObject* dummyObject in mutableArrayOne) { [dummyObject setValue:100]; } </code></pre> <p><strong>Problem</strong> Now here starts the problem when I am printing the values for both array objects:-</p> <h1>Printing First Array</h1> <pre><code>for (DummyObject* dummyObject in mutableArrayOne) { [dummyObject printObjectValue]; } </code></pre> <p>*<em>Output Log (from first array) *</em></p> <pre><code>100 100 </code></pre> <h1>Printing second Array</h1> <pre><code>for (DummyObject* dummyObject in mutableArrayTwo) { [dummyObject printObjectValue]; } </code></pre> <p>*<em>Output Log (from second array) *</em></p> <pre><code>2 </code></pre> <p>So here we can see that MutableArray is keeping the copy of the object, however, I want to store only the reference. That means, on changing the value of the object in 1st array should reflect in 2nd array.</p> <p>How can we do that? Do we any other alternative?</p> <p>Thanks, <strong>Paras Mendiratta</strong></p>
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    1. COis there a typing address on the code example? the output from the first array returns 2 100s, and the one from the second returns 1 2. which means that you are adding 2 objects to the first array and 1 to the second, contrary to what your code says. (which makes me believe your spelling mistake is making you add them to the first array)
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    2. COThanks, I have fixed the sample code.
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    3. COIf your code is exactly like that, are you sure than when you print the second mutable array you are not gettin 100?
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