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PONSArray sortedArrayUsingDescriptors: New Copy or Retain?
 

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    <p>According to <code>NSArray</code> class reference there are 4 type of methods to sort array:</p> <p>1- <code>sortedArrayUsingComparator</code>:</p> <p>2- <code>sortedArrayUsingSelector</code>:</p> <p>3- <code>sortedArrayUsingFunction:context</code>:</p> <p>4- <code>sortedArrayUsingDescriptors</code>:</p> <p>For first three methods it mentioned : The new array contains references to the receiving array’s elements, not copies of them. But for the forth method (descriptor) it mentioned: A copy of the receiving array sorted as specified by <code>sortDescriptors</code>.</p> <p>But following example shows like the other 3 methods, descriptor also retain original array and do not return a new copy of it:</p> <pre><code>NSString *last = @"lastName"; NSString *first = @"firstName"; NSMutableArray *array = [NSMutableArray array]; NSDictionary *dict; NSMutableString *FN1= [NSMutableString stringWithFormat:@"Joe"]; NSMutableString *LN1= [NSMutableString stringWithFormat:@"Smith"]; NSMutableString *FN2= [NSMutableString stringWithFormat:@"Robert"]; NSMutableString *LN2= [NSMutableString stringWithFormat:@"Jones"]; dict = [NSDictionary dictionaryWithObjectsAndKeys: FN1, first, LN1, last, nil]; [array addObject:dict]; dict = [NSDictionary dictionaryWithObjectsAndKeys: FN2, first, LN2, last, nil]; [array addObject:dict]; // array[0].first = "Joe" , array[0].last = "Smith" // array[1].first = "Robert" , array[1].last = "Jones" NSSortDescriptor *lastDescriptor =[[NSSortDescriptor alloc] initWithKey:last ascending:YES selector:@selector(localizedCaseInsensitiveCompare:)]; NSSortDescriptor *firstDescriptor =[[NSSortDescriptor alloc] initWithKey:first ascending:YES selector:@selector(localizedCaseInsensitiveCompare:)]; NSArray *descriptors = [NSArray arrayWithObjects:lastDescriptor, firstDescriptor, nil]; NSArray *sortedArray = [array sortedArrayUsingDescriptors:descriptors]; // array[1] == sortedArray[0] == ("Robert" , "Jones") // comparing array entries whether they are same or not: NSLog(@" %p , %p " , [array objectAtIndex:1] , [sortedArray objectAtIndex:0] ); // 0x10010c520 , 0x10010c520 </code></pre> <p>it shows objects in both arrays are same,</p>
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