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copied!<p>you need to release anything containing the word new, alloc/init or copy.</p> <p>also, you don't need to alloc/init this:</p> <pre><code>UIButton *placeHolderButton = [[UIButton alloc] init]; placeHolderButton = sender; </code></pre> <p>another way of doing this is:</p> <pre><code>UIButton *placeHolderButton = (UIButton *)sender; </code></pre> <p>in your version, it is allocating an instance with a retain count of +1, but you are immediately replacing the reference, so there is no way of releasing the memory later.</p> <p>you are creating a lot of instances with alloc/init, and then replacing their references with autoreleased instances.</p> <p>you could use</p> <pre><code> NSString *placeHolderString = [placeHolderString stringByAppendingString:firstValue.text]; </code></pre> <p>instead of</p> <pre><code> NSString *placeHolderString = [[NSString alloc] init]; placeHolderString = [placeHolderString stringByAppendingString:firstValue.text]; </code></pre> <p>which is again replacing a manually managed instance created on the first line, with an autoreleased instance on the second.</p> <p>infact you could replace every alloc/init in this with the factory method and not have to deal with memory at all in it as they would be autoreleased instances.</p> <pre><code>-(IBAction)inputNumbersFromButtons:(id)sender { //cast sender as a UIButton to suppress compiler warning, and allow us to reference it as placeholder button UIButton *placeHolderButton = (UIButton *) sender; int i = placeHolderButton.tag; NSString *addThisNumber = [NSString stringWithFormat:@"%i", i]; [firstValue setText:[firstValue.text stringByAppendingString:addThisNumber]]; } </code></pre> <p>If you look at the class docs for NSString, any method with a + next to it(ie +stringWithString:(NSString *)string) is a class method, don't use these methods on a reference after you have called alloc/init on it. </p>

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