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POMutual changes in two NSMutableArray objects
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copied!<p>Assume, your .h file looks like this:</p> <pre><code>@property (retain, nonatomic) NSMutableArray *songs; - (NSMutableArray *)popularSongs; - (void)make20PercentDiscountToPopularSongs </code></pre> <p>Your .m file looks like this:</p> <pre><code>- (NSMutableArray *)popularSongs { NSMutableArray *popularSongs = [NSMutableArray array]; for (Song *song in self.songs) { if (song.isPopular) { [popularSongs addObject:song]; } } return popularSongs; } - (void)make20PercentDiscountToPopularSongs { for (Song *song in self.popularSongs) { song.price = song.price * 0.8; } } </code></pre> <p>The code above adds a 20% discount to popular songs. I recognise that there is a more simplistic way of doing this. You could have the "make20PercentDiscountToPopularSongs" and "popularSongs" function in a single function but let's assume that the code is written the way it is written above.</p> <p>In the example above, will the line:</p> <pre><code>song.price = song.price * 0.8; </code></pre> <p>Actually, make any changes to the object:</p> <pre><code>@property (retain, nonatomic) NSMutableArray *songs; </code></pre> <p>Or not? Because, it seems as if the line will change the newly created popularSongs NSMutableArray rather than the songs NSMutableArray, am I right? This problem is bothering me for a lot of time now. <strong>I would like to make changes just to the original songs array. To me popularSongs works as if you are storing the pointers to the songs in the songs array.</strong></p>

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