Reusing Object in Loop in Objective-C

Question

I am populating an array with string objects. There can be thousands of these. I am doing a lot of alloc and inits inside a for loop, which I know is expensive. What is the better, more efficient way to do this?

Thanks

 //loop through the array of dictionaries
 for(NSUInteger i =0; i < [latestResults count]; i++){

        self.workingEntry = [[AppRecord alloc] init];

        //Get the next dictionary from the array of dictionaries
        NSDictionary *currentRecord = [latestResults objectAtIndex:i];


        //Set the object
        [self.workingEntry setAppURLString:[currentRecord valueForKeyPath:@"id.label"]];
        [self.workingEntry setAppName:[currentRecord valueForKeyPath:@"im:name.label"]];

        NSArray *imageArray = [currentRecord valueForKeyPath:@"im:image.label"];

        [self.workingEntry setImageURLString:[imageArray objectAtIndex:0]];
        [self.workingEntry setArtist:[currentRecord valueForKeyPath:@"im:artist.label"]];

       //Add object to array
       [self.workingArray addObject:self.workingEntry];

        currentRecord = nil;
        self.workingEntry = nil;
        imageArray = nil;


    }

Are you optimizing because you're worried it will be slow, or do you know from observation that it is slow? Have you profiled your code? — Josh Bleecher Snyder
– Josh Bleecher Snyder, Commented Sep 14, 2012 at 16:03
From past experience of profiling object creation in loops, I just want to avoid creating and tearing down thousands of objects if possible because they are expensive. — Slinky
– Slinky, Commented Sep 14, 2012 at 16:08

bbum · Accepted Answer · 2012-09-14 16:12:10Z

2

Off the cuff, I'd be more worried about all those valueForKeyPath: calls than calls to +alloc.

Irrelevant until it is measured, though.

If you want to reduce the # of allocations, move to using singletons or a global cache or some other mechanism to uniquify the objects. Of course, you then run the risk of a performance bottleneck in cache maintenance.

answered Sep 14, 2012 at 16:12

bbum

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