Loading images into NSArray using initWithObjects crashes but not with an NSMutableArray?

Question

I'm doing some lazy loading of images into an array when the app has loaded. I have tried using an NSMutableArray and an NSArray (I don't need to alter the array once it's been created) but the latter crashes on me. ``` ... [self performSelectorInBackground:@selector(loadImageArrays) withObject:nil]; ... - (void)loadImageArrays { NSAutoreleasePool *pool; pool = [[NSAutoreleasePool alloc] init]; NSString *fileName; imageArray = [[NSMutableArray alloc] init]; for(int i = 0; i <= x; i++) { fileName = [NSString stringWithFormat:@"image_0000%d.png", i]; [imageArray addObject:[UIImage imageNamed:fileName]]; } [pool drain]; } ``` vs ``` NSAutoreleasePool *pool; pool = [[NSAutoreleasePool alloc] init]; imageArray = [[NSArray alloc] initWithObjects: [UIImage imageNamed:@"image_00000.png"], [UIImage imageNamed:@"image_00001.png"], [UIImage imageNamed:@"image_0000X.png"], nil]; [pool drain]; ``` NSZombieEnabled = YES tells me that [UIImage retain] was sent to deallocated instance when using the…

Accepted Answer

`UIImage` is part of UIKit, which is not thread safe. For example, the method `imageNamed:` could corrupt the global name-image dictionary that the `UIImage` class uses for caching.

You have to use Core Graphics if you want to load images on a background thread.

Edit to answer your comment:

You can load PNG files with:

```
CGDataProviderRef source = CGDataProviderCreateWithURL((CFURLRef)url);
CGImageRef image = CGImageCreateWithPNGDataProvider(source, NULL, NO, kCGRenderingIntentDefault);
CFRelease(source);
```

A `CGImage` is a core foundation object and can be stored in an `NSArray`. You can then make a `UIImage` from it (on the main thread, of course):

```
[[UIImage alloc] initWithCGImage:image]
```

Loading images into NSArray using initWithObjects crashes but not with an NSMutableArray?

Solution

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