iOS SpriteKit how to create a node with an image from a folder within app bundle?

Question

I'm trying to create a sprite of a random monster where my images are stored in a folder referenced within the main bundle.

NSString* bundlePath = [[NSBundle mainBundle] bundlePath];
NSString* resourceFolderPath = [NSString stringWithFormat:@"%@/monsters", bundlePath];

NSArray* resourceFiles = [[NSFileManager defaultManager] contentsOfDirectoryAtPath:resourceFolderPath  error:nil];

NSInteger randomFileIndex = arc4random() % [resourceFiles count];
NSString* randomFile = [resourceFiles objectAtIndex:randomFileIndex];

SKSpriteNode* tile = [SKSpriteNode spriteNodeWithImageNamed:randomFile];

When I run my code above, I get this error

SKTexture: Error loading image resource: "random_monster.png"

The code works if I reference the image from the main bundle. How can I use a random image from a folder within the app bundle and pass it to SKSpriteNode?

Answer 1

In that case you can't use the spriteNodeWithImageNamed: method. You have to create the texture yourself from an absolute path and initialize your sprite with that texture:

NSImage *image = [[NSImage alloc] initWithContentsOfFile:absolutePath];
SKTexture *texture = [SKTexture textureWithImage:image];
SKSpriteNode *sprite = [SKSpriteNode spriteNodeWithTexture:texture];

Note that doing so you will lose the performance optimizations that come with using spriteNodeWithImageNamed: (such as caching and better memory handling)

I recommend putting your images in the main bundle and use a specific naming scheme like this:

monster_001.png
monster_002.png
monster_003.png
etc...

Alternatively, consider using texture atlases.