Use multiple asset folders in xCode - ios

Question

So I am working on a game in SpriteKit. I have a function that generates a level for the player.
The function uses images placed in assets.xcassets to generate levels. The game has multiple themes , namely fire water and electricity. Each theme has its own set of images with the same names but each theme image set is in its separate folder/group. Is it possible for me to programmatically tell the function to use a specific folder so that I can generate levels for other themes without renaming images. Or is it possible for me to use multiple asset folders and change which one the function uses at runtime. I want to use a random theme every time the player restarts the level.

Answer 1

Sprite Atlas / Sprite Sheet
You can use a Sprite Atlas (also known as Sprite Sheet).
If you don't know what I'm talking about have a look at these 2 nice videos:
Sprite Sheets - The Movie Part 1
Sprite Sheets - The Movie Pt. 2 - Performance
How to use it
If you have watched the videos now you know that the main target of a Sprite Atlas is loading into the GPU all and only (as far as possible) the images needed for the current scene or level. This way drawing each frame becomes much faster because all the resources al already on the GPU and the CPU only needs to transmit the coordinates.
Namespace
Ok but how does it solve your problem?
Xcode allows you to create a namespace for each Sprite Atlas. So you can use the same name for resources in different Sprite Atlas.
How to create a Sprite Atlas.
This is pretty simple.
With Xcode open you Asset Catalog
Tap on the + button you see in the image below
Click on New Sprite Atlas
You'll se a new "Folder", that's your Sprite Atlas.
5. Now click on the Provides Namespacecheckbox on the right.
That's it. Now just drop your images into the Sprites folder in order to add them to your sprite atlas.
In this example I'm going to rename the Sprite Atlas as Sprites0 and will add a red circle named circle.
Then
will create another Sprite Atlas
will check again the Provides Namespacecheckbox
will name Sprites1
and finally will add a green circle names circle.
Here's the final result
Code
Let's see now how to use it.
import SpriteKit
class GameScene: SKScene {
override func didMove(to view: SKView) {
let textureAtlas0 = SKTextureAtlas(named: "Sprites0")
let texture0 = textureAtlas0.textureNamed("circle")
let sprite0 = SKSpriteNode(texture: texture0)
sprite0.position.y = 100
addChild(sprite0)
let textureAtlas1 = SKTextureAtlas(named: "Sprites1")
let texture1 = textureAtlas1.textureNamed("circle")
let sprite1 = SKSpriteNode(texture: texture1)
sprite1.position.y = -100
addChild(sprite1)
}
}
Result
How does it work
Step 1: you load the Sprite Atlas
let textureAtlas0 = SKTextureAtlas(named: "Sprites0")
Step 2: you load a specific texture from the texture atlas
let texture0 = textureAtlas0.textureNamed("circle")
Step 3: you use your texture as you want
let sprite0 = SKSpriteNode(texture: texture0)
sprite0.position.y = 100
addChild(sprite0)