[swift-users] Lazily populated dictionary

[Rudolf Adamkovič]

Hi there!

In my app, I have a very simple class that serves as a key-value cache. The whole thing is basically a lazily populated [String: AVAudioPCMBuffer] dictionary with a String -> AVAudioPCMBuffer function that generates values as needed:

final class PlayerAudioCache {
    
    // MARK: Retrieving audio buffers
    
    func audioBufferForAssetWithName(name: String) -> AVAudioPCMBuffer? {
        addAudioBufferForAssetWithNameIfNeeded(name)
        return cachedAudioBuffers[name]
    }
    
    // MARK: Adding audio buffers
    
    func addAudioBufferForAssetWithNameIfNeeded(name: String) {
        guard cachedAudioBuffers[name] == nil else { return }
        addAudioBufferForAssetWithName(name)
    }
    
    private func addAudioBufferForAssetWithName(name: String) {
        guard let dataAsset = NSDataAsset(name: name) else { fatalError() }
        cachedAudioBuffers[name] = dataAsset.map { URL -> AVAudioPCMBuffer in
            AVAudioPCMBuffer(contentsOfURL: URL)!
        }
    }
    
    private var cachedAudioBuffers: [String: AVAudioPCMBuffer] = [:]
    
}

I feel like there is a pre-made type in Swift’s standard library for what I’m doing here. Am I right?

Ideas? Pointers?

Thank you!

R+
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