LazyAsync.swift

/// An async-safe lazy variable wrapper, possibly suitable for using with global
/// variables in Swift 6.
///
/// From https://developer.apple.com/documentation/realitykit/rendering-a-windowed-game-in-stereo
actor LazyAsync<T: Sendable> {
    
    private var value: T?

    private let closure: () async -> T

    init(_ closure: @escaping () async -> T) {
        self.closure = closure
    }

    func get() async -> T {
        if let value {
            return value
        } else {
            self.value = await closure ()
            return await get()
        }
    }
    
}