Pool.swift

private var metaPool = [String:[Any]]()

protocol Poolable: Any {
    init()
}
class Pool<T: Poolable> {
    private static var typeKey: String {
        return "\(T.self)"
    }

    static func get() -> T {
        if metaPool[typeKey] == nil {
            metaPool[typeKey] = [T]()
        }
        if metaPool[typeKey]!.isEmpty {
           return
        }
        return metaPool[typeKey]!.popLast() as? T ?? T()
    }

    static func release(_ element: T) {
        metaPool[typeKey]!.append(element)
    }
}