Closure Example

    func test() {
        // c1
//        request() { (json: String?, errorCode: Int?) in
//            print("json", json!)
//        }
        // c2
//        request(completion: {(json: String?, errorCode: Int?) in
//            print(json!)
//        })
        // c3
        let myVar2 : Completion  = { (json: String?, errorCode: Int?) -> () in
            print("json ", json!)
        }
        request(completion: myVar2)

    }

    typealias Completion = (_ result: String?, _ errorCode: Int?) -> ()

    func request(completion: Completion? = nil) {
        GET(completion: completion)
    }

    private func GET(completion: Completion? = nil) {
        if let callback = completion {
            callback("Thieu Mao", 1)
        }
    }