Swift 用 return 值编写一个 async/await 方法

Question

我想编写一个具有 return 值的异步等待方法，但我的代码不起作用。我还尝试了另一种方式，例如 DispatchQueue.global DispatchGroup() 等等。
这是我的代码：

func checkPassCode() -> Bool {

        var result = false

        let closure = { (_ flag:Bool) -> Void in
            result = flag
        }

        if var pin = self.keychain.get("pin") {
            let userPin = self.pin.joined(separator: "")
            let encryptedData = NSData(base64Encoded: pin, options: [])

            AsymmetricCryptoManager.sharedInstance.decryptMessageWithPrivateKey(encryptedData! as Data) { (success, result, error) -> Void in
                if success {
                    pin = result!
                    print("userPin is: \(userPin)")
                    print("storePin is: \(pin)")
                    closure(userPin == pin)
                } else {
                    print("Error decoding base64 string: \(String(describing: error))")
                    closure(false)
                }
            }
        }
        return result
    }

Answer 1

谢谢，vadian 评论。我使用闭包作为方法的输入参数。

// MARK: - PassCode Methods
func checkPassCode(completionHandler:@escaping (_ flag:Bool) -> ()) {
    let storePin = getStorePin()
    let userPin = self.pin.joined(separator: "")
    AsymmetricCryptoManager.sharedInstance.decryptMessageWithPrivateKey(storePin as Data) { (success, result, error) -> Void in
        if success {
            let pin = result!
            print("userPin is: \(userPin)")
            print("storePin is: \(pin)")
            completionHandler(userPin == pin)
        } else {
            print("Error decoding base64 string: \(String(describing: error))")
            completionHandler(false)
        }
    }
}

func getStorePin() -> NSData {
    if let pin = self.keychain.get("pin") {
        return NSData(base64Encoded: pin, options: []) ?? NSData()
    }
    return NSData()
}

然后调用这个方法：

checkPassCode { success in
                    if success {
                        print("sucess")
                    } else {
                        print("not sucess!")
                    }
                }

Answer 2

您可以将此框架用于 Swift 协程 - https://github.com/belozierov/SwiftCoroutine

当你调用 await 时，它不会阻塞线程，只会挂起协程，所以你也可以在主线程中使用它。

func awaitCheckPassCode() throws -> Bool {
    let storePin = getStorePin()
    let userPin = self.pin.joined(separator: "")
    let manager = AsymmetricCryptoManager.sharedInstance
    let (success, result, _) = try Coroutine.await {
        manager.decryptMessageWithPrivateKey(storePin as Data, completion: [=10=])
    }
    return success && userPin == result
}

然后在协程中调用这个方法：

DispatchQueue.main.startCoroutine {
    let success = try awaitCheckPassCode()

    if success {
        print("sucess")
    } else {
        print("not sucess!")
    }
}

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