Question

我遇到了一个场景，我必须在swift 3中调用枚举函数中的函数。方案如下：

class SomeViewController: UIViewController {

enum Address {
    case primary
    case secondary

    func getAddress() {

       let closure = { (text: String) in
            showAlert(for: "")
        }
    }
}

func showAlert(for text: String) {
    let alertController = UIAlertController(title: text, message: nil, preferredStyle: .alert)
    alertController.addAction(UIAlertAction(title:NSLocalizedString("OK", comment:"OK button title"), style: .cancel, handler: nil))
    present(alertController, animated: true, completion: nil)
}

}

从上面的代码中可以看出，我在第10行(showAlert(for: ""))

上收到错误

错误是：

实例成员showAlert不能用于SomeViewController类型;你的意思是使用这种类型的值吗？

如何从枚举函数中调用函数呢？

Answer 1

替代方法：

您可以使用static method SomeViewController来展示alert。

<强> 实施例

static func showAlert(for text: String)
{
    let alertController = UIAlertController(title: text, message: nil, preferredStyle: .alert)
    alertController.addAction(UIAlertAction(title:NSLocalizedString("OK", comment:"OK button title"), style: .cancel, handler: nil))
    UIApplication.shared.keyWindow?.rootViewController?.present(alertController, animated: true, completion: nil)
}

使用它：

enum Address
{
    case primary
    case secondary

    func getAddress()
    {
        let closure = { (text: String) in
            SomeViewController.showAlert(for: "")
        }
        closure("hello")
    }
}

override func viewDidLoad()
{
    super.viewDidLoad()
    let addr = Address.primary
    addr.getAddress()
}

Answer 2

enum不知道实例，因此无法访问其成员。处理这种情况的一种方法是告知客户enum出现问题。

class SomeViewController: UIViewController {
    enum Address {
        case primary
        case secondary

        func getAddress() -> String? {
            //allGood == whatever your logic is to consider a valid address
            if allGood {
                return "theAddress"
            } else {
                return nil;
            }
        }
    }

    func funcThatUsesAddress() {
        let address = Address.primary
        guard let addressString = address.getAddress() else {
            showAlert(for: "")
            return
        }
        // use your valid addressString here
        print(addressString)

    }

    func showAlert(for text: String) {
        let alertController = UIAlertController(title: text, message: nil, preferredStyle: .alert)
        alertController.addAction(UIAlertAction(title:NSLocalizedString("OK", comment:"OK button title"), style: .cancel, handler: nil))
        present(alertController, animated: true, completion: nil)
    }
}

在枚举函数中调用函数在同一个类中

2 个答案: