守卫让错误:条件绑定的初始化程序必须具有可选类型而不是“字符串" [英] guard let error: Initializer for conditional binding must have Optional type not 'String'

问题描述

我在使用 guard let 时遇到了致命错误.这是错误:

<块引用>

条件绑定的初始化器必须具有可选类型，而不是'字符串'

在我使用的代码下面:

@IBAction func signUpButtonPressed(sender: UIButton) {守卫让电子邮件= emailTextField.text！其中 emailTextField.text!.characters.count >0 其他 {//警报返回}守卫让密码= passwordTextField.text！其中 passwordTextField.text!.characters.count >0 其他 {//警报返回}self.registerUserAsync(电子邮件，密码:密码)}

解决方案

你应该非常小心选择选项.使用 ! 你告诉 Swift 编译器你可以保证这个值是存在的.尝试这样做:

@IBAction func signUpButtonPressed(sender: UIButton) {guard let email = emailTextField.text where email.characters.count >0 其他 {//警报返回}guard let password = passwordTextField.text 其中 password.characters.count >0 其他 {//警报返回}self.registerUserAsync(电子邮件，密码:密码)

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Swift 还引入了可选类型，用于处理没有值的情况.可选项表示有一个值，它等于 x"或根本没有值".

更多关于可选项的信息，您可以在这里找到 https://developer.apple.com/library/ios/documentation/Swift/Conceptual/Swift_Programming_Language/TheBasics.html#//apple_ref/doc/uid/TP40014097-CH5-ID309

I got fatal error While using guard let. Here's the error:

Initializer for conditional binding must have Optional type not 'String'

Below my code which i have used:

@IBAction func signUpButtonPressed(sender: UIButton) {
    guard let email = emailTextField.text! where emailTextField.text!.characters.count > 0 else {
        // alert
        return
    }

    guard let password = passwordTextField.text! where passwordTextField.text!.characters.count > 0 else {
    // alert
       return
   }

     self.registerUserAsync(email, password: password)
}

解决方案

You should be very carefull with optionals. Using ! you tell to Swift compiler that you can guarantee that the value is exists. Try to do it like this:

@IBAction func signUpButtonPressed(sender: UIButton) {
    guard let email = emailTextField.text where email.characters.count > 0 else {
        // alert
        return
    }

    guard let password = passwordTextField.text where password.characters.count > 0 else {
        // alert
        return
    }

    self.registerUserAsync(email, password: password)

Swift also introduces optional types, which handle the absence of a value. Optionals say either "there is a value, and it equals x" or "there isn’t a value at all".

More about optionals you can find here https://developer.apple.com/library/ios/documentation/Swift/Conceptual/Swift_Programming_Language/TheBasics.html#//apple_ref/doc/uid/TP40014097-CH5-ID309

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