iOs - 无法识别的选择器发送到 TextAction 上的实例

Question

我对这个错误有一些疑问:

ProjectName.ViewController textAction:]: unrecognized selector sent to instance 0x7fa60bc3840

当我尝试创建警报时出现错误。这是代码:

@IBAction func trySearch(sender: UIButton) {
    self.api.getUser(self.textField.text!) { isResponse in
        if (isResponse.count == 0) {
//Still crash HERE.
            let alert = UIAlertController(title: "Error", message: "This username doesn't exist", preferredStyle: UIAlertControllerStyle.Alert)
                alert.addAction(UIAlertAction(title: "Ok", style: UIAlertActionStyle.Default, handler: nil))
            self.presentViewController(alert, animated: true, completion: nil)
        }
        else {
            print("existing username")
        }
    }

如果我注释所有警报代码并用简单的打印替换它，它就可以工作...我真的不明白为什么...谢谢!

获取用户函数:

func getUser(user: String, completion: ((isReponse: AnyObject) -> Void)) {

    let request = NSMutableURLRequest(URL: NSURL(string: "https://********")!)
    request.HTTPMethod = "GET"
    request.setValue("Bearer \(self.loadToken())", forHTTPHeaderField: "Authorization")

    Alamofire.request(request)
        .responseJSON { response in
            switch response.result {
            case .Success(let JSON):
                completion(isReponse: JSON)
            case .Failure(let error):
                print("Request failed with error: \(error)")
            }
        }
}

更新:当我点击我的 TextField 的“完成”时出现同样的错误。 + 我添加了 getUser 函数。

Answer 1

您可能在错误的线程中，因为您是在 block 中显示警报，请尝试:

dispatch_async(dispatch_get_main_queue(), { _ in 
    let alert = UIAlertController(title: "Error", message: "This username doesn't exist", preferredStyle: UIAlertControllerStyle.Alert)
    alert.addAction(UIAlertAction(title: "Ok", style: UIAlertActionStyle.Default, handler: nil))
    self.presentViewController(alert, animated: true, completion: nil)
})