Swift-在UIButton事件后将字段设置为Null

Question

我有一个UIButton操作，它根据4个文本字段中的值向PHP脚本发送数据。提交表单后，字段应重置为null。然而，我在设置字段时遇到了问题。这是我的代码——要设置null的变量是脚本底部的用户名、密码、名称和电子邮件。感谢任何帮助：

    @IBOutlet weak var txtUsername: UITextField!
    @IBOutlet weak var txtPassword: UITextField!
    @IBOutlet weak var txtName: UITextField!
    @IBOutlet weak var txtEmailAddress: UITextField!
    @IBAction func btnSubmit(sender: UIButton) {
        //Fields from app.
        var username = txtUsername.text
        var password = txtPassword.text
        var name = txtName.text
        var email = txtEmailAddress.text
        let myUrl = NSURL(string: "http://localhost/phpPost/demo.php");
        let request = NSMutableURLRequest(URL: myUrl!);
        request.HTTPMethod = "POST";
        let postString = "username=" + username + "&password=" + password + "&name=" + name + "&email=" + email;
        request.HTTPBody = postString.dataUsingEncoding(NSUTF8StringEncoding);
        let task = NSURLSession.sharedSession().dataTaskWithRequest(request) {
            data, response, error in
            if error != nil {
                println("error=(error)")
                return
            }
            println("******response = (response)")
            // Print out response body
            let responseString = NSString(data: data, encoding: NSUTF8StringEncoding)
            println("****response data=(responseString)")
            //Convert response sent from a server side script to a NSDictionary object:
            var err: NSError?
            var myJSON = NSJSONSerialization.JSONObjectWithData(data, options: .MutableLeaves, error:&err) as? NSDictionary
            if let parseJSON = myJSON {
                var name = parseJSON["name"] as? String
                println("name: (name)")
            }
            username = ""
            password = ""
            name = ""
            email = ""
        }
        task.resume()
    }

Answer 1

您没有做任何事情来更改文本字段，它应该是这样的。您需要直接访问文本字段。你现在正在做的是从中复制字符串并更改它。

@IBOutlet weak var txtUsername: UITextField!
@IBOutlet weak var txtPassword: UITextField!
@IBOutlet weak var txtName: UITextField!
@IBOutlet weak var txtEmailAddress: UITextField!
@IBAction func btnSubmit(sender: UIButton) {
    let myUrl = NSURL(string: "http://localhost/phpPost/demo.php");
    let request = NSMutableURLRequest(URL: myUrl!);
    request.HTTPMethod = "POST";
    let postString = "username=" + username + "&password=" + password + "&name=" + name + "&email=" + email;
    request.HTTPBody = postString.dataUsingEncoding(NSUTF8StringEncoding);
    let task = NSURLSession.sharedSession().dataTaskWithRequest(request) {
        data, response, error in
        if error != nil {
            println("error=(error)")
            return
        }
        println("******response = (response)")
        // Print out response body
        let responseString = NSString(data: data, encoding: NSUTF8StringEncoding)
        println("****response data=(responseString)")
        //Convert response sent from a server side script to a NSDictionary object:
        var err: NSError?
        var myJSON = NSJSONSerialization.JSONObjectWithData(data, options: .MutableLeaves, error:&err) as? NSDictionary
        if let parseJSON = myJSON {
            var name = parseJSON["name"] as? String
            println("name: (name)")
        }
        self.txtUsername.text = ""
        self.txtPassword.text = ""
        self.txtName.text = ""
        self.txtEmailAddress.text = ""
    }
    task.resume()
}

如果无论如何都需要清除文本字段，则可以将set文本字段放在块外。因为块是在响应之后异步调用的。

@IBOutlet weak var txtUsername: UITextField!
@IBOutlet weak var txtPassword: UITextField!
@IBOutlet weak var txtName: UITextField!
@IBOutlet weak var txtEmailAddress: UITextField!
@IBAction func btnSubmit(sender: UIButton) {
    let myUrl = NSURL(string: "http://localhost/phpPost/demo.php");
    let request = NSMutableURLRequest(URL: myUrl!);
    request.HTTPMethod = "POST";
    let postString = "username=" + username + "&password=" + password + "&name=" + name + "&email=" + email;
    request.HTTPBody = postString.dataUsingEncoding(NSUTF8StringEncoding);
    let task = NSURLSession.sharedSession().dataTaskWithRequest(request) {
        data, response, error in
        if error != nil {
            println("error=(error)")
            return
        }
        println("******response = (response)")
        // Print out response body
        let responseString = NSString(data: data, encoding: NSUTF8StringEncoding)
        println("****response data=(responseString)")
        //Convert response sent from a server side script to a NSDictionary object:
        var err: NSError?
        var myJSON = NSJSONSerialization.JSONObjectWithData(data, options: .MutableLeaves, error:&err) as? NSDictionary
        if let parseJSON = myJSON {
            var name = parseJSON["name"] as? String
            println("name: (name)")
        }
    }
    self.txtUsername.text = ""
    self.txtPassword.text = ""
    self.txtName.text = ""
    self.txtEmailAddress.text = ""
    task.resume()
}

Answer 2

不要将字符串值设置为null或空字符串或任何东西，设置UITextField属性的text值：

txtUsername.text = ""
txtPassword.text = ""
txtName.text = ""
txtEmailAddress.text = ""

更改username只会更改作用域为当前函数的字符串，它与值来源的文本字段不再有任何关系。因此，更改其值对文本字段没有影响。