如何在键入（Swift）时进行实时UITextField计数？

问题描述

当用户使用swift输入 UITextField 时，我想计算该字符。

I would like to count the character when user keep typing in UITextField with swift.

字段和标签的图像：

我已经放置了UITextField和UILabel，只是没有找到有关Stack溢出的任何信息，如果你可以在 UITextView中做一个我也很感激。

I have already placed UITextField and UILabel, just haven't found any information on Stack overflow, also if you can do one in UITextView I also appreciate it.

推荐答案

要使用下面的函数，您需要实现要计算的文本字段的UITextFieldDelegate协议，每次UITextField更改时都会调用此函数价值：

To use the function below you need to implement the UITextFieldDelegate protocol of the text field you want to count, this function gets called everytime the UITextField change value:

您的班级声明应如下所示

Your class declaration should look something like this

class ViewController: UIViewController, UITextFieldDelegate

你应该有一个 @IBOutlet 与此类似

@IBOutlet var txtValue：UITextField

在viewDidLoad中，您将委托方法设置为self

In viewDidLoad you set the delegate method to self

override func viewDidLoad() {
    super.viewDidLoad()
    txtValue.delegate = self
}

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
    let newLength = count(textField.text.utf16) + count(string.utf16) - range.length
    //change the value of the label
    mylabel.text =  String(newLength)
    //you can save this value to a global var
    //myCounter = newLength
    //return true to allow the change, if you want to limit the number of characters in the text field use something like
    return newLength <= 25 // To just allow up to 25 characters
    return true
}

记住这个函数被调用到所有UITextField所以如果你有很多UITextField你需要添加一个逻辑来知道一个人正在调用这个函数，只需添加一个不同的标签每个UITextField并使用switch语句查找UITextField调用函数

Remember this function is called to all UITextField so if you have many UITextField you will need to add a logic to know witch one is calling this function, just add a different tag to each UITextField and use a switch statement to find with UITextField call the function

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