在UITextField中检测退格事件 [英] Detect backspace Event in UITextField

问题描述

我正在寻找有关如何捕获退格事件的解决方案，大多数堆栈溢出答案都在Objective-C中，但是我需要使用Swift语言。

I am searching for solutions on how to capture a backspace event, most Stack Overflow answers are in Objective-C but I need on Swift language.

首先我有为UITextField设置委托并将其设置为self

First I have set delegate for the UITextField and set it to self

self.textField.delegate = self;

然后我知道使用 shouldChangeCharactersInRange 委托方法检测是否按下了退格键是所有代码都在Objective-C中。我需要在Swift中使用以下方法，如下所示。

Then I know to use shouldChangeCharactersInRange delegate method to detect if a backspace was pressed is all code are in Objective-C. I need in Swift these following method as below is used.

-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
    const char * _char = [string cStringUsingEncoding:NSUTF8StringEncoding];
    int isBackSpace = strcmp(_char, "\b");

    if (isBackSpace == -8) {
        // NSLog(@"Backspace was pressed");
    }

    return YES;
}

推荐答案

Swift 4.2

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
    if let char = string.cString(using: String.Encoding.utf8) {
        let isBackSpace = strcmp(char, "\\b")
        if (isBackSpace == -92) {
            print("Backspace was pressed")
        }
    }
    return true
}

较早的Swift版本

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
    let  char = string.cStringUsingEncoding(NSUTF8StringEncoding)!
    let isBackSpace = strcmp(char, "\\b")

    if (isBackSpace == -92) {
        println("Backspace was pressed")
    }
    return true
}

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