ios - 在 UITextField 中检测退格事件

Question

我正在寻找有关如何捕获退格事件的解决方案，大多数 Stack Overflow 答案都是用 Objective-C 编写的，但我需要使用 Swift 语言。

首先，我为 UITextField 设置了委托(delegate)并将其设置为 self

self.textField.delegate = self;

然后我知道使用 shouldChangeCharactersInRange 委托(delegate)方法来检测是否按下了退格键，所有代码都在 Objective-C 中。我需要在 Swift 中使用以下这些方法。

-(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;
}

Answer 1

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
}

旧的 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
}