ios shouldChangeCharactersInRange 如何在 Swift 中工作？

How shouldChangeCharactersInRange works in Swift?

提问by Ryan

I'm using shouldChangeCharactersInRangeas a way of using on-the-fly type search.

我使用shouldChangeCharactersInRange作为使用动态类型搜索的一种方式。

However I'm having a problem, shouldChangeCharactersInRangegets called before the text field actually updates:

但是我遇到了一个问题，shouldChangeCharactersInRange在文本字段实际更新之前被调用：

In Objective C, I solved this using using below:

在目标 C 中，我使用以下方法解决了这个问题：

-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    NSString * searchStr = [textField.text stringByReplacingCharactersInRange:range withString:string];

    return YES;
}

However, I've tried writing this in Swift:

但是，我试过用 Swift 写这个：

func textField(textField: UITextField!, shouldChangeCharactersInRange range: NSRange, replacementString string: String!) -> Bool {
    let txtAfterUpdate:NSString = self.projectSearchTxtFld.text as NSString
    txtAfterUpdate.stringByReplacingCharactersInRange(range, withString: string)

    self.callMyMethod(txtAfterUpdate)
    return true
}

The method still gets called before I get a value?

在我获得值之前该方法仍然被调用？

回答by Vyacheslav

Swift 4, Swift 5

斯威夫特 4、斯威夫特 5

This method doesn't use NSString

这个方法不使用 NSString

// MARK: - UITextFieldDelegate

extension MyViewController: UITextFieldDelegate {
    func textField(_ textField: UITextField,
                   shouldChangeCharactersIn range: NSRange,
                   replacementString string: String) -> Bool {
        if let text = textField.text,
           let textRange = Range(range, in: text) {
           let updatedText = text.replacingCharacters(in: textRange,
                                                       with: string)
           myvalidator(text: updatedText)
        }
        return true
    }
}

Note. Be careful when you use a secured text field.

笔记。使用安全文本字段时要小心。

回答by Mike Pollard

stringByReplacingCharactersInRangereturn a new string, so how about:

stringByReplacingCharactersInRange返回一个新字符串，那么如何：

func textField(textField: UITextField!, shouldChangeCharactersInRange range: NSRange, replacementString string: String!) -> Bool {
    if let text = textField.text as NSString? {
        let txtAfterUpdate = text.replacingCharacters(in: range, with: string)
        self.callMyMethod(txtAfterUpdate)
    }
    return true
}

回答by Mobile Dan

Swift 3 & 4

斯威夫特 3 & 4

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
    let textFieldText: NSString = (textField.text ?? "") as NSString
    let txtAfterUpdate = textFieldText.replacingCharacters(in: range, with: string)
    callMyMethod(txtAfterUpdate)

    return true
}

func textFieldShouldClear(_ textField: UITextField) -> Bool {
    callMyMethod("")
    return true
}

Swift 2.2

斯威夫特 2.2

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
    let textFieldText: NSString = textField.text ?? ""
    let txtAfterUpdate = textFieldText.stringByReplacingCharactersInRange(range, withString: string)
    callMyMethod(txtAfterUpdate)

    return true
}

func textFieldShouldClear(textField: UITextField) -> Bool {
    callMyMethod("")
    return true
}

Though the textField.textproperty is an optional, it cannot be set to nil. Setting it to nil is changed to empty string within UITextField. In the code above, that is why textFieldTextis set to empty string if textField.textis nil (via the nil coalescing operator ??).

虽然该textField.text属性是可选的，但不能设置为 nil。将其设置为 nil 将更改为UITextField. 在上面的代码中，这就是为什么textFieldText设置为空字符串 if textField.textis nil （通过 nil 合并运算符??）。

Implementing textFieldShouldClear(_:)handles the case where the text field's clear button is visible and tapped.

实现textFieldShouldClear(_:)处理文本字段的清除按钮可见并被点击的情况。

回答by Andrey Gordeev

In Swift 3it would look like this:

在Swift 3 中，它看起来像这样：

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
    let text: NSString = (textField.text ?? "") as NSString
    let resultString = text.replacingCharacters(in: range, with: string)

    return true
}

回答by blackjacx

Swift 3

斯威夫特 3

---

---

If you want to pre-process the characters the user typed or pasted, the following solution workes like a charm

如果您想预处理用户输入或粘贴的字符，以下解决方案就像一个魅力

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {

    let strippedString = <change replacements string so it fits your requirement - strip, trim, etc>

    // replace current content with stripped content
    if let replaceStart = textField.position(from: textField.beginningOfDocument, offset: range.location),
        let replaceEnd = textField.position(from: replaceStart, offset: range.length),
        let textRange = textField.textRange(from: replaceStart, to: replaceEnd) {

        textField.replace(textRange, withText: strippedString)
    }
    return false
}

Find it here: https://gist.github.com/Blackjacx/2198d86442ec9b9b05c0801f4e392047

在这里找到：https: //gist.github.com/Blackjacx/2198d86442ec9b9b05c0801f4e392047

回答by Pavle Mijatovic

To get the exact text in the my UITextField component in Swift 3.0 I used:

要在 Swift 3.0 中的 UITextField 组件中获取确切的文本，我使用了：

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
   let enteredTxt = textField.text! + string
   doSomethingWithTxt(enteredTxt) //some custom method
}