在 Swift 中使用 stringByReplacingCharactersInRange

Question

我正在尝试在 Swift/Xcode6 中使用 UITextFieldDelegate，但我正在为我应该使用 stringByReplacingCharactersInRange 的方式而苦苦挣扎。编译器错误是'无法将表达式的类型'String'转换为类型'$T8'。

func textField(textField: UITextField!, shouldChangeCharactersInRange range: NSRange, replacementString string: String!) -> Bool
{
    let s = textField.text.stringByReplacingCharactersInRange(range:range, withString:string)
    if countElements(s) > 0 {

    } else {

    }
    return true
}

Xcode 6 Beta 5 的更新：问题是 shouldChangeCharactersInRange 提供了一个 NSRange 对象，我们需要一个 Swift Range 对象用于 stringByReplacingCharactersInRange。这仍然可以被认为是一个错误，因为我不明白为什么我们仍然应该处理 NS* 对象？委托方法的 String 参数无论如何都是 Swift 类型。

Answer 1

以下是在各种 Swift 版本中计算结果字符串的方法。

请注意，所有方法都以完全相同的方式使用-[NSString stringByReplacingOccurrencesOfString:withString:]，只是语法不同。

这是计算结果字符串的首选方法。转换为 Swift Range 并在 Swift String 上使用它很容易出错。例如，在对非 ASCII 字符串进行操作时，Johan 的回答在几个方面是不正确的。

斯威夫特 3：

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
    let result = (textField.text as NSString?)?.replacingCharacters(in: range, with: string) ?? string
    // ... do something with `result`
}

斯威夫特 2.1：

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
    let result = (textField.text as NSString?)?.stringByReplacingCharactersInRange(range, withString: string)
    // ... do something with `result`
}

Swift 1（仅留作参考）：

let result = textField.text.bridgeToObjectiveC().stringByReplacingCharactersInRange(range, withString:string)

Answer 2

我为NSRange创建了一个扩展，转换为Range<String.Index>

extension NSRange {
    func toRange(string: String) -> Range<String.Index> {
        let startIndex = advance(string.startIndex, location)
        let endIndex = advance(startIndex, length)
        return startIndex..<endIndex
    }
}

所以我可以像这样创建字符串

let text = textField.text
let newText = text.stringByReplacingCharactersInRange(range.toRange(text), withString: string)

在 Swift 2.1 中，扩展看起来像：

extension NSRange {
    func toRange(string: String) -> Range<String.Index> {
        let startIndex = string.startIndex.advancedBy(location)
        let endIndex = startIndex.advancedBy(length)
        return startIndex..<endIndex
    }
}

Answer 3

我发现的最简单的解决方案是使用as NSString - 这使我们能够使用NSRange。

var textField : UITextField = UITextField()
textField.text = "this is a test"

let nsRange : NSRange = NSRange(location: 0, length: 4)

let replaced = (textField.text as NSString)
               .stringByReplacingCharactersInRange(nsRange, withString: "that");

NSLog("Replaced: %@", replaced); //prints "that is a test"

Answer 4

let newString = (textField.text as NSString).stringByReplacingCharactersInRange(range, withString: string)

bridgeToObjectiveC 可以在即将到来的更新中移除

Answer 5

除了以下之外，没有什么对我有用：（仅供参考，我使用的是 Xcode7.0 GM、Swift 2.0、iOS9GM）

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
    let currentText = textField.text ?? ""
    let prospectiveText = (currentText as NSString).stringByReplacingCharactersInRange(range, withString: string)
    print("prospectiveText", prospectiveText)
    return true;
}

Answer 6

这是来自this question 的交叉帖子，但没有办法制作Range<String.Index> Swift 原生String.stringByReplacingCharactersInRange() 是非常没用的。所以，这是一个生成Range<String.Index>的函数：

func RangeMake(#start:Int, #end:Int) -> Range<String.Index> {
    assert(start <= end, "start must be less than or equal to end")
    func rep(str: String, count: Int) -> String {
        var result = ""
        for i in 0..count {
            result += str
        }
        return result
    }
    let length = end - start
    let padding = rep(" ", start)
    let dashes = rep("-", length)
    let search = padding + dashes
    return search.rangeOfString(dashes, options: nil, range: Range(start: search.startIndex, end: search.endIndex), locale: NSLocale.systemLocale())
}

let sourceString = "Call me Ishmael."
let range = RangeMake(start: 8, end: 15)    
let name = sourceString.substringWithRange(range)
// name = "Ishmael"

Answer 7

工作和测试

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

    print(newString)

      return true;
}

Answer 8

从 Swift 4 开始，这有点简单，就像 Alexander Volkov 的回答一样，但没有扩展。

   func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
        let revisedText: String
        if let text = textField.text, let swiftRange = Range(range, in: text) {
            revisedText = text.replacingCharacters(in: swiftRange, with: string)
        } else {
            revisedText = string
        }
        // Do something with the text and return boolean.
   }

Answer 9

创建 String.Index 很麻烦。

let string = "hello"
let range = string.startIndex .. string.startIndex.succ().succ()
let result = string.stringByReplacingCharactersInRange(range, withString: "si")

Answer 10

对于 iOS 8.3，使用以下代码

 func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool
{
    if textField.isEqual(<textField whose value to be copied>)
    {
        <TextField to be updated>.text = (textField.text as NSString).stringByReplacingCharactersInRange(range, withString: string)
    }

    return true
}

Answer 11

在 Swift 2.0 中，必须更改来自 Durul 的答案，因为必须使用 characters.count 而不是 count()。

必须执行以下操作。

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
    let length = textField.text!.characters.count - range.length + string.characters.count
    if length > 0 {
        submitButton.enabled = true
    } else {
        submitButton.enabled = false
    }
    return true
}

Answer 12

import UIKit

class LoginViewController: UIViewController, UITextFieldDelegate {

    @IBOutlet weak var submitButton: UIButton!

    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view.
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }



    func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
        let length = count(textField.text) - range.length + count(string)
        if length > 0 {
            submitButton.enabled = true
        } else {
            submitButton.enabled = false
        }
        return true
    }
}

Answer 13

斯威夫特 4：

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
    var text = textField.text ?? ""
    text.replaceSubrange(range.toRange(string: text), with: string)
    ...
    return true
}

extension NSRange {

    /// Convert to Range for given string
    ///
    /// - Parameter string: the string
    /// - Returns: range
    func toRange(string: String) -> Range<String.Index> {
        let range = string.index(string.startIndex, offsetBy: self.lowerBound)..<string.index(string.startIndex, offsetBy: self.upperBound)
        return range
    }
}