NSR 范围到范围<String.Index>

Question

如何在 Swift NSRange转换为Range<String.Index> ？

我想使用以下UITextFieldDelegate方法：

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

textField.text.stringByReplacingCharactersInRange(???, withString: string)

Answer 1

从Swift 4 (Xcode 9) 开始，Swift 标准库提供了在 Swift 字符串范围 ( Range<String.Index> ) 和NSString范围 ( NSRange ) 之间进行转换的方法。 例子：

let str = "a👿b🇩🇪c"
let r1 = str.range(of: "🇩🇪")!

// String range to NSRange:
let n1 = NSRange(r1, in: str)
print((str as NSString).substring(with: n1)) // 🇩🇪

// NSRange back to String range:
let r2 = Range(n1, in: str)!
print(str[r2]) // 🇩🇪

因此，文本字段委托方法中的文本替换现在可以作为

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

    if let oldString = textField.text {
        let newString = oldString.replacingCharacters(in: Range(range, in: oldString)!,
                                                      with: string)
        // ...
    }
    // ...
}

---

（Swift 3 及更早版本的旧答案:)

从 Swift 1.2 开始， String.Index有一个初始值设定项

init?(_ utf16Index: UTF16Index, within characters: String)

可用于将NSRange正确转换为Range<String.Index> （包括所有表情符号、区域指标或其他扩展字素簇），无需中间转换为NSString ：

extension String {
    func rangeFromNSRange(nsRange : NSRange) -> Range<String.Index>? {
        let from16 = advance(utf16.startIndex, nsRange.location, utf16.endIndex)
        let to16 = advance(from16, nsRange.length, utf16.endIndex)
        if let from = String.Index(from16, within: self),
            let to = String.Index(to16, within: self) {
                return from ..< to
        }
        return nil
    }
}

此方法返回一个可选的字符串范围，因为并非所有NSRange都对给定的 Swift 字符串有效。

UITextFieldDelegate委托方法可以写成

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

    if let swRange = textField.text.rangeFromNSRange(range) {
        let newString = textField.text.stringByReplacingCharactersInRange(swRange, withString: string)
        // ...
    }
    return true
}

逆转换是

extension String {
    func NSRangeFromRange(range : Range<String.Index>) -> NSRange {
        let utf16view = self.utf16
        let from = String.UTF16View.Index(range.startIndex, within: utf16view) 
        let to = String.UTF16View.Index(range.endIndex, within: utf16view)
        return NSMakeRange(from - utf16view.startIndex, to - from)
    }
}

一个简单的测试：

let str = "a👿b🇩🇪c"
let r1 = str.rangeOfString("🇩🇪")!

// String range to NSRange:
let n1 = str.NSRangeFromRange(r1)
println((str as NSString).substringWithRange(n1)) // 🇩🇪

// NSRange back to String range:
let r2 = str.rangeFromNSRange(n1)!
println(str.substringWithRange(r2)) // 🇩🇪

Swift 2 更新：

Swift 2 版本的rangeFromNSRange()已经由 Serhii Yakovenko 在这个答案中给出，为了完整起见，我将它包括在这里：

extension String {
    func rangeFromNSRange(nsRange : NSRange) -> Range<String.Index>? {
        let from16 = utf16.startIndex.advancedBy(nsRange.location, limit: utf16.endIndex)
        let to16 = from16.advancedBy(nsRange.length, limit: utf16.endIndex)
        if let from = String.Index(from16, within: self),
            let to = String.Index(to16, within: self) {
                return from ..< to
        }
        return nil
    }
}

NSRangeFromRange()的 Swift 2 版本是

extension String {
    func NSRangeFromRange(range : Range<String.Index>) -> NSRange {
        let utf16view = self.utf16
        let from = String.UTF16View.Index(range.startIndex, within: utf16view)
        let to = String.UTF16View.Index(range.endIndex, within: utf16view)
        return NSMakeRange(utf16view.startIndex.distanceTo(from), from.distanceTo(to))
    }
}

Swift 3 (Xcode 8) 的更新：

extension String {
    func nsRange(from range: Range<String.Index>) -> NSRange {
        let from = range.lowerBound.samePosition(in: utf16)
        let to = range.upperBound.samePosition(in: utf16)
        return NSRange(location: utf16.distance(from: utf16.startIndex, to: from),
                       length: utf16.distance(from: from, to: to))
    }
}

extension String {
    func range(from nsRange: NSRange) -> Range<String.Index>? {
        guard
            let from16 = utf16.index(utf16.startIndex, offsetBy: nsRange.location, limitedBy: utf16.endIndex),
            let to16 = utf16.index(utf16.startIndex, offsetBy: nsRange.location + nsRange.length, limitedBy: utf16.endIndex),
            let from = from16.samePosition(in: self),
            let to = to16.samePosition(in: self)
            else { return nil }
        return from ..< to
    }
}

例子：

let str = "a👿b🇩🇪c"
let r1 = str.range(of: "🇩🇪")!

// String range to NSRange:
let n1 = str.nsRange(from: r1)
print((str as NSString).substring(with: n1)) // 🇩🇪

// NSRange back to String range:
let r2 = str.range(from: n1)!
print(str.substring(with: r2)) // 🇩🇪

Answer 2

NSString版本（与 Swift String 相对）的replacingCharacters(in: NSRange, with: NSString)接受NSRange ，因此一个简单的解决方案是先将String转换为NSString 。 Swift 3 和 2 中的委托和替换方法名称略有不同，因此取决于您使用的 Swift：

斯威夫特 3.0

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

  let nsString = textField.text as NSString?
  let newString = nsString?.replacingCharacters(in: range, with: string)
}

斯威夫特 2.x

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

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

Answer 3

Martin R 的这个答案似乎是正确的，因为它考虑了 Unicode。

然而，在发布时（Swift 1），他的代码无法在 Swift 2.0（Xcode 7）中编译，因为他们删除了advance()函数。 更新版本如下：

斯威夫特 2

extension String {
    func rangeFromNSRange(nsRange : NSRange) -> Range<String.Index>? {
        let from16 = utf16.startIndex.advancedBy(nsRange.location, limit: utf16.endIndex)
        let to16 = from16.advancedBy(nsRange.length, limit: utf16.endIndex)
        if let from = String.Index(from16, within: self),
            let to = String.Index(to16, within: self) {
                return from ..< to
        }
        return nil
    }
}

斯威夫特 3

extension String {
    func rangeFromNSRange(nsRange : NSRange) -> Range<String.Index>? {
        if let from16 = utf16.index(utf16.startIndex, offsetBy: nsRange.location, limitedBy: utf16.endIndex),
            let to16 = utf16.index(from16, offsetBy: nsRange.length, limitedBy: utf16.endIndex),
            let from = String.Index(from16, within: self),
            let to = String.Index(to16, within: self) {
                return from ..< to
        }
        return nil
    }
}

斯威夫特 4

extension String {
    func rangeFromNSRange(nsRange : NSRange) -> Range<String.Index>? {
        return Range(nsRange, in: self)
    }
}

Answer 4

您需要使用Range<String.Index>而不是经典的NSRange 。 我做的方式（也许有更好的方法）是通过利用字符串的String.Index一个与移动它advance 。

我不知道您要替换的范围是什么，但让我们假设您要替换前 2 个字符。

var start = textField.text.startIndex // Start at the string's start index
var end = advance(textField.text.startIndex, 2) // Take start index and advance 2 characters forward
var range: Range<String.Index> = Range<String.Index>(start: start,end: end)

textField.text.stringByReplacingCharactersInRange(range, withString: string)

Answer 5

这与 Emilie 的回答类似，但是因为您特别询问了如何将NSRange转换为Range<String.Index>您将执行以下操作：

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

     let start = advance(textField.text.startIndex, range.location) 
     let end = advance(start, range.length) 
     let swiftRange = Range<String.Index>(start: start, end: end) 
     ...

}

Answer 6

对@Emilie 的精彩答案的即兴演奏，而不是替代/竞争答案。
(Xcode6-Beta5)

var original    = "🇪🇸😂This is a test"
var replacement = "!"

var startIndex = advance(original.startIndex, 1) // Start at the second character
var endIndex   = advance(startIndex, 2) // point ahead two characters
var range      = Range(start:startIndex, end:endIndex)
var final = original.stringByReplacingCharactersInRange(range, withString:replacement)

println("start index: \(startIndex)")
println("end index:   \(endIndex)")
println("range:       \(range)")
println("original:    \(original)")
println("final:       \(final)")

输出：

start index: 4
end index:   7
range:       4..<7
original:    🇪🇸😂This is a test
final:       🇪🇸!his is a test

请注意索引占多个代码单元。 标志（区域指示符符号字母 ES）是 8 个字节，（FACE WITH TEARS OF JOY）是 4 个字节。 （在这种特殊情况下，UTF-8、UTF-16 和 UTF-32 表示的字节数是相同的。）

将它包装在一个函数中：

func replaceString(#string:String, #with:String, #start:Int, #length:Int) ->String {
    var startIndex = advance(original.startIndex, start) // Start at the second character
    var endIndex   = advance(startIndex, length) // point ahead two characters
    var range      = Range(start:startIndex, end:endIndex)
    var final = original.stringByReplacingCharactersInRange(range, withString: replacement)
    return final
}

var newString = replaceString(string:original, with:replacement, start:1, length:2)
println("newString:\(newString)")

输出：

newString: !his is a test

Answer 7

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

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

 }

Answer 8

在 Swift 2.0 中假设func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool { :

var oldString = textfield.text!
let newRange = oldString.startIndex.advancedBy(range.location)..<oldString.startIndex.advancedBy(range.location + range.length)
let newString = oldString.stringByReplacingCharactersInRange(newRange, withString: string)

Answer 9

这是我最大的努力。 但这不能检查或检测错误的输入参数。

extension String {
    /// :r: Must correctly select proper UTF-16 code-unit range. Wrong range will produce wrong result.
    public func convertRangeFromNSRange(r:NSRange) -> Range<String.Index> {
        let a   =   (self as NSString).substringToIndex(r.location)
        let b   =   (self as NSString).substringWithRange(r)

        let n1  =   distance(a.startIndex, a.endIndex)
        let n2  =   distance(b.startIndex, b.endIndex)

        let i1  =   advance(startIndex, n1)
        let i2  =   advance(i1, n2)

        return  Range<String.Index>(start: i1, end: i2)
    }
}

let s   =   "🇪🇸😂"
println(s[s.convertRangeFromNSRange(NSRange(location: 4, length: 2))])      //  Proper range. Produces correct result.
println(s[s.convertRangeFromNSRange(NSRange(location: 0, length: 4))])      //  Proper range. Produces correct result.
println(s[s.convertRangeFromNSRange(NSRange(location: 0, length: 2))])      //  Improper range. Produces wrong result.
println(s[s.convertRangeFromNSRange(NSRange(location: 0, length: 1))])      //  Improper range. Produces wrong result.

结果。

😂
🇪🇸
🇪🇸
🇪🇸

细节

NSString NSRange计算 UTF-16代码单元。 而 Swift String中的Range<String.Index>是一个不透明的相对类型，它只提供相等和导航操作。 这是故意隐藏的设计。

尽管Range<String.Index>似乎映射到 UTF-16 代码单元偏移量，但这只是一个实现细节，我找不到任何关于任何保证的提及。 这意味着可以随时更改实施细节。 Swift String内部表示不是很明确，我不能依赖它。

NSRange值可以直接映射到String.UTF16View索引。 但是没有将其转换为String.Index 。

Swift String.Index是迭代 Swift Character索引，Swift Character是一个Unicode 字素簇。 然后，您必须提供合适的NSRange来选择正确的字素簇。 如果像上面的例子一样提供错误的范围，它会产生错误的结果，因为无法计算出正确的字素簇范围。

如果保证String.Index是UTF-16 代码单元偏移量，那么问题就变得简单了。 但这不太可能发生。

逆转换

无论如何，可以精确地完成逆转换。

extension String {
    /// O(1) if `self` is optimised to use UTF-16.
    /// O(n) otherwise.
    public func convertRangeToNSRange(r:Range<String.Index>) -> NSRange {
        let a   =   substringToIndex(r.startIndex)
        let b   =   substringWithRange(r)

        return  NSRange(location: a.utf16Count, length: b.utf16Count)
    }
}
println(convertRangeToNSRange(s.startIndex..<s.endIndex))
println(convertRangeToNSRange(s.startIndex.successor()..<s.endIndex))

结果。

(0,6)
(4,2)

Answer 10

我发现最干净的 swift2 唯一解决方案是在 NSRange 上创建一个类别：

extension NSRange {
    func stringRangeForText(string: String) -> Range<String.Index> {
        let start = string.startIndex.advancedBy(self.location)
        let end = start.advancedBy(self.length)
        return Range<String.Index>(start: start, end: end)
    }
}

然后从 for 文本字段委托函数调用它：

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
    let range = range.stringRangeForText(textField.text)
    let output = textField.text.stringByReplacingCharactersInRange(range, withString: string)

    // your code goes here....

    return true
}

Answer 11

extension StringProtocol where Index == String.Index {

    func nsRange(of string: String) -> NSRange? {
        guard let range = self.range(of: string) else {  return nil }
        return NSRange(range, in: self)
    }
}

Answer 12

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
    
    guard let current = textField.text, let r = Range(range, in: current) else {
        return false
    }
    
    let text = current.replacingCharacters(in: r, with: string)
    // ...
    return true
}

Answer 13

Swift 3.0 beta 官方文档在UTF16View Elements Match NSString Characters 标题中的标题String.UTF16View下提供了针对这种情况的标准解决方案

Answer 14

在接受的答案中，我发现选项很麻烦。 这适用于 Swift 3，并且表情符号似乎没有问题。

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

  guard let value = textField.text else {return false} // there may be a reason for returning true in this case but I can't think of it
  // now value is a String, not an optional String

  let valueAfterChange = (value as NSString).replacingCharacters(in: range, with: string)
  // valueAfterChange is a String, not an optional String

  // now do whatever processing is required

  return true  // or false, as required
}

Answer 15

因为NSRange在NSString操作中使用时，表示 UTF-16 单元的位置。 然后转换为String.Index的最短方法是通过String.Index(utf16Offset: Int, in: StringProtocol)初始化程序进行初始化。

let string = "...."
let nsRange = NSRange(....) // This NSRange belongs to `string` variable.
let range = String.Index(utf16Offset: nsRange.lowerBound, in: string)
        ..< String.Index(utf16Offset: nsRange.upperBound, in: string)

例子：

let string = "a-\u{1112}\u{1161}\u{11AB}-🐶-\u{E9}\u{20DD}-‼-𓀀-(العلاجية)-f"
let rangeOfLeftParenthesis = (string as NSString).range(of: "(")
let rangeOfRightParenthesis = (string as NSString).range(of: ")")
print("string: \(string)")
let lowerBound = String.Index.init(utf16Offset: rangeOfLeftParenthesis.upperBound, in: string)
let upperBound = String.Index.init(utf16Offset: rangeOfRightParenthesis.lowerBound, in: string)
let arabicSentenceRange = lowerBound ..< upperBound // Instance of `Range<String.Index>`
print("arabicSentenceRange: \(string[arabicSentenceRange])")

输出：

string: a-한-🐶-é⃝-‼-𓀀-(العلاجية)-f
arabicSentenceRange: العلاجية

Answer 16

Swift 5 解决方案

带有主要扩展名的简短回答

extension NSRange {

    public init(range: Range<String.Index>, 
                originalText: String) {

        self.init(location: range.lowerBound.utf16Offset(in: originalText),
                  length: range.upperBound.utf16Offset(in: originalText) - range.lowerBound.utf16Offset(in: originalText))
    }
}

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