NSRange 到 Range

我怎样才能转换NSRange to Range<String.Index>在斯威夫特？

我想使用以下内容UITextFieldDelegate method:

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

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

As of Swift 4(Xcode 9)，Swift 标准 库提供了在 Swift 字符串范围之间进行转换的方法 (Range<String.Index>) and NSString范围（NSRange）。 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 现在可以做为

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有一个初始化程序

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

可以用来转换NSRange to Range<String.Index>正确地 （包括表情符号、区域指标或其他扩展的所有情况 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
    }
}

该方法返回一个optional字符串范围，因为并非全部NSRanges 对于给定的 Swift 字符串有效。

The UITextFieldDelegate委托方法可以写为

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
}

逆变换为

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rangeFromNSRange()已经给出了 作者：谢尔希·雅科文科这个答案 https://stackoverflow.com/a/32379600/1187415，我把它包括在内 为了完整性，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
    }
}

Swift 2 版本NSRangeFromRange() is

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) 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
    }
}

Example:

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)) // ????????