如何转换 NSRange至 Range<String.Index>在 swift ？

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)

最佳答案

从 Swift 4 (Xcode 9) 开始，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> ) 和 NSString范围(NSRange)。 示例:

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(delegate)方法中的文本替换 现在可以完成

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 及更早版本的较旧答案:)

自 Swift 1.2 起，String.Index有一个初始化器

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

可用于转换NSRange至 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
    }
}

此方法返回一个可选 字符串范围，因为不是所有NSRange秒 对给定的 Swift 字符串有效。

UITextFieldDelegate委托(delegate)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:

rangeFromNSRange() 的 Swift 2 版本已经给了 通过 Serhii Yakovenko 在 this answer ，我包括它 这里是为了完整性:

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) 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)) // ??

关于nsstring - NSRange 到 Range<String.Index>，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/25138339/