ios - Swift Range 的 NSRange？

Question

问题: NSAttributedString 采用 NSRange，而我使用的是使用 Range 的 Swift String

let text = "Long paragraph saying something goes here!"
let textRange = text.startIndex..<text.endIndex
let attributedString = NSMutableAttributedString(string: text)

text.enumerateSubstringsInRange(textRange, options: NSStringEnumerationOptions.ByWords, { (substring, substringRange, enclosingRange, stop) -> () in

    if (substring == "saying") {
        attributedString.addAttribute(NSForegroundColorAttributeName, value: NSColor.redColor(), range: substringRange)
    }
})

产生以下错误:

error: 'Range' is not convertible to 'NSRange' attributedString.addAttribute(NSForegroundColorAttributeName, value: NSColor.redColor(), range: substringRange)

Answer 1

swift String范围和NSString范围不“兼容”。例如，像 😄 这样的表情符号算作一个 Swift 字符，但算作两个 NSString字符(所谓的 UTF-16 代理对)。

因此，如果字符串，您建议的解决方案将产生意外的结果包含这样的字符。示例:

let text = "😄😄😄Long paragraph saying!"
let textRange = text.startIndex..<text.endIndex
let attributedString = NSMutableAttributedString(string: text)

text.enumerateSubstringsInRange(textRange, options: NSStringEnumerationOptions.ByWords, { (substring, substringRange, enclosingRange, stop) -> () in
    let start = distance(text.startIndex, substringRange.startIndex)
    let length = distance(substringRange.startIndex, substringRange.endIndex)
    let range = NSMakeRange(start, length)

    if (substring == "saying") {
        attributedString.addAttribute(NSForegroundColorAttributeName, value: NSColor.redColor(), range: range)
    }
})
println(attributedString)

输出:

😄😄😄Long paragra{}ph say{    NSColor = "NSCalibratedRGBColorSpace 1 0 0 1";}ing!{}

As you see, "ph say" has been marked with the attribute, not "saying".

Since NS(Mutable)AttributedString ultimately requires an NSString and an NSRange, it is actuallybetter to convert the given string to NSString first. Then the substringRangeis an NSRange and you don't have to convert the ranges anymore:

let text = "😄😄😄Long paragraph saying!"
let nsText = text as NSString
let textRange = NSMakeRange(0, nsText.length)
let attributedString = NSMutableAttributedString(string: nsText)

nsText.enumerateSubstringsInRange(textRange, options: NSStringEnumerationOptions.ByWords, { (substring, substringRange, enclosingRange, stop) -> () in

    if (substring == "saying") {
        attributedString.addAttribute(NSForegroundColorAttributeName, value: NSColor.redColor(), range: substringRange)
    }
})
println(attributedString)

输出:

😄😄😄Long paragraph {}saying{    NSColor = "NSCalibratedRGBColorSpace 1 0 0 1";}!{}

Update for Swift 2:

let text = "😄😄😄Long paragraph saying!"
let nsText = text as NSString
let textRange = NSMakeRange(0, nsText.length)
let attributedString = NSMutableAttributedString(string: text)

nsText.enumerateSubstringsInRange(textRange, options: .ByWords, usingBlock: {
    (substring, substringRange, _, _) in

    if (substring == "saying") {
        attributedString.addAttribute(NSForegroundColorAttributeName, value: NSColor.redColor(), range: substringRange)
    }
})
print(attributedString)

Swift 3 更新:

let text = "😄😄😄Long paragraph saying!"
let nsText = text as NSString
let textRange = NSMakeRange(0, nsText.length)
let attributedString = NSMutableAttributedString(string: text)

nsText.enumerateSubstrings(in: textRange, options: .byWords, using: {
    (substring, substringRange, _, _) in

    if (substring == "saying") {
        attributedString.addAttribute(NSForegroundColorAttributeName, value: NSColor.red, range: substringRange)
    }
})
print(attributedString)

Swift 4 更新:

从 Swift 4 (Xcode 9) 开始，Swift 标准库提供在Range<String.Index>之间进行转换的方法和NSRange 。转换为NSString不再需要:

let text = "😄😄😄Long paragraph saying!"
let attributedString = NSMutableAttributedString(string: text)

text.enumerateSubstrings(in: text.startIndex..<text.endIndex, options: .byWords) {
    (substring, substringRange, _, _) in
    if substring == "saying" {
        attributedString.addAttribute(.foregroundColor, value: NSColor.red,
                                      range: NSRange(substringRange, in: text))
    }
}
print(attributedString)

这里substringRange是 Range<String.Index> ，并将其转换为对应NSRange与

NSRange(substringRange, in: text)