包含某些字符的字符串导致 UITextView 过早换行

Question

上下文

我正在尝试在文本视图中输入一堆随机文本并将其换行，以便该框完全充满符号。似乎文本视图正试图根据文本中的某些字符进行换行。我已将导致文本视图错误换行的字符列表缩小到以下内容：

]}).>/+

其余可以显示的字符有：

[<{(#@=*~

在 Playground 中运行的以下代码将导致 UITextView 在该行的最后一个字符之前换行。

import UIKit

func generateRandomText() -> NSAttributedString {
    let characterLimit = 9500
    let segmentSize = 500
    // problem characters
    // ] } ) . > / +
    let characterOptions = ["[","<","{","(","#","@","=","*","~","+","]","}",")",".",">","/"]
    let codeString = NSMutableAttributedString.init(string: "")

    while codeString.string.characters.count < segmentSize {
        let addition = NSAttributedString.init(string: characterOptions[Int(arc4random_uniform(16))], attributes: [NSForegroundColorAttributeName : UIColor.whiteColor()])
        codeString.appendAttributedString(addition)
    }

    while codeString.string.characters.count < characterLimit {
        codeString.appendAttributedString(codeString)
    }

    return codeString
}

let textView = UITextView.init(frame: CGRectMake(0, 0, 700, 700))
textView.textContainer.lineBreakMode = .ByCharWrapping

let codeFont = UIFont.init(name: "Menlo", size: 12)
textView.font = codeFont
textView.backgroundColor = UIColor.blackColor()
textView.attributedText = generateRandomText()

结果：

但是，没有问题字符的相同代码会产生我正在寻找的结果。

import UIKit    

func generateRandomText() -> NSAttributedString {
    let characterLimit = 9500
    let segmentSize = 500
    // problem characters
    // ] } ) . > / +
    let characterOptions = ["[","<","{","(","#","@","=","*","~"]
    let codeString = NSMutableAttributedString.init(string: "")

    while codeString.string.characters.count < segmentSize {
        let addition = NSAttributedString.init(string: characterOptions[Int(arc4random_uniform(9))], attributes: [NSForegroundColorAttributeName : UIColor.whiteColor()])
        codeString.appendAttributedString(addition)
    }

    while codeString.string.characters.count < characterLimit {
        codeString.appendAttributedString(codeString)
    }

    return codeString
}

let textView = UITextView.init(frame: CGRectMake(0, 0, 700, 700))
textView.textContainer.lineBreakMode = .ByCharWrapping

let codeFont = UIFont.init(name: "Menlo", size: 12)
textView.font = codeFont
textView.backgroundColor = UIColor.blackColor()
textView.attributedText = generateRandomText()

结果：

问题

当字符串包含某些字符时，什么会导致文本视图换行？

Answer 1

这些特定字符是系统用来定义单词边界的字符，用于自动换行。

打电话

textView.textContainer.lineBreakMode = .ByCharWrapping

由于UITextView 不支持字符换行，因此无效。

---

文档：

https://developer.apple.com/library/ios/documentation/Cocoa/Conceptual/Strings/Articles/stringsParagraphBreaks.html

http://www.unicode.org/reports/tr29/#Word_Boundaries

请注意，定义单词边界有复杂的规则。例如，“1.0”被认为是一个词，而“a.1”被认为是两个。

此外，Unicode 规范可能没有完全遵循。