包含某些字符的字符串，导致UITextView过早换行

Question

上下文

我正在尝试将一堆随机文本输入到文本视图中，并将字符包装起来，以便框中的符号完整。似乎文本视图试图在基于文本中的某些字符进行包装时变得聪明。我缩小了导致文本视图错误地包装到下面的字符列表：

] } ) . > / +

可以显示的其他字符是：

[ < { ( # @ = * ~

在Playground中运行的以下代码将导致UITextView在行中的最后一个字符之前进行换行。

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字边界的字符，用于换行。

调用

textView.textContainer.lineBreakMode = .ByCharWrapping

由于UITextView不支持字符换行，

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”被认为是一个单词，但“a.1”被认为是两个单词。

此外，可能没有完全遵循Unicode规范。