UITextView – 不能在文本上设置下划线或删除线属性？答案

【问题标题】：UITextView – can't set underline or strikethrough attributes on text?UITextView – 不能在文本上设置下划线或删除线属性？
【发布时间】：2017-11-06 03:48:21
【问题描述】：

每当我尝试在 UITextView 的属性文本上设置下划线或删除线属性时，都会遇到运行时故障。其他属性，如字体和背景颜色没有问题。这是一个代码sn-p。我所拥有的只是一个带有单个 UITextView 的测试项目。我使用的是 iOS 11。

class ViewController: UIViewController {

    @IBOutlet weak var myTextView: UITextView!

    var myMutableString = NSMutableAttributedString(string: "")

    override func viewDidLoad() {
        super.viewDidLoad()

        let string = "The cow jumped over the moon" as NSString
        myMutableString = NSMutableAttributedString(string: string as String)

        let underlineAttribute = [NSAttributedStringKey.underlineStyle: NSUnderlineStyle.styleSingle]

        myMutableString.addAttributes(underlineAttribute, range: string.range(of: "cow"))

        myTextView.attributedText = myMutableString
    }
}

这会导致文本消失并打印一些错误：

2017-11-05 19:43:34.708830-0800 UITextView_Test[11771:907014]
-[_SwiftValue _getValue:forType:]: unrecognized selector sent to instance 0x60c00004eb50 2017-11-05 19:43:34.709351-0800 UITextView_Test[11771:907014] <NSATSTypesetter: 0x60800016be80>: Exception -[_SwiftValue _getValue:forType:]: unrecognized selector sent to instance 0x60c00004eb50 raised during typesetting layout manager <NSLayoutManager: 0x6080001fe400>
    1 containers, text backing has 28 characters
    Currently holding 28 glyphs.
    Glyph tree contents:  28 characters, 28 glyphs, 1 nodes, 64 node bytes, 64 storage bytes, 128 total bytes, 4.57 bytes per character,
4.57 bytes per glyph
    Layout tree contents:  28 characters, 28 glyphs, 0 laid glyphs, 0 laid line fragments, 1 nodes, 64 node bytes, 0 storage bytes, 64 total bytes, 2.29 bytes per character, 2.29 bytes per glyph, 0.00 laid glyphs per laid line fragment, 0.00 bytes per laid line fragment , glyph range {0 28}. Ignoring... 2017-11-05 19:43:34.709827-0800 UITextView_Test[11771:907014] -[_SwiftValue _getValue:forType:]: unrecognized selector sent to instance 0x60c00004eb50 2017-11-05 19:43:34.710014-0800 UITextView_Test[11771:907014] <NSATSTypesetter: 0x60800016be80>: Exception -[_SwiftValue _getValue:forType:]: unrecognized selector sent to instance 0x60c00004eb50 raised during typesetting layout manager <NSLayoutManager: 0x6080001fe400>
    1 containers, text backing has 28 characters
    Currently holding 28 glyphs.
    Glyph tree contents:  28 characters, 28 glyphs, 1 nodes, 64 node bytes, 64 storage bytes, 128 total bytes, 4.57 bytes per character,
4.57 bytes per glyph
    Layout tree contents:  28 characters, 28 glyphs, 0 laid glyphs, 0 laid line fragments, 1 nodes, 64 node bytes, 0 storage bytes, 64 total bytes, 2.29 bytes per character, 2.29 bytes per glyph, 0.00 laid glyphs per laid line fragment, 0.00 bytes per laid line fragment , glyph range {0 28}. Ignoring...

【问题讨论】：

标签： ios uikit uitextview appkit textkit

【解决方案1】：

您的下划线样式无效。更改此行：

let underlineAttribute = 
    [NSAttributedStringKey.underlineStyle: NSUnderlineStyle.styleSingle]

到这里：

let underlineAttribute = 
    [NSAttributedStringKey.underlineStyle: NSUnderlineStyle.styleSingle.rawValue]

结果：

【讨论】：

轰隆隆，就是这样！谢谢你。为什么这里需要 rawValue？我承认我对 Swift 还很陌生，但这似乎过于冗长和丑陋。我认为 swift 应该更干净、更简单。
来自developer.apple.com/documentation/foundation/…——“这个属性[underlineStyle]的值是一个包含整数的NSNumber对象”。我不明白为什么 NSNumber 作为键值对中的值无效。
你自己给出了答案。枚举不是整数。它的原始值是整数。
Swift 枚举：太聪明了一半
我想说，问题不在于 Swift，而在于 Cocoa，它是用 Objective-C 编写的，对 Swift 枚举一无所知。因此，正如您自己所说，这个字典值是一个整数——而不是 Swift 枚举。因此，要与 Cocoa 对话，我们必须通过获取枚举的原始值来“过桥”。