UITextView - 不能在文本上设置下划线或删除线属性？

Question

每当我尝试在UITextView的attributedText上设置下划线或删除线属性时，我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。这是一段代码片段。我所拥有的只是一个带有单个UITextView的测试项目。我在iOS 11上。

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
    }
}

这导致文本消失并打印出一些错误：

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...

Answer 1

您的下划线样式无效。改变这一行：

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

到此：

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

结果：