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UITextView - 无法在文本上设置下划线或删除线属性？

iosuikituitextviewappkittextkit
16
我在尝试给UITextView的attributedText设置下划线或删除线属性时遇到了运行时错误。其他属性，如字体和背景色没有问题。这里是一个代码片段。我只有一个带有单个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...
1个回答
57

您的下划线样式无效。请更改此行：

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

到这个：

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

结果：

在此输入图片描述

2
太好了，就这样！谢谢。为什么这里需要rawValue？我承认我在Swift方面相对较新，但那似乎过于冗长和丑陋。我原本以为Swift应该更加简洁明了。 - Adam Bryant
从 https://developer.apple.com/documentation/foundation/nsattributedstringkey/1524865-underlinestyle - “此属性[underlineStyle]的值是包含整数的NSNumber对象。” 我不知道为什么NSNumber不能作为键值对中的值。 - Adam Bryant
你已经给出了答案。枚举不是整数，它的原始值是整数。 - matt
Swift 枚举：聪明过头 - Adam Bryant
4
我认为问题不在于Swift本身，而是因为Cocoa是用Objective-C编写的，不了解Swift的枚举类型。因此，正如你自己所说，这个字典值实际上是一个整数，而不是Swift的枚举类型。因此，为了与Cocoa交互，我们需要通过使用枚举的原始值来“跨越桥梁”。 - matt
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