NSAttributedString与UIFontWeightTraits

Question

我试图生成一个NSAttributedString基本上只有默认字体，是斜体和不同的文字颜色。足够简单，到目前为止。

现在我想要这整个字符串的不同子串到另外要粗体。它应该基本看起来像这样：

从约翰史密斯于25.08。在8:00

（只是用不同的颜色。）

它看起来像我越来越字典错了，我传递到NSMutableAttributedString的addAttributes(_:_:)功能。从documentation，我明白，这本字典应该是这样的：

[UIFontDescriptorTraitsAttribute: 
    [UIFontWeightTrait: NSNumber(double: Double(UIFontWeightBold))] 

但这似乎并没有工作。所有我最终都是字符串的斜体版本。我明明在这里弄错了。任何想法？

更新：添加简单的例子

// Preparation 
let rawString = "from John Smith on 25.08. at 8:00" 
let attributedString = NSMutableAttributedString(string: rawString) 
let nameRange = (rawString as NSString).rangeOfString("John Smith") 
let italicFont = UIFont.italicSystemFontOfSize(14) 

// Make entire string italic: works! 
attributedString.addAttributes([NSFontAttributeName : italicFont], range: NSMakeRange(0, 33)) 
// Make the name string additionally bold: doesn't work! 
attributedString.addAttributes([UIFontDescriptorTraitsAttribute: 
     [UIFontWeightTrait: NSNumber(double: Double(UIFontWeightBold))]], range: nameRange) 

// Show it on the label 
attributedStringLabel.attributedText = attributedString 

谢谢！

Answer 1

UIFontDescriptorTraitsAttribute没有在NSAttributedString一个公认的关键属性字典，所以在获得您需要重建UIFont和使用NSFontAttributeName关键性状。

//prepare the fonts. we derive the bold-italic font from the italic font 
    let italicFont = UIFont.italicSystemFontOfSize(14) 
    let italicDesc = italicFont.fontDescriptor() 
    let italicTraits = italicDesc.symbolicTraits.rawValue 
    let boldTrait = UIFontDescriptorSymbolicTraits.TraitBold.rawValue 
    let boldItalicTraits = UIFontDescriptorSymbolicTraits(rawValue:italicTraits | boldTrait) 
    let boldItalicDescriptor = italicDesc.fontDescriptorWithSymbolicTraits(boldItalicTraits) 
    let boldItalicFont = UIFont(descriptor: boldItalicDescriptor, size: 0.0) 

    //prepare the string 
    let rawString = "from John Smith on 25.08. at 8:00" 
    let attributedString = NSMutableAttributedString(string: rawString) 

    let fullRange = NSMakeRange(0, 33) 
    let nameRange = (rawString as NSString).rangeOfString("John Smith") 

    attributedString.addAttributes([NSFontAttributeName:italicFont], range: fullRange) 
    attributedString.addAttributes([NSFontAttributeName:boldItalicFont], range: nameRange) 

还看到：NSAttributedString: Setting FontAttributes doesn't change font