NSAttributedString與UIFontWeightTraits

Question

我試圖生成一個NSAttributedString基本上只有默認字體，是斜體和不同的文字顏色。足夠簡單，到目前爲止。

現在我想要這整個字符串的不同子串到另外要粗體。它應該基本看起來像這樣：

從約翰史密斯於25.08。在8:00

（只是用不同的顏色。）

它看起來像我越來越字典錯了，我傳遞到NSMutableAttributedString的addAttributes(_:_:)功能。從documentation，我明白，這本字典應該是這樣的：

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

但這似乎並沒有工作。所有我最終都是字符串的斜體版本。我明明在這裏弄錯了。任何想法？

更新：添加簡單的例子

// 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 

謝謝！

Answer 1

UIFontDescriptorTraitsAttribute沒有在NSAttributedString一個公認的關鍵屬性字典，所以在獲得您需要重建UIFont和使用NSFontAttributeName關鍵性狀。

//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) 

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