在目标C中创建包含分数的字体描述符

Question

即使相应的代码在Swift中工作，我也无法在Objective C中显示分数。我必须失去一些非常明显的东西？

Swift代码：

override func viewWillAppear(_ animated: Bool) { 
    super.viewWillAppear(animated) 

    //: Playground - noun: a place where people can play 

    let pointSize = self.label.font.pointSize 

    let systemFontDesc = UIFont.systemFont(ofSize: pointSize, weight: UIFontWeightLight).fontDescriptor 

    let fractionFontDesc = systemFontDesc.addingAttributes(
     [ 
      UIFontDescriptorFeatureSettingsAttribute: [ 
       [ 
        UIFontFeatureTypeIdentifierKey: kFractionsType, 
        UIFontFeatureSelectorIdentifierKey: kDiagonalFractionsSelector, 
        ], ] 
     ]) 

    print(fractionFontDesc) 
    self.label.font = UIFont(descriptor: fractionFontDesc, size:pointSize) 

    print("label.font.descriptor: \(self.label.font.fontDescriptor)") 
} 

结果：

在目标C

等效代码

-(void) viewDidAppear:(BOOL)animated { 
    [super viewDidAppear:animated]; 

    CGFloat pointSize = _label.font.pointSize; 

    UIFontDescriptor *systemFontDesc = [UIFont systemFontOfSize:pointSize weight:UIFontWeightLight].fontDescriptor; 

    UIFontDescriptor *fractionDescriptor = [systemFontDesc fontDescriptorByAddingAttributes:@{ UIFontDescriptorFeatureSettingsAttribute : @{ 
                             UIFontFeatureTypeIdentifierKey: @(11), // kFractionsType 
                             UIFontFeatureSelectorIdentifierKey: @(2)}}]; // kDiagonalFractionsSelector 

    NSLog(@"%@\n\n", fractionDescriptor); 

    UIFont *fracFont = [UIFont fontWithDescriptor:fractionDescriptor size:pointSize]; 

    NSLog(@"fracFont.fontDescriptor: %@\n\n", fracFont.fontDescriptor); 

    [_label setFont: fracFont]; 

    NSLog(@"label.font.descriptor: %@\n\n", _label.font.fontDescriptor); 
} 

结果：

Answer 1

的问题是表达

fontDescriptorByAddingAttributes:@{ 
    UIFontDescriptorFeatureSettingsAttribute : @{ 

这最后@{表明您UIFontDescriptorFeatureSettingsAttribute是一本字典。那是错的。它需要是一个数组字典。 （仔细看看你原来的Swift代码，你会发现这是如此。）

在我看来，在一行中形成你的字典，在另一行中创建一个数组，并且在第三行中拨打fontDescriptorByAddingAttributes。这样你就可以清楚你在做什么。现在，你只是混淆了所有那些嵌套的字面问题...