UIFontCascadeList.m

NSArray *cascadeList = @[[UIFontDescriptor fontDescriptorWithName:@"Helvetica" size:20.0],
                         [UIFontDescriptor fontDescriptorWithName:@"PingFangTC-Regular" size:20.0]];
CTFontDescriptorRef descriptor = CTFontDescriptorCreateWithAttributes((CFDictionaryRef) @{(id)kCTFontCascadeListAttribute: cascadeList});
UIFont *font = (__bridge_transfer UIFont *) CTFontCreateWithFontDescriptor(descriptor, 20, NULL);
CFRelease(descriptor);
self.label.font = font;
self.label.text = @"Helvetica fallback 到 PingFangTC-Regular 汉体书写信息技术标准相容档案下载使用界面简单支援服务升级资讯专业制作创意空间快速无线上网";