ios 系统字体：字体样式

// 设置字体
 label.font = [UIFont fontWithName:@"Helvetica-Bold" size:17.f]; 

- (void)TestFontFamily {
            for (NSString *fontFamily in [UIFont familyNames]) {
                NSLog(@"%@", fontFamily);
                for (NSString *fontName in [UIFont fontNamesForFamilyName:fontFamily]) {
                    NSLog(@"    %@", fontName);
                }
            }        
}

知识点：（加载外部字体）

iOS - 手动添加新的字体

_timeL.font = [UIFont fontWithName:@"SourceHanSerifCN-Heavy" size:[UIScreen mainScreen].bounds.size.width/375*25];