字体的下划线

NSString * sit= @"忘记密码";

NSMutableAttributedString *sti =[[NSMutableAttributedString alloc]initWithString:sit];

//设置背景颜色以及下划线

NSDictionary * dict1 = @{//字体颜色

NSForegroundColorAttributeName:[UIColor colorWithRed:33/255.0 green:125/255.0 blue:192/255.0 alpha:1],
                             NSFontAttributeName:[UIFont fontWithName:@"Helvetica-Bold" size:19],
                             NSUnderlineStyleAttributeName:@"1"};
   
    //从下标14开始，长度为6的内容添加多个属性，dict1里面写的就是添加的属性

[sti addAttributes:dict1 range:NSMakeRange(0, 4) ];