1、添加中划线
NSString *primeCost = @"9998";
UILabel * strikeLabel = [[UILabel alloc] initWithFrame:(CGRectMake(64, 64, 100, 30))];
NSString *textStr = [NSString stringWithFormat:@"%@元", primeCost];
//中划线
NSDictionary *attribtDic = @{NSStrikethroughStyleAttributeName: [NSNumber numberWithInteger:NSUnderlineStyleSingle]};
NSMutableAttributedString *attribtStr = [[NSMutableAttributedString alloc]initWithString:textStr attributes:attribtDic];
// 赋值
strikeLabel.attributedText = attribtStr;
[self.view addSubview:strikeLabel];

2、添加下划线
UILabel *underlineLabel = [[UILabel alloc] initWithFrame:(CGRectMake(10, 10, 50, 30))];
NSString *textStr = [NSString stringWithFormat:@"%@元", primeCost];
// 下划线
NSDictionary *attribtDic = @{NSUnderlineStyleAttributeName: [NSNumber numberWithInteger:NSUnderlineStyleSingle]};
NSMutableAttributedString *attribtStr = [[NSMutableAttributedString alloc]initWithString:textStr attributes:attribtDic];
//赋值
underlineLabel.attributedText = attribtStr;
[self.view addSubview:underlineLabel];