UILabel自动计算高度和换行

self.dizhiLabel = [[UILabel alloc]init];     self.dizhiLabel.textColor = [UIColor grayColor];    //折行     self.dizhiLabel.lineBreakMode = NSLineBreakByWordWrapping;    //必须写，否则只显示一行    [ self.dizhiLabel setNumberOfLines:0];    [self.contentView addSubview: self.dizhiLabel];    [ self.dizhiLabel mas_makeConstraints:^(MASConstraintMaker *make) {                make.left.equalTo(self.zuobiaoImageView.mas_right).offset(20);        make.right.equalTo(self.contentView.mas_right).offset(-20);        make.top.equalTo( self.zuobiaoImageView.mas_top);            }];        //根据文字内容和字体计算高度    CGSize textSize = CGSizeZero;    // 多行必需使用NSStringDrawingUsesLineFragmentOrigin，网上有人说不是用NSStringDrawingUsesFontLeading计算结果不对    NSStringDrawingOptions opts = NSStringDrawingUsesLineFragmentOrigin | NSStringDrawingUsesFontLeading;        NSMutableParagraphStyle *style = [[NSMutableParagraphStyle alloc] init];    [style setLineBreakMode:NSLineBreakByCharWrapping];        NSDictionary *attributes = @{ NSFontAttributeName : [UIFont systemFontOfSize:17], NSParagraphStyleAttributeName : style };        CGRect rect = [ self.dizhiLabel.text boundingRectWithSize:(CGSize){ self.dizhiLabel.frame.size.width, MAXFLOAT}                                                options:opts                                             attributes:attributes                                                context:nil];    textSize = rect.size;         self.dizhiLabel.frame = CGRectMake(85, 15, textSize.width, textSize.height);