（转载）iOS UILabel自定义行间距时获取高度

　#import "TTTAttributedLabel.h"

NSString *str = @"UILabel自定义行间距时获取高度,UILabel自定义行间距时获取高度,UILabel自定义行间距时获取高度,UILabel自定义行间距时获取高度,UILabel自定义行间距时获取高度,UILabel自定义行间距时获取高度,UILabel自定义行间距时获取高度.";
    
    //创建tttLabel
    TTTAttributedLabel *tttLabel = [[TTTAttributedLabel alloc] initWithFrame:CGRectMake(30, 55, 300, 100)];
    tttLabel.lineBreakMode = NSLineBreakByCharWrapping;
    tttLabel.lineSpacing = 6;//设置行间距
    tttLabel.font = [UIFont systemFontOfSize:12];
    tttLabel.numberOfLines = 0; //设置行数为0
    [tttLabel setText:str];
    tttLabel.textAlignment = NSTextAlignmentLeft;
    tttLabel.backgroundColor = [UIColor redColor];
    [self.view addSubview:tttLabel];
    
    //获取tttLabel的高度
    //先通过NSMutableAttributedString设置和上面tttLabel一样的属性,例如行间距,字体
    NSMutableAttributedString *attrString = [[NSMutableAttributedString alloc] initWithString:str];
    //自定义str和TTTAttributedLabel一样的行间距
    NSMutableParagraphStyle *paragrapStyle = [[NSMutableParagraphStyle alloc] init];
    [paragrapStyle setLineSpacing:6];
    //设置行间距
    [attrString addAttribute:NSParagraphStyleAttributeName value:paragrapStyle range:NSMakeRange(0, str.length)];
    //设置字体
    [attrString addAttribute:NSFontAttributeName value:[UIFont systemFontOfSize:12] range:NSMakeRange(0, str.length)];
    
    //得到自定义行间距的UILabel的高度
    CGFloat height = [TTTAttributedLabel sizeThatFitsAttributedString:attrString withConstraints:CGSizeMake(300, MAXFLOAT) limitedToNumberOfLines:0].height;
    
    //重新改变tttLabel的frame高度
    CGRect rect = tttLabel.frame;
    rect.size.height = height;
    tttLabel.frame = rect;