（转载）iOS UILabel自定义行间距时获取高度

　#import "TTTAttributedLabel.h"

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//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;