//宽度,高度,和字体大小 CGSize size = [contentString boundingRectWithSize:CGSizeMake(width, MAXFLOAT) options:NSStringDrawingUsesLineFragmentOrigin attributes:@{NSFontAttributeName:[UIFont boldSystemFontOfSize:16.0]} context:nil].size;
原文：http://www.cnblogs.com/mrcz/p/4143148.html