iOS 根据UIlabel字体大小和宽度自适应高度

-(float)heightForString:(NSString *)value fontSize:(float)fontSize andWidth:(float)width

{

   float height = [[NSString stringWithFormat:@"%@\n",value] boundingRectWithSize:CGSizeMake(width, CGFLOAT_MAX) options:NSStringDrawingUsesLineFragmentOrigin | NSStringDrawingUsesFontLeading attributes:[NSDictionary dictionaryWithObjectsAndKeys:[UIFont systemFontOfSize:fontSize],NSFontAttributeName, nil] context:nil].size.height;

 

   return height;

}