//获取Label高度
-(CGFloat)heightFromString:(NSString*)text withFont:(UIFont*)font constraintToWidth:(CGFloat)width
{
if (text && font) {
CGRect rect = [text boundingRectWithSize:CGSizeMake(width, 1000) options:NSStringDrawingUsesLineFragmentOrigin|NSStringDrawingUsesFontLeading attributes:@{NSFontAttributeName:font} context:nil];
return rect.size.height;
}
return 0;
}