计算label上文字的宽度

-(CGSize)getAttributeSizeWithText:(NSString *)text fontSize:(int)fontSize
{
    CGSize size=[text sizeWithAttributes:@{NSFontAttributeName: [UIFont systemFontOfSize:fontSize]}];
    if (isIOS7) { //ios7之后
        size=[text sizeWithAttributes:@{NSFontAttributeName: [UIFont systemFontOfSize:fontSize]}];
    }else{
        NSAttributedString *attributeSting = [[NSAttributedString alloc] initWithString:text attributes:@{NSFontAttributeName: [UIFont systemFontOfSize:fontSize]}];
        size = [attributeSting size];
    }
    return size;
}