Exam in Fundamental Object Oriented Programming. Code snippet

Question

I'm attending an exam at Tuesday in FOOP (described in title), and I've handed in a programme. Problem is that I don't quite understand the following bit. It's a method for calculating a persons age:

public static int CalculateAge(DateTime dob)
{
    int years = DateTime.Now.Year - dob.Year;

    if ((dob.Month > DateTime.Now.Month) || (dob.Month == DateTime.Now.Month && dob.Day > DateTime.Now.Day))
        years--;

    return years;
}

I couldn't figure it out myself, so I looked it up on the internet. I don't know what happens inside the if statement. It should be mentioned that I've a Datetime variable called dob

OK today is 18 June 2016. Compare my ages if I was born on 1st January 2000, 17th June 2000, and 19th June 2000 — Rhumborl, Jun 18 '16 at 19:44
There is a less confusing way of calculating age, see this: http://stackoverflow.com/questions/9/how-do-i-calculate-someones-age-in-c — Victor Zakharov, Jun 18 '16 at 19:45
It is taken from [one of the answers to this question](http://stackoverflow.com/questions/9/how-do-i-calculate-someones-age-in-c) — Steve, Jun 18 '16 at 19:49
I think you should just spend more time thinking about this yourself. — Ian, Jun 18 '16 at 20:06
You need a [Rubber duck](https://en.wikipedia.org/wiki/Rubber_duck_debugging) — Ňɏssa Pøngjǣrdenlarp, Jun 18 '16 at 20:26
@Plutonix nice reference to rubber-duck debugging. Have you actually read the pragmatic programmer? — Snoop, Jun 18 '16 at 21:06

score 1 · Accepted Answer · answered Jun 18 '16 at 21:01

What this code is doing, is determining a person's age based on their date-of-birth relative to the current date.

Let's take a look at the first line of code:

int years = DateTime.Now.Year - dob.Year;

What they are doing on the line above is determining overall how many years that the person has been alive.

Now, let's take a look at the conditions inside of the if statement. First, we will take a look at the left-hand-side of the || (means or-else, but will be treated as or for this code-snippet) operator.

(dob.Month > DateTime.Now.Month)

What this statement does is evaluate whether or not the current month is ahead of the person's birth-month. Then, consider the right-hand-side of the || operator.

(dob.Month == DateTime.Now.Month && dob.Day > DateTime.Now.Day)

The above conditional asks the question of whether or not this is their birth-month, and if so, is their birthday in the future? If the answer to either or these conditionals is yes, then the person has not reached their birthday. So, we subtract off one year from the total number of years as follows:

years--;

To help you think about this better, one could ask "just because this is the 16th year you've lived during, does that mean you are actually 16 complete years old?"

I really think you should have left the OP to think about this for as long as it took. — Ian, Jun 18 '16 at 21:51

Exam in Fundamental Object Oriented Programming. Code snippet

1 Answers1