Keep it Simple, Stupid

cwilliams — Tue, 05 Jul 2005 22:16:00 +0000

At my job, I program in Java nearly 100% of the time. It was only recently that I began my own project where I use Ruby on Rails – the original project that I was hired to work on, and that I still help develop, is written fully in Java.

The Ruby on Rails project loads the underlying data into the database by performing a number of transforms on data in another corporate DB that I have no control over. I normalize the data and make it compatible with ActiveRecord.

I created small programs in Java to do the transformations initially, purely because to me everything still looks like a nail. After some time I also did the transforms in Ruby. Here’s a simple example of my continuing education in The Ruby Way, or essentially how dumb I can be when I write Ruby code.

Ranges

In the transform program I typically will load data from the previous day, but may want to load data over any given range of dates. So I created a simple DateRange class to handle this.

public class DateRange {
  private Date start;
  private Date end;

  public DateRange(Date start, Date end) {
    this.start = start;
    this.end = end;
    // omitting the comparsions to make sure start is really the earlier date
  }
  
  public boolean contains(Date check) {
    return (check.after(start) || check.equals(start)) 
      && (check.before(end) || check.equals(end));
  }
}

This code works all right, but it can get ugly to try and specify Dates quickly. So I added more methods to the class, such as:

public static Date date(int month, int day, int year)) {
  Calendar cal = Calendar.getInstance();
  cal.set(Calendar.YEAR, year - 1900);  // since Java Calendar years start at 1900
  cal.set(Calendar.DAY_OF_MONTH, day);
  cal.set(Calendar.MONTH, month - 1); // Since Java months are zero-based
  cal.set(Calendar.HOUR, 0);
  cal.set(Calendar.MINUTE, 0);
  cal.set(Calendar.SECOND, 0);
  cal.set(Calendar.MILLISECOND, 0);
  return cal.getTime();
}

I’ll spare you the numerous static methods I created to help myself out. Beyond being so verbose, the Java version irks me because I’m adding static methods to a DateRange class to create Date objects easier. The Date class should be doing that…

Ruby

In Ruby, I was ‘tainted’ by the Java implementation. I started work on my Ruby DateRange…

class DateRange
  def initialize(start, end)
     @start, @end = start, end
     # omitting the comparisons to make sure start is really the earlier date
  end

  def contains?(date)
    date >= @start or date <= @end
  end
end

The seasoned Ruby programmers can all snicker now. Here’s how I used it:

range = DateRange.new(Time.local(4, 1, 2005), Time.local(5, 1, 2005))

I quickly realized I couldn’t easily iterate over the range. I needed to mixin Enumerable and implement an each method!

class DateRange
  include Enumerable
  # ...
  def each
    (@start..@end).each do |date|
      yield date
    end
  end
  # ...
end

If full-out laughter has not erupted yet, you must not program in Ruby. I was very proud of this code for a while, and the transform programs were finished quickly.

About a month later I returned to edit the transforms and create some new ones. I looked at the code and thought something just wasn’t right. Duh! Ranges are embedded in Ruby! I never needed to create my own class.

I quickly refactored all of my code to look like:

range = Time.local(4,1,2005)..Time.local(5,1,2005)

Problem solved, right? Wrong. I broke the each method. Time returns the next millisecond for succ, so when each tries to iterate over the range, it will bring up the next millisecond – I want the next day.

My next brilliant solution:

class Time
  def succ
    Time.at(self.to_i + (24 * 60 * 60))
  end
end

I redefined the succ method to return 24 hours later. So why is this wrong? Because in Ruby there are the classes Time, Date and DateTime - each for different reasons. What I wanted all along was a range of Date objects, not Time objects – thats why I named the first class DateRange to begin with.

So our next try:

range = Date.civil(2005, 4, 1)..Date.civil(2005, 5, 1)

And we’re working again. Date defines succ to return the next day, we never had to create any extra code to handle our date ranges, and we’ve learned a number of very wring ways to solve the problem.

Late to the Party: Keep it Simple, Stupid

Keep it Simple, Stupid