Question

With some help, I was able to take a method that displays a word count for each day in a project and reduce it down to pretty much one database quere. Here’s the method

def project_range(project, start, finish, &blk)
  words = project.words.where(:wrote_on => start..finish)
  word_map = words.index_by(&:wrote_on)
  for day in start..finish
    word_count = word_map[day] ? word_map[day].quantity : 0
    blk.call(day, word_count)
  end
end

The original question is here:

Reducing database hits in Rails

Now though, we want to change the way users enter word counts for each day, however — we want to give them a chance to enter multiple counts for a day, instead of just one per day. This method, however, only returns the word count for the last day entered, not all the word counts for that specific day.

I tried changing index_by to group_by, but I got an undefined method error for quantity. So, my question is… how can I handle multiple entries for the same day, where there are two wrote_on objects for say, 5/4/2012?

Answer 1

group_by worked with another modification. Changes are commented out.

def project_range(project, start, finish, &blk)
    words = project.words.where(:wrote_on => start..finish)
    #word_map = words.index_by(&:wrote_on)
    word_map = words.group_by(&:wrote_on)
    for day in start..finish
      #word_count = word_map[day] ? word_map[day].quantity : 0
      word_count = word_map[day] ? word_map[day].sum(&:quantity) : 0
      blk.call(day, word_count)
    end
  end