Question

I’m building a small app that takes things entered into an input field and displays them directly below that input field when entered.

My goal with this code is to separate those entries by date so that all things posted on June 1 are posted with one line break between them and the first entry of June 2 has 2 spaces between it and the entries from June 1.

This is my code and it’s not acting as planned but I can’t figure out why, I think it stems from line 3 and something I’m doing incorrectly. (Note: I’m aware this doesn’t account for changes in month or year yet. I’ll get to that once I figure out proper date spacing)

<% for i in (0..(@allLessons.count-1)) %>

<b><%= @date[i].created_at.strftime('%b %d')%></b><br/>

<% if @date[i].created_at.strftime('%d') == @date[i-1].created_at.strftime('%d') %>

<%= @date[i].created_at.strftime('%d') %> <br />

<% else %>

<%= @date[i].created_at.strftime('%d') %><br /><br />

<% end %>           
<% end %>

From the controller:

@allLessons = Lesson.all
@date = Lesson.find(:all, :order => 'created_at ASC')

Any help you could lend on this would be hugely appreciated!

Answer 1

Blocks and iterators are where it’s at.

@allLessons = Lesson.order('created_at ASC')
@dates = @allLessons.group_by { |lesson| lesson.created_at.beginning_of_day }.sort

<% @dates.each do |date, lessons| %>
  <% lessons.each do |lesson| %>
    <b><%= lesson.created_at.strftime("%d") %></b><br />
  <% end %>
  <br />
<% end %>

Annotated

First we get all of the lessons together. This is equivilant to find(:all, :order => ‘created_at ASC’), but I like this newer, compact syntax

@allLessons = Lesson.order('created_at ASC')

Then we group them all together into a hash where the key is the date and the value is an array of records that were created on that day. beginning_of_day converts a DateTime into a Date where the time is set to 00:00:00. So, 2012-05-25 18:00 becomes 2012-05-25 00:00:00. This is so we can group the dates themselves without the time getting in the way

@dates = @allLessons.group_by { |lesson| lesson.created_at.beginning_of_day }.sort

@dates is now a hash where the keys are dates and the values are arrays of lessons from that date. for example, { '2012-05-24 00:00:00' => [ lesson_1 ], 2012-05-25 00:00:00' => [ lesson_2, lesson_3 ]

We then pass the hash into a block, where the key is the date, and the value is the array of lessons. This is saying, for each date…

<% @dates.each do |date, lessons| %>

Give me the lessons that belong to that date. And for each of those…

  <% lessons.each do |lesson| %>

print out the date of the lesson

    <b><%= lesson.created_at.strftime("%d") %></b><br />
  <% end %>

before moving on to the next date, print a <br />

  <br />
<% end %>