Rails Loop Through ActiveRecord By Attribute Value

Question

Lets say I have an array of Match objects, each belonging to a round in a round robin tournament structure...

Matches

Round     | Registrant_ID     |Registrant_ID_2    |Winner_id
1         |    1              |    2              |   2 
1         |    3              |    4              |   4
1         |    5              |    6              |   5
1         |    7              |    8              |   8
2         |    1              |    4              |   1
2         |    3              |    6              |   3
2         |    5              |    8              |   5
2         |    7              |    2              |   2
3         |    1              |    6              |   1
...

What I wish to do is group all of the matches by Round and loop through that round and list the matches.

The desired output would be something like...

 <h1>Round 1</h1>    
 <table>
 <thead>
  <tr>
   <th>Player 1</th>
   <th>Player 2</th>
   <th>Winner</th>
  </tr>
 </thead>
 <tbody>
  <tr>
    <td>1</td>
    <td>2</td>
    <td>2</td>
  </tr>
  <tr>
    <td>3</td>
    <td>4</td>
    <td>4</td>
  </tr>
  <tr>
    <td>5</td>
    <td>6</td>
    <td>5</td>
  </tr>
  <tr>
    <td>7</td>
    <td>8</td>
    <td>8</td>
  </tr>
 </tbody>
</table>

The problem I'm facing is that I don't know how to loop through the match records by their round attribute. I'm not sure if something like in_groups_of can be used because the number of players that participate in a round will vary, it won't always be 8 as seen here.

Here is my code thus far which simply loops through all records and creates a table for every match(I'm looking for tables for individual rounds):

- @matches.each do |match|
  %h1= "Round #{match.round}"
  %table.table.table-bordered
    %thead
      %tr
        %th.span4 Player 1
        %th.span4 Player 2
        %th.span4 Winner
    %tbody
      %tr
        %td= match.register.user.username
        %td= match.register_2.user.username
        %td= match.winner.user.username unless match.winner.nil?

Here's what the output is meant to look like, notice separate tables for separate rounds:

round robin match listing

megas · Accepted Answer · 2012-09-14 21:04:13Z

1

Maybe you mean to group matches by round, like this:

- @matches.group_by(&:round).each do |round, matches|
  %h1= "Round #{round}"
  %table.table.table-bordered
    %thead
    %tr
      %th.span4 Player 1
      %th.span4 Player 2
      %th.span4 Winner
    %tbody
      - matches.each do |match|
        %tr
          %td= match.register.user.username
          %td= match.register_2.user.username
          %td= match.winner.user.username unless match.winner.nil?

edited Sep 14, 2012 at 21:04

answered Sep 14, 2012 at 20:35

megas

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3 Comments

Noz Over a year ago

Thanks Megas but that wasn't quite what I had in mind have a look at my screen-shot for a visual

megas Over a year ago

You want one table but several sections in that table, am I right?

Noz Over a year ago

Nope, I need a table for each round.

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