Re: [Rails] Using group_by in a Rails view

[Walter Lee Davis]

On Aug 15, 2012, at 11:14 AM, AmateurCoder wrote:

> I have a blog application where I would like to display on the post view a list of keyword categories and associated keyword types.
>
> #views/post.html.erb
>
> .
> .
> .
> <% @post.keywords.group_by(&:keyword_category_id).each do |category, type| %>
> <li><%= category %></li>
> <% type.each do |type| %>
> <%= type.keyword_type_id %>
> <% end %>
> <% end %>
> .
> .
> .
>
>
> The keyword categories and keyword types are in separate models. The association for the models are:
>
> #keyword_category.rb
> has_many :keyword_types
>
> #keyword_type.rb
> belongs_to :keyword_category
>
> #post.rb
>
> has_many :keywords
> has_many :keyword_types, through: :keywords
> has_many :keyword_categories, through: :keywords
>
> I am using a join table called 'keywords', for keeping track of the keyword categories and keyword types for a post.
>
> The keywords table has the following fields.
> post_id
> keyword_category_id
> keyword_type_id
>
>
>
> The issue I am having is the view is displaying the ids and I can't figure out how to do something like category.keyword_category.name? Any ideas on what I am doing wrong? Thanks in advance for your help.

That's what your view is requesting.

<%= type.keyword_type_id %>

It's not clear from the model code you have posted where the name lives, and whether it is the name of the category you want to show or the name of the keyword. Could you post your schema? Usually, if you have a whatever_id available, you can also get at the whatever itself directly, and then branch off of that to show the particular property of that object that you want to show. Maybe it's this:

<%= type.keyword_type.name %>

But I'm not sure, because your relationships seem to be one-sided.

Walter

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[AmateurCoder]

Walter,

Thanks for your reply. 

I am going for a display like the following:


Fruit
  Apple
  Orange
   Peach
Meat
  Beef
  Fish
  Poultry

Fruit and Meat are  category names and apple, orange, peach, etc are  type names.

This information is being stored in a join table that look like the following:

post_id  keyword_category_id   keyword_type_id
1              1                                    1
1              1                                    2       
1              1                                    3                 

The schema look like the following:

keywords table
id :integer
post_id: integer
keyword_category_id :integer
keyword_type_id :integer

keyword_categories table
id  :integer
name: string

keyword_types table
id: integer
name: string
keyword_category_id :integer

I thought I could do the following:
.
<% @post.keywords.group_by(&:keyword_category).each do |category, type| %>
  <li><%= category.keyword_category.name %></li>

    <% type.each do |type| %>

  <%= type.keyword_type.name %>

  <% end %>
<% end %>

This code doesn't work.

I had to use &:keyword_category_id as in the code below.  The output look like

 1
   1
   2
   3
 2
   4
   5
   6
  

I want to display the category names and type names instead of the foreign key ids.  I think I am using group_by wrong or even perhaps i need an association in the other direction.  I am just baffled at the moment.


Any ideas?

[Walter Lee Davis]

You might want to look at this blog post (kind of old, but it might help): http://ariejan.net/2007/01/12/rails-group-results-by-week-using-group_by/

You might also want to read through the Rails Guide on Associations, and see if you can parse out what's missing in your relationships. Make sure that each has_many is balanced on the other side by a belongs_to.

Walter

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