Using group_by in a Rails view

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|
%>

  • <%= category %>

  • <% 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.

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

        <%= type.keyword_type_id %>
    

    has_many :keyword_types
    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

    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|
    %>

  • <%= category.keyword_category.name %>
  • <% 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?

    On Aug 16, 2012, at 3:45 PM, AmateurCoder wrote:

    Peach
    1 1 1

    .
    1

    Any ideas?

    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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