Rails "Undefined Method for Activerecord_Associations_Collectionproxy"

undefined method `commentable' for # ActiveRecord::Associations::CollectionProxy [] (accesing commentable id and type via polymorphic association)

As the error message says, you can't call commentable on @question.comments - an association. Pass an array to the form_for method with the commentable (Question) object and the comment object. You don't need to set any hidden fields.

<%= form_for [@question, @comment] do |f| %>
  <div><%= f.label :content %></div>
  <div><%= f.text_area :content %></div>
  <div><%= f.submit 'Post' %></div>
<% end %>

Replace content with the field where you're storing the comment's content.

This should generate a form tag with an action attribute of /questions/1/comments which upon submission is processed by CommentsController#create.

class CommentsController < ApplicationController
  before_action :set_commentable

  def create
    @comment = @commentable.comments.new(comment_params)
    if @comment.save
      redirect_to @commentable, notice: 'Comment created'
    else
      render :new
    end
  end

  private

  def set_commentable
    # e.g. request.path => '/questions/1/comments'
    resource, id = request.path.split('/')[1, 2] # ['questions', '1']
    @commentable = resource.singularize.classify.constantize.find(id)
  end

  def comment_params
    params.require(:comment).permit(:content)
  end
end

In the set_commentable method, the commentable type and its id are detected from the request path. Since resource is 'questions', resource.singularize.classify.constantize returns the Question model. The commentable object is then found using the find method. The CommentsController#create method creates the comment and redirects to the commentable object which is the question show page (/questions/:id). If there's an error, it renders the new view (you have to create views/comments/new.html.erb to render the form with errors).

undefined method `keys' for # ActiveRecord::Associations::CollectionProxy []

Rename attributes as that's what is causing you issues

if you have a has_many called attributes, you can’t access to your
object attributes anymore; only the associated objects Original Rails
Wiki - additional words

Relevant link:

http://reservedwords.herokuapp.com/words/attributes

Rails 3 HABTM yields ActiveRecord::Associations::CollectionProxy objects

Having a hard time trying to find the error here.. But maybe some of these will help you:

I think you are missing the multiple field index:

add_index : volunteer_circles_users, [:volunteer_circles_id, :user_id]
add_index : volunteer_circles_users, [:user_id, :volunteer_circles_id]

And the create_join_table creates it in alphabetical order, so it would be user_volunteer_circles instead. So, maybe you could need to do something like:

class VolunteerCircle < ActiveRecord::Base 
    has_and_belongs_to_many :users, :join_table => : volunteer_circles_users
end

Hope it helps..

Sort order for ActiveRecord::Associations::CollectionProxy in table rails

I would add a class method on the Room model in order to return for a given collection the number of free rooms and reserved rooms:

class Room < ApplicationRecord
  belongs_to :hotel, optional: true
  accepts_nested_attributes_for :hotel

  def self.reserved_count
    where(reserved: true).count
  end

  def self.free_count
    where(reserved: false).count
  end
end

Once you have implemented, you can call it from the relationship declared in Hotel model:

class Hotel < ApplicationRecord
  has_many :rooms, dependent: :destroy
  accepts_nested_attributes_for :rooms

  def reserved_rooms
    rooms.reserved_count
  end

  def free_rooms
    rooms.free_count
  end
end

Your view will look finally like this:

<table>
  <tr>
    <th>Name</th>
    <th>Rooms count</th>
    <th>Rooms status: in reserved || free</th>    
  </tr>

  <% @hotels.each do |hotel| %>
    <tr>
      <td><%= hotel.name %></td>
      <td><%= hotel.rooms_count %></td>
      <td><%= "#{hotel.reserved_rooms} || #{hotel.free_rooms}" %></td>      
      <td ><%= link_to 'Show', hotel_path(hotel) %></td>
      <td><%= link_to 'Destroy', hotel, method: :delete, data: { confirm: 'Are you sure?' } %>
    </tr>
  <% end %>
</table>

Sorting the Hotels in your controller

In your controller make sure that you eager load Rooms for Hotel:

@hotels = Hotel.includes(:rooms).sort_by { |h| h.free_rooms.to_i }.reverse

You could eventually implement it as Hotel.includes(:rooms).sort_by(&:free_rooms).reverse.

In this way you won't need any join or helper.

Regarding your comment, free_rooms is implemented as an instance method (e.g. Hotel.first.free_rooms), so it will not be available for an ActiveRecord_Relation (e.g. Hotel.all.free_rooms)

Rails loop through ActiveRecord::Associations:CollectionProxy

You can do this completely in SQL/ActiveRecord. The query you want to run ultimately is

SELECT article_id, min(date), sum(views)
FROM   daily_value_metrics -- Or whatever your table is called
GROUP BY article_id

You can run this with ActiveRecord with the following:

table = DailyValueMetric.arel_table
results = DailyValueMetric.select(table[:article_id], 
  table[:date].minimum.as('date'), 
  table[:views].sum.as('views')).group(:article_id).to_a
# Calling to_a so I can call first for the example
results.first.date #=> date
results.first.views #=> views
results.first.article_id #=> Id

The records will look like

[#<DailyViewMetric id: nil, article_id: 1089536>, ...]

Because the SQL query does not return an id column in the result set. This is because of the way that ActiveRecord::Base#inspect shows the columns defined on the table, and not the returned values outside of the table columns. Views and Date will not necessarily be shown, unless there is a column with the same name, but if you call those attributes on the model instance, you will be able to get the value

Access attributes in ActiveRecord::Associations::CollectionProxy

I am trying to write a custom function that will throw an error if the amount of associated objects are >=4

You are overcomplicating things. If you just want to count the number of records in a collection then you can simply do animal.animal_images.size. So your model will look like this:

class Animal < ActiveRecord::Base
  has_many :animal_images
  validate :max_num_of_images

  def max_num_of_images
    errors.add(:base, "Max of 3 images allowed") if self.animal_images.size >= 4
  end
end

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