"Couldn't find <object> without an ID"

Question

I'm having problems implementing a kind of comments form, where comments (called "microposts") belong_to both users and posts, users have_many comments, and posts (called "propositions") have_many comments.

My code for the comments form is:

<%= form_for @micropost do |f| %>
  <div class="field">
      <%= f.text_area :content %>
  </div>

  <div class="actions">
    <%= f.submit "Submit" %>
  </div>
<% end %>

The MicropostsController has this in the create action:

  def create

      @proposition = Proposition.find(params[:proposition_id])

  @micropost = current_user.microposts.build(params[:micropost])
  @micropost.proposition = @proposition
  if @micropost.save
      flash[:success] = "Contribution submitted"
      redirect_to root_path
  else
          @feed_items = []    
      render 'pages/home'
  end
  end

The form for creating a new micropost is on the same page as a proposition, yet the proposition id doesn't seem to get passed at any point.

This is the error I get on submitting the micropost form:

ActiveRecord::RecordNotFound in MicropostsController#create

Couldn't find Proposition without an ID

Parameters are:

{"commit"=>"Submit", "micropost"=>{"proposition_id"=>"", "content"=>"First comment"}, "authenticity_token"=>"TD6kZaHv3CPWM7xLzibEbaLJHI0Uw43H+pq88HLZFjc=", "utf8"=>"✓"}

I'm completely new to rails and very new to coding anything at all, so I'd be grateful for any help you can give me!

Thanks in advance.

Answer 1

Your params are:

"micropost"=>{"proposition_id"=>"", "content"=>"First comment"}

So to get proposition_id, you have to do :

params[:micropost][:proposition_id]

But this is empty. And there is nowhere else to get this id, that's why this line retrieves nil:

@proposition = Proposition.find(params[:proposition_id])

Making this fail:

@micropost.proposition = @proposition

You must either:

• add the proposition_id as an hidden_field

• store it in session

But I don't know your context enough to give you the proper solution here.

EDIT:

In your link, replace:

<%= f.hidden_field :proposition_id %>

with:

<%= f.hidden_field :proposition_id, :value => @proposition.id %>

If it doesn't work, show your params.

Note: it's bad practice to rely on instance variables, you should send local variable to each partial