Question

I’ve currently got three models: Songs have many Setlists and vice versa, through the Allocations model.

I’m trying to use a nested form to add existing songs to a setlist.

My current view for the nested form:

<div>
  <%=form_for @allocation do|builder|%>
    <%=builder.label :song_id, "Pick a song" %>

     <%= builder.hidden_field :setlist_id, value: @setlist.id %>

     <%= builder.select(:song_id, options_for_select(@selections), {}, {multiple: true, size: 7}) %>

    <%=builder.submit "Add Song", class: "btn btn-large btn-primary" %>
  <% end %>
</div>

and my controller for editing setlists:

  def edit
    @songs = Song.all(order: 'title')
    @setlist = Setlist.find(params[:id])
    @allocations = @setlist.allocations
    @allocation = Allocation.new
    @selections = Song.all.collect {|s| [ [s.title, s.artist].join(" by "), s.id ]   }
  end

  def update

    @setlist = Setlist.find(params[:id])
    @selections = Song.all.collect {|s| [ [s.title, s.artist].join(" by "), s.id] }
    @allocations = @setlist.allocations
    @allocation = Allocation.new

    params[:allocation][:song_id].reject! { |c| c.empty? }

    if @setlist.update_attributes(params[:setlist])
      if @allocation.save
        flash[:success] = "SETLIST SAVED!"
        redirect_to setlist_path(@setlist)
      else
        flash[:fail] = "Setlist not saved"
        render 'edit'
      end
    else
      flash[:fail] = "FAIL!"
      render 'edit'
    end
  end

Whenever I submit the form to add a song to the setlist I get an error back saying:

Validation failed: Setlist can't be blank, Song can't be blank

All the parameters appear to being passed correctly so I’m stumped. Here’s the parameters returned:

   {"utf8"=>"✓",
 "_method"=>"put",
 "authenticity_token"=>"ThIXkLeizRYtZW77ifHgmQ8+UmsGnDhdZ93RMIpppNg=",
 "setlist"=>{"date(1i)"=>"2012",
 "date(2i)"=>"7",
 "date(3i)"=>"11",
 "morning"=>"false"},
 "allocation"=>{"setlist_id"=>"1",
 "song_id"=>["5"]},
 "commit"=>"Add Song",
 "id"=>"1"}

Thank you for any help in advance

Answer 1

You’re allowing multiple selections in the :song_id field, one option of which I imagine has a blank value. That option and one other must be getting selected, causing the ["", 13] response.

params[:allocation][:song_id].reject! { |c| c.empty? }

This will clean blank entries from that param. This should be placed in the update method anywhere before this line

if @setlist.update_attributes(params[:setlist])

As for the validation error, I assume it’s coming from the Allocation since that’s what the form is for.

@allocation = Allocation.new

if @allocation.save!

Not knowing all of the attributes have attributes here that require values, like :set_list_id and :song_id. You’re trying to persist an Allocation to the database without first setting any of it’s attributes. This is the likely source of the validation issues you’re having.

Edit:

A nested form in rails is a set of form fields for an object associated with the object for the parent form. Notice how this form has fields_for called on the person_form object. This will result in nested parameters like param[:person][:children][:name].

<% form_for @person do |person_form| %>

  <%= person_form.label :name %>
  <%= person_form.text_field :name %>

  <% person_form.fields_for :children do |child_form| %>
    <%= child_form.label :name %>
    <%= child_form.text_field :name %>
  <% end %>

  <%= submit_tag %>

In the update method for this you could have something as simple as

person = Person.find(params[:id]).update_attributes(params[:person])

The update_attributes on Person can manage the creation, updating, and saving of it’s children association for you with accepts_nested_attributes_for

I think this is what you’re after, and as such you may need to rethink your view and the update method accordingly. This is relatively tricky stuff for an absolute beginner to rails; just keep going back to the documentation (it’s very well written) and asking for help here.