CODEWITHSUNDEEP
ruby-on-railsrubyactiverecordruby-on-rails-4
user3533435
user3533435

Reputation: 5

couldn't find Subject without an ID in @subject = Subject.find(params[:subject_id])

I have a mistake: couldn't find Subject without an ID in @subject = Subject.find(params[:subject_id])
I create many-to-many association. There are three models - teacher, subject and subscription. Subscription model includes following fields: teacher_id and subject_id.

class Subject < ActiveRecord::Base
  has_many :subscriptions
  has_many :teacher, :through => :subscriptions
end

class Teacher < ActiveRecord::Base
  has_many :subscriptions
  has_many :subjects, :through => :subscriptions
end

class Subscription < ActiveRecord::Base
  belongs_to :subject
  belongs_to :teacher
end

teacher_controller

def create
        @subject = Subject.find(params[:subject_id])
                @teacher = Teacher.new(teacher_params)
                respond_to do |format|
                  @teacher.subjects << @subject
                  if @teacher.save
        format.html { redirect_to @teacher, notice: 'Teacher was successfully created.' 
        format.json { render action: 'show', status: :created, location: @teacher }
      else
        format.html { render action: 'new' }
        format.json { render json: @teacher.errors, status: :unprocessable_entity }

      end

    end

    end

_form.html.erb

  <%= form_for(@teacher,:html => { class: 'login-form' })  do |f| %>

    <%= f.fields_for :subject do |n| %>
                <%= n.select(@subject, @subjects.map{|p| [p.name, p.id]}) %>
                <% end %>
    ...
<% form %>


resources :teachers do
    resources :subjects
end

Upvotes: 0

Views: 681

Answers (2)

Bachan Smruty
Bachan Smruty

Reputation: 5734

In the view, _form.html.erb, replace the select_tag 

<%= select_tag "subject_id", options_from_collection_for_select(@subjects, "id", "name") %>

And in the controller code,

def create
  @subject = Subject.where(id: params[:subject_id]).first

  if @subject.present?
    #YOUR CODE GOES HERE.
  else
    render 'new' # OR render to the action where your teacher form resides
  end
end

Upvotes: 0

Rajdeep Singh
Rajdeep Singh

Reputation: 17834

Do this instead

def create
  @subject = Subject.where("id =?", params[:subject_id]).first
  unless @subject.blank?
    @teacher = Teacher.new(teacher_params)
    ......
    ......
  else
    # set flash message and redirect
  end
end

Upvotes: 1

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