I am getting the following error message on the view : http://localhost:3000/microposts/2 SQLite3::SQLException: no such column: answers.micropost_id: SELECT "answers".* FROM "answers" WHERE ("answers".micropost_id = 2)

Here are my migrations:

| db > migration > create micropost |

class CreateMicroposts < ActiveRecord::Migration
  def self.up
    create_table :microposts do |t|
      t.string :content

      t.timestamps
    end
  end

  def self.down
    drop_table :microposts
  end
end

| db > migration > create answer |

class CreateAnswers < ActiveRecord::Migration
  def self.up
    create_table :answers do |t|
      t.string :location
      t.text :body
      t.references :micropost
      t.integer :micropost_id

      t.timestamps
    end

  end

  def self.down
    drop_table :answers
  end
end

The Answer Controler :

def create

    @answer = Answer.new(params[:answer])
    @answer.micropost = @micropost; @answer.save && @micropost.save


    redirect_to micropost_path(@micropost)




    respond_to do |format|
      if @answer.save
        format.html { redirect_to(@answer, :notice => 'Answer was successfully created.') }
        format.xml  { render :xml => @answer, :status => :created, :location => @answer }
      else
        format.html { render :action => "new" }
        for开发者_运维百科mat.xml  { render :xml => @answer.errors, :status => :unprocessable_entity }
      end
    end
  end

and the View:

<p id="notice"><%= notice %></p>

<p>
  <b>Content:</b>
  <%= @micropost.content %>
  <h2>Location Answers:</h2>
  <% @micropost.answers.each do |answer| %>

    <p>
      <b>Answer:</b>
      <%= answer.body%>
    </p>
    <%end %>

  <h2> Answer a location:</h2>
  <%= form_for ([@micropost, @micropost.answers.build]) do |f| %>
    <div class="field">
      <%= f.label :location %><br />
      <%= f.text_field :location %>
    </div>
    <div class="field">
      <%= f.label :body %><br/>
      <%= f.text_area :body %>
    </div>
    <div class="actions">
      <%= f.submit %>
    </div>
    <% end %>

</p>

<%= link_to 'Edit', edit_micropost_path(@micropost) %> |
<%= link_to 'Back', microposts_path %>

I cannot find what's wrong in this application. - I tried to rollback and migrate again it didn't work. - I tried to manually add the "t.integer :micropost_id" in the migration it didn't work My model have the association 'belongs_to" and "has_many" and I added " resources :microposts do resources :answers end to my config.rb file.

I believe the has_many association requires a relationship table to join against. If you had has_one and belongs_to (a one to one association) works with the simple _id column approach but has_many won't. So if you put this join table in and describe the has_many through it, you should get what you want.

Here's a really great guide for rails associations that I use when this stuff becomes unclear to me.

You don't need to set micropost_id in your migration. This is done by t.references

create_table :answers do |t|
  t.string :location
  t.text :body
  t.references :micropost

  t.timestamps
end

Best practice to set and index, for example:

add_index :answers, :micropost_id