Trying to access a join table which has no ID

I've got three tables which all join into one table. Here is the code:

class App < ActiveRecord::Base
  has_many :app_servers
  has_many :servers, :through => :app_servers
  has_many :environments, :through => :app_servers
end

class Server < ActiveRecord::Base
  has_many :app_servers
  has_many :apps, :through => :app_servers
  has_many :environments, :through => :app_servers
end

class Environment < ActiveRecord::Base
  has_many :app_servers
  has_many :apps, :through => :app_servers
  has_many :servers, :through => :app_servers
end

class AppServer < ActiveRecord::Base
  belongs_to :app
  belongs_to :server
  belongs_to :environment
end

I've already used scaffold for the App and Server model and can access them, but when I created a scaffold for AppServer and tried accessing the index page, it gives me this error:

No route matches {:action=>"show", :controller=>"app_servers", :id=>#<AppServer app_id: 3, server_id: 1, environment_id: 2>}

I believe the reason for the error is because when I created the AppServer table, I specified that :id => false.

So what I'm really trying to do, is just have the create page, which then allows me to map currently saved Servers, with currently saved Application to a specific environment. Any ideas on how I can overcome this problem?

Also, is it wrong for my join model to not have an ID, as it was originally a has_and_belongs_to_many model?

Thanks in advance

Edit Here is the index.html.erb file:

<h1>Listing app_servers</h1>

<table>
  <tr>
    <th></th>
    <th></th>
    <th></th>
  </tr>

<% @app_servers.each do |app_server| %>
  <tr>
<td><%= app_server%>开发者_如何学Python;</td>
    <td><%= link_to 'Show', app_server %></td>
    <td><%= link_to 'Edit', edit_app_server_path(app_server) %></td>
<td><%= link_to 'Destroy', app_server, :confirm => 'Are you sure?', :method => :delete %></td>
  </tr>
<% end %>
</table>

<br />

<%= link_to 'New App server', new_app_server_path %>

And also the app_servers_controller.rb file:

class AppServersController < ApplicationController
  # GET /app_servers
  # GET /app_servers.xml
  def index
    @app_servers =AppServer.all

    respond_to do |format|
      format.html # index.html.erb
      format.xml  { render :xml => @app_servers }
    end
  end

  # GET /app_servers/1
  # GET /app_servers/1.xml
  def show
    @app_server = AppServer.find(params[:id])

    respond_to do |format|
      format.html # show.html.erb
      format.xml  { render :xml => @app_server }
    end
  end

  # GET /app_servers/new
  # GET /app_servers/new.xml
  def new
    @app_server = AppServer.new

    respond_to do |format|
      format.html # new.html.erb
      format.xml  { render :xml => @app_server }
    end
  end

  # GET /app_servers/1/edit
  def edit
    @app_server = AppServer.find(params[:id])
  end

  # POST /app_servers
  # POST /app_servers.xml
  def create
    @app_server = AppServer.new(params[:app_server])

    respond_to do |format|
      if @app_server.save
        format.html { redirect_to(@app_server, :notice => 'App server was successfully     created.') }
        format.xml  { render :xml => @app_server, :status => :created, :location =>     @app_server }
      else
    format.html { render :action => "new" }
        format.xml  { render :xml => @app_server.errors, :status =>     :unprocessable_entity }
      end
    end
  end

  # PUT /app_servers/1
  # PUT /app_servers/1.xml
  def update
    @app_server = AppServer.find(params[:id])

    respond_to do |format|
      if @app_server.update_attributes(params[:app_server])
        format.html { redirect_to(@app_server, :notice => 'App server was successfully updated.') }
        format.xml  { head :ok }
      else
        format.html { render :action => "edit" }
        format.xml  { render :xml => @app_server.errors, :status => :unprocessable_entity }
      end
    end
  end

  # DELETE /app_servers/1
  # DELETE /app_servers/1.xml
  def destroy
    @app_server = AppServer.find(params[:id])
    @app_server.destroy

    respond_to do |format|
      format.html { redirect_to(app_servers_url) }
      format.xml  { head :ok }
    end
  end
end

---

Ok. The simplesst solution here is to return id back. Or you should rewrite some standart routes like

get '/app_servers/show', :to => "app_servers#show", :as => :app_server

and remove fetching by id from controllers.

I mean - return IDS back - that's easiear

UPD

Fast and dirty solution here is to add to AppServer model this small method:

def to_param
  "#{environment_it}_#{app_id}_#{server_id}"
end