Ruby on Rails-在我的嵌套路线（及其数据库）中正确导航的问题

Question

I'm fairly new to Ruby on Rails and am currently stuck on a problem involving my app not stepping through my two database tables the way I'd like it to, when navigating my nested routes.

My basic set-up is like this: I have a table called 'countries', and a table called 'relations'. I also have an show.html.erb page for localhost/countries/x/relations/y that is set to request and display the @country.name and the @relation.name instance variables from the two tables.

This is the problem:

-Typing localhost/countries/ 1 /relations/ 1 into my address shows me my countries table's 1st country (right now, a dummy value called 'select a country') and my relations table's 1st relation (right now, Canada). This is what I want to see in this instance. So far, so good!

-Typing localhost/countries/ 1 /relations/ 2 shows me my countries table's 2nd country (currently 'Andorra') and my relation's tables 2nd relation (currently, 'Iran'). Here we have the first mistake: though the address bar call requests 'countries/1' the request is clearly fetching the value of 'countries/2' instead.

-Typing localhost/countries/ 2 /relations/ 2 displays the exact same output as localhost/countries/1/relations/2, a second confirmation of this issue.

-As a final example, typing localhost/countries/ 4 /relations/ 3 displays each table's 3rd entries, instead of the 4th entry in the countries table, and the 3rd entry in the relations table. So we see the theme here.

So what seems to be happening here is something like this: my nested route relations is overriding the persistence of the countries value with whatever happens to be the id called for the relations values.

I can sort of guess why this is happening (the @country.name in the views/relations/show.html.erb page is likely being processed by the relations controller instead of the countries controller and is defaulting to relation's whims if I don't tell it explicitly otherwise). But I have little idea at the moment of how to fix that issue.

The RailsGuides resource Routing from the Outside In got me through a couple of my earlier issues on this broad topic but I couldn't glean the answer from it this time. Any advice on my issue?

Here's what I imagine are the relevant lines of code:

config/routes.rb
Rails.application.routes.draw do
...
...
  resources :countries do
    resources :relations
  end
end

...

app/views/relations/show.html.erb
<strong>Country:</strong>
  <%= @country.name %>
</p>

<p>
  <strong>Relation:</strong>
  <%= @relation.name %>
</p>

...

app/controllers/relations_controller.rb
class RelationsController < ApplicationController
  before_action :set_relation, only: [:show, :edit, :update, :destroy]


  def index
    @relations = Relation.all
  end


  def show
    @country = Country.find(params[:id])
  end

  def new
    @relation = Relation.new
  end
  ...
  ...

...

app/controllers/countries_controller.rb
class CountriesController < ApplicationController
  def show
    @country = Country.find(params[:id])
    @countries = Country.all
  end

  def new
    @country = Country.find(params[:id])
    @countries = Country.all
  end

end

...

app/models/country.rb
class Country < ActiveRecord::Base
  ...
  ...
  has_many :relations
end

...

app/models/relation.rb
class Relation < ActiveRecord::Base
  validates_uniqueness_of :name
  belongs_to :country
end

Thanks for any help or advice! Let me know if you have other questions.

Answer 1

With your nested route countries/1/relations/2 the two ids are assigned to different parameters. This form of the route makes that clear: countries/:country_id/relations/:id. You can see the route in this format if you rake routes .

So your relations controller needs to look something like this:

class RelationsController < ApplicationController
  before_action :set_country
  before_action :set_relation, only: [:show, :edit, :update, :destroy]

  def index
    @relations = @county.relations
  end


  def show
    # don't need anything here as set_relation already assigning @relation
  end

  def new
    @relation = @country.relations.build
  end

  ....

  private
  def set_country
    @country = Country.find(params[:country_id])
  end

  def set_relation
    @relation = @country.relations.find(params[:id])
  end
end