How to load a selection list into the method new of a controller?

Hi friends!
I’m relatively new with Rails and I’m struggling for a long time with this problem (it should have a pattern solution but until now I didn’t find it): I have the following models: Institution, City, State and Country.

class Country < ActiveRecord::Base
has_many :states
has_many :cities, :through => :states
end

== Schema Information

Table name: countries

id :integer not null, primary key

sigla :string(2) not null

nome :string(30) not null

class State < ActiveRecord::Base
has_many :cities
has_many :institutions, :through => :cities
belongs_to :country
end

== Schema Information

Table name: states

id :integer not null, primary key

country_id :integer not null

sigla :string(2) not null

nome :string(40) not null

class City < ActiveRecord::Base
has_many :institutions
belongs_to :country
belongs_to :state
end

== Schema Information

Table name: cities

id :integer not null, primary key

country_id :integer not null

state_id :integer not null

nome :string(40) not null

class Institution < ActiveRecord::Base
belongs_to :city
end

== Schema Information

Table name: institutions

id :integer not null, primary key

city_id :integer

The table states is pre-loaded with all Brazil’s states (seed):

State.create!(country_id: Country.find(:first, conditions: “sigla = ‘ZZ’”).id, nome: ‘desconhecido’, sigla: ‘ZZ’)
State.create!(country_id: Country.find(:first, conditions: “sigla = ‘BR’”).id, nome: ‘Distrito Federal’, sigla: ‘DF’)
State.create!(country_id: Country.find(:first, conditions: “sigla = ‘BR’”).id, nome: ‘Acre’, sigla: ‘AC’) … and so on…
City.create!(country_id: Country.find(:first, conditions: “sigla = ‘BR’”).id,
state_id: State.find(:first, conditions: “nome = ‘desconhecido’”).id,
nome: ‘desconhecida’)
City.create!(country_id: Country.find(:first, conditions: “sigla = ‘BR’”).id,
state_id: State.find(:first, conditions: “nome = ‘Paraná’”).id,
nome: ‘Cianorte’)
City.create!(country_id: Country.find(:first, conditions: “sigla = ‘BR’”).id,
state_id: State.find(:first, conditions: “nome = ‘São Paulo’”).id,
nome: ‘Campinas’) … and so on…

When I create a new institution, I have to select a city from a drop-down list. But I need to constrain this list with the state the cities belong to. So I tried this way:

routes.rb:
Application.routes.draw do
get “states/index”
resources :institutions do
post ‘selstate’
end
resources :cities
resources :states, only: :index

rake routes:
states_index GET /states/index(.:format) states#index
institution_selstate POST /institutions/:institution_id/selstate(.:format) institutions#selstate
institutions GET /institutions(.:format) institutions#index
POST /institutions(.:format) institutions#create
new_institution GET /institutions/new(.:format) institutions#new

Institution new template:
<%= form_for(@institution) do |f| %>

Cidade onde se localiza a instituição
Estado selecionado: <%= @estado_selecionado %> <%= link_to "Selecionar estado...", states_path %>
<%= f.label :cidade %> <%= f.collection_select :city_id, @cities, :id, :nome, include_blank: true %> (to be included later)
<% end %>

State index template:

Selecione um estado

<% @states.each do |s| %> <% end %>
<%= s.sigla %> <%= s.nome %> <%= button_to 'Selecionar', institution_selstate_path( s ) %>

class StatesController < ApplicationController
def index
@states = State.where(‘nome != ?’, ‘desconhecido’).order(:nome)
end

class InstitutionsController < ApplicationController
def new
@institution = Institution.new
if session[:state_id].nil?
session[:state_id] = State.find_by_sigla(‘ZZ’).id
end
@estado_selecionado = State.find(session[:state_id]).nome
if @estado_selecionado == ‘desconhecido’
@cities = City.all
else
@cities = City.where(‘state_id = ?’, session[:state_id]).order(:nome)
end
respond_to do |format| …
end
end

def create
@institution = Institution.new(params[:institution])
respond_to do |format|
if @institution.save
end

def selstate
session[:state_id] = params[:id]
redirect_to new_institution_path
end
end

As you can see, after select the state, I return to the Institution new action. My hope was to have a state selected and the cities list constrained to those pertaining to that state. But nothing happens. I receive the same screen before the state selection. I have many similar situations in my system… all waiting for this solution :slight_smile: .
Is my approach correct?
Any help will be very appreciated. Sorry my bad english!
Thanks in advance!

Luis

Hi friends!
I'm relatively new with Rails and I'm struggling for a long time with this
problem (it should have a pattern solution but until now I didn't find it):
I have the following models: Institution, City, State and Country.

class Country < ActiveRecord::Base
has_many :states
has_many :cities, :through => :states
end
# == Schema Information
# Table name: countries
# id :integer not null, primary key
# sigla :string(2) not null
# nome :string(30) not null

class State < ActiveRecord::Base
has_many :cities
has_many :institutions, :through => :cities
belongs_to :country
end
# == Schema Information
# Table name: states
# id :integer not null, primary key
# country_id :integer not null
# sigla :string(2) not null
# nome :string(40) not null

class City < ActiveRecord::Base
has_many :institutions
belongs_to :country

That is not right, a cities country is accessible through the state
via @city.state.country.

belongs_to :state
end
# == Schema Information
# Table name: cities
# id :integer not null, primary key
# country_id :integer not null

Above is not needed.

I have not even read the rest, you have provided much too much
information. If you still have a problem then simplify it down to to
the smallest amount of code that demonstrates it and post that.

Colin

Thank you for your fast reply!
Yes, I agree it isn’t necessary to put a direct relation to country inside the city model. But I did it because sometimes the user will not know to which state a new city belongs to, and at least he will know the country.

Luis

Thank you for your fast reply!
Yes, I agree it isn't necessary to put a direct relation to country inside
the city model. But I did it because sometimes the user will not know to
which state a new city belongs to, and at least he will know the country.

With it in you could get into a situation where @city.country is not
the same as @city.state.country. Also note that @country.cities will
only include those accessed via state.

Please don't top post, it makes it difficult to follow the thread.
Insert you reply at appropriate points in the previous message.
Thanks.

Colin

Hmmmm, I didn’t think in this situation… you are right. I will exclude country_id from de city model.
Well. Filtering my models to simplify the explanation of my problem, I end up with these:

class State < ActiveRecord::Base
has_many :cities
has_many :institutions, :through => :cities
belongs_to :country
end

class City < ActiveRecord::Base
has_many :institutions
belongs_to :state
end

class Institution < ActiveRecord::Base
belongs_to :city
end

The table states is pre-loaded with all Brazil’s states (seed):

State.create!(country_id: Country.find(:first, conditions: “sigla = ‘ZZ’”).id, nome: ‘desconhecido’, sigla: ‘ZZ’)
State.create!(country_id: Country.find(:first, conditions: “sigla = ‘BR’”).id, nome: ‘Distrito Federal’, sigla: ‘DF’)
State.create!(country_id: Country.find(:first, conditions: “sigla = ‘BR’”).id, nome: ‘Acre’, sigla: ‘AC’) … and so on…
City.create!(state_id: State.find(:first, conditions: “nome = ‘desconhecido’”).id, nome: ‘desconhecida’)
City.create!(state_id: State.find(:first, conditions: “nome = ‘Paraná’”).id, nome: ‘Cianorte’)
City.create!(state_id: State.find(:first, conditions: “nome = ‘São Paulo’”).id, nome: ‘Campinas’) … and so on…

When I create a new institution, I have to select a city from a drop-down list. But I need to constrain this list with the state the cities belong to. So I tried this way:

routes.rb:
Application.routes.draw do
get ‘states/index’
resources :institutions do
post ‘selstate’
end
resources :cities

rake routes:
states_index GET /states/index(.:format)
states#index
institution_selstate POST /institutions/:institution_id/selstate(.:format) institutions#selstate
institutions GET /institutions(.:format) institutions#index
POST /institutions(.:format) institutions#create
new_institution GET /institutions/new(.:format) institutions#new

Institution new template:
<%= form_for(@institution) do |f| %>


Estado selecionado: <%= @estado_selecionado %>
<%= link_to “Selecionar estado…”, states_path %>

<%= f.label :cidade %>
<%= f.collection_select :city_id, @cities, :id, :nome, include_blank: true %>

<% end %>

State index template:

Selecione um estado

<% @states.each do |s| %> <% end %>
<%= s.sigla %> <%= s.nome %> <%= button_to 'Selecionar', institution_selstate_path( s ) %>

class StatesController < ApplicationController
def index
@states = State.all
end

class InstitutionsController < ApplicationController
def new
@institution = Institution.new
if session[:state_id].nil?
session[:state_id] = State.find_by_sigla(‘ZZ’).id
end
@estado_selecionado = State.find(session[:state_id]).nome
if @estado_selecionado == ‘desconhecido’
@cities = City.all
else
@cities = City.where(‘state_id = ?’, session[:state_id]).order(:nome)
end
respond_to do |format| …
end
end

def create
@institution = Institution.new(params[:institution])
respond_to do |format|
if @institution.save
end

def selstate
session[:state_id] = params[:id]
redirect_to new_institution_path
end
end

As
you can see, after select the state, I return to the Institution new action. My hope was to have a state selected and the cities list constrained to those pertaining to that state. But nothing happens. I receive the same screen before the state selection. Is my approach correct?

Thanks!
Luis