Ruby on rails 从两个表中查询活动记录

我正在学习RubyonRails，我制作了一个非常简单的应用程序。 这是schema.rb：

ActiveRecord::Schema.define(version: 20160112141616) do

  create_table "cities", force: :cascade do |t|
    t.string   "name"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
    t.integer  "state_id",   null: false
  end

  add_index "cities", ["state_id"], name: "index_cities_on_state_id"

  create_table "states", force: :cascade do |t|
    t.string   "name"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
  end

end

我装载了一些州和城市。 我不知道如何使用Active Record进行这样的查询：

SELECT cities.name, states.name FROM cities INNER JOIN states ON cities.state_id = states.id

我想在视图中打印所有城市的名称和州的名称

谢谢

编辑：

model city.rb：

class City < ActiveRecord::Base
  belongs_to :states
  validates :state_id, presence: true
end

model state.rb：

class State < ActiveRecord::Base
  has_many :cities
end

城市控制器.rb：

class CitiesController < ApplicationController
  def index
    #@cities = City.all.order(state_id: :asc)
    #@cities = State.joins(:cities).select('cities.name, states.name')
    @cities = City.joins(:states).select('cities.name, states.name')
  end

  def new
    @city = City.new
    @states = State.all.order(name: :asc)
  end

  def create
    @city = City.new(city_params)
    if @city.save(:validate=> true)
      redirect_to :back
    else
      render :new
    end
  end

  def city_params
    params.require(:city).permit(:name, :state_id)
  end
end

---

下面的查询就可以了

City.joins(:states).select("cities.name, states.name")

NameError:未初始化的常量City:：State

所属对象的关联名称应为单数，因此在city.rb模型中将states更改为state

---

尝试了您的解决方案，但我遇到了以下错误：irbmain:004:0>City.joins:states.select'cities.name，states.name'NameError:uninitialized constant City:：states然后我尝试了以下操作：State.joins:cities.select'cities.name'State Load 0.1ms select cities.name，states.name FROM states internal JOIN cities ON cities.state_id=states.id=>@kofran您能在问题中发布您的模型代码吗。

class City < ActiveRecord::Base
  belongs_to :state
  validates :state_id, presence: true
end