ruby on rails 随记

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rails new myapp

bundle install

rails generate controller mycontroller

rails generate model mymodl

rake db:migrate   updates the database with the new messages data model

rake db:seed  seeds the database with sample data from db/seeds.rb

Ruby on Rails defines seven standard controller actions can be used to do common things such as display and modify data.

If you want to create routes for all seven actions in your app, you can add aresource route to your routes file. This resource route below maps URLs to the Messages controller's seven actions (index, show, new, create, edit,update, and destroy):

resources :messages

If you only want to create routes for specific actions, you can use :only to fine 

tune the resource route. This line maps URLs only to the Message controller'sindex and show actions.

resources :messages, only: [:index, :show]

• has_many :destinations denotes that a single Tag can have multiple Destinations.
• belongs_to :tag denotes that each Destination belongs to a single Tag.

Open the migration file in db/migrate/ for the tags table, and add the following columns:

• a string column called title
• a string column called image

Next in the migration file for the destinations table, add the following columns:

• a string column called name
• a string column called image
• a string column called description
• the line t.references :tag

def show
    @tag = Tag.find(params[:id])
    @destinations = @tag.destinations
  end

The  @destinations = @tag.destinations  retrieves all the destinations that belong to the tag, and stores them in  @destinations

 def update
    @destination = Destination.find(params[:id])
    if @destination.update_attributes(destination_params)
      redirect_to(:action => 'show', :id => @destination.id)
      else
      render "edit"
    end
  end
  
  private 
  def destination_params
  params.require(:destination).permit(:name, :description)
    end