Controllers handle web requests from users and interact with views and models. Views display templates filled with application data and convert it to HTML. Models represent and wrap application data stored in the database. Helpers assist models, views, and controllers. Common Rails methods include link_to for creating links and migrations for modifying the database schema by adding, removing, or changing columns.

1. Architecture Rails:
Controllers: Rails look to find controllers classes. A controllers handles a web request from user.
Views: Holds the display templates to fill in with data from our application, convert to HTML, and
return to the user's browser.
Models: Holds the classes that model and wrap the data stored in our application's database.
Helpers: Holds any helper classes used to assist the model, view, and controllers classes
Methods:
link_to → creates a hyperlink to an action
example: <%= link_to "Hello", say_hello_path %>
Marshaling Objects: Take an object and convert it into a stream of bytes that can be stored outside the
app.
rails generate migration add_columnname_to_tablename columnname:datatype
example: rails generate migration add_password_to_users password:string
Problem Solve Take-note
Get URL parameter path = request.fullpath
path_search = URI.parse(path)
parse_url = CGI.parse(path_search.query)
array_facility_choose = parse_url['search[facilities][]']#params['search']['facilities']
name_facility = Array.new # content all name of facility choose
search[prefecture]=&search[departments][]=3&search[facilities][]=2
To create a model
that references
another, use the
rails model
generator:
$ rails g model wheel car:references
class Wheel < ActiveRecord::Base
belongs_to :car
end
class CreateWheels < ActiveRecord::Migration

2. def self.up
create_table :wheels do |t|
t.references :car
t.timestamps
end
end
ActiveRecord Products.connection.execute('UPDATE `products` SET `price`=`free` WHERE 1') If the helpers not enough
Rename column script/generate migration rename_my_column_by_hand
Then edit the file it creates:
class RenameMyColumnByHand <
ActiveRecord::Migration
def self.up
rename_column :my_table, :old_name, :new_name
end
def self.down
rename_column :my_table, :new_name, :old_name
end
end
It executes SQL like:
ALTER TABLE my_table CHANGE old_name new_name
BIGINT;
Change type of
column
class AddColumnToTable < ActiveRecord::Migration
def change
add_column :table, :column, :type
end
end
Rails g migration changetypecolumn
Add column rails generate migration add_password_to_users password:string rails generate migration add_columnname_to_tablename

3. columnname:datatype