Continue: Ruby on Rails simple to understand

A. Then continue on a

1. The length of the limitation Twitter

This limitation in Rails achieve very simple to use verification (Validation) function. To limit the microblogging length of up to 140 characters

. (1) open file: app / models / micropost.rb

class Micropost < ApplicationRecord

  validates :content, length: {maximum: 140}

end

Note: The specific meaning of this sentence Talk to you later, anyway, guess can guess

. (2) Then, to see the effect of:

2. association (a user has many articles Weibo, a microblogging belong to a user)

. (1) open file: app / models / user.rb

class User < ApplicationRecord
  has_many :microposts
end

. (2) Open the file: app / models / micropost.rb

class Micropost < ApplicationRecord
  belongs_to :user
  validates :content, length: {maximum: 140}
end

connection relation:

(3). Interspersed knowledge points, remember! ! Knowledge points! ! !

Printing a first user console corresponding Twitter

# Explain 
rails console: Open the rails console output 
exit: exit the console 
Note: Middle What do you mean, guess yourself

3. Restrictions field can not be empty

. (1) open file: app / models / user.rb

class User < ApplicationRecord
  has_many :microposts
  validates :name, presence: true
  validates :email, presence: true
end

. (2) Open the file: app / models / micropost.rb

class Micropost < ApplicationRecord
  belongs_to :user
  validates :content, length: {maximum: 140}, presence: true
end

Note: try their own

4. A quick look at the inheritance hierarchy Ruby

(1) .User classes and class Mcropost

# Inheritance User class: 
class User < ApplicationRecord 
... 
End 

# inheritance Mcropost class: 
class micropost < ApplicationRecord 
... 
End

NOTE: It can be seen, User, and Micropost ApplicationRecord inherit from classes (by <symbol), and this class inherits from ActiveRecord :: Base class, which is the base class for the model provides the Active Record. This figure shows the inheritance relationship. ActiveRecord :: Base class inheritance, model objects to communicate with the database, the database columns can be seen as Ruby in the property, and so on.

(2) .UsersController classes and class MicropostsController

# UsersController class inherits 
class UsersController < ApplicationController 
... 
End 

# inherit MicropostsController class 
class MicropostsController < ApplicationController 
... 
End 

# ApplicationController class inherits 
class ApplicationController < ActionController :: Base 
... 
End

Note: the controller model inheritance structure is substantially the same. As can be seen, UsersController and MicropostsController inherit from ApplicationController. As shown in the code, ApplicationController inherits from ActionController :: Base. ActionController :: Base is the base class in Action Pack Rails library provided by the controller.

。。。

Simple to understand, it is over, the next formal learning