ActiveRecord

Нистратов Артём

anistratov@go-promo.ru

rails g model Snippet title:string content:text

rails g scaffold

generator

model name

attribute name

attribute type

code = Snippet.new title: 'Test', content: 'a = :foo'

code.new_record?

code.save

code.id

code.persisted?

rails console

Create

h = {}

h = Hash.new

h[:foo] = 'bar'

h[:foo]

'bar'

h[:baz]

nil

h['key'] = 1

Hash

Snippet.new title: 'Test'

Snippet.new(title: 'Test')

params = { title: 'Test' }
Snippet.new params

Snippet.new({ title: 'Test' })

Method calls

code = Snippet.new
code.save

Snippet.create

git add -A

git commit -m "add Snippet model"

git checkout -b snippets

new branch name

git push origin snippets

server

branch

Snippet.find(1)

Snippet.where(title: 'Test').first

Snippet.select([:content])
    .where(title: 'Test')
    .order(:created_at)
    .limit(1)

Read

Snippet.limit(10).pluck(:content)

Query API

.where(is_draft: false)

.where('is_draft = ?', false)

.where('is_draft = :draft',
    draft: false)

.where("is_draft = #{params[:draft]}")

rails g model User name:string

rails g migration AddUserIdToSnippet user_id:integer

rake db:migrate

Relations

class User < ActiveRecord::Base
  has_many :snippets
end

class Snippet < ActiveRecord::Base
  belongs_to :user
end

Snippet.joins(:user)
    .where(user: { name: 'John' })
    .count

User.joins(snippets: :languages)
    .where(languages: { name: 'Ruby' })
    .take(10)

rails g model Language name:string
rails g migraion CreateSnippetsLanguages \
  snippet_id:integer language_id:integer

has_and_belongs_to_many :snippets

Update

snippet.content = 'Some information'

snippet.save

snippet.updated_at

snippet.update_attributes(title: 'Yay')

snippet.assign_attributes(content: '._.')

snippet.changed

snippet.changes

Delete

snippet.destroy

Snippet.destroy(ids)

Snppet.where(title: 'Test').destroy_all

Snippet.where(title: nil).each { |post| post.destroy }

Snippet.where(...).find_each { |code| ... }

Enumerator

[1, 2, 3].each { |i| puts i * 2 }

[1, 2, 3].each do |i|
    puts i * 2
end

array.map { |value| ... }
    .sort.reverse.with_index
    .reduce do |result, (value, index)| 
        ...
    end

second