本文旨在记录常用的rails相关的命令
Concepts
Model Layer: 这一层由业务模型类组成。在Rails中有两种类型。1. 是继承自ActiveRecord::Base。2. 实现了ActiveModel中相应接口的普通ruby类。
Controller Layer: 这一层主要用来处理http请求。在Rails中由ActionDispatch和ActionController组成。
View Layer: ActionView通过模板生成各种资源。
Basic Startup
初始化项目以及基本使用。
# Initialize a proejct
rails new demo
cd demo
rake about # try to see if everything is OK
rails server # start web server
Rails Generate
代码生成
rails generate controller Say hello goodbye
rails g scaffold Product title:string # generate module/action/view for Product, upper case seems not of usage
rails g migration add_quantity_to_line_items quantity:integer # name of the migration will help rails to guess what's your meanning
rails g model payment_type name:string # generate model
rails destroy model Oops # opposite of generate
Debug
rails console
rails dbconsole
rails runner script/load_orders.rb
prd = Product.new
prd.save # => false
prd.errors.full_messages # => view error message
Database Console
mysqld --verbose --help # lookup mysql configuration
sqlite3 -line db/development.md
Rake - Ruby Make
rake -T doc # view document related task
rake --describe task # get detail description of a task
rake --tasks # list available task for this project
rake db:create # create the database by database.yml
rake db:migrate # make schema change
rake db:rollback # revert schema change
rake db:seed # load data defined in db/seeds.rb
rake db:migrate:status # track status of migrate
rake assets:clean # remove compiled assets
rake assets:precompile # compile all assets
rake doc:app # generates documentation
Action Model
Attribute Magic
class Person
include ActiveModel::AttributeMethods
attribute_method_prefix 'clear_'
define_attribute_methods :name, :age
attr_accessor :name, :age
def clear_attribute(attr)
send("#{attr}=", nil)
end
end
person = Person.new
person.clear_name
person.clear_age
Callbacks
class Person
extend ActiveModel::Callbacks
define_model_callbacks :create
def create
run_callbacks :create do
# Your create action methods here
end
end
end
Tracking value changes
class Person
include ActiveModel::Dirty
define_attribute_methods :name
def name
@name
end
def name=(val)
name_will_change! unless val == @name
@name = val
end
def save
# do persistence work
changes_applied
end
end
person = Person.new
person.name # => nil
person.changed? # => false
person.name = 'bob'
person.changed? # => true
person.changed # => ['name']
person.changes # => { 'name' => [nil, 'bob'] }
person.save
person.name = 'robert'
person.save
person.previous_changes # => {'name' => ['bob, 'robert']}
Adding Errors Inteface to Objects
class Person
def initialize
@errors = ActiveModel::Errors.new(self)
end
attr_accessor :name
attr_reader :errors
def validate!
errors.add(:name, "cannot be nil") if name.nil?
end
def self.human_attribute_name(attr, options = {})
"Name"
end
end
person = Person.new
person.name = nil
person.validate!
person.errors.full_messages
# => ["Name cannot be nil"]
Model name introspection
class NamedPerson
extend ActiveModel::Naming
end
NamedPerson.model_name # => "NamedPerson"
NamedPerson.model_name.human # => "Named person"
making objects serializable
class SerialPerson
include ActiveModel::Serialization
attr_accessor :name
def attributes
{'name' => name}
end
end
s = SerialPerson.new
s.serializable_hash # => {"name"=>nil}
class SerialPerson
include ActiveModel::Serializers::JSON
end
s = SerialPerson.new
s.to_json # => "{\"name\":null}"
class SerialPerson
include ActiveModel::Serializers::Xml
end
s = SerialPerson.new
s.to_xml # =>
I18n support
class Person
extend ActiveModel::Translation
end
Person.human_attribute_name('my_attribute')
# => "My attribute"
Validation
class Person
include ActiveModel::Validations
attr_accessor :first_name, :last_name
validates_each :first_name, :last_name do |record, attr, value|
record.errors.add attr, 'starts with z.' if value.to_s[0] == ?z
end
end
person = Person.new
person.first_name = 'zoolander'
person.valid? # => false
Custom Validators
class HasNameValidator < ActiveModel::Validator
def validate(record)
record.errors[:name] = "must exist" if record.name.blank?
end
end
class ValidatorPerson
include ActiveModel::Validations
validates_with HasNameValidator
attr_accessor :name
end
p = ValidatorPerson.new
p.valid? # => false
p.errors.full_messages # => ["Name must exist"]
p.name = "Bob"
p.valid? # => true
ActionRecord
Validation
class Product < ActiveRecord::Base
validates :title, presence: true
validates :terms, acceptance: true
validates :password, confirmation: true
validates :username, exclusion: { in: %w(admin superuser) }
validates :email, format: { with: /\A([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})\Z/i, on: :create }
validates :age, inclusion: { in: 0..9 }
validates :first_name, length: { maximum: 30, message: 'must be less than 30' }
validates :age, numericality: true
validates :username, presence: true
validates :username, uniqueness: true
end
Associations
class Firm < ActiveRecord::Base
has_many :clients
has_one :account
belongs_to :conglomerate
end
How to add connection table in rails
Table LineItem is connection table for product and cart.
rails generate scaffold LineItem product:references cart:belongs_to
class LineItem < ActiveRecord::Base
belongs_to :product
belongs_to :cart
end
To add method for reverse finding from Cart we should modify Cart's model
ruby
class Cart < ActiveRecord::Base
has_many :line_items, dependent: :destroy
end
Aggregations of value objects
值对象的关联。
class Account < ActiveRecord::Base
composed_of :balance, class_name: 'Money',
mapping: %w(balance amount)
composed_of :address,
mapping: [%w(address_street street), %w(address_city city)]
end
Transactions
# Database transaction
Account.transaction do
david.withdrawal(100)
mary.deposit(100)
end
Create Records
an_order = Order.new
an_order.name = "Dave Thomas"
an_order.save
Order.new do |do|
o.name = "Dave"
o.save
end
anOrder = Order.new(
name: "Mike")
anOrder.save
anOrder = Order.create(name: "Jason", email: "x@qad.com")
Attribute Query Method
user = User.new(name: "David")
user.name? # => true
anonymous = User.new(name: "")
anonymous.name? # => false
Find Records/Where Clauses
使用Where Clause，find_by等函数，保持查找函数的统一性。
Book.where(author: 'Albert Yu')
Book.find_all_by_title('Rails 4') # r3 way
Book.find_last_by_author('Albert Yu') # r3 way
Book.where(title: 'Rails 4') # r4 way
Book.where(author: 'Albert Yu').last # r4 way
Book.find_by_title('Rails 4') # 接收单个参数的用法在 r3 & r4 都可以
Book.find_by(title: 'Rails4') # 不过 r4 更偏爱这样写
Book.find_by_title('Rails 4', conditions: { author: 'Albert Yu' }) # 这就不好了，得改
Book.find_by(title: 'Rails4', author: 'Albert Yu') # Wow! 太棒了！
# 容易使人迷惑的用法
Book.where(title: 'Rails 4').first_or_create
# 若找不到…
Book.where(title: 'Rails 4').create
Where Clause的详细用法
name = params[:name]
pos = Order.where(["name = ? and pay_type = 'po'", name])
name = params[:name]
pay_type = params[:pay_type]
pos = Order.where("name = :name and pay_type = :pay_type",
pay_type: pay_type, name: name)
pos = Order.where("name = :name and pay_type = :pay_type",
params[:order])
pos = Order.where(params[:order])
pos = Order.where(name: params[:name],
pay_type: params[:pay_type])
# Doesn't work
User.where("name like '?%'", params[:name])
# Works
User.where("name like ?", params[:name]+"%")
Subsetting the Records found
# The view wants to display orders grouped into pages,
# where each page shows page_size orders at a time.
# This method returns the orders on page page_num (starting
# at zero).
def Order.find_on_page(page_num, page_size)
order(:id).limit(page_size).offset(page_num*page_size)
end
orders = Order.where(name: 'Dave').
order("pay_type, shipped_at DESC").
limit(10)
Lock of Active Record
Account.transaction do
ac = Account.where(id: id).lock("LOCK IN SHARE MODE").first
ac.balance -= amount if ac.balance > amount
ac.save
end
Statics of Result
average = Order.average(:amount) # average amount of orders
max = Order.maximum(:amount)
min = Order.minimum(:amount)
total = Order.sum(:amount)
number = Order.count
Scopes : to reuse simple data.
class Order < ActiveRecord::Base
scope :last_n_days, lambda { |days| where('updated < ?' , days) }
scope :checks, -> { where(pay_type: :check) }
end
orders = Order.last_n_days(7)
orders = Order.checks.last_n_days(7)
Update on ActiveRecord
# fetch and update record, id is used as first parameter
order = Order.update(12, name: "Barney", email: "barney@bedrock.com")
# where clause is the second parameter
# return result depends on database adapter
result = Product.update_all("price = 1.1*price", "title like '%Java%'")
Delete Rows
# delete method bypass the validation and ActiveRecord callback
Order.delete(123)
User.delete([2,3,4,5])
# when no condition is given, all rows are deleted.
Product.delete_all(["price > ?", @expensive_price])
Active Record Callback
class Order < ActiveRecord::Base
before_validation :normalize_credit_card_number
after_create do |order|
logger.info "Order #{order.id} created"
end
protected
def normalize_credit_card_number
# Notice we have to use self. since this is class method???/
self.cc_number.gsub!(/[-\s]/, '')
end
end
Serialized Object to Database
class User < ActiveRecord::Base
serialize :preferences
end
user = User.create(preferences: { "background" => "black", "display" => large })
User.find(user.id).preferences # => { "background" => "black", "display" => large }
Apply Migration
Rails defines a TableDefinition class to describe the schema. It could be init like below: (p.64)
create_table :product do |t|
t.text :title, limit: 50,
t.decimal :price, precision:8, scale:2
end
Add Test Data
Make full use of seeds.rb to add test data. Notice ActiveRecord::Base#Create and ActiveRecord::Base#Create! are differenct. The second one will raise an exception if the record is invalid. (p. 69)
Action View
Basic Helper Functions
<%= link_to "Goodbye", say_goodbye_path %>!
<%= link_to "Destroy', product, method: :delete, data: { confirm: 'Are you sure?' } %>
<tr class = "<%= cycle('list_line_odd', 'list_line_even') %>" >
Using link_to method in program
Need more knowledge on url routine (p7x)
Modify Unit Test
Not known about products(:one) (p. 81)
Resize image with image_tag
we could pass size as option size: '30x30'
Cache in ruby
Rails 4 supports key based cache which could be referenced here (p.104) We have following steps to enable cache in rails 1. set enable in config 2. change view (*.erb) for fragments that needs to cache 3. set storage method for cache
Dependency for controller code in rails
The following code could run in rails, so what is in the running environment. How could the ActiveSupport, ActiveRecord and Cart be found? We could also pay attention to the private mark. This would prevent rails to treat the set_cart method as controller method.
Answers:
1. modules in app/controllers/concern/ could be accessed in all controllers
module CurrentCart
extend ActiveSupport::Concern
private
def set_cart
@cart = Cart.find(session[:cart_id])
rescue ActiveRecord::RecordNotFound
@cart = Cart.create
session[:cart_id] = @cart
end
end
How to choose Get/Post methods
links_to method will generate Http Get method. button_to will generate POST method.
Parameters of method in ActionPack
There are always kind of function has the following signature (name = nil, options = nil, html_options = nil, &block). I cann't see there is a need for such parameters.
Passing objects between controllers
params is used to pass values between controllers.
Error when using session
cookieOverflow exception throws when add item to cart. By searching the web, it is because session data is too large to store by cookie. Change it to use database to store the value. A new gem activerecord-session_store is introduced.
Q: I still don't know there is the document for 'cookieOverflow'. Not in the api doc.
++ operator is not support in Ruby
activerecord#destroy will trigger callback, however activerecord#delete won't.
Flash in rails
Flash is hash-like object, which could pass information to following requests.
Test in Rails
assertequal, assertnot_equal, assert_select usage for controller auto testing
Ruby js
ruby js may generate code with not exists node, in this time, it will be ignored.
Run ruby scripts under rails
Order.transaction do
(1..100) do |i|
Order.create (...)
end
end
rails runner script/load_orders.rb
Rails send email
rails generate mailer Notifier order_received order_shipped
# create app/mailers/notifier.rb
# create ap/views/notifier/order_received.text.erb
# create ap/views/notifier/order_shipped.text.erb
# create test/functional/notifier_test.rb
Notifer.order_received(@order).deliver
Rails integration test
rails g integration_test user_stories
# create test/integration/user_stories_test.rb
Deploy ruby program on environment
apache used as front-server to process http request, and passenger will dispatch ruby reqest to rails processes.
CRUD With ActiveRecord
Action Pack
Action Dispatch helps to find controller and method for processing request. There are two ways to defined the routes, pre-defined and self-defined.
Depot::Application.routes.draw do
# pre-defined,
# This assumes there is a controller named 'ProductController' and several methods with given names
resources :products
resources :comments, except: [:update, :destroy] # update, destroy is not in need.
# sef-defined
resources :products do
get :who_bought, on: :member # :collection ~
end
end
We could use rake routes to review the generated routes.
Notes: 'GET /products(.:format) products#index' the /products(.:format) stands for '/product/1.html` or '/product/1.xml'
There are 7 methods that rails generate for us. index,create,new,show,destroy,edit,update
Diff: create and new, create receives a bunch of attributes from POST request and create a new source and save it. new method is only create a empty resource used to gather inputs from client, resource is not saved. It is like initialized method in Base Module
edit and update, edit returns the content of a resource identified by params[:id], update will update the resource by params[:id] with data associated with request.
We could fire a request on client by ruby methods
<% link_to 'Show', product %>
# link_to generate a HTTP GET by default, so need to specify using DELETE instead.
<% link_to 'Destroy', product, method: :delete %>
Rails uses one controller method to handle all types of output(xml/json/html). This may increase difficulty for error handling.
Q&A
- Where to find the document for phantom method, since they are created dynamically? e.g. find*
- Rails method has return type, however it is hard to find them.
- Help function
content_tagis no use in my sample - Duplicate item is added when click image.
- How to create class method like before_validate, it could use a class instance as parameter, which method it knows to call.
- It is not safe to store primary key in the url. The default route of rails needs to changed? p309
- In RESTful design, the server only works on CRUD of resources. Is there any concern about the validation?? p310
- Nested routes will provide all resource information on the full path? p318
- Error handling when user specify illegal URI.
http://192.168.33.15:3000/products/1/who_bought.sfas - What is a permanent/temporary redirect? what's the differences?
- How we could build a custom program avoid using ActionPack
- How to deploy with passenger? There is no content under public directory. p237.