ActiveRecord 范围需要一个 Callable 对象。
在 Rails 4 中，所有 ActiveRecord 范围必须使用一个 callable 对象来定义：
#Rails 3.2
scope :recent, where(created_at: Time.now - 2.weeks)
#Rails 4
scope :recent, -> { where("created_at > ?", Time.now - 2.weeks).order("created_at desc") }
scope :active, -> { where(status: 'active') }
Activerecord-deprecated-finders 是 Rails 4.0 中默认提供废弃功能的依赖包，但它也将在 4.1 版本中被删除。因此你需要密切关注所有的警告信息，并开始修复这些警告。
Rails 指南 提供一个很有用的解释，关于在大多数情况下如何修改动态查找器：
所有动态的方法除了 findby… 和 findby…! 外都已废弃，你可以使用如下的替代方法：
find_all_by_...改为 where(...).
find_last_by_...改为 where(...).last.
scoped_by_...改为 where(...).
find_or_initialize_by_...改为 where(...).first_or_initialize.
find_or_create_by_...改为 find_or_create_by(...) 或者 where(...).first_or_create.
find_or_create_by_...!改为 find_or_create_by!(...) 或者 where(...).first_or_create!.
#1 Caching with Instance Variables
@current_user ||= User.find(session[:user_id])
#2 Dynamic find_by Methods
@tasks = Task.find(:all, :conditions => ['complete = ?', false]) => @tasks = Task.find_all_by_complete(false) @task = Task.find(:first, :conditions => ['complete =?', false], :order => 'created_at DESC') => @task = Task.find_by_complete(false, :order => 'created_at DESC')
#3 Find Through Association
from @tasks = Task.find(:all, :conditions => ['project_id = ? AND complete = ?', @project.id, false]) to (推荐使用，用association 进行关联) @project = Project.find(params[:id]) @tasks = Task.find(:all, :conditions => ['project_id = ? AND complete = ?', @project.id, false])
#4 Move Find into Model
Move a find into the model to clean up the controllers and remove duplication.
将 find 转移到model中，清洁controllers
from
class TaskController < ApplicationController
def index
@tasks = Task.find_all_by_complete(:false, :order => "created_at DESC")
end
end
to
class Task < ActiveRecord::Base
belongs_to :project
def self.find_incomplete
find_all_by_complete(:false, :order => "created_at DESC")
end
end
#5 Using with_scope
class Task < ActiveRecord::Base
belongs_to :project
def self.find_incomplete(options = {})
with_scope :find => options do
find_all_by_complete(false, :order => 'created_at DESC')
end
end
end
@tasks = @project.tasks.find_incomplete :limit => 20
#6 Shortcut Blocks with Symbol to_proc
projects.collect { |p| p.name } => ["Write another ASCIIcast", "Go out walking"]
projects.collect {&:name} => ["Write another ASCIIcast", "Go out walking"]
projects.collect(&:name).collect(&:upcase) => ["WRITE ANOTHER ASCIICAST", "GO OUT WALKING"]
projects.each {|project| project.save!}
==
projects.each(&:save!)
#16: Virtual Attributes (revised)
简介：对原生的attributes(collums)，进行逻辑封装
schema.rb
create_table "products", :force => true do |t|
t.string "name"
t.integer "price_in_cents"
t.datetime "released_at"
... ...
end
1、转换 {price_in_cents => price_in_dollars}
<%= f.label :price_in_dollars %>
<%= f.text_field :price_in_dollars %>
attr_accessible :name, :price_in_dollars
def price_in_dollars
price_in_cents.to_d/100 if price_in_cents
end
def price_in_dollars=(dollars)
self.price_in_cents = dollars.to_d*100 if dollars.present?
end
2、对 released_at 进行逻辑封装 {release_at => relese_at_text}
attr_writer :released_at_text
validate :check_released_at_text
before_save :save_released_at_text
def released_at_text
@released_at_text || released_at.try(:strftime, "%Y-%m-%d %H:%M:%S")
end
def save_released_at_text
self.released_at = Time.zone.parse(@released_at_text) if @released_at_text.present?
end
def check_released_at_text
if @released_at_text.present? && Time.zone.parse(@released_at_text).nil?
errors.add :released_at_text, "cannot be parsed"
end
rescue ArgumentError
errors.add :released_at_text, "is out of range"
end
3、支持创建新的 category
<%= f.label :category_id %>
<%= f.collection_select :category_id, Category.order(:name), :id, :name %>
or create one:<%= f.text_field :new_category %>
attr_accessible :new_category
attr_accessor :new_category
before_save :create_category #在保存 product 前，先前所依赖的 category创建出来
def create_category
self.category = Category.create!(name: new_category) if new_category.present?
end
#17、habtm-checkboxs
典型的多对多的关系 ，且使用关联表Categorization class Product < ActiveRecord::Base has_many :categorizations has_many :categories, through: :categorizations end class Categorization < ActiveRecord::Base belongs_to :category belongs_to :product end class Category < ActiveRecord::Base has_many :categorizations has_many :products, through: :categorizations end rails consle分析 p=produc.first => select "products".* from "products" limit 1 p.category_ids => select categories.id from categories inner join categorizations on categories.id=categorization.category_id where categorizations.product_id=1 p.category_ids=[1,2] => 1、select * from categories where id IN (1,2) 2、select * from categories inner join categorizations on categoris.category_id=categorization.category_id where categorizations.product_id=1 3、insert into categorizations ... values category_id=1,product_id=1 4、insert into categorizations ... values category_id=2,product_id=1 p.categories =>[#,# ] _form.html.erb <%= hidden_field_tag "product[category_ids][]", nil %> <% Category.all.each do |category| %> <%= check_box_tag "product[category_ids][]", category.id, @product.category_ids.include?(category.id), id: dom_id(category) %> <%= label_tag dom_id(category), category.name %> <% end %>