脚手架的使用
生成脚手架
手动生成migration,然后每个字段生成脚手架rails generate scaffold Article title:string location:string excerpt:string body:text published_at:datetime --skip-migration
数据库操作
1.生成新的记录
①使用new构造函数
>> article = Article.new
=> #<Article id: nil, title: nil, body: nil, published_at: nil, created_at: nil,
updated_at: nil, excerpt: nil, location: nil>
>> article.new_record?
=> true
>> article.attributes
=> {"body"=>nil, "created_at"=>nil, "excerpt"=>nil, "location"=>nil,
"published_at"=>nil, "title"=>nil, "updated_at"=>nil}
>> article.title = 'RailsConf'
=> "RailsConf"
>> article.body = 'RailsConf is the official gathering for Rails developers..'
=> "'RailsConf is the official gathering for Rails developers.."
>> article.published_at = '2013-04-13'
=> "2013-04-13"
>> article
=> #<Article id: nil, title: "RailsConf", body: "RailsConf is the official
gathering for Rails devel...", published_at: "2013-04-13 00:00:00",
created_at: nil, updated_at: nil, excerpt: nil, location: nil>
>> article.save
(0.1ms) begin transaction
SQL (2.2ms) INSERT INTO "articles" ("body", "created_at", "published_at",
"title", "updated_at") VALUES (?,?,?,?,?) [["body", "RailsConf is the official
gathering for Rails developers.."], ["created_at", Sat, 13 Apr 2013 15:50:29 UTC
+00:00], ["published_at", Wed, 13 Apr 2013 00:00:00 UTC +00:00], ["title",
"RailsConf"], ["updated_at", Sat, 13 Apr 2013 15:50:29 UTC +00:00]]
(2.9ms) commit transaction
=> true
>> Article.count
=> 1
>> article.new_record?
=> false
>> article = Article.new
>> article.title
= "Introduction to SQL"
>> article.body
= "SQL stands for Structured Query Language, .."
>> article.published_at
= Date.today
>> article.save
>> article = Article.new(:title => "Introduction to Active Record",
:body => "Active Record is Rails's default ORM..", :published_at => Date.today)
>> article.save
②使用create方法
>> Article.create(:title => "RubyConf 2013", :body => "The annual RubyConf will
take place in..", :published_at => '2013-04-13')
=> #<Article id: 4, title: "RubyConf 2013", body: "The annual RubyConf will take
place in..", published_at: "2013-04-13 00:00:00", created_at: "2013-04-13
23:17:19", updated_at: "2013-04-13 23:17:19", excerpt: nil, location: nil>
>> attributes = { :title => "Rails Pub Nite", :body
=> "Rails Pub Nite is every
3rd Monday of each month, except in December.", :published_at => "2013-04-13"}
=> {:title=>"Rails Pub Nite", :body=>"Rails Pub Nite is every
3rd Monday of each month, except in December.", :published_at=>" 2013-04-13"}
>> Article.create(attributes)
=> #<Article id: 5, title: "Rails Pub Nite", body: "Rails Pub Nite is every 3rd
Monday of each month, e...", published_at: "2013-04-13 00:00:00",
created_at: "2013-04-13 23:36:07", updated_at: "2013-04-13 23:36:07",
excerpt: nil, location: nil>
>> Article.count
=> 5
③使用id查询单条记录
>> Article.find(3)
=> #<Article id: 3, title: "Introduction to Active Record", body: "Active Record
is Rails's default ORM..", published_at: "2013-04-13 04:00:00",
created_at: "2013-04-13 23:15:37", updated_at: "2013-04-13 23:15:37",
excerpt: nil, location: nil>
>>article = Article.find(3)
=>#<Article id: 3 ...>
>>article.id
=>3
>>article.title
=>"Introduction to Active Record"
④使用first和last查询单条记录
>> Article.first
=> #<Article id: 1, title: "RailsConf", body: "RailsConf is the official
gathering for Rails devel...", published_at: "2013-04-13 00:00:00",
created_at: "2013-04-13 23:12:09", updated_at: "2010-04-13 23:12:09",
excerpt: nil, location: nil>
>> Article.last
=> #<Article id: 5, title: "Rails Pub Nite", body: "Rails Pub Nite is every 3rd
Monday of each month, e...", published_at: "2013-04-13 00:00:00",
created_at: "2013-04-13 23:36:07", updated_at: "2013-04-13 23:36:07",
excerpt: nil, location: nil>
⑤查询多条记录
>> articles = Article.all
=> [#<Article id: 1,..> #<Article id: 2,..>, #<Article id: 3,..>,
#<Article id: 4,..> , #<Article id: 5,..>]
>> articles.class
=> Array
>> articles.size
=> 5
>> articles[0]
=> #<Article id: 1, title: "RailsConf", body: "RailsConf is the official
gathering for Rails devel...", published_at: "2013-04-13 00:00:00",
created_at: "2013-04-13 23:12:09", updated_at: "2013-04-13 23:12:09",
excerpt: nil, location: nil>
>> articles[0].title
=> "RailsConf"
>> articles.first.title
=> "RailsConf"
>> articles.each { |article| puts article.title }
RailsConf
Introduction to SQL
Introduction to Active Record
RubyConf 2010
Rails Pub Nite
=> [#<Article id: 1,..> #<Article id: 2,..>, #<Article id: 3,..>,
#<Article id: 4,..> , #<Article id: 5,..>]
⑥使用order对数据进行排序
默认是降序,我们可以使用DESC改变为升序
>> articles = Article.order("published_at")
=> [#<Article id: 1,..> #<Article id: 2,..>, #<Article id: 3,..>,
#<Article id: 4,..> , #<Article id: 5,..>]
>> articles.each {|article| puts article.published_at }2013-04-13 00:00:00 UTC2013-04-13 04:00:00
UTC2013-04-13 04:00:00 UTC2013-04-13 00:00:00 UTC2013-04-13 00:00:00 UTC
=> [#<Article id: 1,..> #<Article id: 2,..>, #<Article id: 3,..>,
#<Article id: 4,..> , #<Article id: 5,..>]
>> articles = Article.order ('published_at DESC')
=> [#<Article id: 4,..> #<Article id: 5,..>, #<Article id: 2,..>,
#<Article id: 3,..> , #<Article id: 1,..>]
>> articles.each {|article| puts article.published_at }2013-04-13 00:00:00 UTC2013-04-13 00:00:00
UTC2013-04-13 00:00:00 UTC2013-04-13 00:00:00 UTC2013-04-13 00:00:00 UTC
=> [#<Article id: 4,..> #<Article id: 5,..>, #<Article id: 2,..>,
#<Article id: 3,..> , #<Article id: 1,..>]
⑦条件查询
>> Article.where(:title => 'RailsConf').first
=> #<Article id: 1, title: "RailsConf", body: "RailsConf is the official
gathering for Rails devel...", published_at: "2013-04-13 00:00:00",
created_at: "2013-04-13 23:12:09", updated_at: "2013-04-13 23:12:09",
excerpt: nil, location: nil>
>> Article.where(:title => 'RailsConf').all
=> [#<Article id: 1, title: "RailsConf", body: "RailsConf is the official
gathering for Rails devel...", published_at: "2013-04-13 00:00:00",
created_at: "2013-04-13 23:12:09", updated_at: "2013-04-13 23:12:09",
excerpt: nil, location: nil>]
>> Article.where(:title => 'Unknown').all
=> []
⑧更新记录
>> article = Article.first
>> article.title = "Rails 4 is great"
>> article.published_at = Time.now
>> article.save
=> true
也可以一次性更新多个字段
>> article = Article.first
>> article.update_attributes(:title => "RailsConf2013", :published_at => 1.day.ago)
=> true
或者更新一个字段
>> article = Article.first
>> article.update_attribute(:title => "RailsConf2013")
=> true
⑨删除记录
>> article = Article.last
>> article.destroy
=> #<Article id: 5, title: "Rails Pub Nite", body: "Rails Pub Nite is every 3rd
Monday of each month, e...", published_at: "2013-04-13 00:00:00",
created_at: "2013-04-13 23:36:07", updated_at: "2013-04-13 23:36:07",
excerpt: nil, location: nil>
#或者在一行里面操作
>> Article.last.destroy
>> Article.destroy(1)
=> [#<Article id: 1, title: "RailsConf", body: "RailsConf is the official
gathering for Rails devel...", published_at: "2010-02-27 00:00:00",
created_at: "2010-05-01 23:12:09", updated_at: "2010-05-01 23:12:09",
excerpt: nil, location: nil>]
#删除多条记录
>> Article.destroy([2,3])
=> [#<Article id: 2, ..>, #<Article id: 3, ..>]
使用destroy是没有返回值的,如果需要返回值,我们可以使用delete方法来删除记录
>> Article.delete(4)
=> 1
#数据库中不存在5到6的记录,所以返回0
>> Article.delete([5, 6])
=> 0
规定条件删除相应的记录
>> Article.delete_all("published_at < '2011-01-01'")
>> 0
1.在我们的模型中添加下面方法
class Article < ActiveRecord::Base
validates_presence_of :title
validates_presence_of :body
def long_title
"#{title} - #{published_at}"
end
end
我们就使用上面的方法来操作数据库了
#在命令行中操作模型
>> Article.create :title => 'Advanced Active Record', :published_at => Date.today,
:body => 'Models need to relate to each other. In the real world, ...'
=> #<Article id: 6, title: "Advanced Active Record", ...>
>> Article.last.long_title
=> "Advanced Active Record - 2013-04-22 04:00:00 UTC"
2.数据库之间的关系
①一对一关系
首先:我们创建两张表rails generate model User email:string password:string
rails generate model Profile user_id:integer name:string birthday:date bio:text color:string twitter:string
我们分别在两个模型中创建对应的方法
#User模型
class User < ActiveRecord::Base
has_one :profile
end
#Profile模型
class Profile < ActiveRecord::Base
belongs_to :user
end
我们接下来可以在rails命令行中做测试了
>> user = User.create(:email => 'user@example.com', :password => 'secret')
=> #<User id: 1, email: "user@example.com", password: "secret",
created_at: "2013-04-02 15:10:07", updated_at: "2013-04-02 15:10:07">
>> profile = Profile.create(:name => 'John Doe',
:bio => 'Ruby developer trying to learn Rails')
=> #<Profile id: 1, user_id: nil, name: "John Doe", birthday: nil,
bio: "Ruby developer trying to learn Rails", color: nil, twitter: nil,
created_at: "2013-04-02 15:10:55", updated_at: "2013-04-02 15:10:55">
>> user.profile
=> nil
>> user.profile = profile
=> #<Profile id: 1, user_id: 1, name: "John Doe", birthday: nil,
bio: "Ruby developer trying to learn Rails", color: nil, twitter: nil,
created_at: "2013-04-02 15:10:55", updated_at: "2013-04-02 15:10:55">
>> user.profile
=> #<Profile id: 1, user_id: 1, name: "John Doe", birthday: nil,
bio: "Ruby developer trying to learn Rails", color: nil, twitter: nil,
created_at: "2013-04-02 15:10:55", updated_at: "2013-04-02 15:10:55">
>> user.create_profile :name => 'Jane Doe', :color => 'pink'
=> #<Profile id: 2, user_id: 1, name: "Jane Doe", birthday: nil,
bio: nil, color: "pink", twitter: nil, created_at: "2013-04-02 15:18:57",
updated_at: "2013-04-02 15:18:57">
一对一模型中常用方法总结如下:user.profile
返回user对应的profile对象user.profile=(profile)
对user的profile赋值user.profile.nil?
返回user的profile是否为空,为空返回真user.build_profile(attributes={})
返回一条新的user的profile对象,但是不会保存到数据库,需要使用user.profile.save
来保存user.create_profile(attributes={})
返回user的profile对象,直接保存到数据库中
②一对多关系
我们使用user表对应article表,每个用户都有很多的文章,但是每篇文章都只对应一个用户rails generate migration add_user_id_to_articles user_id:integer
#文章表模型
class Article < ActiveRecord::Base
validates_presence_of :title
validates_presence_of :body
belongs_to :user#每篇文章指定属于用户
def long_title
"#{title} - #{published_at}"
end
end
#用户表
class User < ActiveRecord::Base
has_one :profile
has_many :articles
end
我们在rails命令 行中使用示例
>> user = User.first
=> #<User id: 1, email: "user@example.com", password: "secret",
created_at: "2013-04-02 15:10:07", updated_at: "2013-04-02 15:10:07">
>> user.articles
=> []
>> user.articles << Article.first
=> [#<Article id: 6, ..., user_id: 1>]
>> user.articles.size
=> 1
>> user.articles
=> [#<Article id: 6, ..., user_id: 1>]
>> Article.first.user_id
=> 1
>> Article.first.user
=> #<User id: 1, email: "user@example.com", password: "secret",
created_at: "2013-04-02 15:10:07", updated_at: "2013-04-02 15:10:07">
一对多常用方法user.articles
返回用户模型中所有文章对象user.articles=(articles)
替换用户模型的所有文章对象,用articles来代替user.articles << article
添加article对象到user的文章对象中user.articles.delete(articles)
删除文章模型中的一篇或者多篇文章user.articles.empty?
判断用户实例的文章是否是空的user.articles.size
返回用户示例的文章数量user.article_ids
返回用户示例的文章id,以数组形式返回user.articles.clear
清空用户的文章user.articles.find
传入文章的id,返回该文章user.articles.build(attributes={})
创建一个新的用户文章对象,不会保存,需要使用user.articles.last.save
来保存
PS:这种方法一般在实际的应用是这样子使用的
product = Product.find(params[:product_id])
@line_item = @cart.line_items.build(product: prodcut)#将产品实例直接传进来
respond_to do |format|
if @line_item.save#使用它来保存
user.articles.create(attributes={})
直接创建文章对象,并且保存到数据库中。
③关系型数据库扩展
i.定义默认排序
#指定单个的排序
class User < ActiveRecord::Base
has_one :profile
has_many :articles, -> { order('published_at DESC') }
end
#指定多个字段排序
class User < ActiveRecord::Base
has_one :profile
has_many :articles, -> { order('published_at DESC, title ASC')}
end
ii.特殊依赖
当我们删除一个用户时,该用户的所有文章都会被删除
class User < ActiveRecord::Base
has_one :profile
has_many :articles, -> { order('published_at DESC, title ASC')}, :dependent => :destroy
end
当然我们也可以不删除文章,可以设置被删除用户的所有文章的user_id为空
class User < ActiveRecord::Base
has_one :profile
has_many :articles, -> { order('published_at DESC, title ASC')}, :dependent => :nullify
end
④多对多关系
我们假定一篇文章有很多种分类,一个分类也有很多文章,我们使用rails generate model Category name:string
和rails generate migration create_articles_categories
分别创建分类表和中间表,中间表的定义如下
#The db/migrate/20130407002156_create_articles_categories.rb: File
class CreateArticlesCategories < ActiveRecord::Migration
def change
create_table :articles_categories, :id => false do |t|
t.references :article
t.references :category
end
end
def self.down
drop_table :articles_categories
end
end
references
方法和integer
是一样的效果,也就是说我们可以使用下面的方式来创建add_column :articles_categories, :article_id, :integer
,add_column :articles_categories, :category_id, :integer
下面我们分别为Article模型和Category模型添加has_and_belongs_to_many方法
class Article < ActiveRecord::Base
has_and_belongs_to_many :categories
end
class Category < ActiveRecord::Base
has_and_belongs_to_many :articles
end
下面我们在rails命令行中测试,
>> article = Article.last
=> #<Article id: 8, title: "Associations", ...>
>> category = Category.find_by_name('Programming')
=> #<Category id: 1, name: "Programming", ..>
>> article.categories << category
=> [#<Category id: 1, name: "Programming", ..>]
>> article.categories.any?
=> true
>> article.categories.size
=> 1
>> category.articles.empty?
=> false
>> category.articles.size
=> 1
>> category.articles.first.title
>> "Associations"
多对多关系需要注意,我们可以为每个字段添加索引,增加数据库的查询速度,并且可以通过数据库来保证每个字段的唯一性
add_index :articles_categories, :article_id
add_index :articles_categories, :category_id
add_index :articles_categories, [:article_id, :category_id], unique: true
自定义方法来模拟多对多关系
还是通过文章和分类模型来定义多对多关系
1.创建ac数据库
class CreateAcs < ActiveRecord::Migration
def change
create_table :acs do |t|
t.integer :article_id
t.integer :category_id
t.timestamps
end
end
end
2.分别在文章和分类模型中定义下面的方法
文章模型
class Article < ActiveRecord::Base
validates_presence_of :title
validates_presence_of :body
belongs_to :user
has_many :acs, dependent: :destroy #这里我们不需要制定外键,默认是article_id
def long_title
"#{title} -- #{published_at}"
end
def allc
categories = []
self.acs.each {|i| categories << Category.find(i.category_id)}
return categories
end
end
分类模型
class Category < ActiveRecord::Base
has_many :acs, dependent: :destroy#这里我们不需要制定外键,默认是category_id
def alla
articles = []
self.acs.each {|i| articles << Article.find(i.article_id)}
return articles
end
end
最后在ac类中定义下面的方法
class Ac < ActiveRecord::Base
belongs_to :article, class_name: "Article"
belongs_to :category, class_name: "Category"
end
这样我们就可以模拟多对多关系了,应该比默认的方法查询速度要快很多吧!
使用where方式
>> Aricle.where(:title => 'Advanced Active Record')
=> [#<Article id: 6, title: "Advanced Active Record", ...>]
使用原生SQL语句
>> Article.where("created_at > '23-04-2013' OR body NOT LIKE '%model%'")
=> [#<Article id: 7, title: "One-to-many associations", ...>,
#<Article id: 8, title: "Associations", ...>]
>> Article.where("created_at > '23-04-2013' AND body NOT LIKE '%model%'")
=> []
使用数组条件语义
>> Article.where("published_at < ?", Time.now)
=> [#<Article id: 6, title: "Advanced Active Record", ...>]
>> Article.where("published_at < ?", Time.now).to_sql
=> "SELECT
\"articles\".* FROM
\"articles\"
WHERE
(published_at < '2013-04-02 16:27:51.059277')"
>> Article.where("created_at = ?", Article.last.created_at)
=> [#<Article id: 8, title: "Associations", ...>]
>> Article.where("created_at = ? OR body LIKE ?", Article.last.created_at, 'model')
=> [#<Article id: 8, title: "Associations", ...>]
>> Article.where("title LIKE :search OR body LIKE :search",
{:search => '%association%'})
=> [#<Article id: 7, title: "One-to-many associations", ...>,
#<Article id: 8, title: "Associations", ...>]
使用代理模式
>> User.first.articles.all
=> [#<Article id: 8, title: "Associations", ...>]
current_user.articles.create(:title => 'Private', :body => ‘Body here..’)
其他一些常用方法
>> Article.all
=> [#<Article id: 6, title: "Advanced Active Record", ...>,
#<Article id: 7, title: "One-to-many associations", ...>,
#<Article id: 8, title: "Associations", ...>]
>> Article.order("title ASC")
=> [#<Article id: 6, title: "Advanced Active Record", ...>,
#<Article id: 8, title: "Associations", ...>,
#<Article id: 7, title: "One-to-many associations", ...>]
>> Article.limit(1)
=> [#<Article id: 6, title: "Advanced Active Record", ...>]
>> Article.order("title DESC").limit(2)
=> [#<Article id: 7, title: "One-to-many associations", ...>,
#<Article id: 8, title: "Associations", ...>]
>> Article.all
=> [#<Article id: 6, title: "Advanced Active Record", ...>,
#<Article id: 7, title: "One-to-many associations", ...>,
#<Article id: 8, title: "Associations", ...>]
>> Article.order("title ASC")
=> [#<Article id: 6, title: "Advanced Active Record", ...>,
#<Article id: 8, title: "Associations", ...>,
#<Article id: 7, title: "One-to-many associations", ...>]
>> Article.limit(1)
=> [#<Article id: 6, title: "Advanced Active Record", ...>]
>> Article.order("title DESC").limit(2)
=> [#<Article id: 7, title: "One-to-many associations", ...>,
#<Article id: 8, title: "Associations", ...>]
默认作用域
首先我们看看数据库的默认排序方法
>> Category.all
=> [#<Category id: 1, name: "Programming", ...>, #<Category id: 2, name: "Event", ...>,
#<Category id: 3, name: "Travel", ...>, #<Category id: 4, name: "Music", ..>,
#<Category id: 5, name: "TV", ...>]
在category模型中我们添加default_scope
方法,以后的查询结构默认会以分类名排序。
class Category < ActiveRecord::Base
has_and_belongs_to_many :articles
default_scope lambda { order('categories.name') }
end
我们在rails命令行中进行测试
>> reload!
Reloading...
>> Category.all
=> [#<Category id: 2, name: "Event", ...>, #<Category id: 4, name: "Music", ...>,
#<Category id: 1, name: "Programming", ...>, #<Category id: 5, name: "TV", ...>,
#<Category id: 3, name: "Travel", ...>]
自定义作用域
首先我们需要在模型中定义方法,如下
class Article < ActiveRecord::Base
scope :published, lambda { where("articles.published_at IS NOT NULL") }
scope :draft, lambda { where("articles.published_at IS NULL") }
scope :recent, lambda { published.where("articles.published_at > ?",
1.week.ago.to_date)}
scope :where_title, lambda { |term| where("articles.title LIKE ?", "%#{term}%") }
def long_title
"#{title} - #{published_at}"
end
end
我们在命令行中测试
>> Article.published
=> [#<Article id: 6, title: "Advanced Active Record", ...>]
>> Article.draft
=> [#<Article id: 7, title: "One-to-many associations", ...>,
#<Article id: 8, title: "Associations", ...>]
>> Article.recent
=> [#<Article id: 6, title: "Advanced Active Record", ...>]
>> Article.draft.where_title("one")
=> [#<Article id: 7, title: "One-to-many associations", ...>]
>> Article.where_title("Active")
=> [#<Article id: 6, title: "Advanced Active Record", ...>]
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