Activerecord memo (3)

ActiveRecord::Base
save, save!, create, create!, update_attribute, update_attributes, update, update_all, delete, delete_all, destroy, destroy_all

1. save vs save!
save 成功 => true
save 失敗 => fasle

另外 save(perform_validation = true), save 還可以丟個參數進去, save(false) 的話, 一堆validate 都不跑, 可是會跑before_*, 失敗一樣是return false

save! 成功 => true
save! 失敗 => validate 失敗：RecordInvalid execption,
before_* 失敗 : RecordNotSaved

---

2. create vs create!
create 成功 => ActiveRecord object
<br />>> f = Forum.create(:subject => 'jaifjai', :content => 'fhauehf', :user_id => 3)<br />=> #<Forum id: 29, subject: "jaifjai", content: "fhauehf", created_at: "2009-02-05 10:22:55", user_id: 3, comments_count: 0, group_id: nil, last_comment_time: "2009-02-05 10:22:55", public: nil><br />

create 失敗 => ActiveRecord object, 所以要確認成功失敗可以用 errors.empty? 檢查
<br />=> #<Forum id: nil, subject: "jaifjai", content: nil, created_at: nil, user_id: nil, comments_count: 0, group_id: nil, last_comment_time: nil, public: nil><br /><br />>> f.errors<br />=> #<ActiveRecord::Errors:0xb70289f8 @errors={"content"=>["can't be blank"]}, @base=#<Forum id: nil, subject: "jaifjai", content: nil, created_at: nil, user_id: nil, comments_count: 0, group_id: nil, last_comment_time: nil, public: nil>><br /><br />>> f.errors.empty?<br />=> false<br />

create! 成功 => ActiveRecord object
create! 失敗 => RecordInvalid

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3. 如果是資料庫的validate 就會爆 StatementInvalid
例如有這樣的設定 t.column :user_id, :integer, :null => false
沒填user_id 就會爆StatementInvalid

---

4. update_attribute vs update_attributes
除了可以更新update的多寡之外,
還有 update_attribute 是 save(false), 它不跑 validate

同樣成功true, 失敗false

---

5 update, update_all
丟的參數差很多
update(id, attributes)
update_all(updates, conditions = nil, options = {})
<br /> Forum.update([6,7], [{:user_id => 2}, {:user_id => 3}])<br /><br /> # Updating multiple records:<br /> people = { 1 => { "first_name" => "David" }, 2 => { "first_name" => "Jeremy" } }<br /> Person.update(people.keys, people.values)<br /><br /> # Update all billing objects with the 3 different attributes given<br /> Billing.update_all( "category = 'authorized', approved = 1, author = 'David'" )<br /><br /> # Update records that match our conditions<br /> Billing.update_all( "author = 'David'", "title LIKE '%Rails%'" )<br /><br /> # Update records that match our conditions but limit it to 5 ordered by date<br /> Billing.update_all( "author = 'David'", "title LIKE '%Rails%'",<br /> :order => 'created_at', :limit => 5 )<br />

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6.delete_all, delete, destroy, destroy_all
delete 是不會跑before_, after_ destroy 還有 dependent 也是不跑的

destroy_all(conditions = nil)
delete_all(conditions = nil)
<br /> #delete, destroy 也可以這樣用<br /> # Delete a single row<br /> Todo.delete(1)<br /><br /> # Delete multiple rows<br /> Todo.delete([2,3,4])<br /><br /> # Destroy a single object<br /> Todo.destroy(1)<br /><br /> # Destroy multiple objects<br /> todos = [1,2,3]<br /> Todo.destroy(todos)<br />

---

7. ConnectionAdapters::DatabaseStatements

connection.select_all

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8. ActiveRecord::ConnectionAdapters::AbstractAdapter

ActiveRecord::Base.connection returns an AbstractAdapter object,

validate,before,create,define_method,callback

http://api.rubyonrails.org/classes/ActiveRecord/Callbacks.html#M001618
http://www.ruby-doc.org/core/classes/Module.html#M001682

* (-) save
* (-) valid
* (1) before_validation
* (2) before_validation_on_create
* (-) validate
* (-) validate_on_create
* (3) after_validation
* (4) after_validation_on_create
* (5) before_save
* (6) before_create
* (-) create
* (7) after_create
* (8) after_save

<br /> class CreditCard < ActiveRecord::Base<br /> # Strip everything but digits, so the user can specify "555 234 34" or<br /> # "5552-3434" or both will mean "55523434"<br /> def before_validation_on_create<br /> self.number = number.gsub(/[^0-9]/, "") if attribute_present?("number")<br /> end<br /> end<br /><br /> class Subscription < ActiveRecord::Base<br /> before_create :record_signup<br /><br /> private<br /> def record_signup<br /> self.signed_up_on = Date.today<br /> end<br /> end<br /><br /> class Firm < ActiveRecord::Base<br /> # Destroys the associated clients and people when the firm is destroyed<br /> before_destroy { |record| Person.destroy_all "firm_id = #{record.id}" }<br /> before_destroy { |record| Client.destroy_all "client_of = #{record.id}" }<br /> end<br />

---

define_method: 動態產生method 的好物
<br /> class ArticleVersion < ActiveRecord::Base<br /> STATES = { :edit => 'Edit',<br /> :edit_check => 'Edit Check',<br /> :sub_edit => 'Sub Edit',<br /> :publish_ready => 'Publish Ready',<br /> :published => 'Published' }<br /> STATES.each do |key, value|<br /> define_method "#{key}?", {<br /> self.state == "#{value}"<br /> }<br /> end<br /> end<br />

<br />#Defines an instance method in the receiver. The method parameter can be a Proc or Method object. If a block is specified, it is used as the method body. This block is evaluated using instance_eval, a point that is tricky to demonstrate because define_method is private. (This is why we resort to the send hack in this example.)<br /><br /> class A<br /> def fred<br /> puts "In Fred"<br /> end<br /> def create_method(name, &block)<br /> self.class.send(:define_method, name, &block)<br /> end<br /> define_method(:wilma) { puts "Charge it!" }<br /> end<br /> class B < A<br /> define_method(:barney, instance_method(:fred))<br /> end<br /> a = B.new<br /> a.barney<br /> a.wilma<br /> a.create_method(:betty) { p self }<br /> a.betty<br /><br />produces:<br /><br /> In Fred<br /> Charge it!<br /> #<B:0x401b39e8><br />

create table, column

  def self.up
    create_table :mugshots do |t|
      t.column :user_id, :integer
      t.column :created_at, :datetime
      t.column :parent_id,  :integer
      t.column :content_type, :string
      t.column :filename, :string
      t.column :thumbnail, :string
      t.column :size, :integer
      t.column :width, :integer
      t.column :height, :integer
    end
  end

CREATE TABLE `mugshots` (`id` int(11) DEFAULT NULL auto_increment 
PRIMARY KEY, `user_id` int(11) DEFAULT NULL NULL, `created_at` 
datetime DEFAULT NULL NULL, `parent_id` int(11) DEFAULT NULL NULL, 
`content_type` varchar(255) DEFAULT NULL NULL, `filename` 
varchar(255) DEFAULT NULL NULL, `thumbnail` varchar(255) DEFAULT 
NULL NULL, `size` int(11) DEFAULT NULL NULL, `width` int(11) DEFAULT
 NULL NULL, `height` int(11) DEFAULT NULL NULL) ENGINE=InnoDB