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

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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

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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

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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 />

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7. ConnectionAdapters::DatabaseStatements

connection.select_all

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8. ActiveRecord::ConnectionAdapters::AbstractAdapter

ActiveRecord::Base.connection returns an AbstractAdapter object,

update_all

http://api.rubyonrails.org/classes/ActiveRecord/Base.html#M001308

  # Update all billing objects with the 3 different attributes given
Billing.update_all( "category = 'authorized', approved = 1, author = 'David'" )

# Update records that match our conditions
Billing.update_all( "author = 'David'", "title LIKE '%Rails%'" )

# Update records that match our conditions but limit it to 5 ordered by date
Billing.update_all( "author = 'David'", "title LIKE '%Rails%'",
                      :order => 'created_at', :limit => 5 )