[ruby on rails] 跟我學之基於rails console的查增刪改操作

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本章節展開對model的介紹：包括查增刪改操作。緊接著上面一節《[ruby on rails] 跟我學之HelloWorld》

建立模型使用命令建立模型

建立表post,預設內建兩欄位 title :string, content:text ,  在模型裡面按照約定使用單數post而不是複數posts

cd blograils g model post title:string content:text

輸出：

      invoke  active_record      create    db/migrate/20141203105453_create_posts.rb      create    app/models/post.rb      invoke    test_unit      create      test/models/post_test.rb      create      test/fixtures/posts.yml

db/migrate/20141203105453_create_posts.rb檔案內容如下：

class CreatePosts < ActiveRecord::Migration  def change    create_table :posts do |t|      t.string :title      t.text :context      t.timestamps    end  endend

以上只是產生了遷移檔案，而沒有正式產生資料庫。 需要運行以下指令來產生資料庫。

rake db:migrate

相當於django的syncdb。 輸出如下：

== 20141203105453 CreatePosts: migrating ======================================-- create_table(:posts)   -> 0.0021s== 20141203105453 CreatePosts: migrated (0.0029s) =============================

　

 

從控制台訪問模型

進入控制台，類似於django的manage shell指令，ror使用以下指令：

rails console

簡寫為 rails c

新增記錄：

模型類.new -> 模型執行個體變數.save

2.1.5 :001 > p = Post.new(:title => "My First Post", :context=>"this is my first post") => #<Post id: nil, title: "My First Post", context: "this is my first post", created_at: nil, updated_at: nil>2.1.5 :002 > p.save()   (0.5ms)  begin transaction  SQL (0.7ms)  INSERT INTO "posts" ("context", "created_at", "title", "updated_at") VALUES (?, ?, ?, ?)  [["context", "this is my first post"], ["created_at", "2014-12-03 11:44:50.954572"], ["title", "My First Post"], ["updated_at", "2014-12-03 11:44:50.954572"]]   (23.0ms)  commit transaction => true

模型類.create

2.1.5 :003 > Post.create(:title => "create test", :context=>"test of create")   (0.2ms)  begin transaction  SQL (0.4ms)  INSERT INTO "posts" ("context", "created_at", "title", "updated_at") VALUES (?, ?, ?, ?)  [["context", "test of create"], ["created_at", "2014-12-03 11:48:08.779270"], ["title", "create test"], ["updated_at", "2014-12-03 11:48:08.779270"]]   (21.9ms)  commit transaction => #<Post id: 2, title: "create test", context: "test of create", created_at: "2014-12-03 11:48:08", updated_at: "2014-12-03 11:48:08">

查詢記錄

模型類.all

2.1.5 :004 > posts = Post.all  Post Load (0.6ms)  SELECT "posts".* FROM "posts" => #<ActiveRecord::Relation [#<Post id: 1, title: "My First Post", context: "this is my first post", created_at: "2014-12-03 11:44:50", updated_at: "2014-12-03 11:44:50">, #<Post id: 2, title: "create test", context: "test of create", created_at: "2014-12-03 11:48:08", updated_at: "2014-12-03 11:48:08">]>

模型類.find(id)

2.1.5 :005 > post = Post.find(2)  Post Load (0.6ms)  SELECT  "posts".* FROM "posts"  WHERE "posts"."id" = ? LIMIT 1  [["id", 2]] => #<Post id: 2, title: "create test", context: "test of create", created_at: "2014-12-03 11:48:08", updated_at: "2014-12-03 11:48:08">

可以用[執行個體變數].[成員變數]的方式訪問資料，如下：

2.1.5 :006 > post.title => "create test"2.1.5 :007 > post.context => "test of create"

　

更新記錄

模型執行個體變數.update -> 模型執行個體變數.save()

2.1.5 :008 > post.title = "test update" => "test update"2.1.5 :009 > post.save()   (0.4ms)  begin transaction  SQL (1.2ms)  UPDATE "posts" SET "title" = ?, "updated_at" = ? WHERE "posts"."id" = 2  [["title", "test update"], ["updated_at", "2014-12-03 11:57:08.964494"]]   (10.0ms)  commit transaction => true

模型執行個體變數.update_attribute(field,value)

2.1.5 :010 > post.update_attribute(:context,"test operation of update_attribute")   (0.4ms)  begin transaction  SQL (1.4ms)  UPDATE "posts" SET "context" = ?, "updated_at" = ? WHERE "posts"."id" = 2  [["context", "test operation of update_attribute"], ["updated_at", "2014-12-03 12:01:12.051869"]]   (32.3ms)  commit transaction => true

模型執行個體變數.update_attributes(hash)

2.1.5 :013 > post.update_attributes(:title=>"test update_attribute 2", :context =>"content for test of update_attribute 2")   (1.4ms)  begin transaction  SQL (1.2ms)  UPDATE "posts" SET "context" = ?, "title" = ?, "updated_at" = ? WHERE "posts"."id" = 2  [["context", "content for test of update_attribute 2"], ["title", "test update_attribute 2"], ["updated_at", "2014-12-03 12:05:16.878764"]]   (26.1ms)  commit transaction => true

 

刪除記錄

模型執行個體變數.destroy

2.1.5 :016 > post.destroy   (0.3ms)  begin transaction  SQL (1.3ms)  DELETE FROM "posts" WHERE "posts"."id" = ?  [["id", 2]]   (23.6ms)  commit transaction => #<Post id: 2, title: "test update_attribute 2", context: "content for test of update_attribute 2", created_at: "2014-12-03 11:48:08", updated_at: "2014-12-03 12:05:16">

 

轉載請註明本文來自：http://www.cnblogs.com/Tommy-Yu/p/4141122.html，謝謝！

[ruby on rails] 跟我學之基於rails console的查增刪改操作