迁移后删除rails模型

Question

对我来说,创建模型,运行迁移,销毁它,再次创建相同模型报告SQL异常似乎很奇怪:

project|master ? rails g model name name
      invoke  active_record
      create    db/migrate/20130417185814_create_names.rb
      create    app/models/name.rb
project|master? ? rake db:migrate
==  CreateNames: migrating ====================================================
-- create_table(:names)
   -> 0.0020s
==  CreateNames: migrated (0.0021s) ===========================================
project|master? ? rails d model name
      invoke  active_record
      remove    db/migrate/20130417185814_create_names.rb
      remove    app/models/name.rb
project|master? ? rake db:migrate
project|master? ? rails g model name test
      invoke  active_record
      create    db/migrate/20130417185845_create_names.rb
      create    app/models/name.rb
project|master? ? rake db:migrate
==  CreateNames: migrating ====================================================
-- create_table(:names)
rake aborted!
An error has occurred, this and all later migrations canceled:

SQLite3::SQLException: table "names" already exists: CREATE TABLE "names" ("id" INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, "test" varchar(255), "created_at" datetime NOT NULL, "updated_at" datetime NOT NULL) /path/project/db/migrate/20130417185845_create_names.rb:3:in `change'
-- create_table("names", {:force=>true})
   -> 0.0100s
-- initialize_schema_migrations_table()
   -> 0.0025s
-- assume_migrated_upto_version(20130417185814, ["/path/project/db/migrate"])
   -> 0.0010s
You have 1 pending migrations:
  20130417185845 CreateNames
Run `rake db:migrate` to update your database then try again.

也许,我做错了什么？迁移具有删除表的代码 - 它是否仅用于回滚？

解

删除模型和数据库表并生成一个新表非常简单:

1. 创建模型: rails g model user name
2. 迁移: rake db:migrate
3. 实现一些东西,突然想起你需要删除模型
4. 恢复特定迁移:rake db:migrate:down VERSION=20130417185814,20130417185814迁移ID 在哪里(可以在rake db:migrate:status中看到)
5. 删除模型: rails d model user
6. 突然想起你需要这个模型,但是需要其他领域
7. 创建模型: rails g model user email group:references
8. 成功迁移数据库: rake db:migrate

Answer 1

rails d model name 

这只是删除模型而不是您运行的迁移(在数据库中创建了表).

如果要删除模型和表,则必须执行以下操作

rake db:rollback 
rails d model name