为什么我在迁移过程中会收到错误以及默认数据？

发布于 2024-11-05 23:29:19 字数 1357 浏览 0 评论 0原文

    rails g migration CreateStates

然后将以下代码添加到迁移中：

=============================

class CreateStates < ActiveRecord::Migration
  def self.up
    create_table :states do |t|
      t.column :name, :string
      t.column :abbreviation, :string
    end

    State.create :name => 'Alabama', :abbreviation => 'AL'
    State.create :name => 'Alaska', :abbreviation => 'AK'
    State.create :name => 'Arizona', :abbreviation => 'AZ'
  end

  def self.down
    drop_table :states
  end
end

============== ==============

我收到错误：

** Invoke db:migrate (first_time)
** 调用环境（first_time）
** 执行环境
** 执行 db:migrate
== CreateStates: 迁移 ================================================= ======
-- create_table(:states)
-> 0.0010s
耙子中止！
发生错误，此迁移和所有后续迁移均已取消：

未初始化常量 CreateStates::State
/Users/jondoe/.rvm/rubies/ruby-1.8.7-p330/lib/ruby/gems/1.8/gems/rspec-core-2.5.1/lib/rspec/core/backward_compatibility.rb:20:in ` const_missing'

========

看起来应该可以做到这一点：
http://api.rubyonrails.org/classes/ActiveRecord/Migration.html

我还尝试创建一个模型而不仅仅是一个迁移文件。还是同样的错误。我还尝试创建 2 个迁移（一个用于创建表，一个用于添加数据），但这也不起作用。有什么想法吗？

原文

    rails g migration CreateStates

Then add the following code to the migration:

===========================

class CreateStates < ActiveRecord::Migration
  def self.up
    create_table :states do |t|
      t.column :name, :string
      t.column :abbreviation, :string
    end

    State.create :name => 'Alabama', :abbreviation => 'AL'
    State.create :name => 'Alaska', :abbreviation => 'AK'
    State.create :name => 'Arizona', :abbreviation => 'AZ'
  end

  def self.down
    drop_table :states
  end
end

============================

I get an error:

** Invoke db:migrate (first_time)
** Invoke environment (first_time)
** Execute environment
** Execute db:migrate
== CreateStates: migrating ===================================================
-- create_table(:states)
-> 0.0010s
rake aborted!
An error has occurred, this and all later migrations canceled:

uninitialized constant CreateStates::State
/Users/jondoe/.rvm/rubies/ruby-1.8.7-p330/lib/ruby/gems/1.8/gems/rspec-core-2.5.1/lib/rspec/core/backward_compatibility.rb:20:in `const_missing'

========

It seems like this should be able to do this:
http://api.rubyonrails.org/classes/ActiveRecord/Migration.html

I have also tried to create a model instead of a just a migration file. Still same error. I have also tried creating 2 migrations (one to create table, then one to add data) and that didn't work either. Any ideas?

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樱花细雨 2024-11-12 23:29:19

尝试

State.reset_column_information

在 State.create 之前

执行以下操作：文档

Try doing:

State.reset_column_information

before your State.create.

documentation

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巴黎夜雨 2024-11-12 23:29:19

您的代码将完美运行，除非您实际上没有 State 类。 Rails 了解此类的唯一方法是在 app/models/state.rb 中将其定义为 Class State Class State ActiveRecord::Base...

我建议运行以下代码行，而不是运行自定义迁移：

rails g model State name:string abbreviation:string

这将：

创建模型（和单元测试文件）
创建一个名为 20110508223913_create_states 的迁移.rb，它看起来与您上面尝试的迁移几乎相同。

然后您需要做的就是添加您的 State.create... 行，然后就可以开始了。

Your code would work perfectly, except that you don't actually have a State class. The only way Rails would know about this class is if you defined it in app/models/state.rb as Class State < ActiveRecord::Base...

Rather than running a custom migration, I'd recommend running this line of code:

rails g model State name:string abbreviation:string

This will:

Create your model (and unit test files)
Create a migration named something like 20110508223913_create_states.rb, which will look nearly identical to your attempted migration above.

Then all you need to do is add your State.create... lines and you should be good to go.

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