[英]Use model field for default value in Rails migration
In my Rails 4 application, I would like to add a 'username' field to my User model. 在我的Rails 4应用程序中,我想向用户模型添加一个“用户名”字段。 Since I already have users in the database, I'd like to use their email (which is currently a part of the model) as the default username in my migration. 由于我已经在数据库中有用户,因此我想在迁移中使用他们的电子邮件(当前是模型的一部分)作为默认用户名。 Here's what I have so far: 这是我到目前为止的内容:
class AddUsernameColumnToUsers < ActiveRecord::Migration
def change
add_column :users, :username, :string, null: false
add_index :users, :username, unique: true
end
end
So, I'd like do something akin to: 所以,我想做些类似的事情:
add_column :users, :username, :string, null: false, default: this.email
But that code is not valid. 但是该代码无效。 Any thoughts? 有什么想法吗? Thanks in advance. 提前致谢。
You can solve it like this 你可以这样解决
class AddUsernameColumnToUsers < ActiveRecord::Migration def up add_column :users, :username, :string, null: false add_index :users, :username, unique: true query = 'UPDATE users SET username = email' ActiveRecord::Base.connection.execute(query) end def down remove_column :users, :username end end
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