Question

我在Rails世界中有点新，我尝试在设计模式中添加一个新字段。

我发现了这个：

rails generate model NAME [field[:type][:index] field[:type]

并尝试应用命令：

rails generate devise User linkedin:string

这个过程似乎是正确的：

invoke  active_record
  create    db/migrate/20130902085306_add_devise_to_users.rb
  insert    app/models/user.rb
   route  devise_for :users

但是当我启动db：migrate时会发生错误：

PG::Error: ERROR:  column "email" of relation "users" already exists

我做错了什么？为什么它说（并且它是相关的）电子邮件是错的，而它之前还可以吗？

非常感谢！

以下是迁移文件结果：

class AddDeviseToUsers < ActiveRecord::Migration
def self.up
change_table(:users) do |t|
  ## Database authenticatable
  t.string :email,              :null => false, :default => ""
  t.string :encrypted_password, :null => false, :default => ""

  ## Recoverable
  t.string   :reset_password_token
  t.datetime :reset_password_sent_at

  ## Rememberable
  t.datetime :remember_created_at

  ## Trackable
  t.integer  :sign_in_count, :default => 0
  t.datetime :current_sign_in_at
  t.datetime :last_sign_in_at
  t.string   :current_sign_in_ip
  t.string   :last_sign_in_ip

  ## Confirmable
  # t.string   :confirmation_token
  # t.datetime :confirmed_at
  # t.datetime :confirmation_sent_at
  # t.string   :unconfirmed_email # Only if using reconfirmable

  ## Lockable
  # t.integer  :failed_attempts, :default => 0 # Only if lock strategy is :failed_attempts
  # t.string   :unlock_token # Only if unlock strategy is :email or :both
  # t.datetime :locked_at

  ## Token authenticatable
  # t.string :authentication_token

  t.string :linkedin

  # Uncomment below if timestamps were not included in your original model.
  # t.timestamps
end

add_index :users, :email,                :unique => true
add_index :users, :reset_password_token, :unique => true
# add_index :users, :confirmation_token,   :unique => true
# add_index :users, :unlock_token,         :unique => true
# add_index :users, :authentication_token, :unique => true
end

def self.down
# By default, we don't want to make any assumption about how to roll back a migration when your
# model already existed. Please edit below which fields you would like to remove in this migration.
raise ActiveRecord::IrreversibleMigration
end
end

Answer 1

您的用户表是否已有电子邮件字段？似乎有，您必须通过从迁移中删除它来再次删除创建电子邮件字段，并确保它在user.rb模型中未被引用两次

db/migrate/20130902085306_add_devise_to_users.rb

Answer 2

确定！我发现了什么问题：我创建了一个新表而不是更新现有表。所以好的任务是：

rails g migration add_columnLinkedin_to_users

然后添加新创建的迁移文件：

change_table :users do |t|
  t.string   :linkedin
end

db：migrate是成功的！

感谢您的帮助！

rails generate devise迁移时的用户错误

2 个答案: