遷移時，rails會產生devise用戶錯誤

Question

我在Rails世界中有點陌生，我嘗試在devise模式中添加一個新字段。

我找到了這個 ：

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

並嘗試應用命令：

rails generate devise User linkedin:string

該過程似乎是正確的：

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

但是，當我啟動db：migrate時，會發生錯誤：

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

我做錯了什么 ？ 為什么以前沒問題，但它說（和有關）電子郵件是錯誤的？

非常感謝 ！

---

這是遷移文件的結果：

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

您的用戶表是否已經有電子郵件字段？ 似乎有，您必須通過從遷移中刪除它來再次刪除創建電子郵件字段，並確保在user.rb模型中沒有兩次對其進行引用

db/migrate/20130902085306_add_devise_to_users.rb

Answer 2

好！ 我發現了問題所在：我創建了一個新表，而不是更新現有表。 因此，好的任務是：

rails g migration add_columnLinkedin_to_users

然后添加新創建的遷移文件：

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

db：migrate成功了！

感謝您的幫助！