問題與安裝設計

Question

，這裏是我當前的用戶模式：

# == Schema Information 
# 
# Table name: users 
# 
# id   :integer   not null, primary key 
# first_name :string 
# last_name :string 
# created_at :datetime   not null 
# updated_at :datetime   not null 
# 
require 'elasticsearch/model' 

class User < ActiveRecord::Base 
    searchkick word_start: [:user] 
    has_many :posts 
    validates :first_name, :last_name, presence: true 
end 

這些都是我能夠在問題出現之前要經過的步驟擡起了頭：

rails generate devise:install  
rails generate devise user   
rake db:migrate 

一次我嘗試遷移它，這是什麼出現：

== 20160707230510 AddDeviseToUsers: migrating ================================= 
-- change_table(:users) 
rake aborted! 
StandardError: An error has occurred, this and all later migrations canceled: 

PG::DuplicateColumn: ERROR: column "email" of relation "users" already exists 
: ALTER TABLE "users" ADD "email" character varying DEFAULT '' NOT NULL 
/Users/aa/Documents/railsy/basicProject/db/migrate/20160707230510_add_devise_to_users.rb:5:in `block in up' 
/Users/aa/Documents/railsy/basicProject/db/migrate/20160707230510_add_devise_to_users.rb:3:in `up' 
ActiveRecord::StatementInvalid: PG::DuplicateColumn: ERROR: column "email" of relation "users" already exists 
: ALTER TABLE "users" ADD "email" character varying DEFAULT '' NOT NULL 
/Users/aa/Documents/railsy/basicProject/db/migrate/20160707230510_add_devise_to_users.rb:5:in `block in up' 
/Users/aa/Documents/railsy/basicProject/db/migrate/20160707230510_add_devise_to_users.rb:3:in `up' 
PG::DuplicateColumn: ERROR: column "email" of relation "users" already exists 
/Users/aa/Documents/railsy/basicProject/db/migrate/20160707230510_add_devise_to_users.rb:5:in `block in up' 
/Users/aa/Documents/railsy/basicProject/db/migrate/20160707230510_add_devise_to_users.rb:3:in `up' 
Tasks: TOP => db:migrate 
(See full trace by running task with --trace) 

正如你可以從我以前的用戶架構告訴，沒有郵件列那裏。所以...爲什麼這個錯誤出現？

**編輯 - 應該已經發布了色器件遷移文件 - 不工作的一個**

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, null: false 
     t.datetime :current_sign_in_at 
     t.datetime :last_sign_in_at 
     t.inet  :current_sign_in_ip 
     t.inet  :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, null: false # Only if lock strategy is :failed_attempts 
     # t.string :unlock_token # Only if unlock strategy is :email or :both 
     # t.datetime :locked_at 


     # Uncomment below if timestamps were not included in your original model. 
     # t.timestamps null: false 
    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 
    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 

再次編輯

當我運行rails g devise user ...這是什麼來up：

Running via Spring preloader in process 72318 
     invoke active_record 
     create db/migrate/20160707230510_add_devise_to_users.rb 
     insert app/models/user.rb 
     route devise_for :users 

Answer 1

要消除重複字段上的遷移錯誤，請使用t.change，如下所示。

t.change :email, :string,  :null => false, :default => "" 

請注意，要使t.change正常工作，您必須指定要更改字段的類型。在上述電子郵件遷移的情況下，電子郵件字段是字符串類型。

你可以參考在：devise wiki

Answer 2

打開了所有我所要做的就是做rake db:setup它再現了分貝。然後我跑了rake db:migrate，這次沒有問題出現。

僅供參考。希望這可以幫助那裏的人。