祖先db：迁移 [英] Ancestry db:migrate

问题描述

我试图安装Ancestry gem，但是我遇到了 rake db：migrate 的问题。

I am trying to install the Ancestry gem but I am having problems with rake db:migrate.

我正在遵循Ancestry github页面上的说明。在我完成 rails g迁移后，add_ancestry_to_message ancestry：string
我正在编辑迁移文件（在railcast＃262后面）：

I am following the instructions on the Ancestry github page. After I have done rails g migration add_ancestry_to_message ancestry:string I am editing the migration file (following railcast #262) to be:

class AddAncestryToMessage < ActiveRecord::Migration
  def self.up
    add_column :messages, :ancestry, :string
    add_index :messages, :ancestry
  end

  def self.down
    remove_index :messages, :ancestry
    remove_column :messages, :ancestry
  end
end

当我运行 rake db：migrate 时出现以下错误：

When I then run rake db:migrate I am getting the following error:

==  AddAncestryToMessage: migrating ===========================================
-- add_column(:messages, :ancestry, :string)
rake aborted!
An error has occurred, this and all later migrations canceled:

SQLite3::SQLException: no such table: Shipmgr: ALTER TABLE "Message" ADD "ancestry" varchar(255)

Tasks: TOP => db:migrate

我已经在新创建的rails应用程序和现有的rails应用程序上尝试了这个，但是我我仍然无法得到这个工作。有人对这个问题有任何建议吗？

I have tried this on a newly created rails app and on an existing rails app but I am still unable to get this to work. Does anyone have any advice on this issue?

推荐答案

您应该尝试将迁移类名称更改为复数（表格）消息'：

You should try changing the migration class name to the pluralized (table) form 'Messages':

class AddAncestryToMessages < ActiveRecord::Migration

或者更准确地说，将迁移生成器命令更改为：

or, more accurately, change the migration generator command to:

rails g migration add_ancestry_to_messages ancestry:string

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