Question

我有一个新表的迁移：

class CreateContentCategories < ActiveRecord::Migration
  def change
    create_table :content_categories do |t|
      t.string :title, default: '', null: false

      t.timestamps null: false
    end
  end
end

当我尝试使用选项create或find_or_create_by新记录时：

def self.assign_titles_to_app(titles, app)
  # somewhere inside ( class scope )
  title = 'movies'
  content_category = find_by_title(title) || create(title: title)
  puts "title: #{title} category: #{content_category.inspect}"

有效记录不使用我的标题

title: movies category: #<ContentCategory id: 1050, title: "", created_at: "2015-06-25 15:42:57", updated_at: "2015-06-25 15:42:57">

find_or_create_by的结果相同：

title = 'movies'
content_category = find_or_create_by(title: title)
title: movies category: #<ContentCategory id: 1062, title: "", created_at: "2015-06-25 15:45:25", updated_at: "2015-06-25 15:45:25">

文件说：

:default - The column's default value. Use nil for NULL.

出了什么问题？如何解决？

信息：

rails 4.2.1
activerecord 4.2.1
ruby 2.2.2

更新：我忘记了attr_accessible：

class ContentCategory < ActiveRecord::Base
# attr_accessible :title <- I forgot to add this line, oh
end

Answer 1

您的代码没有任何问题，也许您需要重新启动应用程序（和弹簧），或者问题可能在您未显示的代码中。为了演示，我将您的确切代码添加到了一个vanilla 4.2应用程序中：

[9] pry(main)> ContentCategory.assign_titles_to_app 1, 2
  ContentCategory Load (0.2ms)  SELECT  "content_categories".* FROM "content_categories" WHERE "content_categories"."title" = ? LIMIT 1  [["title", "movies"]]
   (0.1ms)  begin transaction
  SQL (0.7ms)  INSERT INTO "content_categories" ("title", "created_at", "updated_at") VALUES (?, ?, ?)  [["title", "movies"], ["created_at", "2015-06-25 16:31:59.192793"], ["updated_at", "2015-06-25 16:31:59.192793"]]
   (0.5ms)  commit transaction
title: movies category: #<ContentCategory id: 1, title: "movies", created_at: "2015-06-25 16:31:59", updated_at: "2015-06-25 16:31:59">
=> nil

Rails：create方法不能覆盖迁移默认值

1 个答案: