ruby-on-rails - 如何在ActiveRecord中为ruby设置非null约束？

Question

我有一个看起来像这样的迁移:

class CreatePosts < ActiveRecord::Migration
  def change
     create_table :posts do |t|
      t.string  :title 
      t.string  :content
      t.string  :author
      t.timestamps
    end
  end
end

如何将标题设置为NOT NULL？如果这是一个SQL查询，我会这样做:

CREATE TABLE "posts" 
    ("id" serial primary key, 
     "title" character varying(255) NOT NULL, 
     "content" character varying(255), 
     "author" character varying(255), 
     "created_at" timestamp NOT NULL, 
     "updated_at" timestamp NOT NULL) 

那么如何将查询转换为ActiveRecord？

Answer 1

要在数据库级别设置非null约束，请将null: false添加到ActiveRecord迁移中。例如，

class CreatePosts < ActiveRecord::Migration
  def change
     create_table :posts do |t|
      t.string  :title,   null: false
      t.string  :content, null: false
      t.string  :author,  null: false
      t.timestamps
    end
  end
end

您还应该(或者可以选择)在模型中添加一个状态验证器，该验证器在Rails级别上运行，并向最终用户提供信息丰富的错误消息:

class Post < ActiveRecord::Base
  validates :title, :content, :author, presence: true
end

有关更多信息，请参见Rails Guides on presence validation。