Rails 模型外键验证

Question

我需要验证我的一个模型中是否存在由外键引用的行。情况是这样的：

Project.rb

class Project < ActiveRecord::Base
  has_one :project_category

  # -----------------------------------------------------------------
  # this does not work because the attribute is actually called 
  # 'category_id' instead of the rails expected 'project_category_id'
  # -----------------------------------------------------------------
  validates :project_category, presence: true
end

项目迁移

class CreateProjects < ActiveRecord::Migration
  def change
    create_table :projects do |t|

      # ----------------------------------------------
      # this is why the column is called 'category_id'
      # ---------------------------------------------- 
      t.references :category, references: :project_categories, null: false

      # all of my other fields here, unimportant
    end
    add_foreign_key :projects, :project_categories, column: :category_id
  end
end

我知道我可以编写一个自定义验证方法来检查 :category_id 是否存在于 project_categories 表中，但如果有办法，我更愿意让 rails 处理验证，所以我可以保持我的代码 DRY .

编辑

ProjectCategory.rb

class ProjectCategory < ActiveRecord::Base
  belongs_to :project

  validates :name, presence: true, uniqueness: { case_sensitive: false }
end

项目类别迁移

class CreateProjectCategories < ActiveRecord::Migration
  def change
    create_table :project_categories do |t|
      t.string :name, null: false
    end
  end
end

Answer 1

看来您只需将foreign_key 选项添加到您的has_one 声明中，即可指定您指定的自定义列名称，即category_id 而不是project_category_id。详情请见Options for has_one。

# app/modeles/project.rb

class Project < ActiveRecord::Base
  has_one :project_category, foreign_key: 'category_id'

  # -----------------------------------------------------------------
  # this does not work because the attribute is actually called 
  # 'category_id' instead of the rails expected 'project_category_id'
  # -----------------------------------------------------------------
  validates :project_category, presence: true
end