Question

我想通过一行代码获取所选boards的所有projects的列表：

boards = projects.boards

怎么做？

目前，我在每个项目上单独进行迭代，获取其电路板并在数组中累积结果（下面的代码）

class Project < ActiveRecord::Base
  has_many :boards
end

class Board < ActiveRecord::Base
  belongs_to :project
end

class Account < ActiveRecord::Base
  has_many :projects
end

projects = @account.projects.where("SOME_CONDITION")

# my current code:
boards = []
projects.each do |project|
  boards << project.boards
end

# wanted code:
boards = projects.boards # <--- How to achieve it?

Answer 1

如果我做得对，你想拥有一个帐户项目的董事会。您需要为模型添加更多行。

1

class Project < ActiveRecord::Base  
   has_many :boards  
   belongs_to :account   
end

2

class Board < ActiveRecord::Base
   belongs_to :project  
   belongs_to :account, through: project  
end

3

class Account < ActiveRecord::Base
   has_many :projects
   has_many :boards, through: :projects

   def projects_boards(project_ids)  
     self.boards.where(boards.project_id: project_ids)  
   end  
end

然后就这样称呼它：
boards= @account.boards
编辑以满足您的需求：
boards = @account.projects_boards(projects.map(&:id))

Answer 2

使用此语法

projects = @ account.projects.where（＆＃34; SOME_CONDITION＆＃34;）。last.boards

Answer 3

您可以使用Project.a_scope.includes(:boards).each do |project| projects.boards.do_something end AR语句来获取与每个项目相关的所有电路板

select * from projects where ...

将使用两个SQL查询来获取与所需项目相关的所有板。

select * from boards where boards.project_id in (1,2,3,4...)

project_ids = Project.a_scope.pluck(:id) boards = Board.where(id: project_ids)

如果你想要的只是你自己可以做的那个板子列表

{{1}}

Answer 4

class Project < ActiveRecord::Base
  has_many :boards
end

class Board < ActiveRecord::Base
  belongs_to :project
end

class Account < ActiveRecord::Base
  has_many :projects
  has_many :boards, through: :projects
end

我们只是说

SOME_CONDITION = "projects.state = 'active'"

请使用：

@account.boards.where(SOME_CONDITION)

如何累积has_many关系的结果？

4 个答案: