Question

假设我想创建一个完成编码项目，开发人员及其角色的数据库。

模型看起来像这样：

project has_and_belongs_to_many developers
developers has_and_belongs_to_many projects

developers_projects表如下所示：

int: developer_id, project_id
string: role

让我知道我有3个开发人员和2个项目，其ID和名称分别为

1, Ashley
2, Bob
3, Charles

1, Tic Tac Toe
2, Snake

他们的实际角色是

Project 1:
- Manager: Ashley
- Coder: Bob, Charles

Project 2:
- Manager: Charles
- Coder: Ashley

是否可以在项目下定义经理和编码器对象？

像：

class Project < ActiveRecord::Base
    has_and_belongs_to_many :developers
    has_and_belongs_to_many :managers, :class_name => "developers", :condition => "role = 'manager'"
    has_and_belongs_to_many :coders, :class_name => "developers", :condition => "role = 'coder'"
end

（这不起作用）

提前谢谢你，

Answer 1

has_and_belongs_to_many允许在不声明模型的情况下创建连接表。至于你想在这个表中拥有属性，你应该创建单独的模型，例如，你的案例中的ProjectRoles：

class ProjectRole < ActiveRecord::Base
  belongs_to :developer
  belongs_to :project

  attr_accessible :role
end

class Project < ActiveRecord::Base
  has_many :manager_roles, :class_name => "ProjectRole", 
                           :conditions => { :role => 'manager' }
  has_many :managers, :through => manager_roles
end

class Developer < ActiveRecord::Base
  has_many :project_roles
  has_many :projects, :through => project_roles
end

在rails中为has_and_belongs_to_many关系定义属性

1 个答案: