has_many关系栏3

Question

Hi I have three tables like the following:

    class Workitem < ActiveRecord::Base
      has_many :effort
      attr_protected
    end

    class Effort < ActiveRecord::Base
      attr_protected
      belongs_to :workitem
      belongs_to :person
    end

    class Person < ActiveRecord::Base
      attr_accessible :given_name, :mgrid, :surname, :id
      has_many :effort
    end

The idea is to keep track of how many days a person has spent on a particular work item through efforts table. Could somebody verify if my relationships are correct? But this doesn't seem to work. Am I missing something here? Also, I can't understand the has_many :through kind of associations. Can somebody please give me an idea if that is what I'm supposed to use in this case?

Answer 1

You would usually have the child as a plural object:

class Workitem < ActiveRecord::Base
  has_many :efforts
  attr_protected
end

class Person < ActiveRecord::Base
  attr_accessible :given_name, :mgrid, :surname, :id
  has_many :efforts
end

And I'd recommend using attr_accessible instead of attr_protected

If a Foo had many Bars and the Bars belonged to many Foos, it might look like this:

class Foo < ActiveRecord::Base
  has_many :foo_bar
  has_many :bars, through => :foo_bar
end

class Bar < ActiveRecord::Base
  has_many :foo_bar
  has_many :foos, through => :foo_bar
end

class FooBar
  belongs_to :foo
  belongs_to :bar
end

Something like that anyway. There's a load of help on Railcasts here

Also, there's a trillion examples on SO.

Hope that helps