Ruby on Rails多对多

Question

I have two models Type and Activity. Type has_many activities and Activity has_many types. To do this I used the has_many :through thing. This is how it looks like

Activity

has_many :typeitems
has_many :types, :through => :typeitem

Typeitem

belongs_to :activity
belongs_to :type

Type

has_many :typeitems
belongs_to :activity

This does not feel right though. I would want to query 2 things

1. Activities of a particular type
2. Types of a particular activity

When I went into rails console and typed types.activity I got a nil which means I will get a single object. Should I change the belongs_to in Type model to has_many .But then it's back to many-to-many . There should be a way.

I looked at the docs and found has_and_belongs_to_many . I also read this

You should use has_many :through if you need validations, callbacks, or extra attributes on the join model.

I am not using it now but I might want to in the future.

Answer 1

Both sides need a has_many :through :

Activity

has_many :typeitems
has_many :types, :through => :typeitem

Typeitem

belongs_to :activity
belongs_to :type

Type

has_many :typeitems
has_many :activities, through: :typeitems