Help me! ... Problem with associations,

Hi there,

I’ve three tables: release, branch and platform defined as follows:

release (id)
branch (id, release_id)
platform (id)


  1. Each branch belongs to zero or more platforms
  2. Each platform has zero or more branches
    ==> To maintain this association, I’ve created the ‘join’ table as
    branches_platforms(branch_id, platform_id)
    and in the models,
    Branch: has_and_belongs_to :platforms
    Platform: has_and_belongs_to :branches
  3. Each branch belongs to exactly one release
  4. Each release has zero or more branches
    ==> Release: has_many :branches
    Branch : belongs_to :release

Now, if I would like to know the releases a platform supports or the
platforms a release is applicable to, how do I define the

For time-being, I’m using :finder_sql to specificy the complete SQL
query, as shown below. Is there an easy way to specify such an
association? Your help would be very invaluable.

Platform: has_many :releases, :finder_sql => 'SELECT releases.* '+
'FROM releases '+
'INNER JOIN branches '+
'ON =
branches.release_id '+
'WHERE branches.branch_id '+
branches_platforms.branch_id '+
’ FROM branches_platforms ‘+
branches_platforms.platform_id= #{id}’

Release: has_many :platforms, :finder_sql => 'SELECT platforms.* '+
'FROM platforms '+
'INNER JOIN branches_platforms
'ON =
branches_platforms.platform_id '+
branches_platforms.branch_id '+
’ FROM branches ‘+
’ WHERE branches.release_id=
Thanks in advance.

Could someone please help me with this?

On 3/24/07, askme [email protected] wrote:

Could someone please help me with this?

Have a look at “has_many :through”, that should do what you need.



thank you very much. I’ve tried the following,

In release.rb (model),

has_many :platforms, :through => :branches

this results in an error, which asks to specify, :source also (I
doubt this is because platform_id is not present in the branches table

neither :source => release nor :source => platforms works.

I’m stuck here!