has_many :through with join table as a has_many FK issue

rubyonrails-talk
1

I have a join table:

sitedata belongs_to :tb1 belongs_to tb2

has_many :tb3

When I add a relationship in the join table I then add data to the tb3 table and that populates the FK in tb3 with the id of the join table. no problems there.

when I delete the row in the join table the data stays in the tb3 table. how do I get the tb3 data to delete?

Is not has_many supposed to delete the data on the other end when the primary table no longer has a reference?

If I go into the DB and make the FK a constraint with a delete on cascade it works when the data in the join table is deleted.

2

Your example doesn't make much sense from here, but you'll probably want to look into the various :dependent options to has_many.

--Matt Jones

3

you have to add :dependent => :destroy in the association

you B table has_many A

then the B model will looks like

has_many :A , :dependent => :destroy

so when you destroy an object of B it will automatically delete all the As that was associated with that B

4

Here is the layout,

TBa → TBb → TBc > TBd

TBa has_many TBc :through => :TBb

TBb is the join table.

TBb has_many :TBd, :dependent => destroy.

TBd data stays there even though the data in TBb is deleted.

In my program I make the relationship dynamically and then I add data to TBd for the relationship in TBb.

When I delete the relationship in the join table the data still remains in TBd.