Converting join table to join model table

Rails
1

I have a join table (foos_bars) which used to just be a join table in a
HABTM
relationship.

Now I want to create a FooBars model to hold extra attributes about the
relationship without losing any of the data in the table, however I
can’t think
of a way to add the promary key column without an error. How do I do it?

Thanks

2

doesn’t rails add an id column anyway?

3

A HABTM association doesn’t use an id primary key in the table
definition. The structure is similar to:

table ‘table1_table2’
t.column table1_id, :integer
t.column table2_id, :integer

Since you’re now stating you want the join to be pushed to a separate
model now, with attributes; you’ll change both model definitions to
have has_many :myNewJoinyThing. The model will also have the same
association. Since it is a separate model you can add attributes as
well.

4

Gareth A. wrote:

I have a join table (foos_bars) which used to just be a join table in a
HABTM relationship.

Now I want to create a FooBars model to hold extra attributes about the
relationship without losing any of the data in the table, however I
can’t think
of a way to add the promary key column without an error. How do I do it?

Turning a join table into a full-fledged join model requires a few
changes:

  1. Rename the table from foos_bars to fubars, or whatever is compatible
    with your model name.
  2. Add an ‘id’ field for the primary key, auto-increment int
  3. Fix all the associations that used habtm to use has_many :through.

I’ve heard reports that doing step 2 using migrations can cause
problems. It might be better to create the new join model table and
transfer the data from the old table to the new one.

–
Josh S.
http://blog.hasmanythrough.com