Updating attributes in HABTM association

Rails
1

Hi,

I am trying to find a way tp update attributes in a habtm association. I
am trying to use the code from ticket #2462, but as my
association_class_primary_key_name seems to be empty the generated sql
code is corrupt. I hope thats not a problem of my model that this
variable is empty.
What would you recommend to update those attributes (rails 1.1)

THANKS!!!

2

Henrik Badekow wrote:

Hi,

I am trying to find a way tp update attributes in a habtm association. I
am trying to use the code from ticket #2462, but as my
association_class_primary_key_name seems to be empty the generated sql
code is corrupt. I hope thats not a problem of my model that this
variable is empty.
What would you recommend to update those attributes (rails 1.1)

THANKS!!!

Could you post the code you’re using?

Thanks,

Adam

3

Henrik Badekow wrote:

I am trying to find a way tp update attributes in a habtm association. I
am trying to use the code from ticket #2462, but as my
association_class_primary_key_name seems to be empty the generated sql
code is corrupt. I hope thats not a problem of my model that this
variable is empty.
What would you recommend to update those attributes (rails 1.1)

There is no recommended way to update attributes on a habtm association.
In fact, rich associations (habtm with attributes) have been deprecated
and won’t be supported at all come 2.0 release. Use a join model
(has_many :through) instead.

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

4

Josh S. wrote:

There is no recommended way to update attributes on a habtm association.
In fact, rich associations (habtm with attributes) have been deprecated
and won’t be supported at all come 2.0 release. Use a join model
(has_many :through) instead.

Correct me if I’m wrong, but these are technically called “polymorphic
joins”
aren’t they? I would recommend we try to use the right terms when we
can, so
that hopefully everyone is on the same page. Saying just “use a join
model”
easily means more than one thing, just in a Rails context, doesn’t it?

-Brian

5

Brian V. Hughes wrote:

Josh S. wrote:

There is no recommended way to update attributes on a habtm association.
In fact, rich associations (habtm with attributes) have been deprecated
and won’t be supported at all come 2.0 release. Use a join model
(has_many :through) instead.

Correct me if I’m wrong, but these are technically called “polymorphic
joins”
aren’t they? I would recommend we try to use the right terms when we
can, so
that hopefully everyone is on the same page. Saying just “use a join
model”
easily means more than one thing, just in a Rails context, doesn’t it?

Brian, I don’t think Henrik was talking about polymorphism. The usual
habtm join table has nothing to do with polymorphism, and I’m not sure
how to make it work with polymorphic associations anyway.

I’m pretty sure I was using the right terminology. In Rails parlance a
“join model” is a join table that has been promoted to full model status
by adding a primary key and probably other attribute fields as well. It
also has a Model class, which habtm join tables don’t, so its table name
corresponds to its model name in the usual fashion, rather than being
constructed from names of the tables it is joining.

You can use polymorphic associations in a join model, but it gets
tricky. I just blogged about that a couple days ago in fact.

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

6

Josh S. wrote:

Brian, I don’t think Henrik was talking about polymorphism. The usual
habtm join table has nothing to do with polymorphism, and I’m not sure
how to make it work with polymorphic associations anyway.

Hmm… OK. I thought that the has_many :through designation is what
signified a
polymorphic join. Obviously, I have that wrong. :slight_smile:

I’m pretty sure I was using the right terminology. In Rails parlance a
“join model” is a join table that has been promoted to full model status
by adding a primary key and probably other attribute fields as well. It
also has a Model class, which habtm join tables don’t, so its table name
corresponds to its model name in the usual fashion, rather than being
constructed from names of the tables it is joining.

Sure. I’m willing to go with that. Like I said, the real goal of my
email was to
make sure we’re all using the same (or mostly the same) vocab,
especially when
talking about some of the more involved Rails concepts/features.

You can use polymorphic associations in a join model, but it gets
tricky. I just blogged about that a couple days ago in fact.

Well, I’ll definitely need to check out that post so I can figure out
what the
hell I thought I was talking about! ;->

-Brian