Unique entries

Rails
1

I have this table associating airlines with rental cars. It has four
columns - user_id, airline_id, rentalcar_id and id. I need to make sure
that the combo of airline_id and rentalcar_id is always unique - in
other words, a user cannot have two fields with the same airline_id and
rentalcar_id. Is this done with one of the validation commands in the
model? I have look at the one that I can find and none seems to fit all
that well. Thanks,

-S

2

I have this table associating airlines with rental cars. It has four
columns - user_id, airline_id, rentalcar_id and id. I need to make sure
that the combo of airline_id and rentalcar_id is always unique - in
other words, a user cannot have two fields with the same airline_id and
rentalcar_id. Is this done with one of the validation commands in the
model? I have look at the one that I can find and none seems to fit all
that well. Thanks,

Create a unique index on user_id, airline_id, rentalcar_id in your
migration… that would be one way

3

You could try:

validates_uniqueness_of :rentalcar_id, :scope => :airline_id

Whichever is the widest scope (e.g., can an airline have a lot of
rental cars? Or the other way around?) should probably go with
:scope. I don’t think it would affect anything, but for modeling’s
sake it should be that way. :slight_smile:

–Jeremy

On 10/11/07, Shandy N. [email protected] wrote:

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Posted via http://www.ruby-forum.com/.

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4

[email protected] wrote:

I second that. I’m using validates_uniquemess_of with :scope for the
same purpose in one of my projects. In the testing I have done it did
not matter which one went in the :scope. I agree that the widest
would be the better choice for readability later.

On Oct 11, 5:36 pm, “Jeremy McAnally” [email protected]

What I was trying to do was to have a user with an airline membership be
associated to as many rental car companies as they desired, but to
insure the integrity of the database, I didn’t want an entry that had
all three columns the same - user_id, airline_id, and rentalcar_id. The
same user_id and airline_id was ok as long as they all had different
rentalcar_id’s. Hope this makes some sense, because it was confusing the
hell out of me. Anyway, here is what I did:

validates_uniqueness_of :rentalcar_id, :scope => :airline_id and
:_user_id

and it seems to work. I didn’t know that I could say and but apperently
I can. Thanks all,

-S

5

On 10/12/07, Shandy N. [email protected] wrote:

validates_uniqueness_of :rentalcar_id, :scope => :airline_id and
:_user_id

and it seems to work. I didn’t know that I could say and but apperently
I can. Thanks all,

Well, you can “say” it, but Ruby will parse that as:

validates_uniqueness_of(:rentalcar_id, :scope => :airline_id) and
:_user_id

The “and” part is a no-op, which I’m guessing isn’t what you intend.

If you want to use two columns for the scope, the syntax is:

:scope => [:airline_id, :user_id]

which is illustrated in the API docs for validates_uniqueness_of

6

I second that. I’m using validates_uniquemess_of with :scope for the
same purpose in one of my projects. In the testing I have done it did
not matter which one went in the :scope. I agree that the widest
would be the better choice for readability later.

On Oct 11, 5:36 pm, “Jeremy McAnally” [email protected]