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maestro777

2008-May-14 21:33 UTC

Model relationship design question.

I have the following scenario.

Three tables - Companies, Users and Submissions.

Starting with Companies. Each company has many users. Each user can
have one or more submissions (of articles related to a company). Hence
each submission needs to be linked to a company. Up to this stage, I
could probably use :through to link submissions to Companies. So far
so good.

But the complication comes in as such: Each user can make a submission
related not only to the company he belongs to but also to other
companies available on record. In which case the :through option may
not work any more in this scenario, I think.

I have been thinking about this for days and due to my limited
knowledge of relationships, I couldn''t come up with a feasible
solution. So far I came up with the following relationships:

class Company < ActiveRecord::Base
    has_many :users
    has_many :submissions
end

class User < ActiveRecord::Base
    belongs_to :company
    has_many :submisions
end

class Submission < ActiveRecord::Base
    belongs_to :company
    belongs_to :user
end

I have a suspicion that this setup will not work. The more I think
about it, the more confused I become. If someone could help with some
inputs/advice as how to go about this, it will be greatly appreciated.

Thanks in advance.
Steve


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Ryan Bigg (Radar)

2008-May-14 22:27 UTC

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Re: Model relationship design question.

Company

has_many :users
has_many :submissions, :through => :users


User
belongs_to :company
has_many :submissions

Submission
belongs_to :user


has_many :through is awesome.

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maestro777

2008-May-14 23:54 UTC

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Re: Model relationship design question.

Thanks Ryan for your input.
I thought over you have suggested, and I think it doesn''t quite work
for the case that I have.

Let me try to explain my scenario again.

I have a table of companies. Each company has multiple users.
Each user can submit one or more articles.
Each article is about a company (that exists in the company table) and
that company may or may not be the same company that the user
(submitting the article) belongs to.

For example.
I have a User1 who belongs to Company A. He creates an article
submission about Company B.

How do I link the submission to Company B, since the article is about
company B?. Using the has_many :through => users  as you have
suggested, I believe it will link the submission to Company A instead.

Maybe the model I am using to approach the problem may not be correct.
I am open to learning a better approach to this type of scenario.

Thanks again





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Pardee, Roy

2008-May-15 00:26 UTC

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Re: Model relationship design question.

Off top, I''m thinking you want to keep your 1:M relationships between
companies and users, and between users and submissions, but go M:M on
the one between companies & submissions.  IOW, make the relationship
between submissions & companies independent of the user.  So something
like:

class User < ar::base
  belongs_to :company
  has_many :submissions
end

class CompaniesSubmissions < ar::base
  belongs_to :company
  belongs_to :submission
end

class Submission < ar::base
  belongs_to :user
  has_many :companies_submissions
  has_many :companies, :through => :companies_submissions
end

class Company < ar::base
  has_many :users
  has_many :companies_submissions
  has_many :submissions, :through => :companies_submissions
end

You''ll probably at least want to default the addition of the submitting
user''s company to Submission.companies (if not actually enforce that as
a validation requirement.)  Not sure what the most graceful way to do
that would be...

HTH,

-Roy

-----Original Message-----
From: rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
[mailto:rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org] On Behalf Of
maestro777
Sent: Wednesday, May 14, 2008 2:33 PM
To: Ruby on Rails: Talk
Subject: [Rails] Model relationship design question.


I have the following scenario.

Three tables - Companies, Users and Submissions.

Starting with Companies. Each company has many users. Each user can have
one or more submissions (of articles related to a company). Hence each
submission needs to be linked to a company. Up to this stage, I could
probably use :through to link submissions to Companies. So far so good.

But the complication comes in as such: Each user can make a submission
related not only to the company he belongs to but also to other
companies available on record. In which case the :through option may not
work any more in this scenario, I think.

I have been thinking about this for days and due to my limited knowledge
of relationships, I couldn''t come up with a feasible solution. So far I
came up with the following relationships:

class Company < ActiveRecord::Base
    has_many :users
    has_many :submissions
end

class User < ActiveRecord::Base
    belongs_to :company
    has_many :submisions
end

class Submission < ActiveRecord::Base
    belongs_to :company
    belongs_to :user
end

I have a suspicion that this setup will not work. The more I think about
it, the more confused I become. If someone could help with some
inputs/advice as how to go about this, it will be greatly appreciated.

Thanks in advance.
Steve




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Andrew Skegg

2008-May-15 01:25 UTC

head link

Re: Model relationship design question.

maestro777 wrote:> Thanks Ryan for your input.
> I thought over you have suggested, and I think it doesn''t quite
work
> for the case that I have.
> 
> Let me try to explain my scenario again.
> 
> I have a table of companies. 
OK

class Company < ActiveRecord::Base
end
>Each company has multiple users.
class Company < ActiveRecord::Base
  has_many :users
end

class User < ActiveRecord::Base
  belong_to :company
end
> Each user can submit one or more articles.
class Article < ActiveRecord::Base
  belongs_to :user
end

class Company < ActiveRecord::Base
  has_many :users
end

class User < ActiveRecord::Base
  belong_to :company
  has_many :articles
end
> Each article is about a company (that exists in the company table) and
> that company may or may not be the same company that the user
> (submitting the article) belongs to.
class Article < ActiveRecord::Base
  belongs_to :user
  belongs_to :company
end

class Company < ActiveRecord::Base
  has_many :users
  has_many :articles
end

class User < ActiveRecord::Base
  belong_to :company
  has_many :articles
end


I am not sure you need :through relationships at all.
-- 
Posted via http://www.ruby-forum.com/.

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Ryan Bigg (Radar)

2008-May-15 01:35 UTC

head link

Re: Model relationship design question.

You don''t need the through relationships. It wasn''t clear to
me originally
what he wanted, so I assumed he wanted to see what submissions were made by
the users of a company, and has_many :through came to mind.

Andrew''s solution seems to fit the bill, I think.

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Andrew Skegg

2008-May-15 01:49 UTC

head link

Re: Model relationship design question.

Ryan Bigg wrote:> You don''t need the through relationships. It wasn''t clear
to me
> originally
> what he wanted, so I assumed he wanted to see what submissions were made 
> by
> the users of a company, and has_many :through came to mind.
> 
> Andrew''s solution seems to fit the bill, I think.
What''s more - it''s exactly what maestro777 started with.

I suspect he might be having problems getting the results he wants using 
this structure.
-- 
Posted via http://www.ruby-forum.com/.

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Ryan Bigg (Radar)

2008-May-15 01:54 UTC

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Re: Model relationship design question.

I noticed this too.

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maestro777

2008-May-15 03:40 UTC

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Re: Model relationship design question.

Thanks guys for all the input.

I''m glad to find out that I was on the right track after all from the
beginning, with my models set up. It wasn''t that I was having problem
getting the result I wanted. Rather the source of my confusion came
from a misunderstanding on what I was reading in one of the ROR books
about model relationship. Now that you confirmed I was on the right
track, I went back to read the same passage again and realized that it
was talking about a different kind of relationship, than what I had in
mind.

Thanks again for the help.





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Larry

2008-May-15 20:10 UTC

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Re: Model relationship design question.

One user (who coincidentally happens to belong to a company) writes an
article about zero or more companies. You will need, in addition to
users, submissions, and companies, a new table (and model) that has
all three ids: user_id, submission_id, and company_id.

On May 14, 11:40 pm, maestro777
<isig...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:> Thanks guys for all the input.
>
> I''m glad to find out that I was on the right track after all from
the
> beginning, with my models set up. It wasn''t that I was having
problem
> getting the result I wanted. Rather the source of my confusion came
> from a misunderstanding on what I was reading in one of the ROR books
> about model relationship. Now that you confirmed I was on the right
> track, I went back to read the same passage again and realized that it
> was talking about a different kind of relationship, than what I had in
> mind.
>
> Thanks again for the help.--~--~---------~--~----~------------~-------~--~----~
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Pardee, Roy

2008-May-15 20:16 UTC

head link

Re: Model relationship design question.

Or, since a submission is the product of only one user, you put user_id in
submissions, and then do a many:many between submissions and companies (so you
have a submissions_companies join table w/submission_id and company_id).

-----Original Message-----
From: rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
[mailto:rubyonrails-talk@googlegroups.com] On Behalf Of Larry
Sent: Thursday, May 15, 2008 1:10 PM
To: Ruby on Rails: Talk
Subject: [Rails] Re: Model relationship design question.


One user (who coincidentally happens to belong to a company) writes an article
about zero or more companies. You will need, in addition to users, submissions,
and companies, a new table (and model) that has all three ids: user_id,
submission_id, and company_id.

On May 14, 11:40 pm, maestro777
<isig...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:> Thanks guys for all the input.
>
> I''m glad to find out that I was on the right track after all from
the
> beginning, with my models set up. It wasn''t that I was having
problem
> getting the result I wanted. Rather the source of my confusion came 
> from a misunderstanding on what I was reading in one of the ROR books 
> about model relationship. Now that you confirmed I was on the right 
> track, I went back to read the same passage again and realized that it 
> was talking about a different kind of relationship, than what I had in 
> mind.
>
> Thanks again for the help.

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Carsten Gehling

2008-May-15 20:39 UTC

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Re: Model relationship design question.

Andrew Skegg wrote:
>> Each article is about a company (that exists in the company table) and
>> that company may or may not be the same company that the user
>> (submitting the article) belongs to....

+1 to Andrew''s suggestion. And let me explain why i think you are 
confused:

Your original suggestion mirrors that of Andrew. I''ve drawn it up in a 
diagram:

Company 1---n User    (Relation1)

User 1----n Article   (Relation2)

Company 1---n Article (Relation3)

The confusion might come because you think, that this design implies 
this rule:

Company CA has a user U1

U1 writes the article Ai

Then you automatically believe, that company CA is related to the 
article Ai.

And it is, but can actually be related in TWO different was:

Company CA "owns" (has authored) article Ai (through Relation1 & 
Relation2)

but at the same article Ai can relate to company CA (as the article''s 
subject) or relate to an entirely different company - through Relation3.

Sometimes (probably a lot of the times) the owner of the article and the 
subject of the article will be the same company. Therefore you believe, 
that this relation structure is redundant. It is. But at the same time 
it is a "necessary evil" to accomplice what you want.

I hope this clarifies some things. Your relation structure is sound, but 
you probably didn''t know why. :-)

- Carsten
-- 
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Rails - May 2008 - Model relationship design question.

Model relationship design question.

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