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agolaru-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org

2007-Jun-09 09:42 UTC

create 2 fk referencing the same table

Hi everyone! I have a problem with defining 2 fk referencing the same
table. I have a Program table and a Team table. The Program should
have an away team and a home team fk. From my understanding, "the fk
column should be named after the class of the target table, converted
to lowercase, with _id appended". But, in my case, I have 2 fk
referencing the same table. How can I do this?


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Morgan Whitney

2007-Jun-09 10:41 UTC

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Re: create 2 fk referencing the same table

On 6/9/07, agolaru-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org
<agolaru-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:>
> Hi everyone! I have a problem with defining 2 fk referencing the same
> table. I have a Program table and a Team table. The Program should
> have an away team and a home team fk. From my understanding, "the fk
> column should be named after the class of the target table, converted
> to lowercase, with _id appended". But, in my case, I have 2 fk
> referencing the same table. How can I do this?
I think this might work, but I didn''t set up a DB or an app to test it

class Program
  belongs_to :team, :foreign_key => "home_team_id"
  belongs_to :team, :foreign_key => "away_team_id"
end

-- 
F. Morgan Whitney
http://www.blizzo.com

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Lionel Bouton

2007-Jun-09 10:55 UTC

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Re: create 2 fk referencing the same table

Morgan Whitney wrote the following on 09.06.2007 12:41 :> On 6/9/07, agolaru-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org
<agolaru-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>   
>> Hi everyone! I have a problem with defining 2 fk referencing the same
>> table. I have a Program table and a Team table. The Program should
>> have an away team and a home team fk. From my understanding, "the
fk
>> column should be named after the class of the target table, converted
>> to lowercase, with _id appended". But, in my case, I have 2 fk
>> referencing the same table. How can I do this?
>>     
>
> I think this might work, but I didn''t set up a DB or an app to
test it
>
> class Program
>   belongs_to :team, :foreign_key => "home_team_id"
>   belongs_to :team, :foreign_key => "away_team_id"
> end
>
>   
class Program
    belongs_to :home_team, :class_name => :team
    belongs_to :away_team, :class_name => :team
end


To avoid mistakes, just remember that

belongs_to <sym>

creates the:

model.<sym>, model.<sym>=, ...

accessors so you obviously don''t want several "belongs_to
<sym> ..."
with identical values of <sym>.

(Note that this memento is mostly valid for other kinds of associations)

The foreign key should be computed automatically (by adding _id in this
example), if it doesn''t suits you, then you can use the :foreign_key
parameter.

See ActiveRecord docs for more.

Lionel.

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Lionel Bouton

2007-Jun-09 10:56 UTC

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Re: create 2 fk referencing the same table

Lionel Bouton wrote the following on 09.06.2007 12:55 :> Morgan Whitney wrote the following on 09.06.2007 12:41 :
>   
>> On 6/9/07, agolaru-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org
<agolaru-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>>   
>>     
>>> Hi everyone! I have a problem with defining 2 fk referencing the
same
>>> table. I have a Program table and a Team table. The Program should
>>> have an away team and a home team fk. From my understanding,
"the fk
>>> column should be named after the class of the target table,
converted
>>> to lowercase, with _id appended". But, in my case, I have 2 fk
>>> referencing the same table. How can I do this?
>>>     
>>>       
>> I think this might work, but I didn''t set up a DB or an app to
test it
>>
>> class Program
>>   belongs_to :team, :foreign_key => "home_team_id"
>>   belongs_to :team, :foreign_key => "away_team_id"
>> end
>>
>>   
>>     
>
> class Program
>     belongs_to :home_team, :class_name => :team
>   
better be :class_name => "Team"

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agolaru-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org

2007-Jun-09 11:27 UTC

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Re: create 2 fk referencing the same table

Thanks guys... I will try it out and get back to you...

On Jun 9, 1:56 pm, Lionel Bouton
<lionel-subscript...-WTamNBQcZIx7tPAFqOLdPg@public.gmane.org>
wrote:> Lionel Bouton wrote the following on 09.06.2007 12:55 :
>
>
>
> > Morgan Whitney wrote the following on 09.06.2007 12:41 :
>
> >> On 6/9/07, agol...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org
<agol...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>
> >>> Hi everyone! I have a problem with defining 2 fk referencing
the same
> >>> table. I have a Program table and a Team table. The Program
should
> >>> have an away team and a home team fk. From my understanding,
"the fk
> >>> column should be named after the class of the target table,
converted
> >>> to lowercase, with _id appended". But, in my case, I have
2 fk
> >>> referencing the same table. How can I do this?
>
> >> I think this might work, but I didn''t set up a DB or an
app to test it
>
> >> class Program
> >>   belongs_to :team, :foreign_key => "home_team_id"
> >>   belongs_to :team, :foreign_key => "away_team_id"
> >> end
>
> > class Program
> >     belongs_to :home_team, :class_name => :team
>
> better be :class_name => "Team"

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Josh Susser

2007-Jun-09 17:28 UTC

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Re: create 2 fk referencing the same table

agolaru-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org wrote:> Hi everyone! I have a problem with defining 2 fk referencing the same
> table. I have a Program table and a Team table. The Program should
> have an away team and a home team fk. From my understanding, "the fk
> column should be named after the class of the target table, converted
> to lowercase, with _id appended". But, in my case, I have 2 fk
> referencing the same table. How can I do this?
For non-standard association names, you have to specify both the foreign 
key and the class name. Try this:

class Program
  belongs_to :home_team,
    :class_name => "Team", :foreign_key =>
"home_team_id"
  belongs_to :away_team,
    :class_name => "Team", :foreign_key =>
"away_team_id"
end

class Team
  has_many :home_programs,
    :class_name => "Program", :foreign_key =>
"home_team_id"
  has_many :away_programs,
    :class_name => "Program", :foreign_key =>
"away_team_id"
end

--
Josh Susser
http://blog.hasmanythrough.com

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

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James

2007-Jun-09 17:47 UTC

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Re: create 2 fk referencing the same table

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agolaru-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org

2007-Jun-09 19:51 UTC

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Re: create 2 fk referencing the same table

Hi, guys! I''m back...Thanks for your feedback...it worked ...great
advices from all of you...

On Jun 9, 8:28 pm, Josh Susser
<rails-mailing-l...-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:> agol...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org wrote:
> > Hi everyone! I have a problem with defining 2 fk referencing the same
> > table. I have a Program table and a Team table. The Program should
> > have an away team and a home team fk. From my understanding, "the
fk
> > column should be named after the class of the target table, converted
> > to lowercase, with _id appended". But, in my case, I have 2 fk
> > referencing the same table. How can I do this?
>
> For non-standard association names, you have to specify both the foreign
> key and the class name. Try this:
>
> class Program
>   belongs_to :home_team,
>     :class_name => "Team", :foreign_key =>
"home_team_id"
>   belongs_to :away_team,
>     :class_name => "Team", :foreign_key =>
"away_team_id"
> end
>
> class Team
>   has_many :home_programs,
>     :class_name => "Program", :foreign_key =>
"home_team_id"
>   has_many :away_programs,
>     :class_name => "Program", :foreign_key =>
"away_team_id"
> end
>
> --
> Josh Susserhttp://blog.hasmanythrough.com
>
> --
> Posted viahttp://www.ruby-forum.com/.

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