create 2 fk referencing the same table

rubyonrails-talk
1

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?

2

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

3

Morgan Whitney wrote the following on 09.06.2007 12:41 :

  

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.

4

Lionel Bouton wrote the following on 09.06.2007 12:55 :

Morgan Whitney wrote the following on 09.06.2007 12:41 :   

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"

5

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

6

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7

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