Create 2 fk referencing the same table

Rails
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

On 6/9/07, [email protected] [email protected] 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

3

Morgan Whitney wrote the following on 09.06.2007 12:41 :

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

creates the:

model., model.=, …

accessors so you obviously don’t want several “belongs_to …”
with identical values of .

(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 B. wrote the following on 09.06.2007 12:55 :

referencing the same table. How can I do this?

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…

On Jun 9, 1:56 pm, Lionel B. [email protected]

6

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

On Jun 9, 8:28 pm, Josh S. [email protected]

7

[email protected] 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 S.
http://blog.hasmanythrough.com