Rails - Aug 2006 - ActiveRecord, single inheritance (STI)

Hi, when using STI, Do I have to set type column''s value explicity or
is it set by Rails?


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Eduardo Yáñez Parareda wrote:
> Hi, when using STI, Do I have to set type column''s value explicity
or
> is it set by Rails?
Rails handles it all for you.

Chris


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On 24 Aug 2006, at 11:22, Eduardo Yáñez Parareda wrote:
>
> Hi, when using STI, Do I have to set type column''s value explicity
or
> is it set by Rails?
It''s set by rails, assuming you have a type column

------
Alastair Moore
Standards compliant web development with Ruby On Rails, PHP and ASP
www.kozmo.co.uk
07738 399038




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> It''s set by rails, assuming you have a type column
Well, I asked it because I have this migration:

class CreateFormations < ActiveRecord::Migration
  def self.up
    create_table :formations do |t|
      # Esta columna es para soportar herencia entre Formation y
TeamFormation
      t.column :type, :string
      t.column :name, :string, :limit => 16, :null => false

      # Atributos para TeamFormations
      t.column :match_id, :integer
      t.column :team_id, :integer
    end

    # Creamos por defecto el tipo de alineación 4-4-2
    formation = Formation.create(:name => :''4-4-2'')   
<---- HERE I
CREATE AN OBJECT AND
    formation.save!
    SAVE IT
  end

  def self.down
    drop_table :formations
  end
end

Within there I save a new Formation but after that type column is null.


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On 24 Aug 2006, at 12:04, Eduardo Yáñez Parareda wrote:
>
>> It''s set by rails, assuming you have a type column
>
> Well, I asked it because I have this migration:
>
> class CreateFormations < ActiveRecord::Migration
>   def self.up
>     create_table :formations do |t|
>       # Esta columna es para soportar herencia entre Formation y
> TeamFormation
>       t.column :type, :string
>       t.column :name, :string, :limit => 16, :null => false
>
>       # Atributos para TeamFormations
>       t.column :match_id, :integer
>       t.column :team_id, :integer
>     end
>
>     # Creamos por defecto el tipo de alineación 4-4-2
>     formation = Formation.create(:name => :''4-4-2'')   
<---- HERE I
> CREATE AN OBJECT AND
>     formation.save!
>     SAVE IT
>   end
>
>   def self.down
>     drop_table :formations
>   end
> end
>
> Within there I save a new Formation but after that type column is  
> null.
I think that is because it is assumed unless you''re inheriting the  
model Formation, in your example, you''re  creating a new Formation.  
If you were to create a TeamFormation model -

class TeamFormation < Formation

and then

TeamFormation.create :name => ''4-4-2''

in your Formation table, it will insert the type TeamFormation.  
Formation isn''t inheriting anything.

------
Alastair Moore
Standards compliant web development with Ruby On Rails, PHP and ASP
www.kozmo.co.uk
07738 399038




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On 8/24/06, Eduardo Yáñez Parareda
<eduardo.yanez-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
>
>
> > It''s set by rails, assuming you have a type column
>
> Well, I asked it because I have this migration:
>
> class CreateFormations < ActiveRecord::Migration
>   def self.up
>     create_table :formations do |t|
>       # Esta columna es para soportar herencia entre Formation y
> TeamFormation
>       t.column :type, :string
>       t.column :name, :string, :limit => 16, :null => false
>
>       # Atributos para TeamFormations
>       t.column :match_id, :integer
>       t.column :team_id, :integer
>     end
>
>     # Creamos por defecto el tipo de alineación 4-4-2
>     formation = Formation.create(:name => :''4-4-2'')   
<---- HERE I
> CREATE AN OBJECT AND
>     formation.save!
>     SAVE IT
>   end
>
>   def self.down
>     drop_table :formations
>   end
> end
>
> Okay so Formation has your type column then. I don''t believe that
you want
to be creating objects based on it directly. Try this

class Specialformation < Formation
end
class Differentformation < Formation
end

sf= Specialformation.create(:name => ''4-4-2'')
df = Differentformation.create(:name => ''3-5-2'')
If you peek into your formations table, you should see two new records, with
correct type fields.

HTH,
Howard


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