Rails - Dec 2005 - Single Table Inheritance question

Hello,

I''m having a heck of a time getting Single Table Inheritance to work in
my app.
I have the following models and have scaffolded out Person and Contact.

person.rb
class Person < ActiveRecord::Base
  has_many :contacts
end

client.rb
class Client < Person
end

contact.rb
class Contact < ActiveRecord::Base
  belongs_to :person
end

phone.rb
class Phone < Contact
end

In script/console I’ve run:
 c = Client.find :first
 c.phones.create :contactdata => “555-555-5555”

and get “NoMethodError : undefined method ‘phones’ etc…”

I tried moving the relationships in to the client and phone models but then
there was an SQL error: “Unknown column contacts.client_id” because the
contacts table has a person_id column not a client_id column. Any help would be
greatly appreciated.

Hugh


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On Dec 19, 2005, at 10:54 AM,
hkelsey-EcXoqBC4F/kd5Ot1ntKM6ZqQE7yCjDx5@public.gmane.org wrote:
> Hello,
>
> I''m having a heck of a time getting Single Table Inheritance to  
> work in my app.
> I have the following models and have scaffolded out Person and  
> Contact.
>
> person.rb
> class Person < ActiveRecord::Base
>   has_many :contacts
> end
>
> client.rb
> class Client < Person
> end
>
> contact.rb
> class Contact < ActiveRecord::Base
>   belongs_to :person
> end
>
> phone.rb
> class Phone < Contact
> end
>
> In script/console I’ve run:
>  c = Client.find :first
>  c.phones.create :contactdata => “555-555-5555”
>
> and get “NoMethodError : undefined method ‘phones’ etc…”
>
You need to create a phone and then add it to the list of phones:

c = Client.find :first
p = Phone.create :contactdata => ''555-555-5555''
c.phones << p
> I tried moving the relationships in to the client and phone models  
> but then
> there was an SQL error: “Unknown column contacts.client_id” because  
> the
> contacts table has a person_id column not a client_id column. Any  
> help would be
> greatly appreciated.
>
> Hugh
>
>
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> This message was sent using IMP, the Internet Messaging Program.
>
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> Rails mailing list
> Rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
Duane Johnson
(canadaduane)
http://blog.inquirylabs.com/

On Dec 19, 2005, at 11:31 AM, Duane Johnson wrote:
>
> On Dec 19, 2005, at 10:54 AM,
hkelsey-EcXoqBC4F/kd5Ot1ntKM6ZqQE7yCjDx5@public.gmane.org wrote:
>
>> Hello,
>>
>> I''m having a heck of a time getting Single Table Inheritance
to
>> work in my app.
>> I have the following models and have scaffolded out Person and  
>> Contact.
>>
>> person.rb
>> class Person < ActiveRecord::Base
>>   has_many :contacts
>> end
>>
>> client.rb
>> class Client < Person
>> end
>>
>> contact.rb
>> class Contact < ActiveRecord::Base
>>   belongs_to :person
>> end
>>
>> phone.rb
>> class Phone < Contact
>> end
>>
>> In script/console I’ve run:
>>  c = Client.find :first
>>  c.phones.create :contactdata => “555-555-5555”
>>
>> and get “NoMethodError : undefined method ‘phones’ etc…”
>>
> You need to create a phone and then add it to the list of phones:
>
> c = Client.find :first
> p = Phone.create :contactdata => ''555-555-5555''
> c.phones << p
Hrm.  And it also appears that your relationship is actually  
has_many :contacts, so you''d do this instead:

c = Client.find :first
p = Phone.create :contactdata => ''555-555-5555''
c.contacts << p


Duane Johnson
(canadaduane)
http://blog.inquirylabs.com/

So, I have a model called Organization.  Chapter and Committee inherit from it.

I''m letting the user create new Organizations.  So, they were able to
select whether or not the Organization was a Chapter or Committee.

When I tried to do stuff like <%= radio_button
''organization'', ''type
%>, I got a ton of warning messages about how I should be using #class
and not #type.  And doing tests on the type field of an organization
also reported a bunch of warnings.

I was able to fix the whole thing by using a ''kind'' column
(instead of
''type'') in the organizations table and using that as the
inheritance
column, but it seems weird that I had to do stuff like that.

Any thoughts?

On 12/30/05, Joe Van Dyk
<joevandyk-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> So, I have a model called Organization.  Chapter and Committee inherit from
it.
>
> I''m letting the user create new Organizations.  So, they were able
to
> select whether or not the Organization was a Chapter or Committee.
>
> When I tried to do stuff like <%= radio_button
''organization'', ''type
> %>, I got a ton of warning messages about how I should be using #class
> and not #type.  And doing tests on the type field of an organization
> also reported a bunch of warnings.
>
> I was able to fix the whole thing by using a ''kind''
column (instead of
> ''type'') in the organizations table and using that as the
inheritance
> column, but it seems weird that I had to do stuff like that.
>
I''ve ended up doing the same.  My base class is
''Rule'', so I went with
rule_type as the inheritance column.

While we''re here, does anyone have a better suggestion than this?
I''ve got a postback-style action called new_rule, which contains a
select box for the user to select which kind of ''rule''
they''d like,
etc, etc.
Because it''s a postback, there are no ''rule''
parameters the first time
through.  I''ve got something like this going, but I''m always
paranoid
about making things difficult for myself.

def new_rule
  rule_type = ''Rule''
  if params[:rule]
    rule_type = params[:rule][:rule_type] || ''Rule''
  end
  klass = Object.const_get(rule_type)
  @rule = klass.new(params[:rule])

  if request.post? and @rule.save
    flash[:notice] = "#{@rule.class} was successfully created."
    redirect_to :action => ''show_rule'', :id => @rule
  end
end

With this, @rule starts out as an instance of Rule, but ends up as
something more specific, such as DomainRule, before being saved.

Hi, Joe,

this is adressed in "agile web development with rails" as a less
obvious
constraint of the rails model of sti. The attribute type is also a name 
of a ruby method. therefore you shouldn''t adress it directly but via
the
objects indexing interface, using (in your case): organization[:type] = 
your radio_button parameter

regards
jan

Joe Van Dyk wrote:
>So, I have a model called Organization.  Chapter and Committee inherit from
it.
>
>I''m letting the user create new Organizations.  So, they were able
to
>select whether or not the Organization was a Chapter or Committee.
>
>When I tried to do stuff like <%= radio_button
''organization'', ''type
>%>, I got a ton of warning messages about how I should be using #class
>and not #type.  And doing tests on the type field of an organization
>also reported a bunch of warnings.
>
>I was able to fix the whole thing by using a ''kind'' column
(instead of
>''type'') in the organizations table and using that as the
inheritance
>column, but it seems weird that I had to do stuff like that.
>
>Any thoughts?
>_______________________________________________
>Rails mailing list
>Rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
>http://lists.rubyonrails.org/mailman/listinfo/rails
>
>  
>

On 12/30/05, Wilson Bilkovich
<wilsonb-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> On 12/30/05, Joe Van Dyk
<joevandyk-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> > So, I have a model called Organization.  Chapter and Committee inherit
from it.
> >
> > I''m letting the user create new Organizations.  So, they were
able to
> > select whether or not the Organization was a Chapter or Committee.
> >
> > When I tried to do stuff like <%= radio_button
''organization'', ''type
> > %>, I got a ton of warning messages about how I should be using
#class
> > and not #type.  And doing tests on the type field of an organization
> > also reported a bunch of warnings.
> >
> > I was able to fix the whole thing by using a ''kind''
column (instead of
> > ''type'') in the organizations table and using that as
the inheritance
> > column, but it seems weird that I had to do stuff like that.
> >
> I''ve ended up doing the same.  My base class is
''Rule'', so I went with
> rule_type as the inheritance column.
Seems like that should be the default, instead of ''type''.  The
default
choice seems broken (unless I''m understanding it wrong).

said that (obj.type as a deprecated synonym for Object#class in ruby: 
http://www.ruby-doc.org/core/classes/Object.html#M001065) your approach 
seems to me as a fine workaround.

regards
Jan

Joe Van Dyk wrote:
>So, I have a model called Organization.  Chapter and Committee inherit from
it.
>
>I''m letting the user create new Organizations.  So, they were able
to
>select whether or not the Organization was a Chapter or Committee.
>
>When I tried to do stuff like <%= radio_button
''organization'', ''type
>%>, I got a ton of warning messages about how I should be using #class
>and not #type.  And doing tests on the type field of an organization
>also reported a bunch of warnings.
>
>I was able to fix the whole thing by using a ''kind'' column
(instead of
>''type'') in the organizations table and using that as the
inheritance
>column, but it seems weird that I had to do stuff like that.
>
>Any thoughts?
>_______________________________________________
>Rails mailing list
>Rails@lists.rubyonrails.org
>http://lists.rubyonrails.org/mailman/listinfo/rails
>
>  
>

On 12/30/05, Jan Prill <JanPrill@blauton.de>
wrote:
> Joe Van Dyk wrote:
>
> >So, I have a model called Organization.  Chapter and Committee inherit
from it.
> >
> >I''m letting the user create new Organizations.  So, they were
able to
> >select whether or not the Organization was a Chapter or Committee.
> >
> >When I tried to do stuff like <%= radio_button
''organization'', ''type
> >%>, I got a ton of warning messages about how I should be using
#class
> >and not #type.  And doing tests on the type field of an organization
> >also reported a bunch of warnings.
> >
> >I was able to fix the whole thing by using a ''kind''
column (instead of
> >''type'') in the organizations table and using that as
the inheritance
> >column, but it seems weird that I had to do stuff like that.
>
> Hi, Joe,
>
> this is adressed in "agile web development with rails" as a less
obvious
> constraint of the rails model of sti. The attribute type is also a name
> of a ruby method. therefore you shouldn''t adress it directly but
via the
> objects indexing interface, using (in your case): organization[:type] >
your radio_button parameter
Hi, thanks for pointing that out.

But, doing <%= radio_button "organization", "type" %>
was causing a
ton of warning messages.

It''s not a big deal though.  Anyone know why ''type''
was chosen as
opposed to ''<class>_type''?