Rails - Apr 2012 - one master table to hold symbols: good or bad idea?

(This is may be more of a db design question than a rails question.)

Summary:

I''m thinking of creating a single AR class to hold constant symbol
values and use it for :has_many_through relations whenever I need a
constant symbol.  Is this a good idea or a bad idea?

Details:

I notice that I have a lot of models that contain just a name string:

  create_table "natural_resources", :force => true do |t|
    t.string   "name"
  end

  create_table "roles", :force => true do |t|
    t.string   "name"
  end

  ... etc ...

These moels are always joined through a has_many_through relation to
some other object (e.g. User :has_many :roles, :through => :user_roles),
and the names are treated effectively as constant symbols.

So I''m thinking of consolidating these models into a single one:

  create_table :symbols, :force => true do |t|
    t.string :name
  end
  add_index :symbols, :name, :unique=>true

  class Util::Symbol < ActiveRecord::Base
    validates :name, :presence => true
    def self.intern(name)
      (r = where(:name => name.to_s)).create!
    rescue ActiveRecord::RecordNotUnique
      r.first
    end
  end

... and using this wherever I''d previously used separate classes.  This
feels DRYer.

Can anyone give a strong argument for or against this approach?

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What problem are you trying to solve by doing this?

Just seems like it would make your code more complicated with no real 
benefit.

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Tim Shaffer wrote in post #1054854:
> What problem are you trying to solve by doing this?
>
> Just seems like it would make your code more complicated with no real
> benefit.
DRYer code: this approach has fewer distinct tables, fewer distinct 
classes, fewer things to test and maintain.  But I may be missing 
something (which is why I''m asking): what part of the code becomes more
complicated this with this approach?

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On 3 April 2012 18:32, Fearless Fool
<lists-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org>
wrote:
> (This is may be more of a db design question than a rails question.)
>
> Summary:
>
> I''m thinking of creating a single AR class to hold constant symbol
> values and use it for :has_many_through relations whenever I need a
> constant symbol.  Is this a good idea or a bad idea?
>
> Details:
>
> I notice that I have a lot of models that contain just a name string:
>
>  create_table "natural_resources", :force => true do |t|
>    t.string   "name"
>  end
>
>  create_table "roles", :force => true do |t|
>    t.string   "name"
>  end
>
>  ... etc ...
>
> These moels are always joined through a has_many_through relation to
> some other object (e.g. User :has_many :roles, :through => :user_roles),
> and the names are treated effectively as constant symbols.
>
> So I''m thinking of consolidating these models into a single one:
>
>  create_table :symbols, :force => true do |t|
>    t.string :name
>  end
>  add_index :symbols, :name, :unique=>true
>
>  class Util::Symbol < ActiveRecord::Base
>    validates :name, :presence => true
>    def self.intern(name)
>      (r = where(:name => name.to_s)).create!
>    rescue ActiveRecord::RecordNotUnique
>      r.first
>    end
>  end
>
> ... and using this wherever I''d previously used separate classes.
 This
> feels DRYer.
>
> Can anyone give a strong argument for or against this approach?
Do you mean that the only thing in your roles and natural_resources
tables are the names?
If so then you could put them in one table.  Consider the situation
where a role and a natural_resource happened to have the same name
however.  If you decided to change the name of the role then that
would also change the name of the natural_resource.

Colin

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On Tuesday, 3 April 2012 13:32:54 UTC-4, Ruby-Forum.com User
wrote:
>
> (This is may be more of a db design question than a rails question.)
>
> Summary:
>
> I''m thinking of creating a single AR class to hold constant symbol
> values and use it for :has_many_through relations whenever I need a
> constant symbol.  Is this a good idea or a bad idea?
>
>
> Given your examples, I''m not convinced all of the things even need
to BE
in the database. One question I''d ask to help decide this is, "can
an
end-user meaningfully add a new one of these through the web interface?"

For example, "roles" typically would NOT be meaningful to add from the
web
interface - they require additional plumbing (unless you''ve got serious
DB-driven RBAC already) in code above and beyond a simple name.

On the other hand, "categories" on a blog are a classic example of 
something that belongs in the DB; there''s no additional behavior
expected,
they''re just labels that can be attached to other things.

As to your original question, I''d lean towards "bad idea" -
as others have
pointed out, if the items in question are supposed to operate in separate 
domains they should be kept separate. This winds up simplifying lots of 
stuff - for instance, I can''t think of any reason one would want to
display
a drop-down with a mishmash of natural resources and user roles, but a list 
of one or the other makes sense.

If you''re really just looking for the ability to attach
context-sensitive
labels, you may also want to look at acts_as_taggable_on and friends:

https://github.com/mbleigh/acts-as-taggable-on

which will do nearly all of the work for you.

--Matt Jones

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