Rails - Dec 2007 - How would you do a multitable cross reference select box in Rails?

I''ve done this in other languages, but how would you handle the
following issue in Rails?

Assume database tables a, b and c. 
Each table has id,name,text fields 
(and yes, there are reasons why they are separate tables - 
I''m simplifying here)

Any record in any table can cross-reference one or more records 
in that table or another table. The cross reference tables are
 a_a, a_b, a_c, b_b, b_c, c_c [fields are as expected a_id,b_id, etc)

So assume record 1 in table a is referenced by:
record 22 in table a
record 347 in table b and 
record 19 in table c.

When a record is displayed, I have a dropdown select box that shows 
the name of any cross references. The contents are generated by a 
database view created by multiple selects combined with union.

The obvious hurdle in a select box is returning not just the id of the 
selected item, but also the table in which that particular item is located.
In my current (non-ruby, non-rails) implementation, this is solved by 
concatenating the table name with a separator and the record id

The select box thus returns the combined value which is then exploded
 into its parts so that the webapp can display the desired item. This 
isn''t difficult when done manually, but what would be the appropriate 
way of handling the issue in  the "Rails" way?

 


--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

On Dec 23, 2007 11:20 PM, Bryan Emrys
<bryan.emrys-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> The select box thus returns the combined value which is then exploded
>  into its parts so that the webapp can display the desired item. This
> isn''t difficult when done manually, but what would be the
appropriate
> way of handling the issue in  the "Rails" way?
Are you free to modify the database?
I''d probably try making a new model CrossReference with it''s
own table
cross_references.
This table can hold a_id, b_id and c_id, and your A, B and C each
has_many :cross_references.
If it makes sense for your models, A has_many :bs, :through =>
:cross_references etc.
I don''t know exactly what the details are for referencing the same
table (what you have in a_a, b_b and c_c), but I imagine it''s doable.

You''d have to add columns (d_id) to the cross_references table when
you add a table (d) to be cross referenced. But on the other hand, in
your current setup, you''d have to add an increasing number of new
reference-tables a_d, b_d, c_d and d_d.

hmm.. hope that helps
merry x-mas
- Martin

--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

I could modify the database to add a multitable linking table - I
can''t reduce the current number of linking tables because it would
break existing apps that I don''t control. The three real data tables
have a lot of fields that are not in common and serve different
purposes, so they can''t really be combined.

Even if I have a single multi-table linking table, I''m not sure that
solves the problem of how the select box passes the correct info.

A has_many :bs, :through => :cross_references
A has_many :cs, :through => :cross_references

I''m still puzzled at what the return from the single select box will
look like.

Bryan

Martin Svalin wrote:
> On Dec 23, 2007 11:20 PM, Bryan Emrys
<bryan.emrys-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> > The select box thus returns the combined value which is then exploded
> >  into its parts so that the webapp can display the desired item. This
> > isn''t difficult when done manually, but what would be the
appropriate
> > way of handling the issue in  the "Rails" way?
>
> Are you free to modify the database?
> I''d probably try making a new model CrossReference with
it''s own table
> cross_references.
> This table can hold a_id, b_id and c_id, and your A, B and C each
> has_many :cross_references.
> If it makes sense for your models, A has_many :bs, :through =>
> :cross_references etc.
> I don''t know exactly what the details are for referencing the same
> table (what you have in a_a, b_b and c_c), but I imagine it''s
doable.
>
> You''d have to add columns (d_id) to the cross_references table
when
> you add a table (d) to be cross referenced. But on the other hand, in
> your current setup, you''d have to add an increasing number of new
> reference-tables a_d, b_d, c_d and d_d.
>
> hmm.. hope that helps
> merry x-mas
> - Martin
--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

On Dec 24, 9:02 am, bryane
<bryan.em...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> I''m still puzzled at what the return from the single select box
will look like.
> In my current (non-ruby, non-rails) implementation, this is solved by
> concatenating the table name with a separator and the record id
Why can''t you use this method in Rails with options_for_select? You
can pass in an array of 2-element arrays, each of which contains the
text to display and the value to return. You can make the values just
like you did before.

///ark

--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

On Dec 23, 2:20 pm, Bryan Emrys
<bryan.em...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> I''ve done this in other languages, but how would you handle the
following issue in Rails?
>
> Assume database tables a, b and c.
> Each table has id,name,text fields
> (and yes, there are reasons why they are separate tables -
> I''m simplifying here)
>
> Any record in any table can cross-reference one or more records
> in that table or another table. The cross reference tables are
>  a_a, a_b, a_c, b_b, b_c, c_c [fields are as expected a_id,b_id, etc)
>
> So assume record 1 in table a is referenced by:
> record 22 in table a
> record 347 in table b and
> record 19 in table c.
>
> When a record is displayed, I have a dropdown select box that shows
> the name of any cross references. The contents are generated by a
> database view created by multiple selects combined with union.
>
> The obvious hurdle in a select box is returning not just the id of the
> selected item, but also the table in which that particular item is located.
> In my current (non-ruby, non-rails) implementation, this is solved by
> concatenating the table name with a separator and the record id
>
> The select box thus returns the combined value which is then exploded
>  into its parts so that the webapp can display the desired item. This
> isn''t difficult when done manually, but what would be the
appropriate
> way of handling the issue in  the "Rails" way?

It almost sounds like polymorphic table inheritance? (from the agile
book).
I''m having a hard time visualizing what the use-case would be (ie:
Employee < Person; Manager < Person; Mentor < Person subclassing?)
and how that would look in the select box itself.
--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

Think of the use case this way (again it is somewhat simplified)
Table A is text of laws relevant to our company
Table B is external commentary on laws (think articles)
Table C is internal commentary on laws (think internal notes).

Any law can be flagged with one or more references to another law, or
commentaries from either commentary table.
Any commentary (external or internal) can be flagged with one or more
references to one or more laws, or commentary from either commentary
table.

According to our lawyers, we need to keep the external commentary
separate from our internal commentary in order to avoid fights with
our external suppliers.

Bryan.

chovy wrote:
> On Dec 23, 2:20 pm, Bryan Emrys
<bryan.em...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> > I''ve done this in other languages, but how would you handle
the following issue in Rails?
> >
> > Assume database tables a, b and c.
> > Each table has id,name,text fields
> > (and yes, there are reasons why they are separate tables -
> > I''m simplifying here)
> >
> > Any record in any table can cross-reference one or more records
> > in that table or another table. The cross reference tables are
> >  a_a, a_b, a_c, b_b, b_c, c_c [fields are as expected a_id,b_id, etc)
> >
> > So assume record 1 in table a is referenced by:
> > record 22 in table a
> > record 347 in table b and
> > record 19 in table c.
> >
> > When a record is displayed, I have a dropdown select box that shows
> > the name of any cross references. The contents are generated by a
> > database view created by multiple selects combined with union.
> >
> > The obvious hurdle in a select box is returning not just the id of the
> > selected item, but also the table in which that particular item is
located.
> > In my current (non-ruby, non-rails) implementation, this is solved by
> > concatenating the table name with a separator and the record id
> >
> > The select box thus returns the combined value which is then exploded
> >  into its parts so that the webapp can display the desired item. This
> > isn''t difficult when done manually, but what would be the
appropriate
> > way of handling the issue in  the "Rails" way?
>
>
> It almost sounds like polymorphic table inheritance? (from the agile
> book).
> I''m having a hard time visualizing what the use-case would be (ie:
> Employee < Person; Manager < Person; Mentor < Person subclassing?)
> and how that would look in the select box itself.
--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

Perhaps a commentaries table with ''type'' attribute (externel
or
internal), and an foreign key that references the laws table and its
id.

Would look something like:


create_table commentaries:
   id => :integer,
   type => :string, #=> (internal or external)
   comment => :text
   law_id => :integer #=> references laws.id
end

create_table laws:
  id => :integer,
  name => :string,
  text => :text
end




On Dec 25, 12:45 pm, bryane
<bryan.em...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> Think of the use case this way (again it is somewhat simplified)
> Table A is text of laws relevant to our company
> Table B is external commentary on laws (think articles)
> Table C is internal commentary on laws (think internal notes).
>
> Any law can be flagged with one or more references to another law, or
> commentaries from either commentary table.
> Any commentary (external or internal) can be flagged with one or more
> references to one or more laws, or commentary from either commentary
> table.
>
> According to our lawyers, we need to keep the external commentary
> separate from our internal commentary in order to avoid fights with
> our external suppliers.
>
> Bryan.
>
> chovy wrote:
> > On Dec 23, 2:20 pm, Bryan Emrys
<bryan.em...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> > > I''ve done this in other languages, but how would you
handle the following issue in Rails?
>
> > > Assume database tables a, b and c.
> > > Each table has id,name,text fields
> > > (and yes, there are reasons why they are separate tables -
> > > I''m simplifying here)
>
> > > Any record in any table can cross-reference one or more records
> > > in that table or another table. The cross reference tables are
> > >  a_a, a_b, a_c, b_b, b_c, c_c [fields are as expected a_id,b_id,
etc)
>
> > > So assume record 1 in table a is referenced by:
> > > record 22 in table a
> > > record 347 in table b and
> > > record 19 in table c.
>
> > > When a record is displayed, I have a dropdown select box that
shows
> > > the name of any cross references. The contents are generated by a
> > > database view created by multiple selects combined with union.
>
> > > The obvious hurdle in a select box is returning not just the id
of the
> > > selected item, but also the table in which that particular item
is located.
> > > In my current (non-ruby, non-rails) implementation, this is
solved by
> > > concatenating the table name with a separator and the record id
>
> > > The select box thus returns the combined value which is then
exploded
> > >  into its parts so that the webapp can display the desired item.
This
> > > isn''t difficult when done manually, but what would be
the appropriate
> > > way of handling the issue in  the "Rails" way?
>
> > It almost sounds like polymorphic table inheritance? (from the agile
> > book).
> > I''m having a hard time visualizing what the use-case would be
(ie:
> > Employee < Person; Manager < Person; Mentor < Person
subclassing?)
> > and how that would look in the select box itself.
--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---