Rails - Jul 2009 - How to access nested params in controller

Hello,

I''m trying to check some value in the controller so that I can change
the behavior accordingly.  I have a form set up such that when
submitted, the params looks like this:

{
 "transport"=>{
 "from_location"=>"Portland",

 "transports_transits_attributes"=>{"1246482280809"=>{"city"=>"Osaka",
 "country"=>"2"},
 "0"=>{"city"=>"Seattle",
 "country"=>"1"}},

 "to_location"=>"Tokyo",
 "departure_date"=>"01-Jul-2009",
 "arrival_date"=>"02-Jul-2009"}
}

My question is in regards to the nested table "transports_transits"
that you see in the middle with two records.  How would I access the
specific values in the nested table?  I know I can populate the model
by @transport = Transport.new(params[:transport]), but what if I want
to access one of the values in "transports_transits" table, say, to
get value "Osaka"?

Thanks!

2009/7/1 khagimoto
<kumi.hagimoto-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>:
>
> Hello,
>
> I''m trying to check some value in the controller so that I can
change
> the behavior accordingly.  I have a form set up such that when
> submitted, the params looks like this:
>
> {
>  "transport"=>{
>  "from_location"=>"Portland",
>
>
 "transports_transits_attributes"=>{"1246482280809"=>{"city"=>"Osaka",
>  "country"=>"2"},
>  "0"=>{"city"=>"Seattle",
>  "country"=>"1"}},
>
>  "to_location"=>"Tokyo",
>  "departure_date"=>"01-Jul-2009",
>  "arrival_date"=>"02-Jul-2009"}
> }
>
> My question is in regards to the nested table
"transports_transits"
> that you see in the middle with two records.  How would I access the
> specific values in the nested table?  I know I can populate the model
> by @transport = Transport.new(params[:transport]), but what if I want
> to access one of the values in "transports_transits" table, say,
to
> get value "Osaka"?
>
If I understand the question correctly you eant something like
params[:transports_transits_attributes][:1246482280809][:city] I
think.

Colin

Thanks, Colin.
I tried what you suggested like this (with quotes around the number),
and it worked.

params[:transport][:transports_transits_attributes][:"0"][:city]
==>
gets me "Seattle" from the initial example.

The problem I have now is that the numbers ("0" and
"1246482280809")
are auto-assigned, so I don''t know how I would access them then.  The
first one always seem to get "0", but there can be many more
transports_transits for one transport, and all but the first will get
a random number assigned.  Is there a way I can access them without
referring to these numbers?  For example, I can get the length of the
array like this:

len = params[:transport][:transports_transits_attributes].length

and I would love to be able to iterate through the array like this
(sorry for the bad syntax, but you get the idea..):

for (int i=0; i<len; i++)
  params[:transport][:transports_transits_attributes](i)[:city]

but I can''t seem to do that.  Any suggestions?
Thanks!
Kumi

2009/7/2 khagimoto
<kumi.hagimoto-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>:
>
> Thanks, Colin.
> I tried what you suggested like this (with quotes around the number),
> and it worked.
>
> params[:transport][:transports_transits_attributes][:"0"][:city]
==>
> gets me "Seattle" from the initial example.
>
> The problem I have now is that the numbers ("0" and
"1246482280809")
> are auto-assigned, so I don''t know how I would access them then.
 The
> first one always seem to get "0", but there can be many more
> transports_transits for one transport, and all but the first will get
> a random number assigned.  Is there a way I can access them without
> referring to these numbers?  For example, I can get the length of the
> array like this:
>
> len = params[:transport][:transports_transits_attributes].length
>
> and I would love to be able to iterate through the array like this
> (sorry for the bad syntax, but you get the idea..):
>
> for (int i=0; i<len; i++)
>  params[:transport][:transports_transits_attributes](i)[:city]
>
> but I can''t seem to do that.  Any suggestions?
It should be [i] not (i) but a much more railsy way is

params[:transport][:transports_transits_attributes].each do |attr|
  # do something with attr[:city]
end

However, I have to say that you seem to be doing rather unusual things
which, when I find myself in such a situation, usually means I am
tackling something in the wrong way.  Can I ask why are you parsing
the params in the first place rather than using them to build objects
in the usual way?

Colin

That did cross my mind, but I also wanted to know how to do something
like this if it was possible.  attr[:city] didn''t work..

But here''s what I''m really trying to do.
I have a form that lets user enter transport information like arrival/
departure airports, time, etc.  If there are transits in between, user
can add as many transits as they like - or None.  When the form is
submitted, even when there are no transits, there is one empty
transports_transits_attributes, and I''m trying to catch that somehow
so it doesn''t get saved to the database with blanks.

Here''s the model:

--------------------------------------------
class Transport < ActiveRecord::Base

  has_many :users, :through => :transports_users
  has_many :transports_transits, :dependent => :destroy
  accepts_nested_attributes_for :transports_transits, :allow_destroy
=> true

end
--------------------------------------------

and the form snippet for where transits are added/removed

--------------------------------------------
<div id="transits" style="display: none">
  <% f.fields_for :transports_transits do |i| %>
    <%= render :partial => ''transport_transit'', :locals
=> { :form =>
i } %>
  <% end %>
</div>
<%= add_transport_transit_link(f) %>
--------------------------------------------

and in the helper, I have
--------------------------------------------
def add_transport_transit_link(form_builder)
  link_to_function ''Add transits'' do |page|
    form_builder.fields_for :transports_transits,
TransportsTransit.new, :child_index => ''NEW_RECORD'' do |f|
      html = render(:partial => ''transport_transit'',
:locals =>
{ :form => f })
      page << "if($(''transits'').visible())
$(''transits'').insert
({ bottom: ''#{escape_javascript(html)}''.replace(/NEW_RECORD/g,
new Date
().getTime()) }); else $(''transits'').show();"
    end
  end
end
--------------------------------------------

As you can see, at first, this div is invisible and only becomes
visible when the add_transport_transit_link is clicked for the first
time by the user.  The subsequent click will actually add more
transport_transit form.

*** So the real problem is that the first transit form is there
(although invisible).***

I couldn''t figure out how to not have the first transit initially -
and that''s why I was trying to deal with it after the fact.  I hope
I''m making sense here.

2009/7/2 khagimoto
<kumi.hagimoto-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>:
>
> That did cross my mind, but I also wanted to know how to do something
> like this if it was possible.  attr[:city] didn''t work..
>
Use the debugger to find out why attr[:city] does not work. Google
ruby-debug and look in the ruby guides and railscasts for how to use
it if necessary.
> But here''s what I''m really trying to do.
> I have a form that lets user enter transport information like arrival/
> departure airports, time, etc.  If there are transits in between, user
> can add as many transits as they like - or None.  When the form is
> submitted, even when there are no transits, there is one empty
> transports_transits_attributes, and I''m trying to catch that
somehow
> so it doesn''t get saved to the database with blanks.
>
> Here''s the model:
>
> --------------------------------------------
> class Transport < ActiveRecord::Base
>
>  has_many :users, :through => :transports_users
>  has_many :transports_transits, :dependent => :destroy
>  accepts_nested_attributes_for :transports_transits, :allow_destroy
> => true
>
> end
> --------------------------------------------
>
> and the form snippet for where transits are added/removed
>
> --------------------------------------------
> <div id="transits" style="display: none">
>  <% f.fields_for :transports_transits do |i| %>
>    <%= render :partial => ''transport_transit'',
:locals => { :form =>
> i } %>
>  <% end %>
> </div>
> <%= add_transport_transit_link(f) %>
> --------------------------------------------
>
> and in the helper, I have
> --------------------------------------------
> def add_transport_transit_link(form_builder)
>  link_to_function ''Add transits'' do |page|
>    form_builder.fields_for :transports_transits,
> TransportsTransit.new, :child_index => ''NEW_RECORD'' do
|f|
>      html = render(:partial => ''transport_transit'',
:locals =>
> { :form => f })
>      page << "if($(''transits'').visible())
$(''transits'').insert
> ({ bottom:
''#{escape_javascript(html)}''.replace(/NEW_RECORD/g, new Date
> ().getTime()) }); else $(''transits'').show();"
>    end
>  end
> end
> --------------------------------------------
>
> As you can see, at first, this div is invisible and only becomes
> visible when the add_transport_transit_link is clicked for the first
> time by the user.  The subsequent click will actually add more
> transport_transit form.
>
> *** So the real problem is that the first transit form is there
> (although invisible).***
>
> I couldn''t figure out how to not have the first transit initially
-
> and that''s why I was trying to deal with it after the fact.  I
hope
> I''m making sense here.
This is a bit out of my comfort zone, can anyone else help?

Colin

Thanks, Colin.

I don''t understand why yet, but this seems to get the value in the
nested table.

---------------------------------
params[:transport][:transports_transits_attributes].each do |attr|
  $stderr.puts "DEBUG: city = ''#{attr[1][:city]}''"
end
---------------------------------

I don''t know why it''s attr[1]...  The params looks like this:

---------------------------------
{
 "transport"=>{
 "from_location"=>"",
 "from_country"=>"1",
 "transports_transits_attributes"=>{"1246576128669"=>
{"city"=>"seattle",
 "country"=>"1"},
 "0"=>{"city"=>"portland",
 "country"=>"1"}},
 "departure_time"=>"",
 "to_location"=>"",
 "departure_date"=>"",
 "to_country"=>"1",
 "arrival_time"=>"",
 "arrival_date"=>""}}
---------------------------------

Thanks for pointing me to the ruby-debug.  I''ll get the gem and try it
out.  I''m relatively new to ruby and RoR, so still feeling my way
through more or less.

I''m still searching for alternate way.. if anyone can help with the
problem I mentioned in the 2:22 pm post (two posts above this one),
I''d really appreciate it!

Thanks
Kumi

Please disregard my question above..   I figured out what I was doing
wrong.
In the controller (in "def new"), I had

@transport.transports_transits.build

which was the problem all along.  This was the reason I had one record
in the nested table even when there was no transit record entered by
the user.  I commented it out, deleted the " if visible" part in
helper method, and made the nested transit form visible to start with
and everything works fine now.

Colin, thanks anyway - I learned how to read the params somewhat and
now I know about the ruby-debug gem! :-)

Kumi