Additional model attributes

Hi,
i have a “place” model with 2 columns (id, name).
I’m calling an external api which gives me data to create a new place
object.

I would like to add the address from the external place to the place
object and render it as a json result, without storing it in the
database.

i don’t get any errors, but the address never shows up within the json
output. i’ve tried with attr_accessor but that didn’t work either.

any hints?

thanks

==========================================
place.rb

class Place < ActiveRecord::Base
attr_accessor: address
end

==========================================
places_controller.rb

external_api_place_data = @client.find(place_id)
place = Place.new
place.name = place.name
place.id = place.id

//not showing up in the json result
place.address = external_api_place_data.address

places = []
places << place

respond_to do |format|
format.html # index.html.erb
format.json { render json: places }
end

==========================================

On 25 Oct 2011, at 14:03, “Lukas M.” [email protected] wrote:

output. i’ve tried with attr_accessor but that didn’t work either.
foo.to_json(:methods => [:attr1, :attr2])
Maybe? (assuming that foo.attr1 returns one of your extra attributes)

Fred.

I think for Rails to recognize that the attribute should be included,
you
need to use attr_accessible rather than the Ruby method attr_accessor.

hi,
that works but not in the case when i would like to do something like
this:

user_place = Location.new(:place => place, :user => user)

user_place.to_json //address is missing

hm… no luck with that either. when i try to print out the places object
in the console (logger.debug @place.to_yaml), “address” is missing.

On Tue, Oct 25, 2011 at 5:00 PM, Lukas M. [email protected] wrote:

hm… no luck with that either. when i try to print out the places object
in the console (logger.debug @place.to_yaml), “address” is missing.

From the top of my head (not hard tested now).

Now you refer to to_yaml, in previous mails, you refered to to_json.

Be careful, there is a fundamental difference between to_xml, to_json,
to_yaml on ActiveRecord …

One of them (I believe to_yaml) prints the “raw” database column values,
even if you overwrite that accessor function with a name. The other two
(to_json, to_xml IIRC) use the attribute accessors (from ActiveRecord I
presume), that can be overwritten by your own code.

So, I would expect to_yaml to never work in this scenario (where there
is
no database column). But to_json should be possible in this scenario
(I did some simple tests with ActiveModel and that seemed to work as
expected).

HTH,

Peter

One alternative in terms of dynamically adding an attribute to a model
instance (without having to have pre-defined any attr_… in the
class):


place = Place.new
place.name = place.name
place.id = place.id
place[‘address’] = external_api_place_data.address

From then on, for that instance, you can call place.address, and it
will show up in place.to_json (since to_json is generated from
place.attributes, which now has a k/v for address in attributes).

Jeff

On Oct 25, 8:16am, Frederick C. [email protected]

On 25 Oct 2011, at 16:00, “Lukas M.” [email protected] wrote:

hm… no luck with that either. when i try to print out the places object
in the console (logger.debug @place.to_yaml), “address” is missing.

For json at least you could override the as_json method to add the
attributes you want.

Fred

This forum is not affiliated to the Ruby language, Ruby on Rails framework, nor any Ruby applications discussed here.

| Privacy Policy | Terms of Service | Remote Ruby Jobs