Rails - Jan 2009 - Nested serialization with to_json and to_xml with array and hash element

Title: Nested serialization with to_json and to_xml with array and
hash element

class Person < ActiveRecord::Base
	has_one :address
	has_one :job

	def office()
		return "Executive_Suite"
	end
end


class Address < ActiveRecord::Base
	belongs_to :person
end


class Job < ActiveRecord::Base
	belongs_to :person
	has_one :paygrade

	def Title
		return "Engineer"
	end
end


class PayGrade < ActiveRecord::Base
	belongs_to: job

end


Given an instance of a Person, I am able to serialize in XML and JSON
in some simpler nested manners such as this:

@person = Person.find_by_id(1)


# render the results with multiple peer associations with no drill
down
respond_to do |format|
      format.json { render.json(:json=>@person.to_json(:include=>
[:address, :job], :methods=>:office) }
      format.xml { render.json(:json=>@person.to_json(:include=>
[:address, :job], :methods=>:office) }
      }
end


# render the results with 1 association requiring deep drill down
respond_to do |format|
      format.json { render.json(:json=>@person.to_json(:include=>
{:job=>{:include=>:paygrade}}) }
      format.xml { render.json(:json=>@person.to_json(:include=>{:job=>
{:include=>:paygrade}}) }
      }
end


Where I continually run into problems is where I have multiple peer
associations at the same level
with one of them needing further drill down into one of its
association.

For instance I thought I could simply do this to serialize the Person
instance, along with their address, job with Paygrade.
Whenever I try to do this:
respond_to do |format|
      format.json { render.json(:json=>@person.to_json(:include=>
[:address, {:job=>{:include=>:paygrade}}] }
      format.xml { render.json(:json=>@person.to_json(:include=>
[:address, {:job=>{:include=>:paygrade}}] }
      }
end


I always get the following error: You have a nil object when you
didn''t expect it.  Error evaluating nil.ma.
Based on my understanding the :include is expecting an array but I''m
adding a hash as an element and Rails
is not expecting it in the way I''m specifying?

Where I also continually run into problems is where I have multiple
peer associations at the same level
with one of them needing requiring a custom method to be serialized.



Question 1: What is the correct way to be able to specify that I need
to serialize the Person with address
and job along with the paygrade for the job?  This is the multiple
peers with deep drill down problem mentioned above.

Question 2: What is the correct way to be able to specify that I need
to serialize the Person with address
and job along with the custom Job Title method with the paygrade?
When I try this, I get error:

respond_to do |format|
      format.json { render.json(:json=>@person.to_json(:include=>
[:address, {:job=>{:methods=>:title, :include=>:paygrade}}] }
      format.xml { render.json(:json=>@person.to_json(:include=>
[:address, {:job=>{:methods=>:title, :include=>:paygrade}}] }
      }
end

Please advise, and thanks in advance.

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The error description above was slightly truncated.
The full error is this: You have a nil object when you didn''t expect
it! The error occurred while evaluating nil.macro

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Hi Folks,

I ran into the same problem. Here is my fix, which solved the problem
(I''ve added it to my environment.rb):

module ActiveRecord
  module Serialization
    class Serializer
      def add_includes_with_nested_include(&block)
        if include_associations = options.delete(:include)
          base_only_or_except = { :except => options[:except],
                                  :only => options[:only] }

          include_has_options = include_associations.is_a?(Hash)
          associations = include_has_options ?
include_associations.keys : Array(include_associations)

          for association in associations
            association_has_options = association.is_a?(Hash)
            if association_has_options
              macro_association = association.keys.first
              additional_association_options = association
[macro_association]
            else
              additional_association_options = {}
              macro_association = association
            end
            macro = @record.class.reflect_on_association
(macro_association).macro
            records = case macro
            when :has_many, :has_and_belongs_to_many
              @record.send(macro_association).to_a
            when :has_one, :belongs_to
              @record.send(macro_association)
            end
            unless records.nil?
              association_options = include_has_options ?
include_associations[macro_association] : base_only_or_except
              opts = options.merge(association_options).merge
(additional_association_options)
              yield(macro_association, records, opts)
            end
          end

          options[:include] = include_associations
        end
      end
      alias_method_chain :add_includes, :nested_include
    end
  end
end


If someone wants to commit this to github, more power to you!

scho

On 21 Jan., 04:47, RubyNewbie
<CalvinAnhNgu...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> The error description above was slightly truncated.
> The full error is this: You have a nil object when you didn''t
expect
> it! The error occurred while evaluating nil.macro
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Hi again,

I found out, that the following works as well:
Instead of
[:address, {:job=>{:include=>:paygrade}}]
try
{:address => {}, {:job=>{:include=>:paygrade}}}

scho

On 17 Mrz., 15:56, scho
<georgmeye...-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org>
wrote:
> Hi Folks,
>
> I ran into the same problem. Here is my fix, which solved the problem
> (I''ve added it to my environment.rb):
>
> module ActiveRecord
>   module Serialization
>     class Serializer
>       def add_includes_with_nested_include(&block)
>         if include_associations = options.delete(:include)
>           base_only_or_except = { :except => options[:except],
>                                   :only => options[:only] }
>
>           include_has_options = include_associations.is_a?(Hash)
>           associations = include_has_options ?
> include_associations.keys : Array(include_associations)
>
>           for association in associations
>             association_has_options = association.is_a?(Hash)
>             if association_has_options
>               macro_association = association.keys.first
>               additional_association_options = association
> [macro_association]
>             else
>               additional_association_options = {}
>               macro_association = association
>             end
>             macro = @record.class.reflect_on_association
> (macro_association).macro
>             records = case macro
>             when :has_many, :has_and_belongs_to_many
>               @record.send(macro_association).to_a
>             when :has_one, :belongs_to
>               @record.send(macro_association)
>             end
>             unless records.nil?
>               association_options = include_has_options ?
> include_associations[macro_association] : base_only_or_except
>               opts = options.merge(association_options).merge
> (additional_association_options)
>               yield(macro_association, records, opts)
>             end
>           end
>
>           options[:include] = include_associations
>         end
>       end
>       alias_method_chain :add_includes, :nested_include
>     end
>   end
> end
>
> If someone wants to commit this to github, more power to you!
>
> scho
>
> On 21 Jan., 04:47, RubyNewbie
<CalvinAnhNgu...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>
> > The error description above was slightly truncated.
> > The full error is this: You have a nil object when you didn''t
expect
> > it! The error occurred while evaluating nil.macro
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