ActiveRecord object from json

Hi All

I’m trying to create an ActiveRecord object ‘directly’ from some JSON
data.
By ‘directly’ - I mean without ‘walking’ the parsed JSON data, but
rather
just passing the parsed JSON data to a method that will process all the
data.

To keep the question simple - let’s say I have two objects. A Survey
and a
Question. Each Survey can have many Questions.

Here’s a script containing the json data and my attempt at creating an
ActiveRecord object directly from the json string …

begin test.rb script

json = '{

“name”:“Fundraising Survey”,

“description”:“A survey about a fundraiser”,

“questions”:[

{“text”:“How clearly did our organization explain our fundraising
goals?”},

{“text”:“Was the cost of attending our fundraiser too high, too low,
or
about right?”}

]

}’

survey = Survey.new

survey.attributes = ActiveSupport::JSON.decode(json)

end test.rb script

For reference = here is the ruby code for the Survey and Question
classes

class Survey < ActiveRecord::Base

has_many :questions, :dependent => :destroy

accepts_nested_attributes_for :questions, :allow_destroy => true,

                           :reject_if => lambda {|attrs|

attrs[‘text’].blank? }

attr_accessible :name, :description

end

class Question < ActiveRecord::Base

belongs_to :survey

acts_as_list :scope => :survey

validates_presence_of :text, :message => ‘Text can not be blank’

attr_accessible :survey_id, :text

end

I get this error when I run the test.rb script (see code snippet above)

/Users/dse/.rvm/gems/[email protected]/gems/activerecord-3.2.9/lib/active_record/associations/association.rb:204:in
`raise_on_type_mismatch’: Question(#70357035179920) expected, got
Hash(#70357017137920) (ActiveRecord::AssociationTypeMismatch)

Any help would be greatly appreciated.

Thanks again

Dave

On Wed, Dec 19, 2012 at 5:30 AM, dekhaus [email protected] wrote:

Hi All

Hi,

begin test.rb script

json = '{

“name”:“Fundraising Survey”,

“description”:“A survey about a fundraiser”,

“questions”:[

Try with “questions_attributes” instead. See the doc for
ActiveRecord::NestedAttributes

survey = Survey.new

survey.attributes = ActiveSupport::JSON.decode(json)

survey = Survey.new(ActiveSupport::JSON.decode(json))

I have never tried with survey.attributes.

accepts_nested_attributes_for :questions, :allow_destroy => true,

                           :reject_if => lambda {|attrs|

attrs[‘text’].blank? }

I think you can get rid of this “reject_if” option since you have a
“validates_presence_of :text” in your Question controller.

`raise_on_type_mismatch’: Question(#70357035179920) expected, got


Nicolas D.

On Tuesday, 18 December 2012 23:30:57 UTC-5, dekhaus wrote:

                           :reject_if => lambda {|attrs|

attrs[‘text’].blank? }

attr_accessible :name, :description

end

[snip]

I get this error when I run the test.rb script (see code snippet above) …

/Users/dse/.rvm/gems/[email protected]/gems/activerecord-3.2.9/lib/active_record/associations/association.rb:204:in

`raise_on_type_mismatch’: Question(#70357035179920) expected, got
Hash(#70357017137920) (ActiveRecord::AssociationTypeMismatch)

accepts_nested_attributes creates a writer method on Survey, but it’s
not
‘questions’ (which is the association) but rather
‘questions_attributes’.

–Matt J.

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