ActiveRecord object from json

rubyonrails-talk
1

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/ruby-1.9.3-p327@sq/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

2

Hi All

Hi,

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”:[

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

{“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)

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

I have never tried with survey.attributes.

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? }

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

3

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

[snip]

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

/Users/dse/.rvm/gems/ruby-1.9.3-p327@sq/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 Jones