Nested strong parameters in rails - AssociationTypeMismatch MYMODEL expected, got ActionController::Parameters()

Question

I'm rendering a model and it's children Books in JSON like so:

{"id":2,"complete":false,"private":false, "books" [{ "id":2,"name":"Some Book"},.....

I then come to update this model by passing the same JSON back to my controller and I get the following error:

ActiveRecord::AssociationTypeMismatch (Book (#2245089560) expected, got ActionController::Parameters(#2153445460))

In my controller I'm using the following to update:

@project.update_attributes!(project_params)

private

def project_params
    params.permit(:id, { books: [:id] } )
end

No matter which attributes I whitelist in permit I can't seem to save the child model.

Am I missing something obvious?

Update - another example:

Controller:

def create
    @model = Model.new(model_params)
end
def model_params
    params.fetch(:model, {}).permit(:child_model => [:name, :other])
end

Request:

post 'api.address/model', :model => { :child_model => { :name => "some name" } }

Model:

accepts_nested_attributes_for :child_model

Error:

expected ChildModel, got ActionController::Parameters

Tried this method to no avail: http://www.rubyexperiments.com/using-strong-parameters-with-nested-forms/

Answer 1

Are you using accepts_nested_attributes_for :books on your project model? If so, instead of "books", the key should be "books_attributes".

def project_params
  params.permit(:id, :complete, :false, :private, books_attributes: [:id, :name])
end

Answer 2

I'm using Angular.js & Rails & Rails serializer, and this worked for me:

Model:

• has_many :features
• accepts_nested_attributes_for :features

ModelSerializer:

• has_many :features, root: :features_attributes

Controller:

• params.permit features_attributes: [:id, :enabled]

AngularJS:

• ng-repeat="feature in model.features_attributes track by feature.id

Answer 3

My solution to this using ember.js was setting the books_attributes mannualy.

In controller:

def project_params      
  params[:project][:books_attributes] = params[:project][:books_or_whatever_name_relationships_have] if params[:project][:books_or_whatever_name_relationships_have]
  params.require(:project).permit(:attr1, :attr2,...., books_attributes: [:book_attr1, :book_attr2, ....])

end

So rails checks and filters the nested attributes as it expected them to come