How To Persist Parameters Through Different Rails Controllers Actions In Rails

Question

What should one use to persist instance variables through different controller#actions, without using the session?

Here is an example of the problem:

There is an Hospitalization which has_one Prescription

From hospitalization#show I have a link_to prescription#new with additional parameters as seen bellow:

<%= link_to t('hospitalizations.prescription'), new_prescription_path(hospitalization_id: @hospitalization.id,...)

And the trick is: at prescription#new I can retrieve

@hospitalization = Hospitalization.find_by(id: params[:hospitalization_id])

But when I press submit and it comes to prescription#create, @hospitalization answers to nil when trying to do something like

@prescription = @hospitalization.build_prescription(prescription_params)

How would be the best way to instantiate these parameters so they persist or get easily carried between the controller#actions one needs? How should I instantiate the belonging model Prescription? Should I put the ID directly there, on prescription#new? Like:

@prescription = Prescription.new(hospitalization_id: params[:hospitalization_id])

Answer 1

Use neseted resources this way:

resources hospitalizations do
  resource :prescription
end

This way your path is going to look like this:

/hospitalizations/:hospitalization_id/prescription

and you can use the following to generate it:

new_hospitalization_prescription_path(@hospitalization)

now in your controller you can access the parameter as params[:hospitalization_id] . For example in the create method of your PrescriptionController :

def create
  hospitalization = Hospitalization.find(params[:hospitalization])
  prescription = Prescription.new(hospitalization: hospitalization, ...)
  # ...
end