Error when trying to link to patient profile - ruby-on-rails

Question

I'm getting an error when trying to link_to a patient profile when a provider views his patients list. I have no problem displaying all the names of the patients that belong to the provider but when trying to link to the patient profile I get an undefined method 'id'.
So the way it works is, patients can search for providers and add them to the List model. On the provider side, I just list out all the patients that added that specific provider. Here is my erb code below,
<div class="body">
<div class="body">
<% if #active_patients.count > 0 %>
<table>
<thead>
<tr>
<th>Patient Name</th>
<th>Actions</th>
</tr>
</thead>
<tbody>
<% #active_patients.each do |list| %>
<tr>
<td>
<%= list.patient.role.user.first_name %> <%= list.patient.role.user.last_name %>
</td>
<td>
<%= link_to patient_path(id: #patient.id), class: "btn" do %>View<% end %> . #### THIS IS THE LINE
</td>
</tr>
<% end %>
</tbody>
</table>
<% else %>
<div class="no-records">
<%= image_tag "icon-no-records", class: "image" %>
<div class="text">You have no patients.</div>
</div><!--no-records-->
<% end %>
</div><!--body-->
</div>
Here is my List model,
class List < ApplicationRecord
belongs_to :membershipable, :polymorphic => true
belongs_to :provider
def patient
membershipable_type=='Patient' ? membershipable : nil
end
def provider_user
patient.try(:user)
end
end
Also here's the error message ->

Answer 1

Let Rails do the work of building the path. Each ActiveRecord model has a to_param method which decides how the instance will be encoded in an URL. By default it returns the model id but it could also be a slug based on the title or another property of the model.
Calling your helper like patient_path(patient) should do the trick.
Additionally, in your current code, you're referring to the previously unused #patient variable, even though it looks like you want to refer to list.patient instead.

Answer 2

Here:
<% #active_patients.each do |list| %>
<tr>
<td>
<%= list.patient.role.user.first_name %> <%= list.patient.role.user.last_name %>
</td>
<td>
<%= link_to patient_path(id: #patient.id), class: "btn" do %>View<% end %> . #### THIS IS THE LINE
</td>
</tr>
<% end %>
you have the variable list available to you. It appears that you get the patient by doing list.patient, as you do here:
<%= list.patient.role.user.first_name %> <%= list.patient.role.user.last_name %>
But, then you try to use a variable called #patient, here:
<%= link_to patient_path(id: #patient.id), class: "btn" do %>View<% end %> .
when you don't have the variable #patient. So, you get your nil error.
Instead, it seems you should do:
<%= link_to patient_path(id: list.patient.id), class: "btn" do %>View<% end %> .
Or, as milgner points out, you could simply do:
<%= link_to patient_path(list.patient), class: "btn" do %>View<% end %> .
Also, you might want to look into the Law of Demeter, which you violate (IMO) when you do:
list.patient.role.user.first_name