Unpermitted parameters in Rails 5 using has_many, through - activerecord

Question

I keep getting unpermitted parameters for my appointment model.
Here are my models
class Appointment < ApplicationRecord
belongs_to :client
belongs_to :trainer
end
class Trainer < ApplicationRecord
has_many :appointments
has_many :clients, through: :appointments
end
class Client < ApplicationRecord
has_many :appointments
has_many :trainers, through: :appointments
end
Here's my controller, I just listed my private method for sake of brevity.
def appt_params
params.require(:appointment).permit(:appointment_date, client_id: [],
trainer_id: [])
end
The error says unpermitted parameters for trainer, client.
Am I missing something in my strong parameters method?
Here is my appointments/new view
<%= form_for #appointment do |f| %>
<%= f.datetime_select :appointment_date %>
<%= f.collection_select :trainer, Trainer.all, :id, :first_name %>
<%= f.collection_select :client, Client.all, :id, :name %>
<%= f.submit %>
<% end %>
I added collection to my appt_params method and still getting the same error. I'm still getting the hang of Rails and any help would be appreciated, thanks!

Answer 1

Since you have used associations, only client_id and trainer_id is enough and those should of integer form not array.
So change your strong parameters method code to :
def appt_params
params.require(:appointment).permit(:appointment_date, :client_id,
:trainer_id)
end
And your applications/new view to:
<%= form_for #appointment do |f| %>
<%= f.datetime_select :appointment_date %>
<%= f.collection_select :trainer_id, Trainer.all, :id, :first_name %>
<%= f.collection_select :client_id, Client.all, :id, :name %>
<%= f.submit %>
<% end %>

Answer 2

Was running with the same issue as you and after hours of debugging I was able to solve it:
Was my first time trying associations in Rails with models similar to you, so most documentation online recommends to define the foreign key's as client_ids:[] assuming your ids were arrays, when definitely they are integers as my parameters where
Parameters: {"utf8"=>"✓", "authenticity_token"=>"LEcwQ56xYJGpq2zIs6Cz0YbU7B7mBKRa6rhspVIxo9vEB5/UoFUvHYiN0UC0krTiIp+d0tzhit6DZT1Z8PmYYg==", "califica"=>{"text"=>"hi", "grade"=>"5", "user_id"=>"1", "party_id"=>"1"}, "commit"=>"Create Calification"}
I think this is due to f.collection_select taking as expected one value. So after hours of using the permit of arrays such as :user_id => [] , user_id:[] I was getting always error of Unpermitted parameters.
Tried the answer of #Bharath (which is correct) but it was still not working, that's was when I realized that my old models weren't made with references (ActiveModel::UnknownAttributeError (unknown attribute 'user_id' for Calification.):) so I had to make a references migration to add a foreign key and then it was all working perfectly.