Devise/Rails - undefined method `permit' - ruby-on-rails

Question

Problem: I am trying to create a custom action that allows a teacher to approve a student via the "approve" action. The approve action fetches the appropriate row and changes the status from "pending" to "active" and saves the record. Currently when I click the link, better errors gives me a
"undefined method `permit' for "2":String"
it mentions something about
Devise::ParameterSanitizer#permit
Please keep in mind, I am very new to Devise and am stumped!
Controller
class Teachers::RegistrationsController < Devise::RegistrationsController
# APPROVE
def approve
#ts = TeacherStudent.find_by(teacher_id: params[:teacher], student_id: params[:student])
#ts.status = "active"
#ts.save
redirect_to teachers_path
end
end
View
= link_to "Approve", approve_path(teacher: s.teacher_id, student: s.student_id), method: :put
Routes.rb
put 'teachers' => 'teachers#approve', as: :approve
Error
Started PUT "/teachers?student=14&teacher=2" for ::1 at 2015-06-21 01:06:33 -0500
Processing by Teachers::RegistrationsController#update as HTML
Parameters: {"authenticity_token"=>"VQ2zVIv5gof1+38xdAA9d/Y+bWmHk4bT1SXHvc+xLr3+qTOm2xSMZUFjDw74umk35P36kgpqx4eMftFGyVThSg==", "student"=>"14", "teacher"=>"2"}
[1m[36mTeacher Load (0.6ms)[0m [1mSELECT "teachers".* FROM "teachers" WHERE "teachers"."id" = $1 ORDER BY "teachers"."id" ASC LIMIT 1[0m [["id", 2]]
[1m[35mTeacher Load (0.3ms)[0m SELECT "teachers".* FROM "teachers" WHERE "teachers"."id" = $1 LIMIT 1 [["id", 2]]
Completed 500 Internal Server Error in 5ms (ActiveRecord: 1.0ms)
NoMethodError - undefined method `permit' for "2":String:
() Users/dannysun/.rvm/gems/ruby-2.2.1/bundler/gems/devise-15b99977a2a3/lib/devise/parameter_sanitizer.rb:66:in `permit'
() Users/dannysun/.rvm/gems/ruby-2.2.1/bundler/gems/devise-15b99977a2a3/lib/devise/parameter_sanitizer.rb:58:in `account_update'
() Users/dannysun/.rvm/gems/ruby-2.2.1/bundler/gems/devise-15b99977a2a3/lib/devise/parameter_sanitizer.rb:77:in `default_sanitize'
() Users/dannysun/.rvm/gems/ruby-2.2.1/bundler/gems/devise-15b99977a2a3/lib/devise/parameter_sanitizer.rb:24:in `sanitize'
() Users/dannysun/.rvm/gems/ruby-2.2.1/bundler/gems/devise-15b99977a2a3/app/controllers/devise/registrations_controller.rb:141:in `account_update_params'
() Users/dannysun/.rvm/gems/ruby-2.2.1/bundler/gems/devise-15b99977a2a3/app/controllers/devise/registrations_controller.rb:48:in `update'
actionpack (4.2.1) lib/action_controller/metal/implicit_render.rb:4:in `send_action'
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actionpack (4.2.1) lib/abstract_controller/callbacks.rb:20:in `block in process_action'
activesupport (4.2.1) lib/active_support/callbacks.rb:117:in `call'
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Answer 1

The problem is most likely in your permissions.
Are you using Strong Parameters? If so, you need to permit the fields in there.
Example:
def teacher_params
params.require(:teacher).permit(:email, :current_password, :password, :password_confirmation)
end

Answer 2

Add the following code at the bottom of your Teachers Controller-
private
def user_params
accessible = [:email, _____] # extend with your own params
accessible << [ :password, :password_confirmation ] unless params[:teacher][:password].blank?
params.require(:teacher).permit(accessible)
end