Use a policy for pinning/unpinning

app/policies/answer_policy.rb

@@ -0,0 +1,14 @@
+# frozen_string_literal: true
+
+class AnswerPolicy
+  attr_reader :user, :answer
+
+  def initialize(user, answer)
+    @user = user
+    @answer = answer
+  end
+
+  def pin? = answer.user == user
+
+  def unpin? = answer.user == user
+end

lib/use_case/answer/pin.rb

@@ -7,7 +7,7 @@ module UseCase
       option :answer, type: Types.Instance(::Answer)
 
       def call
-        check_ownership!
+        authorize!(:pin, user, answer)
         check_unpinned!
 
         answer.pinned_at = Time.now.utc
@@ -21,10 +21,6 @@ module UseCase
 
       private
 
-      def check_ownership!
-        raise ::Errors::NotAuthorized unless answer.user == user
-      end
-
       def check_unpinned!
         raise ::Errors::BadRequest if answer.pinned_at.present?
       end

lib/use_case/answer/unpin.rb

@@ -7,7 +7,7 @@ module UseCase
       option :answer, type: Types.Instance(::Answer)
 
       def call
-        check_ownership!
+        authorize!(:unpin, user, answer)
         check_pinned!
 
         answer.pinned_at = nil
@@ -21,10 +21,6 @@ module UseCase
 
       private
 
-      def check_ownership!
-        raise ::Errors::NotAuthorized unless answer.user == user
-      end
-
       def check_pinned!
         raise ::Errors::BadRequest if answer.pinned_at.nil?
       end

lib/use_case/base.rb

@@ -9,5 +9,11 @@ module UseCase
     def self.call(...) = new(...).call
 
     def call = raise NotImplementedError
+
+    private
+
+    def authorize!(verb, user, record, error_class: Errors::NotAuthorized)
+      raise error_class unless Pundit.policy!(user, record).public_send("#{verb}?")
+    end
   end
 end