Directly use ActiveRecord object instead of ID

This change will improve the performance by reducing unnecessary SELECT queries.

app/controllers/concerns/file_parameters.rb

@@ -8,7 +8,7 @@ module FileParameters
         next true if file.nil? || file.hidden || file.read_only
         # avoid that public files from other contexts can be created
         # `next` is similar to an early return and will proceed with the next iteration of the loop
-        next true if file.context_type == 'Exercise' && file.context_id != exercise.id
+        next true if file.context_type == 'Exercise' && file.context != exercise
         next true if file.context_type == 'Submission' && file.context.user != current_user
         next true if file.context_type == 'CommunitySolution' && controller_name != 'community_solutions'
 

app/controllers/concerns/submission_parameters.rb

@@ -21,9 +21,8 @@ module SubmissionParameters
   def merge_user(params)
     # The study_group_id might not be present in the session (e.g. for internal users), resulting in session[:study_group_id] = nil which is intended.
     params.merge(
-      user_id: current_user.id,
+      user: current_user,
-      user_type: current_user.class.name,
+      study_group_id: current_user.current_study_group_id
-      study_group_id: session[:study_group_id]
     )
   end
 end

app/validators/code_ocean/file_name_validator.rb

@@ -3,8 +3,8 @@
 module CodeOcean
   class FileNameValidator < ActiveModel::Validator
     def validate(record)
-      existing_files = File.where(name: record.name, path: record.path, file_type_id: record.file_type_id,
+      existing_files = File.where(name: record.name, path: record.path, file_type: record.file_type,
-        context_id: record.context_id, context_type: record.context_type).to_a
+        context: record.context)
       if !existing_files.empty? && (!record.context.is_a?(Exercise) || record.context.new_record?)
         record.errors.add(:base, 'Duplicate')
       end