Recap - Student Records System

Part of the Object Oriented Programming section of Coddy's GDScript journey. Lesson 30 of 65.

Challenge

Medium

Build a small student records system from two classes.

Student in student.gd keeps its data private:

_init(id, new_name) stores the ID in a private variable and assigns the name through the student_name setter.
student_id is read-only and returns the ID.
student_name has a setter: a name shorter than 2 characters is rejected (the old name stays) and last_error becomes Name must be at least 2 characters. A valid name clears last_error.
add_grade(course, grade) stores the grade for the course in a private Dictionary (a new grade for the same course replaces the old one) and returns true. A grade below 0 or above 100 is not stored and returns false.
average is a read-only computed property: the average of the grades as a float, or 0.0 without grades.
course_count() returns the number of courses with a grade.

StudentRegistry in student_registry.gd keeps the students in a private Dictionary, with the ID as key:

add_student(student) returns false and changes nothing when the ID is taken, otherwise stores the student and returns true.
remove_student(id) returns whether a student was removed.
get_student(id) returns the student, or null.
top_student() returns the student with the highest average (the one added first on a tie), or null when the registry is empty.
get_ids() returns the IDs in the order the students were added.

The supplied code reads the number of commands, then runs one command per line: add ID NAME, grade ID COURSE GRADE, rename ID NAME, remove ID, show ID, tamper ID (tries to overwrite student_id and average, which must not change), top and list. For this input:

10
add 1001 Alice Smith
add 1002 Bob
grade 1001 Math 90
grade 1001 Art 85
grade 1002 Math 95
grade 1002 Art 120
rename 1002 B
show 1002
top
list

it prints:

Added Alice Smith (1001)
Added Bob (1002)
Alice Smith: Math = 90
Alice Smith: Art = 85
Bob: Math = 95
Invalid grade: 120
Rejected: Name must be at least 2 characters
ID: 1002, Name: Bob, Courses: 1, Average: 95.00
Top: Bob (95.00)
ID: 1001, Name: Alice Smith, Courses: 2, Average: 87.50
ID: 1002, Name: Bob, Courses: 1, Average: 95.00

Your code goes in student.gd and student_registry.gd. main.gd holds the supplied input/output code and cannot be edited.

Try it yourself

extends Node

func _ready():
	# Supplied input/output code: keep it as it is
	var registry := StudentRegistry.new()
	var count := int(OS.read_string_from_stdin())
	for i in count:
		var parts := OS.read_string_from_stdin().split(" ", true, 2)
		var command := parts[0]
		if command == "top":
			var best := registry.top_student()
			if best == null:
				print("Top: none")
			else:
				print("Top: %s (%.2f)" % [best.student_name, best.average])
			continue
		if command == "list":
			for listed_id in registry.get_ids():
				print_student(registry.get_student(listed_id))
			continue
		var id := int(parts[1])
		if command == "add":
			var student := Student.new(id, parts[2])
			if student.last_error != "":
				print("Rejected: " + student.last_error)
			elif registry.add_student(student):
				print("Added %s (%d)" % [student.student_name, id])
			else:
				print("Duplicate ID: %d" % id)
			continue
		if command == "remove":
			print(("Removed %d" if registry.remove_student(id) else "No student %d") % id)
			continue
		var student := registry.get_student(id)
		if student == null:
			print("No student %d" % id)
		elif command == "grade":
			var grade_parts := parts[2].split(" ")
			if student.add_grade(grade_parts[0], int(grade_parts[1])):
				print("%s: %s = %s" % [student.student_name, grade_parts[0], grade_parts[1]])
			else:
				print("Invalid grade: " + grade_parts[1])
		elif command == "rename":
			student.student_name = parts[2]
			if student.last_error != "":
				print("Rejected: " + student.last_error)
			else:
				print("Renamed to " + student.student_name)
		elif command == "tamper":
			# Tries to overwrite the read-only properties
			student.student_id = 0
			student.average = 100.0
			print_student(student)
		else:
			print_student(student)

func print_student(student: Student) -> void:
	print("ID: %d, Name: %s, Courses: %d, Average: %.2f" % [student.student_id, student.student_name, student.course_count(), student.average])