Static Functions

Part of the Object Oriented Programming section of Coddy's GDScript journey. Lesson 10 of 65.

A static func belongs to the class, like a static variable. You call it through the class name, with no object, as you did in the lesson on files: Greeter.greet("Ada"). A class can mix static functions with ordinary methods:

# student.gd
class_name Student
extends RefCounted

static var count: int = 0
var student_name: String
var score: int

func _init(new_name: String, new_score: int) -> void:
	student_name = new_name
	score = new_score
	count += 1

static func is_passing(points: int) -> bool:
	return points >= 60

static func from_line(line: String) -> Student:
	var parts := line.split(" ")
	return Student.new(parts[0], int(parts[1]))

print(Student.is_passing(72)) # true
var ada := Student.from_line("Ada 91")
print(ada.score) # 91
print(Student.count) # 1

A static function runs without an object, so it cannot use instance variables or self: score inside is_passing() is an error reported before the program runs. It can use its parameters, constants, static variables and other static functions.

from_line() shows a common use: a static function that builds and returns an object, here from a line of text. It is a second way to create a Student, next to Student.new().

You can also call a static function on an object, as in ada.is_passing(50), but the class name makes it clear that no object is involved.

Challenge

Easy

Write the grading code in two classes.

Grader in grader.gd has only static functions:

letter(points) returns "A" for 90 or more, "B" for 80 or more, "C" for 70 or more, "D" for 60 or more, and "F" below that
is_passing(points) returns true for 60 or more

Student in student.gd already has its properties and constructor. Complete:

the static function from_line(line), which splits a line such as Ada 91 at the space and returns a new Student with that name and score
the method report(), which returns NAME: SCORE (LETTER), passed or NAME: SCORE (LETTER), failed, using the two Grader functions

The supplied code reads how many students follow, creates each one with Student.from_line(), prints its report, and finally counts the passing students. For Ada 91, Bo 42 and Cy 75 it prints:

Ada: 91 (A), passed
Bo: 42 (F), failed
Cy: 75 (C), passed
Passed: 2 of 3

Your code goes in grader.gd and student.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 count := int(OS.read_string_from_stdin())
	var passed := 0
	for i in count:
		var student := Student.from_line(OS.read_string_from_stdin())
		print(student.report())
		if Grader.is_passing(student.score):
			passed += 1
	print("Passed: %d of %d" % [passed, count])