Control Flow & Pattern Matching

Don't add or remove elements of an array while iterating over it; iterate over a duplicate() or collect changes and apply them afterward.

11.1 if / elif / else

if hp <= 0:
	die()
elif hp < 20:
	play_low_health_warning()
else:
	pass   # 'pass' is an empty statement

var label := "even" if n % 2 == 0 else "odd"

11.2 while

var i := 0
while i < 10:
	i += 1
	if i == 3:
		continue
	if i == 8:
		break
	print(i)

11.3 for

Don't add or remove elements of an array while iterating over it; iterate over a duplicate() or collect changes and apply them afterward.

for i in 5:                    # 0..4
	print(i)
for i in range(2, 10, 2):      # 2, 4, 6, 8
	print(i)
for i in range(10, 0, -1):     # 10..1
	print(i)
for item in inventory:
	print(item)
for key in dict:
	print(key, dict[key])
for ch in "abc":
	print(ch)
for child in get_children():
	child.queue_free()
for i: int in 3:               # typed loop variable (4.2+)
	print(i)
for enemy: Enemy in enemies:
	enemy.alert()

11.4 match

match compares a value against patterns; the first matching branch runs (no fall-through in Godot 4).

Pattern guards (4.3+) add an extra condition with when:

42, "text", null, true Constant / enum State.IDLE, MAX Vector2i(0, 0) [1, var y,..] {"key": var v,..}

1, 2, 3 (cannot combine with bindings) var x when x > 10

Godot 3 note: continue inside match used to fall through to the next pattern; this was removed in 4.0.

match command:
	"jump":
		jump()
	"attack", "shoot":                 # multiple patterns
		attack()
	_:                                 # wildcard (default)
		print("Unknown command")

match typeof(value):
	TYPE_INT, TYPE_FLOAT:
		print("number")
	TYPE_STRING:
		print("string")

match position_on_grid:
	Vector2i(0, 0):
		print("origin")
	var other:                         # binding pattern: captures the value
		print("at ", other)

match event_data:
	[]:
		print("empty array")
	[var first, ..]:                   # array pattern with open ending
		print("starts with ", first)

match message:
	{"type": "chat", "text": var text}:
		show_chat(text)
	{"type": "move", "x": var x, "y": var y, ..}:   # .. allows extra keys
		move_to(Vector2(x, y))

match hp:
	var h when h <= 0:
		die()
	var h when h < 25:
		show_warning()
	_:
		pass