Bound Checks

A "bound check" or "boundary check" is when you check if an index is within the bounds of an array.

For example, in the case of the following Array:

var characters := ["Donald", "Scrooge", "Goofy"]

The following indices are valid:

characters[0]
characters[1]
characters[2]

However, the following are not:

characters[3]
characters[4]
characters[1000]

Trying to access those indices will not give you errors in the editor, because Godot cannot infer, or guess, how many items are in the array. But it will give an error at runtime.

Checking if the index we are using is actually valid, like so, is called a "bound check":

func select_character(character_index := 0) -> void:
	if character_index < 0:
		push_error("Index is invalid: it is lower than 0")
	elif character_index >= characters.size():
		push_error("Index is invalid: It is higher than the amount of characters")
	else:
		var selected_character: String = characters[character_index]
		print("Selected character: " + selected_character)