Custom signal

Learn to define custom signals with the signal keyword.

Defining custom signals

To create custom events for your game logic, you use the signal keyword. Signal declarations are typically placed at the very top of the script, before variables.

extends CharacterBody2D

signal health_changed(new_health)
signal player_died

Custom signals can be declared with or without parameters, just like built-in signals.

The power of parameterized signals

Adding parameters to custom signals conveys rich data to listeners. You can also use type hints to clarify the data types transported by the signal.

signal coin_collected(amount: int)
signal level_completed(level_name: String, score: int)

This allows the listener function to receive the necessary values directly as arguments when triggered.

Exercise Define custom signal and print

Define signal oyuna_baslandi at the top. Inside _ready, print "Ozel sinyal tanimlandi" to the console.

Show example solution

extends Node

signal oyuna_baslandi

func _ready():
    print("Ozel sinyal tanimlandi")

Test yourself

How do you declare a custom signal named 'can_degisti' carrying the new health value in GDScript?
- event can_degisti(yeni_can)
- signal can_degisti(yeni_can)
- var can_degisti = Signal(yeni_can)
- def signal can_degisti(yeni_can)
Show answer

signal can_degisti(yeni_can) — In GDScript, custom signals are declared using the 'signal' keyword followed by the name and argument list.

Write custom signal

# Skor degistiginde yayinlanacak sinyal
____ score_updated(new_score: int)

Show answer

# Skor degistiginde yayinlanacak sinyal
signal score_updated(new_score: int)

Signal definition elements

signal

Signal declaration keyword
player_died

Parameterless custom signal example
score_changed(v)

Parameterized custom signal
new_health: int

Typed signal parameter

Next lesson: emit_signal

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