Signal with parameter, sometimes I need to bind it, sometimes not?

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1

Godot Version

4.3 stable

Question

I use signals in my code and just notices something, that I don’t really understand, maybe someone can help. Sometimes I need to use .bind() to use a parameter in a signal method, sometimes I don’t need to use it, examples:

This works:

enemy.combat_started.connect(_on_enemy_combat_started)

func _on_enemy_combat_started(p_enemy: Enemy) -> void:

This does not work:

_dice.pressed.connect(_on_dice_pressed)

func _on_dice_pressed(p_dice: Dice) -> void:

Instead I have to write this:

_dice.pressed.connect(_on_dice_pressed.bind(_dice))

func _on_dice_pressed(p_dice: Dice) -> void:

I wonder why that’s the case?

“enemy” is an Area2D that exists in my node tree in the Editor, “_dice” is a Button that is instanced at runtime.

2

It depends on if the signal emits parameters or not, it would seem that combat_started emits a Enemy, while pressed does not emit a Dice

The p_enemy passed into the connected function is probably not the same one whose signal you are connecting.

Are you sure combat_started works as you think it does?

3

I think you were correct!

My Enemy script looked like this:

signal combat_started(enemy: Enemy)

func _on_body_entered(p_body: Node2D) -> void:
	combat_started.emit(self)

I removed the parameter from the signal signature and the emit call, now I have to bind the parameter in the connect call in my Main script as expected.