Table of Contents

Class Signal

A built-in type representing a signal of an Object.

Signal

Remarks

Signal is a built-in Variant type that represents a signal of an Object instance. Like all Variant types, it can be stored in variables and passed to functions. Signals allow all connected Callables (and by extension their respective objects) to listen and react to events, without directly referencing one another. This keeps the code flexible and easier to manage. You can check whether an Object has a given signal name using Object.has_signal.

In GDScript, signals can be declared with the signal keyword. In C#, you may use the [Signal] attribute on a delegate.

signal attacked

# Additional arguments may be declared.
# These arguments must be passed when the signal is emitted.
signal item_dropped(item_name, amount)

See Also

Using Signals
GDScript Basics

Constructors

Signal

Constructs an empty Signal with no object nor signal name bound.

Signal Signal

Signal(Signal)

Constructs a Signal as a copy of the given Signal.

Signal Signal(Signal from)

Parameters

from Signal

Signal(Object, StringName)

Creates a Signal object referencing a signal named signal in the specified object.

Signal Signal(Object object, StringName signal)

Parameters

object Object
signal StringName

Methods

connect(Callable, int)

Connects this signal to the specified callable. Optional flags can be also added to configure the connection's behavior (see ConnectFlags constants). You can provide additional arguments to the connected callable by using Callable.bind.

A signal can only be connected once to the same Callable. If the signal is already connected, returns @GlobalScope.ERR_INVALID_PARAMETER and pushes an error message, unless the signal is connected with Object.CONNECT_REFERENCE_COUNTED. To prevent this, use Signal.is_connected first to check for existing connections.

for button in $Buttons.get_children():
    button.pressed.connect(_on_pressed.bind(button))

func _on_pressed(button):
    print(button.name, " was pressed")


int connect(Callable callable, int flags)

Parameters

callable Callable
flags int

disconnect(Callable)

Disconnects this signal from the specified Callable. If the connection does not exist, generates an error. Use Signal.is_connected to make sure that the connection exists.

void disconnect(Callable callable)

Parameters

callable Callable

emit(...)

Qualifiers: varargconst

Emits this signal. All Callables connected to this signal will be triggered. This method supports a variable number of arguments, so parameters can be passed as a comma separated list.

void emit(...)

get_connections

Qualifiers: const

Returns an Array of connections for this signal. Each connection is represented as a Dictionary that contains three entries:

  • signal is a reference to this signal;

  • callable is a reference to the connected Callable;

  • flags is a combination of ConnectFlags.

Array get_connections

get_name

Qualifiers: const

Returns the name of this signal.

StringName get_name

get_object

Qualifiers: const

Returns the object emitting this signal.

Object get_object

get_object_id

Qualifiers: const

Returns the ID of the object emitting this signal (see get_instance_id).

int get_object_id

has_connections

Qualifiers: const

Returns true if any Callable is connected to this signal.

bool has_connections

is_connected(Callable)

Qualifiers: const

Returns true if the specified Callable is connected to this signal.

bool is_connected(Callable callable)

Parameters

callable Callable

is_null

Qualifiers: const

Returns true if this Signal has no object and the signal name is empty. Equivalent to signal == Signal().

bool is_null

Operators

!= (Signal)

Returns true if the signals do not share the same object and name.

bool != (Signal right)

Parameters

right Signal

== (Signal)

Returns true if both signals share the same object and name.

bool == (Signal right)

Parameters

right Signal