[Callable] is a built-in [Variant] type that represents a function. It can either be a method within an [Object] instance, or a standalone function not related to any object, like a lambda function. Like all [Variant] types, it can be stored in variables and passed to other functions. It is most commonly used for signal callbacks.
In GDScript, it's possible to create lambda functions within a method. Lambda functions are custom callables that are not associated with an [Object] instance. Optionally, lambda functions can also be named. The name will be displayed in the debugger, or when calling [method get_method].
[codeblock]
func _init():
var my_lambda = func (message):
print(message)
# Prints Hello everyone!
my_lambda.call("Hello everyone!")
# Prints "Attack!", when the button_pressed signal is emitted.
[b]Note:[/b] Methods of native types such as [Signal], [Array], or [Dictionary] are not of type [Callable] in order to avoid unnecessary overhead. If you need to pass those methods as [Callable], use a lambda function as a wrapper.
Returns a copy of this [Callable] with one or more arguments bound. When called, the bound arguments are passed [i]after[/i] the arguments supplied by [method call]. See also [method unbind].
[b]Note:[/b] When this method is chained with other similar methods, the order in which the argument list is modified is read from right to left.
Returns a copy of this [Callable] with one or more arguments bound, reading them from an array. When called, the bound arguments are passed [i]after[/i] the arguments supplied by [method call]. See also [method unbind].
[b]Note:[/b] When this method is chained with other similar methods, the order in which the argument list is modified is read from right to left.
Calls the method represented by this [Callable] in deferred mode, i.e. at the end of the current frame. Arguments can be passed and should match the method's signature.
Calls the method represented by this [Callable]. Unlike [method call], this method expects all arguments to be contained inside the [param arguments] [Array].
Return the bound arguments (as long as [method get_bound_arguments_count] is greater than zero), or empty (if [method get_bound_arguments_count] is less than or equal to zero).
Returns the total amount of arguments bound (or unbound) via successive [method bind] or [method unbind] calls. If the amount of arguments unbound is greater than the ones bound, this function returns a value less than zero.
Returns the 32-bit hash value of this [Callable]'s object.
[b]Note:[/b] [Callable]s with equal content will always produce identical hash values. However, the reverse is not true. Returning identical hash values does [i]not[/i] imply the callables are equal, because different callables can have identical hash values due to hash collisions. The engine uses a 32-bit hash algorithm for [method hash].
Returns [code]true[/code] if this [Callable] is a custom callable. Custom callables are created from [method bind] or [method unbind]. In GDScript, lambda functions are also custom callables.
Returns [code]true[/code] if this [Callable] is a standard callable. This method is the opposite of [method is_custom]. Returns [code]false[/code] if this callable is a lambda function.
Perform an RPC (Remote Procedure Call) on all connected peers. This is used for multiplayer and is normally not available, unless the function being called has been marked as [i]RPC[/i] (using [annotation @GDScript.@rpc] or [method Node.rpc_config]). Calling this method on unsupported functions will result in an error. See [method Node.rpc].
Perform an RPC (Remote Procedure Call) on a specific peer ID (see multiplayer documentation for reference). This is used for multiplayer and is normally not available unless the function being called has been marked as [i]RPC[/i] (using [annotation @GDScript.@rpc] or [method Node.rpc_config]). Calling this method on unsupported functions will result in an error. See [method Node.rpc_id].
Returns a copy of this [Callable] with a number of arguments unbound. In other words, when the new callable is called the last few arguments supplied by the user are ignored, according to [param argcount]. The remaining arguments are passed to the callable. This allows to use the original callable in a context that attempts to pass more arguments than this callable can handle, e.g. a signal with a fixed number of arguments. See also [method bind].
[b]Note:[/b] When this method is chained with other similar methods, the order in which the argument list is modified is read from right to left.
[codeblock]
func _ready():
foo.unbind(1).call(1, 2) # Calls foo(1).
foo.bind(3, 4).unbind(1).call(1, 2) # Calls foo(1, 3, 4), note that it does not change the arguments from bind.
