Callable.xml

<?xml version="1.0" encoding="UTF-8" ?>
<class name="Callable" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../class.xsd">
	<brief_description>
		A built-in type representing a method or a standalone function.
	</brief_description>
	<description>
		[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.
		[b]Example:[/b]
		[codeblocks]
		[gdscript]
		func print_args(arg1, arg2, arg3 = ""):
		    prints(arg1, arg2, arg3)

		func test():
		    var callable = Callable(self, "print_args")
		    callable.call("hello", "world")  # Prints "hello world ".
		    callable.call(Vector2.UP, 42, callable)  # Prints "(0, -1) 42 Node(node.gd)::print_args".
		    callable.call("invalid")  # Invalid call, should have at least 2 arguments.
		[/gdscript]
		[csharp]
		// Default parameter values are not supported.
		public void PrintArgs(Variant arg1, Variant arg2, Variant arg3 = default)
		{
		    GD.PrintS(arg1, arg2, arg3);
		}

		public void Test()
		{
		    // Invalid calls fail silently.
		    Callable callable = new Callable(this, MethodName.PrintArgs);
		    callable.Call("hello", "world"); // Default parameter values are not supported, should have 3 arguments.
		    callable.Call(Vector2.Up, 42, callable); // Prints "(0, -1) 42 Node(Node.cs)::PrintArgs".
		    callable.Call("invalid"); // Invalid call, should have 3 arguments.
		}
		[/csharp]
		[/codeblocks]
		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.
		    button_pressed.connect(func(): print("Attack!"))
		[/codeblock]
		[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.
		[codeblock]
		func _init():
		    var my_dictionary = { "hello": "world" }

		    # This will not work, `clear` is not a callable.
		    create_tween().tween_callback(my_dictionary.clear)

		    # This will work, as lambdas are custom callables.
		    create_tween().tween_callback(func(): my_dictionary.clear())
		[/codeblock]
	</description>
	<tutorials>
	</tutorials>
	<constructors>
		<constructor name="Callable">
			<return type="Callable" />
			<description>
				Constructs an empty [Callable], with no object nor method bound.
			</description>
		</constructor>
		<constructor name="Callable">
			<return type="Callable" />
			<param index="0" name="from" type="Callable" />
			<description>
				Constructs a [Callable] as a copy of the given [Callable].
			</description>
		</constructor>
		<constructor name="Callable">
			<return type="Callable" />
			<param index="0" name="object" type="Object" />
			<param index="1" name="method" type="StringName" />
			<description>
				Creates a new [Callable] for the method named [param method] in the specified [param object].
			</description>
		</constructor>
	</constructors>
	<methods>
		<method name="bind" qualifiers="vararg const">
			<return type="Callable" />
			<description>
				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.
			</description>
		</method>
		<method name="bindv">
			<return type="Callable" />
			<param index="0" name="arguments" type="Array" />
			<description>
				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.
			</description>
		</method>
		<method name="call" qualifiers="vararg const">
			<return type="Variant" />
			<description>
				Calls the method represented by this [Callable]. Arguments can be passed and should match the method's signature.
			</description>
		</method>
		<method name="call_deferred" qualifiers="vararg const">
			<return type="void" />
			<description>
				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.
				[codeblock]
				func _ready():
				    grab_focus.call_deferred()
				[/codeblock]
				See also [method Object.call_deferred].
			</description>
		</method>
		<method name="callv" qualifiers="const">
			<return type="Variant" />
			<param index="0" name="arguments" type="Array" />
			<description>
				Calls the method represented by this [Callable]. Unlike [method call], this method expects all arguments to be contained inside the [param arguments] [Array].
			</description>
		</method>
		<method name="get_bound_arguments" qualifiers="const">
			<return type="Array" />
			<description>
				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).
			</description>
		</method>
		<method name="get_bound_arguments_count" qualifiers="const">
			<return type="int" />
			<description>
				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.
			</description>
		</method>
		<method name="get_method" qualifiers="const">
			<return type="StringName" />
			<description>
				Returns the name of the method represented by this [Callable]. If the callable is a lambda function, returns the function's name.
			</description>
		</method>
		<method name="get_object" qualifiers="const">
			<return type="Object" />
			<description>
				Returns the object on which this [Callable] is called.
			</description>
		</method>
		<method name="get_object_id" qualifiers="const">
			<return type="int" />
			<description>
				Returns the ID of this [Callable]'s object (see [method Object.get_instance_id]).
			</description>
		</method>
		<method name="hash" qualifiers="const">
			<return type="int" />
			<description>
				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].
			</description>
		</method>
		<method name="is_custom" qualifiers="const">
			<return type="bool" />
			<description>
				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.
			</description>
		</method>
		<method name="is_null" qualifiers="const">
			<return type="bool" />
			<description>
				Returns [code]true[/code] if this [Callable] has no target to call the method on.
			</description>
		</method>
		<method name="is_standard" qualifiers="const">
			<return type="bool" />
			<description>
				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.
			</description>
		</method>
		<method name="is_valid" qualifiers="const">
			<return type="bool" />
			<description>
				Returns [code]true[/code] if the callable's object exists and has a valid method name assigned, or is a custom callable.
			</description>
		</method>
		<method name="rpc" qualifiers="vararg const">
			<return type="void" />
			<description>
				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].
			</description>
		</method>
		<method name="rpc_id" qualifiers="vararg const">
			<return type="void" />
			<param index="0" name="peer_id" type="int" />
			<description>
				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].
			</description>
		</method>
		<method name="unbind" qualifiers="const">
			<return type="Callable" />
			<param index="0" name="argcount" type="int" />
			<description>
				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.
				[/codeblock]
			</description>
		</method>
	</methods>
	<operators>
		<operator name="operator !=">
			<return type="bool" />
			<param index="0" name="right" type="Callable" />
			<description>
				Returns [code]true[/code] if both [Callable]s invoke different targets.
			</description>
		</operator>
		<operator name="operator ==">
			<return type="bool" />
			<param index="0" name="right" type="Callable" />
			<description>
				Returns [code]true[/code] if both [Callable]s invoke the same custom target.
			</description>
		</operator>
	</operators>
</class>