Callable

A built-in type representing a method or a standalone function.

描述

Callable is a built-in Variant type that represents a function. It can either be a method within an Object instance, or a custom callable used for different purposes (see is_custom). Like all Variant types, it can be stored in variables and passed to other functions. It is most commonly used for signal callbacks.

    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.

    // 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.
    }

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 get_method.

    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!"))

In GDScript, you can access methods and global functions as Callable s:

    tween.tween_callback(node.queue_free)  # Object methods.
    tween.tween_callback(array.clear)  # Methods of built-in types.
    tween.tween_callback(print.bind("Test"))  # Global functions.

Note: Dictionary does not support the above due to ambiguity with keys.

    var dictionary = {"hello": "world"}
    
    # This will not work, `clear` is treated as a key.
    tween.tween_callback(dictionary.clear)
    
    # This will work.
    tween.tween_callback(Callable.create(dictionary, "clear"))

通过 C# 使用该 API 时会有显著不同，详见 :ref:doc_c_sharp_differences\ 。

构造函数

方法

运算符

构造函数说明

Callable Callable ( )

Constructs an empty Callable, with no object nor method bound.

Callable Callable ( from: Callable )

Constructs a Callable as a copy of the given Callable.

Callable Callable ( object: Object, method: StringName )

Creates a new Callable for the method named method in the specified object.

Note: For methods of built-in Variant types, use create instead.

方法说明

Callable bind ( ... ) vararg¹ const²

Returns a copy of this Callable with one or more arguments bound. When called, the bound arguments are passed after the arguments supplied by call. See also unbind.

Note: When this method is chained with other similar methods, the order in which the argument list is modified is read from right to left.

Callable bindv ( arguments: Array )

Returns a copy of this Callable with one or more arguments bound, reading them from an array. When called, the bound arguments are passed after the arguments supplied by call. See also unbind.

Note: When this method is chained with other similar methods, the order in which the argument list is modified is read from right to left.

Variant call ( ... ) vararg¹ const²

Calls the method represented by this Callable. Arguments can be passed and should match the method's signature.

void call_deferred ( ... ) vararg¹ const²

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.

    func _ready():
        grab_focus.call_deferred()

    public override void _Ready()
    {
        Callable.From(GrabFocus).CallDeferred();
    }

Note: Deferred calls are processed at idle time. Idle time happens mainly at the end of process and physics frames. In it, deferred calls will be run until there are none left, which means you can defer calls from other deferred calls and they'll still be run in the current idle time cycle. This means you should not call a method deferred from itself (or from a method called by it), as this causes infinite recursion the same way as if you had called the method directly.

See also Object.call_deferred.

Variant callv ( arguments: Array ) const²

Calls the method represented by this Callable. Unlike call, this method expects all arguments to be contained inside the arguments Array.

Callable create ( variant: Variant, method: StringName ) static³

Creates a new Callable for the method named method in the specified variant. To represent a method of a built-in Variant type, a custom callable is used (see is_custom). If variant is Object, then a standard callable will be created instead.

Note: This method is always necessary for the Dictionary type, as property syntax is used to access its entries. You may also use this method when variant's type is not known in advance (for polymorphism).

int get_argument_count ( ) const²

Returns the total number of arguments this Callable should take, including optional arguments. This means that any arguments bound with bind are subtracted from the result, and any arguments unbound with unbind are added to the result.

Array get_bound_arguments ( ) const²

Return the bound arguments (as long as get_bound_arguments_count is greater than zero), or empty (if get_bound_arguments_count is less than or equal to zero).

int get_bound_arguments_count ( ) const²

Returns the total amount of arguments bound (or unbound) via successive bind or unbind calls. If the amount of arguments unbound is greater than the ones bound, this function returns a value less than zero.

StringName get_method ( ) const²

Returns the name of the method represented by this Callable. If the callable is a GDScript lambda function, returns the function's name or "<anonymous lambda>".

Object get_object ( ) const²

Returns the object on which this Callable is called.

int get_object_id ( ) const²

Returns the ID of this Callable's object (see Object.get_instance_id).

int hash ( ) const²

Returns the 32-bit hash value of this Callable's object.

Note: Callable s with equal content will always produce identical hash values. However, the reverse is not true. Returning identical hash values does not 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 hash.

bool is_custom ( ) const²

Returns true if this Callable is a custom callable. Custom callables are used:

• for binding/unbinding arguments (see bind and unbind);

• for representing methods of built-in Variant types (see create);

• for representing global, lambda, and RPC functions in GDScript;

• for other purposes in the core, GDExtension, and C#.

bool is_null ( ) const²

Returns true if this Callable has no target to call the method on. Equivalent to callable == Callable().

Note: This is not the same as not is_valid() and using not is_null() will not guarantee that this callable can be called. Use is_valid instead.

bool is_standard ( ) const²

Returns true if this Callable is a standard callable. This method is the opposite of is_custom. Returns false if this callable is a lambda function.

bool is_valid ( ) const²

Returns true if the callable's object exists and has a valid method name assigned, or is a custom callable.

void rpc ( ... ) vararg¹ const²

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 RPC (using @GDScript.@rpc or Node.rpc_config). Calling this method on unsupported functions will result in an error. See Node.rpc.

void rpc_id ( peer_id: int, ... ) vararg¹ const²

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 RPC (using @GDScript.@rpc or Node.rpc_config). Calling this method on unsupported functions will result in an error. See Node.rpc_id.

Callable unbind ( argcount: int ) const²

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 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 bind.

Note: When this method is chained with other similar methods, the order in which the argument list is modified is read from right to left.

    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.

运算符说明

bool operator != ( right: Callable )

Returns true if both Callable s invoke different targets.

bool operator == ( right: Callable )

Returns true if both Callable s invoke the same custom target.