Struct Function

pub struct Function<F: NapiValueT>(/* private fields */);

Implementations

impl<F: NapiValueT> Function<F>

pub fn new<T, R>( env: NapiEnv, name: Option<impl AsRef<str>>, func: impl FnMut(JsObject, T) -> NapiResult<R>, ) -> NapiResult<Function<R>>

where T: FromJsArgs, R: NapiValueT,

This API allows an add-on author to create a function object in native code. This is the primary mechanism to allow calling into the add-on’s native code from JavaScript. The newly created function is not automatically visible from script after this call. Instead, a property must be explicitly set on any object that is visible to JavaScript, in order for the function to be accessible from script. In order to expose a function as part of the add-on’s module exports, set the newly created function on the exports object. A sample module might look as follows:

napi_value SayHello(napi_env env, napi_callback_info info) {
 printf("Hello\n");
 return NULL;
}

napi_value Init(napi_env env, napi_value exports) {
 napi_status status;
 napi_value fn;
 status = napi_create_function(env, NULL, 0, SayHello, NULL, &fn);
 if (status != napi_ok) return NULL;
 status = napi_set_named_property(env, exports, "sayHello", fn);
 if (status != napi_ok) return NULL;
 return exports;
}

NAPI_MODULE(NODE_GYP_MODULE_NAME, Init)

Given the above code, the add-on can be used from JavaScript as follows:

const myaddon = require('./addon');
myaddon.sayHello();

The string passed to require() is the name of the target in binding.gyp responsible for creating the .node file.

Any non-NULL data which is passed to this API via the data parameter can be associated with the resulting JavaScript function (which is returned in the result parameter) and freed whenever the function is garbage-collected by passing both the JavaScript function and the data to napi_add_finalizer.

JavaScript Functions are described in Section 19.2 of the ECMAScript Language Specification.

pub fn call<T>(&self, this: JsObject, args: T) -> NapiResult<F>

where T: ToJsArgs,

This method allows a JavaScript function object to be called from a native add-on. This is the primary mechanism of calling back from the add-on’s native code into JavaScript. For the special case of calling into JavaScript after an async operation, see napi_make_callback.

pub fn new_instance<T, Args>(&self, args: Args) -> NapiResult<JsObject>

where T: NapiValueT, Args: AsRef<[T]>,

This method is used to instantiate a new JavaScript value using a given napi_value that represents the constructor for the object.

Trait Implementations

impl<F: Clone + NapiValueT> Clone for Function<F>

fn clone(&self) -> Function<F>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<F: Debug + NapiValueT> Debug for Function<F>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<F: NapiValueT> NapiValueCheck for Function<F>

fn check(&self) -> NapiResult<bool>

impl<F: NapiValueT> NapiValueT for Function<F>

fn from_raw(env: NapiEnv, raw: napi_value) -> Function<F>

construct value from raw pointer

fn value(&self) -> JsValue

inner value

unsafe fn cast<T: NapiValueT>(&self) -> T

napi_value type cast

fn cast_checked<T: NapiValueT>(&self) -> NapiResult<T>

Upcast to specified value

fn kind(&self) -> NapiResult<NapiValuetype>

Returns napi_ok if the API succeeded.

fn coerce_to_bool(&self) -> NapiResult<JsBoolean>

This API implements the abstract operation ToBoolean() as defined in Section 7.1.2 of the ECMAScript Language Specification.

fn coerce_coerce_to_number(&self) -> NapiResult<JsNumber>

This API implements the abstract operation ToNumber() as defined in Section 7.1.3 of the ECMAScript Language Specification. This function potentially runs JS code if the passed-in value is an object.

fn coerce_to_object(&self) -> NapiResult<JsObject>

This API implements the abstract operation ToObject() as defined in Section 7.1.13 of the ECMAScript Language Specification.

fn coerce_to_string(&self) -> NapiResult<JsString>

This API implements the abstract operation ToString() as defined in Section 7.1.13 of the ECMAScript Language Specification. This function potentially runs JS code if the passed-in value is an object.

fn instance_of(&self, constructor: JsFunction) -> NapiResult<bool>

This API represents invoking the instanceof Operator on the object as defined in Section 12.10.4 of the ECMAScript Language Specification.

fn equals(&self, rhs: impl NapiValueT) -> NapiResult<bool>

This API represents the invocation of the Strict Equality algorithm as defined in Section 7.2.14 of the ECMAScript Language Specification.

fn env(&self) -> NapiEnv

the NapiEnv of current value

fn raw(&self) -> napi_value

the raw-handle of current value

fn null(&self) -> NapiResult<JsNull>

get null singleton

fn undefined(&self) -> NapiResult<JsUndefined>

get undefined singleton

fn global(&self) -> NapiResult<JsGlobal>

get global singleton

fn throw(&self) -> NapiResult<()>

value is throwable

fn define_properties<P>(&self, properties: P) -> NapiResult<()>

where P: AsRef<[NapiPropertyDescriptor]>,

This method allows the efficient definition of multiple properties on a given object. The properties are defined using property descriptors (see napi_property_descriptor). Given an array of such property descriptors, this API will set the properties on the object one at a time, as defined by DefineOwnProperty() (described in Section 9.1.6 of the ECMA-262 specification).

fn gc<Finalizer>(&mut self, finalizer: Finalizer) -> NapiResult<NapiRef>

where Finalizer: FnOnce(NapiEnv) -> NapiResult<()>,

This is a hook which is fired when the value is gabage-collected. For napi >= 5, we use napi_add_finalizer, For napi < 5, we use napi_wrap.

fn finalizer<Finalizer>(&self, finalizer: Finalizer) -> NapiResult<NapiRef>

where Finalizer: FnOnce(NapiEnv) -> NapiResult<()>,

Adds a napi_finalize callback which will be called when the JavaScript object in js_object is ready for garbage collection. This API is similar to napi_wrap() except that:

fn wrap<T>( &mut self, data: T, finalizer: impl FnOnce(NapiEnv, T) -> NapiResult<()>, ) -> NapiResult<NapiRef>

Wraps a native instance in a JavaScript object. The native instance can be retrieved later using napi_unwrap().

fn unwrap<T>(&self) -> NapiResult<Option<&mut T>>

Retrieves a native instance that was previously wrapped in a JavaScript object using napi_wrap().

fn remove_wrap<T>(&mut self) -> NapiResult<T>

Retrieves a native instance that was previously wrapped in the JavaScript object js_object using napi_wrap() and removes the wrapping. If a finalize callback was associated with the wrapping, it will no longer be called when the JavaScript object becomes garbage-collected.

fn type_tag_object(&self, tag: &NapiTypeTag) -> NapiResult<()>

Associates the value of the type_tag pointer with the JavaScript object. napi_check_object_type_tag() can then be used to compare the tag that was attached to the object with one owned by the addon to ensure that the object has the right type. If the object already has an associated type tag, this API will return napi_invalid_arg.

fn check_object_type_tag(&self, tag: &NapiTypeTag) -> NapiResult<bool>

Compares the pointer given as type_tag with any that can be found on js_object. If no tag is found on js_object or, if a tag is found but it does not match type_tag, then result is set to false. If a tag is found and it matches type_tag, then result is set to true.

impl<F: Copy + NapiValueT> Copy for Function<F>