napi-rs Docs

Defining class

Defining class

Real world example

This example creates a class named TestClass which has a js property called count and wraps a rust struct NativeClass on the instance of the object which has a property value. The methods can access both the object's properites and the wrapped struct.

lib.rs
#[macro_use]
extern crate napi_derive;
use std::convert::TryInto;
use napi::{CallContext, JsNumber, JsObject, JsUndefined, Property, Result, Env};
struct NativeClass {
value: i32,
}
#[js_function(1)]
fn test_class_constructor(ctx: CallContext) -> Result<JsUndefined> {
let count: i32 = ctx.get::<JsNumber>(0)?.try_into()?;
let mut this: JsObject = ctx.this_unchecked();
ctx
.env
.wrap(&mut this, NativeClass { value: count + 100 })?;
this.set_named_property("count", ctx.env.create_int32(count)?)?;
ctx.env.get_undefined()
}
#[js_function(1)]
fn add_count(ctx: CallContext) -> Result<JsNumber> {
let add: i32 = ctx.get::<JsNumber>(0)?.try_into()?;
let mut this: JsObject = ctx.this_unchecked();
let count: i32 = this.get_named_property::<JsNumber>("count")?.try_into()?;
this.set_named_property("count", ctx.env.create_int32(count + add)?)?;
this.get_named_property("count")
}
#[js_function(1)]
fn add_native_count(ctx: CallContext) -> Result<JsNumber> {
let add: i32 = ctx.get::<JsNumber>(0)?.try_into()?;
let this: JsObject = ctx.this_unchecked();
let native_class: &mut NativeClass = ctx.env.unwrap(&this)?;
native_class.value += add;
ctx.env.create_int32(native_class.value)
}
#[module_exports]
pub fn init(mut exports: JsObject, env: Env) -> Result<()> {
let test_class = env
.define_class("TestClass", test_class_constructor, &[
Property::new(&env, "addCount")?.with_method(add_count),
Property::new(&env, "addNativeCount")?.with_method(add_native_count),
])?;
exports.set_named_property("TestClass", test_class)?;
Ok(())
}
const { TestClass } = require('./index.node')
const test = new TestClass(100)
test.addCount()
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