Added native class example

boa/examples/classes.rs

@@ -0,0 +1,84 @@
+use boa::builtins::object::{Class, ClassBuilder};
+use boa::builtins::value::*;
+use boa::exec::*;
+use boa::realm::Realm;
+use boa::*;
+
+use gc::{Finalize, Trace};
+
+#[derive(Debug, Trace, Finalize)]
+struct Person {
+    name: String,
+    age: u32,
+}
+
+impl Person {
+    fn say_hello(this: &Value, _: &[Value], ctx: &mut Interpreter) -> ResultValue {
+        if let Some(object) = this.as_object() {
+            if let Some(person) = object.downcast_ref::<Person>() {
+                println!(
+                    "Hello my name is {}, I'm {} years old",
+                    person.name, person.age
+                );
+                return Ok(Value::undefined());
+            }
+        }
+        ctx.throw_type_error("'this' is not a Person object")
+    }
+}
+
+impl Class for Person {
+    const NAME: &'static str = "Person";
+    const LENGTH: usize = 2;
+
+    fn constructor(_this: &Value, args: &[Value], ctx: &mut Interpreter) -> Result<Self, Value> {
+        let name = ctx.to_string(&args.get(0).cloned().unwrap_or_default())?;
+        let age = ctx.to_uint32(&args.get(1).cloned().unwrap_or_default())?;
+
+        let person = Person {
+            name: name.to_string(),
+            age,
+        };
+
+        Ok(person)
+    }
+
+    fn methods(class: &mut ClassBuilder) -> Result<(), Value> {
+        class.method("sayHello", 0, Self::say_hello);
+        class.static_method("is", 1, |_this, args, _ctx| {
+            if let Some(arg) = args.get(0) {
+                if let Some(object) = arg.as_object() {
+                    if object.is::<Person>() {
+                        return Ok(true.into());
+                    }
+                }
+            }
+            Ok(false.into())
+        });
+
+        Ok(())
+    }
+}
+
+fn main() {
+    let realm = Realm::create();
+    let mut context = Interpreter::new(realm);
+
+    context.register_global_class::<Person>().unwrap();
+
+    forward_val(
+        &mut context,
+        r"
+		let person = new Person('John', 19);
+		person.sayHello();
+
+		if (Person.is(person)) {
+			console.log('person is a Person class instance.');
+		}
+		if (!Person.is('Hello')) {
+			console.log('\'Hello\' string is not a Person class instance.');
+		}
+	",
+    )
+    .unwrap();
+}

boa/src/builtins/object/mod.rs

@@ -83,7 +83,7 @@ pub trait Class: NativeObject {
         Self: Sized;
 
     /// Initializes the internals and the methods of the class.
-    fn methods(class: &mut ClassBuilder<'_>) -> ResultValue;
+    fn methods(class: &mut ClassBuilder<'_>) -> Result<(), Value>;
 }
 
 /// Class builder which allows adding methods and static methods to the class.