libjsapi Types

libjsapi introduces four new class types to make dealing with JSAPI a bit easier:

• Value
• Object
• DynamicObject
• DynamicArray

The last three of these classes creates a rs::jsapi::Value instance via a factory Create() function. The parameters for each of these functions can be broken down into:

• getter callbacks
• setter callbacks
• enumerator callbacks (for DynamicObject)
• finalizer callbacks
• length callbacks (for DynamicArray)

The callbacks are implemented using std::function which means they accept C++ 11 lambdas with closures.

The signature of Object::Create looks like:

static bool Create(
        Context& cx, 
        std::initializer_list<const char*> properties,
        const GetCallback& getter, 
        const SetCallback& setter,
        std::initializer_list<Function> functions,
        const FinalizeCallback& finalizer,
        Value& obj);

The rs::jsapi::Value instance returned from Create can be passed to JSAPI functions or libjsapi methods, for example:

// create the new object
rs::jsapi::Value obj(cx);
rs::jsapi::Object::Create(/* ... */, obj);

// append the new object to an arguments instance
rs::jsapi::FunctionArguments args(cx);
args.Append(obj);

// call the JS function passing the new object via the args parameter
cx.Call("myfunc", args);

The getter and setter callbacks are invoked when JS code references the object. The finalizer is invoked when SpiderMonkey collects the object at the end of its life.