Month: May 2017

EventEmitter

Our EventEmitter in PhantomSQL is based on NodeJS version so they should be compatible. Here are couple examples on how to use the emitter.

Basic usage of registering and listening to an event.

"use strict";

const {EventEmitter} = require('events');

// Dump all the args
em.on('hello-event', (...arg)=> {console.info("Hello event handler : " + arg)});
// Handler without args
em.on('hello-event', ()=> {console.info("Another handler")});
// passed in arguments
em.on('hello-event', (id, val)=> {console.info("Handler :"+id +", "+ val)});

// emit event
em.emit('hello-event', 123, 'ABC');

A more typical example would be to extend via prototype.

"use strict";
const {EventEmitter} = require('events');

function HelloService()
{
	// Extends via prototype
	Object.setPrototypeOf(HelloService.prototype, EventEmitter.prototype);
	
	this.hello = function()
	{
		console.info("Hello service called");
		this.emit('hello');
	}
}  

const service = new HelloService();

service.on('hello', ()=> {console.info("Hello Handler called")});
service.hello();

May 30, 2017

Creating Javascript accessible object from C++ / CEF

Example with Chromium Embedded Framework (CEF) on how to create an object in C++ and make it accessible via Javascript.

console.inof(api)
Object {ready: true, version: "psql.0.0.1", info: Object, getVersion: function}

void ExtractEngineApp::OnContextCreated(
	CefRefPtr browser, 
	CefRefPtr frame, 
	CefRefPtr context)
{

	auto info = CefV8Value::CreateObject(NULL, NULL);
	info->SetValue("major", CefV8Value::CreateString("0"), V8_PROPERTY_ATTRIBUTE_READONLY);
	info->SetValue("minor", CefV8Value::CreateString("1"), V8_PROPERTY_ATTRIBUTE_READONLY);
	
	auto global = context->GetGlobal();
	auto api = CefV8Value::CreateObject(NULL, NULL);

	global->SetValue("api", api, V8_PROPERTY_ATTRIBUTE_NONE);

	auto fun = CefV8Value::CreateFunction("getVersion", new engine:: PhantomExtensionHandler(this));
	api->SetValue("getVersion", fun, V8_PROPERTY_ATTRIBUTE_NONE);
	
	// Readonly properties
	api->SetValue("ready", CefV8Value::CreateBool(true), V8_PROPERTY_ATTRIBUTE_READONLY);
	api->SetValue("version", CefV8Value::CreateString("psql.0.0.1"), V8_PROPERTY_ATTRIBUTE_READONLY);

	// Readonly Object access
	api->SetValue("info", info, V8_PROPERTY_ATTRIBUTE_READONLY);
}


class PhantomExtensionHandler : public CefV8Handler
	{
	public:
		explicit PhantomExtensionHandler(CefRefPtr client_app)
			: client_app(client_app)
			, messageId(0)
		{

		}

		virtual bool Execute(const CefString& name,
			CefRefPtr object,
			const CefV8ValueList& arguments,
			CefRefPtr& retval,
			CefString& exception)
		{
			if (name == "getVersion")
			{
				retval = CefV8Value::CreateString("Version(SemVer) # 0.0.1");
			}

			return true;
		}

	private:
		CefRefPtr client_app;
		int32 messageId;

		IMPLEMENT_REFCOUNTING(PhantomExtensionHandler);
	};

May 1, 2017