SystemLynx is a NodeJS framework for building modular web APIs, built on top of ExpressJS and Socket.io. It allows you to create objects and load them from a server into a client application.

SystemLynx comes with the following class that are used for web app development:

const { App, Service, Client, LoadBalancer } = require("systemlynx");

• Service - Used to create and host objects that can be loaded and used by a SystemLynx Client.
• Client - Used in a client application to load a Service, providing access to all the classes hosted by the Service.
• App - provides a modular interface for creating and loading Services.

Find the full API Documentation here.

Use the Service.module(name, constructor/class) method to add an class to be hosted by a SystemLynx Service. This will allows you to load an instance of that class into a client application, and call any methods on that class remotely.

const { Service } = require("systemlynx");

const Users = {};

Users.add = function (data) {
  console.log(data);
  return { message: "You have successfully called the Users.add method" };
};

Service.module("Users", Users);

In the code above we assigned an class to the variable Users and gave it an add method. The Service.module(name, constructor/class function takes the name assigned to the class as the first argument and the class itself as the second argument.

Alternatively, you can use a constructor function instead of an class as the second argument. In the example below we create another Module called "Orders". This time we use a constructor function as the second argument of the to Service.module function. The this value is the initial instance of the Module class. Every method added to the this value will be accessible when the class is loaded by a SystemLynx Client. Note: Module methods can be synchronous or asynchronous functions.

const { Service } = require("systemlynx");

const Users = {};

Users.add = function (data) {
  console.log(data);
  return { message: "You have successfully called the Users.add method" };
};

Service.module("Users", Users);

Service.module("Orders", function () {
  const Orders = this;

  Orders.find = async function (arg1, arg2) {
    console.log(arg1, arg2);
    return { message: "You have successfully called the Orders.find method" };
  };
});

Before we can access the objects hosted by this Service from a client application, we need to call the Service.startService(options) function. This will start an ExpressJS Server and a Socket.io WebSocket Server, and set up routing for the Service. In the example below we added the Service.startService(options) function at the bottom, but the order does not matter.

const { Service } = require("systemlynx");

const Users = {};

Users.add = function (data) {
  console.log(data);
  return { message: "You have successfully called the Users.add method" };
};

Service.module("Users", Users);

Service.module("Orders", function () {
  const Orders = this;

  Orders.find = async function (arg1, arg2) {
    console.log(arg1, arg2);
    return { message: "You have successfully called the Orders.find method" };
  };
});

Service.startService({ route: "test/service", port: "4400", host: "localhost" });

Now lets see how these objects can be loaded into a client application.

The Client.loadService(url) function can be used to load a SystemLynx Service. This method requires the url (string) of the Service you want to load as the first argument, and will return a promise that will resolve into an class that containing all the modules hosted by that service. See below. NOTE: You must be within an async function in order to use the await keyword when returning a promise.

const { Client } = require("systemlynx");

const { Users, Orders } = await Client.loadService("http://localhost:4400/test/service");

console.log(Users, Orders);

Now that we've loaded the Service that we created in the previous example, and have a handle on the Users and Orders class hosted by the Service, we can now call any method on those classes in the same way we would remotely. In the example below, noticed that both the User.add and Orders.find methods will return a promise.

const { Client } = require("systemlynx");

const { Users, Orders } = await Client.loadService("http://localhost:4400/test/service");

console.log(Users, Orders);

const results = await Users.add({ message: "Users.add Test" });

console.log(results);

const response = await Orders.find("hello", "world");

console.log(response);

We can also receive WebSocket events emitted from the remote classes we've loaded using the Client.loadService(url) function. In the example below we're using the Users.on(event_name, callback) method to listen for events coming from the "Users" Module.

const { Client } = require("systemlynx");

const { Users, Orders } = await Client.loadService("http://localhost:4400/test/service");

console.log(Users, Orders);

const results = await Users.add({ message: "Users.add Test" });

console.log(results);

Users.on("new_user", function (event) {
  console.log(event);
});

const response = await Orders.find("hello", "world");

console.log(response);

Now let's go to our server application and call the Users.emit(event_name, data) method to emit a websocket event that can be received by its corresponding Clients. Below, notice that we've added this.emit("new_user", { message:"new_user event test" }) at the end of the Users.add method, so the new_user event will be emitted every time this method is called. The this value of a Module method will always be scoped to the Module itself.

const { Service } = require("systemlynx");

const Users = {};

Users.add = function (data) {
  console.log(data);
  return { message: "You have successfully called the Users.add method" };
  this.emit("new_user", { message: "new_user event test" });
};

Service.module("Users", Users);

Service.module("Orders", function () {
  const Orders = this;

  Orders.find = async function (arg1, arg2) {
    console.log(arg1, arg2);
    return { message: "You have successfully called the Orders.find method" };
  };
});

Service.startService({ route: "test/service", port: "4400", host: "localhost" });