Writing Functions

You can easily extend Space Cloud by writing your custom logic on the backend in the form of simple functions. These functions run as a microservice on the backend. This is how you write a simple service -

const { API, cond } = require('space-api');

const api = new API('my-app', 'http://localhost:4122');

// Make a service
const service = api.Service('service-name');

// Register function to a service
service.registerFunc('function-name', (params, auth, cb) => {
  // Your custom logic goes here

  // Response to be returned to client
  const res = { ack: true, message: 'Functions mesh is amazing!' }
  cb('response', res)

// Start the service

import (

func main() {
	api, err := api.New("books-app", "localhost:4124", false)
	if(err != nil) {
	service := api.Service("service")
	service.RegisterFunc("echo_func", Echo)

func Echo(params, auth *model.Message, fn service.CallBackFunction) {
	var i interface{}
	fn("response", i)

API api = new API("books-app", "localhost", 4124);
Service service = api.service("service");
service.registerFunc("echo_func", new ServiceFunction() {
    public void onInvocation(Message params, Message auth, ReturnCallback cb) {
        cb.send("response", params.getValue(Object.class));
service.start(); // Is blocking

from space_api import API

api = API('books-app', 'localhost:4124')

def my_func(params, auth, cb):  # Function to be registered
    print("Params", params, "Auth", auth)

    # Do Something
    cb('response', {"ack": True})

service = api.service('service')  # Create an instance of service
service.register_func('my_func', my_func)  # Register function
service.start()  # Start service (This is a blocking call)


Use api.Service to initialize an instance of an service. The api.Service function takes only one parameter - serviceName which uniquely identifies the service.

A service can harbour multiple functions which can be invoked by client. service.registerFunc is used to register a function to a service. The registerFunc method takes two parameters:

  • funcName: Name of the function which uniquely identifies a function within a service
  • func: The function to be executed

Function parameters

Any registered function gets three arguments during execution when triggered by client as follows:

  • params: The params object sent by the client.
  • auth: Auth object (consists the claims of JWT Token)
  • cb: Callback function used to return the response back to the client

Sending Response

To send JSON object as a response back to client, call the cb function with type as response and the second parameter being the response object:

// Any object that you want to send as response
const response = { ack: true, message: 'I love functions mesh!' } 
cb('response', response)

Next steps

We just saw how to write custom backend code. Let’s see how to trigger these functions from frontend.

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