Specialized Singleton implementation - oop

Question

I am looking for specialized singleton implementation, probably I might be using wrong terminology and hence looking for expert suggestion. Here is my scenario:
There is common code which can be called by ComponentA or ComponentB. I need to push telemetry data from the common code. Telemetry needs to have information that whether this common code get called by ComponentA or ComponentB.
So common code will have just this line of code:
telemetry.pushData(this._area, data);
where this._area tells the telemetry data is getting pushed for which component
I need to push telemetry data from multiple places so it would be good if object got created once and used through out the code lifetime
One option I can think of passing component context to the common code which in mind doesn't look right, hence looking for suggestion what kind of pattern one should use in this case?
This is what I am thinking
// Telemetry.ts file present in shared code
export class Telemetry extends Singleton {
public constructor() {
super();
}
public static instance(): Telemetry {
return super.instance<Telemetry>(Telemetry);
}
public publishEvent(data): void {
if (!this.area) {
throw new Error("Error: Initialize telemetry class with right area");
}
pushtelemetryData(this.area, data);
}
public area: string;
}
// Create Telemetry object from component A
Telemetry.instance().area = "ComponentA";
// Shared code will call telemetry publishEvent
Telemetry.instance().publishEvent(data);
Thanks

Answer 1

It's not a good pattern to use in TypeScript where you would generally inject dependencies.
If you must absolutely do it then you can do it by faking it somewhat:
namespace Telemetry {
var instance : SingletonSomething;
export function push(data: Any) : void {
if (instance == null) {
instance = new SingletonSomething();
}
instance.push(data);
}
class SingletonSomething() { ... }
}
and then you could call
Telemetry.push(data);

Answer 2

You can imitate the singleton pattern in typescript easily:
class Telemetry {
private static instance: Telemetry;
public static getInstance(): Telemetry {
if (Telemetry.instance == null) {
Telemetry.instance = new Telemetry();
}
return Telemetry.instance;
}
...
}
If you have your code in some sort of closure (module, namespace, etc) then you can replace the static member with:
let telemetryInstance: Telemetry;
export class Telemetry {
public static getInstance(): Telemetry {
if (telemetryInstance == null) {
telemetryInstance = new Telemetry();
}
return telemetryInstance;
}
...
}
But then you can also replace the static method with:
let telemetryInstance: Telemetry;
export function getTelemetryInstance(): Telemetry {
if (telemetryInstance == null) {
telemetryInstance = new Telemetry();
}
return telemetryInstance;
}
export class Telemetry {
...
}
At this point, in case you are using some sort of closure, you might ask yourself if you really need the class at all?
If you use this as a module:
// telemetry.ts
export interface TelemetryData {
...
}
export function pushData(data: TelemetryData): void {
...
}
Then you get exactly what you're looking for, and this is more of the "javascript way" of doing it.
Edit
In the telemetry module there's no need to know the users of it.
If the Telemetry.pushData function needs to have information about the object that called it then define an interface for it:
// telemetry.ts
export interface TelemetryData {
...
}
export interface TelemetryComponent {
name: string;
...
}
export function pushData(data: TelemetryData, component: TelemetryComponent): void {
...
}
Then in the other modules, where you use it:
// someModule.ts
import * as Telemetry from "./telemetry";
class MyComponent implement Telemetry.TelemetryComponent {
// can also be a simple string property
public get name() {
return "MyComponent";
}
fn() {
...
Telemetry.pushData({ ... }, this);
}
}
2nd Edit
Because you are using a module system, your module files are enough to make singletons, there's no need for a class to achieve that.
You can do this:
// telemetry.ts
let area: string;
export interface TelemetryData {
...
}
export function setArea(usedArea: string) {
area = usedArea;
}
export function pushData(data: TelemetryData): void {
...
}
Then:
Telemetry.setArea("ComponentA");
...
Telemetry.publishEvent(data);
The telemetry module will be created only once per page, so you can treat the entire module as a singleton.
Export only the functions that are needed.