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Sabish.M
Sabish.M

Reputation: 2060

What is the equivalent of Java singleton in React Native?

Actually I am a Android Native Developer. I am new to React-Native. In Java i keep the users data and others data in Singleton Class and access from other activities. Then how i achieve this process in React native for access data's from other components or any alternative of singleton in React native.

I just try this but i received the error like getInstance() not defined.

class AppDelegate {
log = "This is AppDelegate";  

  static myInstance = null;
  static getInstance() {
    if (AppDelegate.myInstance == null) {
      AppDelegate.myInstance = new AppDelegate();
    }

    return this.myInstance;
  }

}

Thank you.

Upvotes: 4

Views: 2588

Answers (3)

Alfredo Salzillo
Alfredo Salzillo

Reputation: 142

If you need a singleton don't use a class at all. Export the methods as a function instead.

// File app-delegate.js
let privateIstanceValue;
export const method1 = () => //do something;
export const method2 = () => //do something again;

Import using import * as

import * as appDelegate from './app-delegate.js';

Upvotes: 0

Mosè Raguzzini
Mosè Raguzzini

Reputation: 15851

Imports are cached, so if you export a class, the class will be cached, if you export an instance, the instance will be cached

Upvotes: 3

Estus Flask
Estus Flask

Reputation: 222989

React is UI library, this isn't its responsibility. The question affects any JavaScript application, not only React.

JavaScript modules and ES modules in particular are evaluated only once under normal circumstances, this makes exports singletons:

  // exported for extensibility
  export class AppDelegate {...}

  // a singleton
  export default new AppDelegate;

Singleton class is potentially an antipattern in JavaScript. If there's a need for one object, it could be written as object literal.

Upvotes: 4

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