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e-oz/singleton-only.ts

Last active August 20, 2024 11:38
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singletonOnly
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singleton-only.ts
import { isDevMode } from '@angular/core';
const singletons = new Set<symbol>();
export function singletonOnly(unique: symbol) {
if (!isDevMode() || typeof window === 'undefined') {
return;
}
if (singletons.has(unique)) {
const msg = unique.toString() + ' MUST BE A SINGLETON! It was instantiated more than once.';
if (typeof alert !== 'undefined') {
alert(msg);
} else {
console?.trace(msg);
}
} else {
singletons.add(unique);
}
}
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e-oz commented Aug 9, 2024

Usage example:
File: account-store.ts

const unique = Symbol('AccountStore');

@Injectable({ providedIn: 'root' })  
export class AccountStore {
  constructor() {
    singletonOnly(unique);
  }
}

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