Enhancing TypeScript Modules

Recently, I encountered an issue with my observable extension. Everything was functioning perfectly until I updated to angular 6 and typescript 2.7.2.

import { Observable } from 'rxjs/Observable';
import { BaseComponent } from './base-component';
import { Subscription } from 'rxjs/Subscription';
import { Subscribable } from 'rxjs';

declare module 'rxjs/Observable' {
    export interface Observable<T> {
        safeSubscribe<T>(this: Observable<T>, component: BaseComponent,
            next?: (value: T) => void, error?: (error: T) => void, complete?: () => void): Subscription;
    }
}


export function safeSubscribe<T>(this: Observable<T>, component: BaseComponent,
    next?: (value: T) => void, error?: (error: T) => void, complete?: () => void): Subscription {
    let sub = this.subscribe(next, error, complete);
    component.markForSafeDelete(sub);
    return sub;
}

Observable.prototype.safeSubscribe = safeSubscribe;

However, the code above is now causing issues:

  1. 'Observable' only refers to a type, but is being used as a value here.
  2. Property 'subscribe' does not exist on type 'Observable'.

Visit this link for more information on declaration merging in TypeScript

Answer №1

When combining declarations, it is essential for the module path specified to be an exact match with the actual module path.

For RxJS version 6, you must update your module declaration due to changes in the internal structure. Based on recollection, the new declaration should look like this:

declare module 'rxjs/internal/Observable' {
    export interface Observable<T> {
        safeSubscribe<T>(this: Observable<T>, component: BaseComponent,
            next?: (value: T) => void, error?: (error: T) => void, complete?: () => void): Subscription;
    }
}

To see a practical example, refer to one of the updated imports in rxjs-compat.

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