Is there a necessity for using RXJS combineLatest in conjunction with ActivateRouted.pathFromRoot?

Question

Is there a necessity for using RXJS combineLatest in conjunction with ActivateRouted.pathFromRoot?

The Angular Material Documentation application fetches route parameters from lazy loaded route modules in the following way:

https://github.com/angular/material.angular.io/blob/master/src/app/pages/component-category-list/component-category-list.ts

// Merge parameters from all paths into a single object.
    this.params = combineLatest(
        this._route.pathFromRoot.map(route => route.params), Object.assign);

Do we actually need to use combineLatest for this?

The _route is injected in the constructor, and as I understand it, once the component has a reference to it, the pathFromRoot array of the ActivateRoute instance cannot change.

If that's the case, then do we really require combineLatest?

It seems like we could potentially simplify it like this instead:

const paramArr = this._route.pathFromRoot.map(route => route.params)

this.params = of(Object.assign(paramArr))

Does this approach sound logical?

javascript angular typescript rxjs

Answer 1

Answer №1

When working with the pathFromRoute and route in this code snippet, it's important to note that while pathFromRoute and route remain constant, the route.params can emit new values over time as an Observable. In order to react to these new values, it is necessary to subscribe to each of these Observables individually. This is where the use of combineLatest becomes valuable.

this.params = of(Object.assign(paramArr))

The approach outlined here may not be very helpful as it creates an Observable that emits an array of Observables, requiring additional steps to flatten it out. By utilizing combineLatest, this extra step can be avoided for a more streamlined process.

Answer 2

When working with the pathFromRoute and route in this code snippet, it's important to note that while pathFromRoute and route remain constant, the route.params can emit new values over time as an Observable. In order to react to these new values, it is necessary to subscribe to each of these Observables individually. This is where the use of combineLatest becomes valuable.

this.params = of(Object.assign(paramArr))

The approach outlined here may not be very helpful as it creates an Observable that emits an array of Observables, requiring additional steps to flatten it out. By utilizing combineLatest, this extra step can be avoided for a more streamlined process.

Answer 3

Answer №2

It appears that the use of combineLatest might not be necessary in this case.

In my opinion, it could still be beneficial depending on your desired outcome.

For example, consider the following implementation:

const paramArr = this._route.pathFromRoot.map(route => route.params)

this.params = of(Object.assign(paramArr))

With this method, you will only receive the params from the root ActivatedRoute to the current child once. This means that if the params of a route are updated (e.g., navigating from /1 to /2), you will only receive 1.

However, there is uncertainty about its effectiveness since paramsArr may contain an array of observables (ActivatedRoute.params is typically a BehaviorSubject).

Alternatively, using the approach below:

this.params = combineLatest(
        this._route.pathFromRoot.map(route => route.params), Object.assign);

You will receive notifications for all updates to the params within the ActivatedRoute tree, not just once, but every time they occur.

I have provided more details on how ActivatedRoute functions, among other topics, in this article.

Answer 4

It appears that the use of combineLatest might not be necessary in this case.

In my opinion, it could still be beneficial depending on your desired outcome.

For example, consider the following implementation:

const paramArr = this._route.pathFromRoot.map(route => route.params)

this.params = of(Object.assign(paramArr))

With this method, you will only receive the params from the root ActivatedRoute to the current child once. This means that if the params of a route are updated (e.g., navigating from /1 to /2), you will only receive 1.

However, there is uncertainty about its effectiveness since paramsArr may contain an array of observables (ActivatedRoute.params is typically a BehaviorSubject).

Alternatively, using the approach below:

this.params = combineLatest(
        this._route.pathFromRoot.map(route => route.params), Object.assign);

You will receive notifications for all updates to the params within the ActivatedRoute tree, not just once, but every time they occur.

I have provided more details on how ActivatedRoute functions, among other topics, in this article.

Is there a necessity for using RXJS combineLatest in conjunction with ActivateRouted.pathFromRoot?

Answer №1

Answer №2

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