What is the purpose of using route parameters repeatedly in this Angular guide?

Question

What is the purpose of using route parameters repeatedly in this Angular guide?

I came across the Angular 2 tutorial on routing and found a section where they introduce a route /detail/:id along with an ngOnInit() method to handle this route and extract the :id parameter:

ngOnInit(): void {
  this.route.params.forEach((params: Params) => {
    let id = +params['id'];
    this.heroService.getHero(id)
      .then(hero => this.hero = hero);
  });
}

What confuses me is why they are iterating over route parameters. Since there's only one ID, wouldn't it be possible to retrieve it using this.route.params['id']?

Furthermore, if there were indeed multiple IDs present, what would be the purpose of looping through them as each new hero would simply replace the previous one?

angular typescript routes

Answer 1

Answer №1

If the route undergoes a change where only parameters are modified (such as changing the id in /somepath/:id/otherPath), then the router will not navigate away and back to the same component. Instead, it will remain on the same component and trigger a parameter change event.

Upon each event, (params:Params) => { ... } is executed.

Answer 2

If the route undergoes a change where only parameters are modified (such as changing the id in /somepath/:id/otherPath), then the router will not navigate away and back to the same component. Instead, it will remain on the same component and trigger a parameter change event.

Upon each event, (params:Params) => { ... } is executed.

Answer 3

Answer №2

If you need to fetch a specific identifier, another method is shown below:

const uniqueId = +this.route.snapshot.params['id'];

Answer 4

If you need to fetch a specific identifier, another method is shown below:

const uniqueId = +this.route.snapshot.params['id'];

Answer 5

Answer №3

To achieve this, start by importing the switchMap operator from rxjs library.

import 'rxjs/add/operator/switchMap';

After that, you can use it in your code like below:

this.route.params
    .switchMap((params: Params) => this.heroService.getHero(+params['id']))
    .subscribe(hero => this.hero = hero);

Answer 6

To achieve this, start by importing the switchMap operator from rxjs library.

import 'rxjs/add/operator/switchMap';

After that, you can use it in your code like below:

this.route.params
    .switchMap((params: Params) => this.heroService.getHero(+params['id']))
    .subscribe(hero => this.hero = hero);

Answer 7

Answer №4

Initially, it's important to note that the forEach() method being utilized here is not Array.prototype.forEach(), but rather Rx.Observable.prototype.forEach().

In Angular 2 route.params, you receive an array of Observables. Utilizing forEach() on this array with a lambda function is akin to subscribing to each parameter individually.

One key reason for subscribing to the params is that ngOnInit() is triggered when a component is routed from another component or refreshed. If the parameter values are used without subscribing, they may not work correctly when navigating to the same component with different parameter values, as ngOnInit is not called in that scenario.

For more information, please check out the Rx.Observable.prototype.forEach documentation

Answer 8

Initially, it's important to note that the forEach() method being utilized here is not Array.prototype.forEach(), but rather Rx.Observable.prototype.forEach().

In Angular 2 route.params, you receive an array of Observables. Utilizing forEach() on this array with a lambda function is akin to subscribing to each parameter individually.

One key reason for subscribing to the params is that ngOnInit() is triggered when a component is routed from another component or refreshed. If the parameter values are used without subscribing, they may not work correctly when navigating to the same component with different parameter values, as ngOnInit is not called in that scenario.

For more information, please check out the Rx.Observable.prototype.forEach documentation

Answer 9

Answer №5

You may already be aware of this, but it's important to understand that params is not an array; it's actually an Observable.

console.log(this.route.params['id']); // undefined
this.route.params.forEach(x => console.log(x['id'])); // the id e.g 999

It has been pointed out by others that there are multiple ways to access the id, but caution should be taken when using snapshot as it may not update when components are reused.

Answer 10

You may already be aware of this, but it's important to understand that params is not an array; it's actually an Observable.

console.log(this.route.params['id']); // undefined
this.route.params.forEach(x => console.log(x['id'])); // the id e.g 999

It has been pointed out by others that there are multiple ways to access the id, but caution should be taken when using snapshot as it may not update when components are reused.

What is the purpose of using route parameters repeatedly in this Angular guide?

Answer №1

Answer №2

Answer №3

Answer №4

Answer №5

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