Angular 2: getting RouteParams from parent compone

Question

How do I get the RouteParams from a parent component?

App.ts:

@Component({
  ...
})

@RouteConfig([
  {path: '/', component: HomeComponent, as: 'Home'},
  {path: '/:username/...', component: ParentComponent, as: 'Parent'}
])

export class HomeComponent {
  ...
}

And then, in the ParentComponent, I can easily get my username param and set the child routes.

Parent.ts:

@Component({
  ...
})

@RouteConfig([
  { path: '/child-1', component: ChildOneComponent, as: 'ChildOne' },
  { path: '/child-2', component: ChildTwoComponent, as: 'ChildTwo' }
])

export class ParentComponent {

  public username: string;

  constructor(
    public params: RouteParams
  ) {
    this.username = params.get('username');
  }

  ...
}

But then, how can I get this same 'username' parameter in those child components? Doing the same trick as above, doesn't do it. Because those params are defined at the ProfileComponent or something??

@Component({
  ...
})

export class ChildOneComponent {

  public username: string;

  constructor(
    public params: RouteParams
  ) {
    this.username = params.get('username');
    // returns null
  }

  ...
}

Answer 1

With RxJS's Observable.combineLatest, we can get something close to the idiomatic params handling:

import 'rxjs/add/operator/combineLatest';

import {Component} from '@angular/core';
import {ActivatedRoute, Params} from '@angular/router';
import {Observable} from 'rxjs/Observable';

@Component({ /* ... */ })
export class SomeChildComponent {
  email: string;
  id: string;

  constructor(private route: ActivatedRoute) {}

  ngOnInit() {
    Observable.combineLatest(this.route.params, this.route.parent.params)
        .forEach((params: Params[]) => {
          this.id = params[0]['id'];
          this.email = params[1]['email'];
        });
  }
}

Answer 2

You can take component of parent route inside of child component from injector and then get any from child component. In you case like this

@Component({
  ...
})

export class ChildOneComponent {

  public username: string;

  constructor(
    public params: RouteParams
    private _injector: Injector

  ) {
    var parentComponent = this._injector.get(ParentComponent)

    this.username = parentComponent.username;
    //or
    this.username = parentComponent.params.get('username');
  }

  ...
}

Answer 3

UPDATE:

Now that Angular2 final was officially released, the correct way to do this is the following:

export class ChildComponent {

    private sub: any;

    private parentRouteId: number;

    constructor(private route: ActivatedRoute) { }

    ngOnInit() {
        this.sub = this.route.parent.params.subscribe(params => {
            this.parentRouteId = +params["id"];
        });
    }

    ngOnDestroy() {
        this.sub.unsubscribe();
    }
}

---

ORIGINAL:

Here is how i did it using the "@angular/router": "3.0.0-alpha.6" package:

export class ChildComponent {

    private sub: any;

    private parentRouteId: number;

    constructor(
        private router: Router,
        private route: ActivatedRoute) {
    }

    ngOnInit() {
        this.sub = this.router.routerState.parent(this.route).params.subscribe(params => {
            this.parentRouteId = +params["id"];
        });
    }

    ngOnDestroy() {
        this.sub.unsubscribe();
    }
}

In this example the route has the following format: /parent/:id/child/:childid

export const routes: RouterConfig = [
    {
        path: '/parent/:id',
        component: ParentComponent,
        children: [
            { path: '/child/:childid', component: ChildComponent }]
    }
];

Answer 4

In FINAL with little help of RXJS you can combine both maps (from child and parent):

(route) => Observable
    .zip(route.params, route.parent.params)
    .map(data => Object.assign({}, data[0], data[1]))

Other questions one might have:

• Is it really a good idea to use above - because of coupling (couple child component with parent's param's - not on api level - hidden coupling),
• Is it proper approach in term of RXJS (it would require hardcore RXJS user feedback ;)

Answer 5

I found an ugly but working solution, by requesting the parent (precisely the 2nd ancestor) injector, and by getting the RouteParams from here.

Something like

@Component({
  ...
})
export class ChildOneComponent {
  public username: string;

  constructor(injector: Injector) {
    let params = injector.parent.parent.get(RouteParams);

    this.username = params.get('username');
  }
}

Answer 6

You can do it on the snapshot with the following, but if it changes, your id property will not be updated.

This example also shows how you can subscribe to all ancestor parameter changes and look for the one you are interested in by merging all of the parameter observables. However, be careful with this method because there could be multiple ancestors that have the same parameter key/name.

import { Component } from '@angular/core';
import { ActivatedRoute, Params, ActivatedRouteSnapshot } from '@angular/router';
import { Observable } from 'rxjs/Observable';
import { Subscription } from 'rxjs/Subscription';
import 'rxjs/add/observable/merge';

// This traverses the route, following ancestors, looking for the parameter.
function getParam(route: ActivatedRouteSnapshot, key: string): any {
  if (route != null) {
    let param = route.params[key];
    if (param === undefined) {
      return getParam(route.parent, key);
    } else {
      return param;
    }
  } else {
    return undefined;
  }
}

@Component({ /* ... */ })
export class SomeChildComponent {

  id: string;

  private _parameterSubscription: Subscription;

  constructor(private route: ActivatedRoute) {
  }

  ngOnInit() {
    // There is no need to do this if you subscribe to parameter changes like below.
    this.id = getParam(this.route.snapshot, 'id');

    let paramObservables: Observable<Params>[] =
      this.route.pathFromRoot.map(route => route.params);

    this._parametersSubscription =
      Observable.merge(...paramObservables).subscribe((params: Params) => {
        if ('id' in params) {
          // If there are ancestor routes that have used
          // the same parameter name, they will conflict!
          this.id = params['id'];
        }
      });
  }

  ngOnDestroy() {
    this._parameterSubscription.unsubscribe();
  }
}