Angular 2 get routeParams in a service

问题

I want to shift the logic from component to service. But I found out that I can't get the routeParams in a service.

My component looks like

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

import { MyService }              from '../services/my.service';

@Component({
  moduleId: module.id,
  templateUrl: 'my.component.html',
  styleUrls: ['my.component.css']
})
export class MyComponent implements OnInit {
  constructor(private myService: MyService, private route: ActivatedRoute) {;}

  public ngOnInit() {
    this.route.params
      .subscribe((params: Params) => {
        debugger;
        console.log(params);
      });
    this.myService.getParams()
      .subscribe((params: Params) => {
        debugger;
        console.log('Return1:');
        console.log(params);
      }, (params: Params) => {
        debugger;
        console.log('Return2:');
        console.log(params);
      }, () => {
        debugger;
        console.log('Return3:');
    });
  }
};

My service looks like

import { Injectable }                     from '@angular/core';
import { Params, ActivatedRoute }         from '@angular/router';

import { Observable }                     from 'rxjs';

@Injectable()
export class MyService {
  constructor(private route: ActivatedRoute) {;}

  public getParams(): Observable<Params> {       
    this.route.params.subscribe((params: Params) => {
      debugger;
      console.log('Service1:');
      console.log(params);
    }, (params: Params) => {
      debugger;
      console.log('Service2:');
      console.log(params);
    }, () => {
      debugger;
      console.log('Service3:');
    });
    return this.route.params;
  }
};

When I debug I can see that params are filled in component and empty in service. That's the result

Component:
Object {param: "1"}
Service1:
Object {}
Return1:
Object {}

I'm using Angular 2.0.0. Why the difference in component and service? Is it possible to get params in a service?

EDIT: https://github.com/angular/angular/issues/11023

回答1:

We can pass ActivatedRoute to service from component. Then subscribe to route.params in service class

回答2:

Acording to this you have to traverse down the route tree and get the data from the route at the bottom of the tree.

@Injectable()
export class MyService{

  constructor(private router:Router,private route:ActivatedRoute){   
   this.router.events
    .filter(event => event instanceof NavigationEnd)
     .subscribe((event) => {
         let r=this.route;
         while (r.firstChild) {
            r = r.firstChild
        }
         //we need to use first, or we will end up having
         //an increasing number of subscriptions after each route change.   
         r.params.first().subscribe(params=>{                
           // Now you can use the params to do whatever you want
         });             


    });            
  }
}

回答3:

the problem is the

return this.route.params;

the route params are not ready at that moment -> observables -> asynchronicity

回答4:

I like managing state through the URL, and built a simple state service that observes route navigation end events and exposes observable endpoints for each route parameter.

import { Injectable } from '@angular/core';
import {NavigationEnd, Router} from '@angular/router';
import {BehaviorSubject} from 'rxjs';
import { filter } from 'rxjs/operators';

@Injectable({
  providedIn: 'root'
})
export class DigStateService {
  public state = {};

  constructor(private router: Router) {
    this.router.events.pipe(
      filter(event => event instanceof NavigationEnd)
    ).subscribe(() => {
      let route = this.router.routerState.snapshot.root;
      do {
        const params = route.params;
        const keys = Object.keys(params);
        if (keys.length > 0) {
          keys.forEach(key => {
            const val = params[key];
            if (this.state[key]) {
              this.state[key].next(val);
            } else {
              this.state[key] = new BehaviorSubject(val);
            }
          });
        }
        route = route.firstChild;
      } while (route);
    });
  }

  param(key) {
    // if this key does not exist yet create it so its observable when it is set
    if (! this.state[key]) {
      this.state[key] = new BehaviorSubject(null);
    }
    return this.state[key];
  }
}

Then you can use this service to observe individual route params from anywhere in the tree:

stateService.param('project').subscribe(projectId => {
  console.log('project ' + projectId);
});

来源：https://stackoverflow.com/questions/40219790/angular-2-get-routeparams-in-a-service