需要帮助从Angular 2中的Service访问变量

问题描述

将用户上一页的URL ID传递给我可以在对话框中引用的服务.

issuer.service.ts

  import从'@ angular/core'导入{Injectable，EventEmitter};从'rxjs'导入{可观察的，}从'rxjs'导入{BehaviorSubject};@Injectable()导出类IssuerService {私人urlidSource = new BehaviorSubject< string>('');currentUrlid = this.urlidSource.asObservable();public onChange:EventEmitter< string>=新的EventEmitter< string>();构造函数(){}changeUrlid(urlid:string){this.currentUrlid = of(urlid);this.onChange.emit(urlid);}getUrlid(currentUrlid:string){返回this.currentUrlid;}}  

具有我想要的URL ID(dashboard.component.ts)的页面

 从'./../../issuer.service'导入{IssuerService};从"@ angular/router"导入{ActivatedRoute}；从"@ angular/router"导入{Router}；urlid:字符串;构造函数(专用路由:ActivatedRoute，专用路由器:路由器，私人issuerService:IssuerService，公共对话框:MatDialog){}newUrlid(){this.issuerService.changeUrlid(this.route.snapshot.paramMap.get('id'));console.log(this.urlid);}ngOnInit(){//获取URL IDthis.issuerService.onChange.subscribe(urlid => this.urlid = urlid);this.newUrlid();}  

组件我要读取以下值:

 从'@ angular/router'导入{ActivatedRoute};从"@ angular/router"导入{Router}；从'./../../issuer.service'导入{IssuerService};urlid:字符串;构造函数(专用路由:ActivatedRoute，专用路由器:路由器，私人issuerService:IssuerService，公共对话框:MatDialog){}ngOnInit(){this.issuerService.onChange.subscribe(urlid => {this.urlid =网址id;console.log(this.urlid);});}  

因此，当我当前访问仪表板页面时，它将显示正确的2值.我的目标是，当用户访问任何页面时，我都可以读取此值2.如何访问此值?上面的代码有效，并且我的标题显示2，但仅在仪表板页面上显示.无论用户在哪个页面上，我都需要显示2.

解决方案

，您可以看到此

 导出类IssuerService {私人urlidSource = new ReplaySubject< string>(1);Constructor(){}changeUrlid(urlid:string){this.urlidSource.next(urlid);}getUrlid(){返回this.urlidSource;}}导出类DashboardComponent实现OnInit {urlid:字符串;构造函数(//专用路由:ActivatedRoute，专用路由器:路由器，私人issuerService:IssuerService，//公共对话框:MatDialog){}newUrlid(){//获取URL IDthis.route.queryParams.subscribe((queryParam)=> {const id = queryParam ['id'];如果(！id){返回;}this.issuerService.changeUrlid(id);});}ngOnInit(){this.newUrlid();this.issuerService.getUrlid().subscribe(urlid => {this.urlid =网址id;});}}导出类HelloComponent实现OnInit {urlid;构造函数(私人issuerService:IssuerService){}ngOnInit(){this.issuerService.getUrlid().subscribe(urlid => {this.urlid =网址id;});}}  

Passing the URL id from the last page a user was on to a service that I can reference in a dialog.

issuer.service.ts

import { Injectable, EventEmitter } from '@angular/core';
import { Observable, of } from 'rxjs';
import { BehaviorSubject } from 'rxjs';

@Injectable()
export class IssuerService {


private urlidSource = new BehaviorSubject<string>('');
currentUrlid = this.urlidSource.asObservable();
public onChange: EventEmitter<string> = new EventEmitter<string>();

  constructor () {
  }

  changeUrlid(urlid: string) {
    this.currentUrlid = of(urlid);
    this.onChange.emit(urlid);
  }

  getUrlid(currentUrlid: string) {
    return this.currentUrlid;
  }


}

Page that has the URL id I want (dashboard.component.ts)

import { IssuerService } from './../../issuer.service';
import { ActivatedRoute } from '@angular/router';
import { Router } from '@angular/router';
urlid: string;
  constructor(
    private route: ActivatedRoute,
    private router: Router,
    private issuerService: IssuerService,
    public dialog: MatDialog
  ) {}

newUrlid() {
  this.issuerService.changeUrlid(this.route.snapshot.paramMap.get('id'));
  console.log(this.urlid);
}

  ngOnInit() {
    // Get URL ID
    this.issuerService.onChange.subscribe(urlid => this.urlid = urlid);
    this.newUrlid();
}

Component I want to read the value in:

    import { ActivatedRoute } from '@angular/router';
    import { Router } from '@angular/router';
    import { IssuerService } from './../../issuer.service';

        urlid: string;

        constructor(
          private route: ActivatedRoute,
          private router: Router,
          private issuerService: IssuerService,
          public dialog: MatDialog
        ) {}

  ngOnInit() {
 this.issuerService.onChange.subscribe(urlid => {
           this.urlid = urlid;
           console.log(this.urlid);
   });

  }

So currently when I visit my dashboard page it will display the value of 2 which is correct. My goal is that when a user visits any page I can read this value of 2. How can I access this value? The above code works and my Header displays 2 but only when on the dashboard page. I need it to display 2 no matter what page the user is on.

解决方案

you can see this example, and It's modified list:

• use queryPamas to get query string, not params (DashboardComponent)

• use ReplaySubject(1) to return the last urlId; it's don't have a default value, just return prev one value (IssuerService)

• get observable from getUrlid and subscribe it in components that want to show url id

export class IssuerService {


  private urlidSource = new ReplaySubject<string>(1);

  constructor() {
  }

  changeUrlid(urlid: string) {
    this.urlidSource.next(urlid);
  }

  getUrlid() {
    return this.urlidSource;
  }

}

export class DashboardComponent implements OnInit {

  urlid: string;
  constructor(
    // private route: ActivatedRoute,
    private router: Router,
    private issuerService: IssuerService,
    // public dialog: MatDialog
  ) { }

  newUrlid() {
    // Get URL ID
    this.route.queryParams.subscribe((queryParam) => {
      const id = queryParam['id'];
      if (!id) {
        return;
      }
      this.issuerService.changeUrlid(id);
    });
  }

  ngOnInit() {
    this.newUrlid();

    this.issuerService.getUrlid().subscribe(urlid => {
      this.urlid = urlid;
    });
  }

}

export class HelloComponent implements OnInit {
  urlid;
  constructor(
    private issuerService: IssuerService
  ) { }

  ngOnInit() {
    this.issuerService.getUrlid().subscribe(urlid => {
      this.urlid = urlid;
    });
  }
}

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