在角度组件之间共享数据

Question

I want to share data in angular between two components. I did as explained here and here . Below is my code

login.component.ts

import { Component, OnInit } from '@angular/core';
import { User } from '../domain/User';
import { HttpClient, HttpHeaders } from '@angular/common/http';
import { LoginResponse } from '../domain/LoginResponse'
import { DataSharingService } from '../service/DataSharingService';
import { Router } from '@angular/router';

@Component({
  selector: 'app-login',
  templateUrl: './login.component.html',
  styleUrls: ['./login.component.css'],
  providers: [DataSharingService]
})
export class LoginComponent implements OnInit {

  private user:User = new User();

  private xSSOFamilyId:string = 'BOMO';

  constructor(private httpClient: HttpClient, private dataSharingService: DataSharingService, private router: Router) { }

  ngOnInit() {
  }

  login(): void {

    var authorization:string = 'Basic ' + btoa(this.user.cwopa + ":" + this.user.password);
    var httpHeaders = new HttpHeaders({
      'Authorization': authorization,
      'userId': this.user.cwopa,
      'X-SSO-Family-Id': this.xSSOFamilyId
    });
    this.httpClient.post<LoginResponse>('http://localhost:8081/web-beginner/authenticate', undefined, {headers: httpHeaders}).subscribe(response => {
      this.router.navigate(['dashboard'])
    }, error => {
      console.log("error occured");
    });
  }

  public getApiKey() {
    this.dataSharingService.setData({apikey: '1234'});
  }

}

dashboard.component.ts

import { Component, OnInit } from '@angular/core';
import { DataSharingService } from '../service/DataSharingService';
import { LoginComponent } from '../login/login.component';

@Component({
  selector: 'app-dashboard',
  templateUrl: './dashboard.component.html',
  styleUrls: ['./dashboard.component.css'],
  providers: [DataSharingService, LoginComponent]
})
export class DashboardComponent implements OnInit {

  constructor(private dataSharingService: DataSharingService, private loginComponent: LoginComponent) { }

  ngOnInit() {
    this.dataSharingService.currentData.subscribe(data => {
      console.log(data)
    });
  }

  authorize(appName:string): void {
    console.log(this.loginComponent.getApiKey())
  }
}

I have a link in dashboard.component.html. Each time I click it, onNgInit and authorize functions are called.

Furthermore, the data I want to receive in dashboard.component.ts's authorize function is print undefined and onNgInit is printing the expected value.

Can anyone please tell me whats wrong with the code?

Answer 1

remove providers: [DataSharingService] from login component add DataSharingService to the app.module.ts provider so it will be singleton.

Don't inject component as this through constructor.

private loginComponent: LoginComponent

Just use a service to share data or if your DashboardComponent.html contain LoginComponent as a component, you can use @ViewChild As Sujay's answer. So you can use same DataSharingService for getting api key.

Answer 2

You need to get the reference of the LoginComponent using @ViewChild keyword

    import { Component, OnInit } from '@angular/core';
    import { DataSharingService } from '../service/DataSharingService';
    import { LoginComponent } from '../login/login.component';

    @Component({
      selector: 'app-dashboard',
      templateUrl: './dashboard.component.html',
      styleUrls: ['./dashboard.component.css'],
      providers: [DataSharingService, LoginComponent]
    })
    export class DashboardComponent implements OnInit {
    @ViewChild(LoginComponent) loginComponent: LoginComponent
      constructor(private dataSharingService: DataSharingService) { }

      ngOnInit() {
        this.dataSharingService.currentData.subscribe(data => {
          console.log(data)
        });
      }

      authorize(appName:string): void {
        console.log(this.loginComponent.getApiKey())
      }
    }