我如何将数据从组件A发送到组件B Angular 2

Question

我想在NavbarComponent上显示用户名，数据来自LoginComponent。

login.component.ts

import { Component, OnInit } from '@angular/core';
import { FormBuilder,FormGroup,Validators,FormControl } from '@angular/forms';
import { AuthService } from '../../services/auth.service';
import { Router } from '@angular/router';
import { FlashMessagesService } from 'angular2-flash-messages';


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


  form : FormGroup;
  message;
  messageClass;

  constructor(
    private formBuilder: FormBuilder,
    private authService:AuthService,
    private router: Router,
    private flashMessagesService:FlashMessagesService
    ) { 
    this.createForm();
  }


  createForm(){
    this.form=this.formBuilder.group({
      username:['', Validators.required],
      password:['', Validators.required]
    })
  }

  onLoginSubmit(){

    const user={
      username: this.form.get('username').value,
      password: this.form.get('password').value
    }

    this.authService.login(user).subscribe(data=>{
      if(!data.success){
        this.messageClass="alert alert-danger";
        this.message=data.message;
      }
      else{
        this.messageClass="alert alert-success";
        this.message=data.message;
        this.authService.storeUserData(data.token,data.user);
        setTimeout(()=>{
          this.router.navigate(['/profile']);
        },2000);

        this.flashMessagesService.show('Welcome to bloggy, '+ this.form.get('username').value +' !',{cssClass: 'alert-info'});

      }
    });
  }

}

navbar.component.ts

import { Component, OnInit } from '@angular/core';
import { AuthService } from '../../services/auth.service';
import { Router } from '@angular/router';
import { FlashMessagesService } from 'angular2-flash-messages';


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


  usernameNav;

  constructor(
    private authService:AuthService,
    private router:Router,
    private flashMessagesService:FlashMessagesService
    ) { }  



  onLogoutClick(){
    this.authService.logout();
    this.flashMessagesService.show('You are logged out',{cssClass: 'alert-info'});
    this.router.navigate(['/']);
  }


  ngOnInit() {

  }

}

很抱歉，如果代码太多，但是基本上我想从onLoginSubmit（）函数中的LoginComponent提取data.user.username，将其发送到NavbarComponent，在变量中使用它并在html上显示。 我试图导入NavbarComponent，但是没有用。

Answer 1

相当有趣的问题，基本上您的问题的解决方案是Observable/subscriber ，您需要在登录组件中的值更改时进行侦听并将其发送回navbar组件进行显示。

您可以像这样使用全局Observable

假设您像这样在全局文件中创建一个Observable

public loggedInObs: Rx.Subject<any> = new Rx.Subject<any>();
public loggedInVar: boolean = false;

为了使用这个，你必须像这样导入一些依赖

import { Observable } from 'rxjs/Rx';
import * as Rx from 'rxjs/Rx';
import 'rxjs/add/observable/of';
import 'rxjs/Rx';
import 'rxjs/add/operator/map';

在您的登录组件中，您告诉angular发生了一些更改，例如用户登录成功。 并且可以观察到，因此angular可以在您设置subscriber以监听该用户已登录应用的整个应用中进行监听。 如下代码

this.authService.login(user).subscribe(data=>{
  if(!data.success){
    this.messageClass="alert alert-danger";
    this.message=data.message;
  }
  else{
    this.messageClass="alert alert-success";
    this.message=data.message;

    localStorage.setItem('user_info', JSON.stringify(data.user))
    /*for Global level observable fire here*/
    this.global_service.loggedInVar = true;         //i assume global_service here as your Global service where we declared variables
    this.global_service.loggedInObs.next(this.global_service.loggedInVar);

    this.authService.storeUserData(data.token,data.user);
    setTimeout(()=>{
      this.router.navigate(['/profile']);
    },2000);

    this.flashMessagesService.show('Welcome to bloggy, '+ this.form.get('username').value +' !',{cssClass: 'alert-info'});

  }

现在您可以在导航栏中的应用程序中的任何地方使用订户收听此内容

userdata = JSON.parse(localStorage.getItem('user_info'));  // in case of normal loading page
this.userName = userdata.user_name

this.global_service.loggedInObs.subscribe(res => {       // in case of when without refresh of page
    console.log('changes here in login');
    userdata = JSON.parse(localStorage.getItem('user_info'));
    this.userName = userdata.user_name
})

如有任何疑问，请通知我。