Angular 4订阅observable不会在更改后更新

Question

我有一个带有observable的服务,通过组件订阅.当订户显示初始值时,这似乎有效.我有另一个组件,然后更新observable但是新值不会显示.

服务:

import { Injectable } from '@angular/core';
import { Observable } from 'rxjs/Observable';
import 'rxjs/add/observable/of'; 

@Injectable()

export class BannerService {

    banners$: Observable<any[]> = Observable.of([]);

    getBanners(): Observable<any[]> {
        return this.banners$;
    }

    setBanners(banners: any[]): void {
        this.banners$ = Observable.of(banners);
    }

}

订阅者组件:

import { Component, ViewEncapsulation, OnInit } from '@angular/core';

import { BannerService } from './../banner/banner.service';

@Component({
    selector: '.banner',
    templateUrl: './banner.component.html',
    styleUrls: ['./banner.component.sass'],
    encapsulation: ViewEncapsulation.None
})

export class BannerComponent implements OnInit {

    constructor(private bannerService: BannerService){}

    ngOnInit() {
        this.bannerService.banners$.subscribe(banners => {
            console.log(banners);
        });

    }
}

带有setter的组件:

import { Component, ViewEncapsulation, OnInit } from '@angular/core';

import { BannerService } from './../banner/banner.service';

@Component({
    selector: '.home-component',
    templateUrl: './home.component.html',
    styleUrls: ['./home.component.sass'],
    encapsulation: ViewEncapsulation.None
})

export class HomeComponent implements OnInit {

    data = {
        banners: [
            {
                title: 'Title 1',
                image: '../images/image1.jpg'
            },
            {
                title: 'Title 2',
                image: '../images/image2.jpg'
            },
            {
                title: 'Title 3',
                image: '../images/image3.jpg'
            }
        ]
    }

    constructor(private bannerService: BannerService){}

    ngOnInit(): void {
        this.bannerService.setBanners(this.data.banners);
    }

}

任何帮助都会非常感激,我尝试了很多不同的东西,但却无法正常工作.

Answer 1

您订阅了一个observable,然后用另一个替换了该observable.

这就像给某人一个电子邮件地址,他可以在那里阅读你发给他的邮件,然后每次发送电子邮件时用另一个电子邮件地址替换.显然,如果您将邮件发送到不同的地址,接收方将永远不会收到您的邮件.

您需要使用相同的,唯一的可观察对象,并使其发出新事件.使用主题是最简单的方法:

banners$: Subject<any[]> = new BehaviorSubject<any[]>([]);

setBanners(banners: any[]): void {
    this.banners$.next(banners);
}