Angular2：在组件之间更新和共享数据

Question

寻找一种方法，使服务在必要时将最新数据提供给订阅的组件。例如：组件 3 将更改写入 API

以下是一些片段和一些描述，说明到目前为止我所做的工作：

该服务通过HTTP从API获取数据。组件1和组件2订阅了服务返回的observable：

import { Injectable } from "@angular/core";
import { Http } from "@angular/http";

import 'rxjs/add/operator/map';

@Injectable()

export class GroupService{
    constructor(private _http: Http){}

    getGroups(){
        return this._http.get('/assets/groups.json')
            .map((res) => {
                return res.json();
            });
    }
}

import { Component } from '@angular/core';
import { router } from '../../app.router';
import { GroupService } from '../../services/group.service';
import { Group } from '../../interfaces/group.interface';

@Component({
    selector: 'app-sidebar',
    templateUrl: './sidebar.component.html',
    styleUrls: ['./sidebar.component.scss'],
})

export class SidebarComponent
{
    router;
    groups: Group[];

    constructor(private _groupService: GroupService){
        this.router = router;
        this.getGroups();
    }

    getGroups(){
        this._groupService.getGroups()
            .subscribe((groups) => {
                this.groups = groups;
            });
    }
}

Answer 1

使用BehaviorSubject作为委托可能是您的用例最方便的选择。在服务中注册< code>BehaviorSubject,并在任何组件请求新数据时，在需要更新的所有组件中订阅它。

这是服务的外观：

@Injectable()
export class GroupService {

    groupsSource: BehaviorSubject<any> = new BehaviorSubject(null);

    constructor(private _http: Http) { }

    getGroups(): void {
        this._http.get('/assets/groups.json')
            .map((res) => res.json())
            .subscribe((groups) => this.groupsSource.next(groups)); // Update all components subscribed to the BehaviorSubjet
    }
}

组件1，请求新数据：

export class Component1 implements OnInit {

    groups: any;

    constructor(private _groupService: GroupService) { }

    ngOnInit() {
        this._groupService.groupsSource.subscribe((groups) => {
            this.groups = groups;
        });

        this._groupService.getGroups();
    }
}

组件2会自动更新：

export class Component2 implements OnInit {

    groups: any;

    constructor(private _groupService: GroupService) { }

    ngOnInit() {
        this._groupService.groupsSource.subscribe((groups) => {
            this.groups = groups;
        });
    }
}

export class Component3 implements OnInit{

    groups: any;

    constructor(private _groupService: GroupService) { }

    ngOnInit() {
        this.groups = this._groupService.groupsSource.getValue();
    }
}

Answer 2

这是一种与seidme略有不同的方法，我个人更喜欢:

在 GroupService 中设置数据流，并在组件中使用它。

服务:

import { Injectable } from "@angular/core";
import { Http } from "@angular/http";
import { BehaviorSubject } from 'rxjs/BehaviorSubject';
import { Observable } from 'rxjs/Observable';

import 'rxjs/add/operator/map';

@Injectable()
export class GroupService {
    private groupSource = new BehaviorSubject<any>({});
    public group$: Observable = this.groupSource.asObservable();

    constructor(private _http: Http) {}

    getGroups() {
        this._http.get('/assets/groups.json')
            .map((res) => {
                return res.json();
            })
            .subscribe((groups) => this.groupSource.next(groups));
    }
}

然后在组件中，只需执行以下操作：

import { Component, OnInit } from '@angular/core';
import { router } from '../../app.router';
import { GroupService } from '../../services/group.service';
import { Group } from '../../interfaces/group.interface';
import { Observable } from 'rxjs/Observable';

@Component({
    selector: 'app-sidebar',
    templateUrl: './sidebar.component.html',
    styleUrls: ['./sidebar.component.scss'],
})

export class SidebarComponent implements OnInit {
    router;
    groups: Observable;

    constructor(private _groupService: GroupService){
        this.router = router;
    }

    ngOnInit {
        this.groups = this._groupService.group$;
    }
}

然后在模板中，使用异步管道：{{ 组 |异步 }}。它将负责为您订阅（和处置）可观察量。

现在，每当您从任何组件调用< code > group service . get groups()时，所有其他组件都会自动更新。

此外，使用 OnInit 比在构造函数中执行操作稍微好一些，请参阅构造函数和 ngOnInit 之间的区别。