zoukankan      html  css  js  c++  java
  • [Angular 2] Handle Reactive Async opreations in Service

    When you use ngrx/store and you want to fire a service request. When it sucessfully return the response, you need to dispatch action to tell the store update.

    So one pattern can be considered to follow is:

    import {Http, Headers} from '@angular/http';
    import {Injectable} from '@angular/core';
    import {Store} from '@ngrx/store';
    import {Observable} from "rxjs/Observable";
    import 'rxjs/add/operator/map';
    
    import {AppStore} from '../models/appstore.model';
    import {Item} from '../models/item.model';
    
    const BASE_URL = 'http://localhost:3000/items/';
    const HEADER = { headers: new Headers({ 'Content-Type': 'application/json' }) };
    
    @Injectable()
    export class ItemsService {
      items: Observable<Array<Item>>;
    
      constructor(private http: Http, private store: Store<AppStore>) {
        this.items = store.select('items');
      }
    
      loadItems() {
        this.http.get(BASE_URL)
          .map(res => res.json())
          .map(payload => ({ type: 'ADD_ITEMS', payload }))
          .subscribe(action => this.store.dispatch(action));
      }
    
      saveItem(item: Item) {
        return (item.id) ? this.updateItem(item) : this.createItem(item);
      }
    
      createItem(item: Item) {
         return this.http.post(`${BASE_URL}`, JSON.stringify(item), HEADER)
          .map(res => res.json())
          .do(payload => {
            const action = { type: 'CREATE_ITEM', payload };
            this.store.dispatch(action)
          });
      }
    
      updateItem(item: Item) {
        return this.http.put(`${BASE_URL}${item.id}`, JSON.stringify(item), HEADER)
          .do(action => this.store.dispatch({ type: 'UPDATE_ITEM', payload: item }));
      }
    
      deleteItem(item: Item) {
        return this.http.delete(`${BASE_URL}${item.id}`)
          .do(action => this.store.dispatch({ type: 'DELETE_ITEM', payload: item }));
      }
    }

    In this ItemService, we get Items from store:

      items: Observable<Array<Item>>;
    
      constructor(private http: Http, private store: Store<AppStore>) {
        this.items = store.select('items');
      }

    To change state, it flows the style that

    • Call the backend
    • if success generate action
    • dispatch the action
     createItem(item: Item) {
         return this.http.post(`${BASE_URL}`, JSON.stringify(item), HEADER)
          .map(res => res.json())
          .do(payload => {
            const action = { type: 'CREATE_ITEM', payload };
            this.store.dispatch(action)
          });
      }

    In the controller:

      saveItem(item: Item) {
        this.itemsService.saveItem(item)
          .subscribe( (res) => {this.resetItem()},
                      (err) => {console.error(err)},
                     () => {console.info("Completed")});

    If you notice, in loadItems, I didn't' use do() to dispatch action and subscribe in controller, instead I subscribe in service, this is because in controller, it doesn't expect receive anything from service:

      constructor(private itemsService: ItemsService,
                  private gadgetService: GadgetService,
                  private store: Store<AppStore>) {
        this.items = itemsService.items;
        itemsService.loadItems();
      }

    We base on async pipe to update the dom:

          <items-list [items]="items | async"
            (selected)="selectItem($event)" (deleted)="deleteItem($event)">
          </items-list>

    But for createItem, deleteItem, we use do() to dispatch action and subscribe action, this is because we want to confrim weather it successfully updated, then we want to clear the input fields.

  • 相关阅读:
    网络对抗技术-实验四
    网络对抗技术-实验三
    安卓终端-Termux
    linux杂记
    使用pl/sql导入导出oracle
    systemctl 实现开机自启服务
    Java8 Collectors.toMap的坑
    idea使用lombok插件
    解决Lost connection to MySQL server during query错误方法
    java8之lamda
  • 原文地址:https://www.cnblogs.com/Answer1215/p/5612914.html
Copyright © 2011-2022 走看看