使用angular2 http服务缓存结果

我通过服务公开HTTP GET请求,并且有几个组件正在使用此数据(用户的配置文件详细信息).我希望第一个组件请求实际执行到服务器的HTTP GET请求并缓存结果,以便后续请求将使用缓存数据,而不是再次调用服务器.

这是服务的一个示例,您如何推荐使用Angular2和typescript实现此缓存层.

import {Inject, Injectable} from 'angular2/core';
import {Http, Headers} from "angular2/http";
import {JsonHeaders} from "./BaseHeaders";
import {ProfileDetails} from "../models/profileDetails";

@Injectable()
export class ProfileService{
    myProfileDetails: ProfileDetails = null;

    constructor(private http:Http) {

    }

    getUserProfile(userId:number) {
        return this.http.get('/users/' + userId + '/profile/', {
                headers: headers
            })
            .map(response =>  {
                if(response.status==400) {
                    return "FAILURE";
                } else if(response.status == 200) {
                    this.myProfileDetails = new ProfileDetails(response.json());
                    return this.myProfileDetails;
                }
            });
    }
}

tibbus.. 80

该股份()操作符只在第一次请求,当所有的订阅供应与您共创一个又一个的话,将无法正常工作,就会使另一个请求.(这种情况很常见,因为你总是创建/销毁组件的angular2 SPA)

我使用ReplaySubject来存储http observable 的值.该ReplaySubject观察到可以起到前值到它的用户.

服务:

@Injectable()
export class DataService {
    private dataObs$ = new ReplaySubject(1);

    constructor(private http: HttpClient) { }

    getData(forceRefresh?: boolean) {
        // If the Subject was NOT subscribed before OR if forceRefresh is requested 
        if (!this.dataObs$.observers.length || forceRefresh) {
            this.http.get('http://jsonplaceholder.typicode.com/posts/2').subscribe(
                data => this.dataObs$.next(data),
                error => {
                    this.dataObs$.error(error);
                    // Recreate the Observable as after Error we cannot emit data anymore
                    this.dataObs$ = new ReplaySubject(1);
                }
            );
        }

        return this.dataObs$;
    }
}

组件:

@Component({
  selector: 'my-app',
  template: `
getData from AppComponent
`
})
export class AppComponent {
    constructor(private dataService: DataService) {}

getData() {
    this.dataService.getData().subscribe(
        requestData => {
            console.log('ChildComponent', requestData);
        },
        // handle the error, otherwise will break the Observable
        error => console.log(error)
    );
}
    }
}

完全正常工作PLUNKER
(观察控制台和网络选项卡)

该股份()操作符只在第一次请求,当所有的订阅供应与您共创一个又一个的话,将无法正常工作,就会使另一个请求.(这种情况很常见,因为你总是创建/销毁组件的angular2 SPA)

我使用ReplaySubject来存储http observable 的值.该ReplaySubject观察到可以起到前值到它的用户.

服务:

@Injectable()
export class DataService {
    private dataObs$ = new ReplaySubject(1);

    constructor(private http: HttpClient) { }

    getData(forceRefresh?: boolean) {
        // If the Subject was NOT subscribed before OR if forceRefresh is requested 
        if (!this.dataObs$.observers.length || forceRefresh) {
            this.http.get('http://jsonplaceholder.typicode.com/posts/2').subscribe(
                data => this.dataObs$.next(data),
                error => {
                    this.dataObs$.error(error);
                    // Recreate the Observable as after Error we cannot emit data anymore
                    this.dataObs$ = new ReplaySubject(1);
                }
            );
        }

        return this.dataObs$;
    }
}

组件:

@Component({
  selector: 'my-app',
  template: `
getData from AppComponent
`
})
export class AppComponent {
    constructor(private dataService: DataService) {}

getData() {
    this.dataService.getData().subscribe(
        requestData => {
            console.log('ChildComponent', requestData);
        },
        // handle the error, otherwise will break the Observable
        error => console.log(error)
    );
}
    }
}

完全正常工作PLUNKER
(观察控制台和网络选项卡)

我省略了userId处理.它需要管理一个数组data和一个数组observable(每个请求一个userId).

import {Injectable} from '@angular/core';
import {Http, Headers} from '@angular/http';
import {Observable} from 'rxjs/Observable';
import 'rxjs/observable/of';
import 'rxjs/add/operator/share';
import 'rxjs/add/operator/map';
import {Data} from './data';

@Injectable()
export class DataService {
  private url:string = 'https://cors-test.appspot.com/test';

  private data: Data;
  private observable: Observable;

  constructor(private http:Http) {}

  getData() {
    if(this.data) {
      // if `data` is available just return it as `Observable`
      return Observable.of(this.data); 
    } else if(this.observable) {
      // if `this.observable` is set then the request is in progress
      // return the `Observable` for the ongoing request
      return this.observable;
    } else {
      // example header (not necessary)
      let headers = new Headers();
      headers.append('Content-Type', 'application/json');
      // create the request, store the `Observable` for subsequent subscribers
      this.observable = this.http.get(this.url, {
        headers: headers
      })
      .map(response =>  {
        // when the cached data is available we don't need the `Observable` reference anymore
        this.observable = null;

        if(response.status == 400) {
          return "FAILURE";
        } else if(response.status == 200) {
          this.data = new Data(response.json());
          return this.data;
        }
        // make it shared so more than one subscriber can get the result
      })
      .share();
      return this.observable;
    }
  }
}

class Service {
  _data;
  get data() {
    return this._data;
  }
  set data(value) {
    this._data = value;
  }
}

class App {
  constructor(http: Http, svc: Service) {

    // Some dynamic id
    let someDynamicId = 2;

    // Use the dynamic id in the request
    svc.data = http.get('http://someUrl/someId/'+someDynamicId).share();

    // Subscribe to the result
    svc.data.subscribe((result) => {
      /* Do something with the result */
    });
  }
}