Question

我正在尝试评估Angular 2，我遇到了observables问题。

我正在尝试创建一个最初返回硬编码数组但最终会从Web服务获取数据的简单服务。

但是，我无法让它构建好。

有什么想法吗？

export class FleetListService {

  private data: Observable<Array<IFleet>>;

  constructor() { }

  fleets: IFleet[] = JSON.parse( `[{ "id": 1, "name": "John", "description": "John has been in the Audio/Video industry since 1990. He has led DevAv as its CEO since 2003. When not working hard as the CEO, John loves to golf and bowl. He once bowled a perfect game of 300.", "childCount": 5, "isUsed": true }, 
                                   { "id": 2, "name": "Olivia", "description": "Olivia loves to sell. She has been selling DevAV products since 2012. Olivia was homecoming queen in high school. She is expecting her first child in 6 months. Good Luck Olivia.", "childCount": 5 }, 
                                   { "id": 3, "name": "Robert", "description": "Robert was recently voted the CMO of the year by CMO Magazine. He is a proud member of the DevAV Management Team. Robert is a championship BBQ chef, so when you get the chance ask him for his secret recipe.", "childCount": 4 }, 
                                   { "id": 4, "name": "Greta", "description": "Greta has been DevAV's HR Manager since 2003. She joined DevAV from Sonee Corp.  Greta is currently training for the NYC marathon. Her best marathon time is 4 hours. Go Greta.", "childCount": 11 }, 
                                   { "id": 5, "name": "Brett", "description": "Brett came to DevAv from Microsoft and has led our IT department since 2012.  When he is not working hard for DevAV, he coaches Little League (he was a high school pitcher).", "childCount": 13 }, 
                                   { "id": 6, "name": "Sandra", "description": "Sandra is a CPA and has been our controller since 2008. She loves to interact with staff so if you've not met her, be certain to say hi.  Sandra has 2 daughters both of whom are accomplished gymnasts.", "childCount": 44 }, 
                                   { "id": 7, "name": "Kevin", "description": "Kevin is our hard-working shipping manager and has been helping that department work like clockwork for 18 months.  When not in the office, he is usually on the basketball court playing pick-up games.", "childCount": 5 }, 
                                   { "id": 8, "name": "Cynthia", "description": "Cindy joined us in 2008 and has been in the HR department for 2 years.   She was recently awarded employee of the month. Way to go Cindy!", "childCount": 4 }, 
                                   { "id": 9, "name": "Kent", "description": "As our ombudsman, Kent is on the front-lines solving customer problems and helping our partners address issues out in the field.    He is a classically trained musician and is a member of the Chamber Orchestra.", "childCount": 26 }, 
                                   { "id": 10, "name": "Taylor", "description": "If you are like the rest of us at DevAV, then you've probably reached out for help from Taylor. He does a great job as a member of our IT department.", "childCount": 5 }, 
                                   { "id": 11, "name": "Sam", "description": "Sammy is proud to be a member of the DevAV team. He joined the team in 2012 and has been in the sales department from the beginning.  He has just picked up golf so you can find him on the links every weekend.", "childCount": 11 }, 
                                   { "id": 12, "name": "Kelly", "description": "Kelly loves people and that's why she joined DevAV's support department. One of the funniest people in the company, she does stand-up on the weekends at the Laugh Factory.", "childCount": 5 }, 
                                   { "id": 13, "name": "Natalie", "description": "Natalie travels the US and teaches our partners how to explain the benefits of our products to customers.  She is a proud wife and mom and volunteers her time at the elementary school.", "childCount": 29 }, 
                                   { "id": 14, "name": "Walter", "description": "Walter has been developing apps and websites for DevAV since 2011. His passion is software and if you ever walk by his desk, you'll know why.  Wally once worked 72 hours straight - writing code and fixing bugs.", "childCount": 13 }]`);

  getFleets(): Observable<IFleet[]> {
    return new Observable((data : IFleet[]) => {
      return this.fleets;
    }
  }
}

Answer 1

您可以使用Observable.of方法。

getFleets(): Observable<IFleet[]> {
     return Observable.of(this.fleet)
}

请勿忘记使用以下行导入

   import "rxjs/add/observable/of";  // For RxJs  5.0+

对于RxJS 6.x

getFleets(): Observable<IFleet[]> {
         return of(this.fleet)
    }

＆＃34;＆＃34;＆＃34;

的导入语句

import { of } from "rxjs";

Answer 2

这有点晚了，只是为了澄清。这就是你如何创建一个简单的observable，以防你想要模仿自己的承诺。你做了

let observable=Observable.create(observer => {
      setTimeout(() => {
        observer.next("data to send can be object or anything");
        console.log("am done");
        observer.complete(); // to show we are done with our processing
       // observer.error(new Error("error message"));
      }, 2000);

    })

订阅它很容易

observable.subscribe((data) => {
console.log(data); // should be 'data to send can be object or anything'
});

您也可以使用toPromise() or fromPromise(observable)运算符将其转换为承诺，等等。

Answer 3

为此，您可以使用BehaviorSubject

export class FleetListService {
    public data: any = new BehaviorSubject('your hard coded data goes here');
    getdata() {
        //do your stuff
        this.FleetListService.next('new data got from server');
    }
}

Subjects的一个变体是BehaviorSubject，它具有“当前值”的概念。它存储发布给消费者的最新值，每当新的Observer订阅时，它将立即从BehaviorSubject接收“当前值”。行为主题始终返回最后的数据。更多info

如何在Angular 2中创建一个observable

3 个答案: