Angular 2异步管道无法自动渲染/更新可观察的数据 [英] Angular 2 async pipe not rendering/updating Observable data automatically

问题描述

我遇到了Angular2路由器和异步管道的问题.

I am facing an issue with the Angular2 router and an async pipe.

我正在尝试渲染可观察的RxJs，并且数据不会自动渲染.

I am trying to render an RxJs Observable and the data does not render automatically.

必须单击链接以呈现数据.

One has to click on the link for the route for the data to render.

这是根应用程序:

import {bootstrap}    from 'angular2/platform/browser';
import {HTTP_PROVIDERS} from 'angular2/http';
import {ROUTER_PROVIDERS} from 'angular2/router';
import {AppComponent} from './app.component.ts';

bootstrap(AppComponent, [HTTP_PROVIDERS, ROUTER_PROVIDERS]);

这是根组件:

import {Component} from 'angular2/core';
import {RouteConfig, ROUTER_DIRECTIVES} from 'angular2/router';
import {FirstComponent} from './app.first-component.ts';
import {SecondComponent} from './app.second-component.ts';
import {AppService} from "./app.services.ts";


@Component({
    selector: 'my-app',
    providers: [AppService, FirstComponent, SecondComponent],
    directives: [FirstComponent, SecondComponent, ROUTER_DIRECTIVES],
    template: `<h1>An Angular 2 App</h1>
               <a [routerLink]="['First']">first-default</a> 
               <a [routerLink]="['Second']">second</a> 
               <router-outlet></router-outlet>`
})
@RouteConfig([
    {path: '/', name: 'First', component: FirstComponent, useAsDefault: true},
    {path: '/second', name: 'Second', component: SecondComponent}
])
export class AppComponent {
}

这是第一部分:

import {Component} from "angular2/core";
import {AppService} from "./app.services.ts";
import "rxjs/Rx";


@Component({
    selector: 'my-first',
    template: `
<div>
    <ul>
        <li *ngFor="#s of appService.someObservable$ | async">
           a string: {{ s }}
        </li>
    </ul>
 </div>`
})
export class FirstComponent {

    constructor(private appService:AppService) {
        console.log('constructor', 'first');
    }
}

最后是服务(数据所在的位置):

and finally the service (where the data resides):

import {Injectable} from "angular2/core";
import {Observable} from "rxjs/Rx";

@Injectable()
export class AppService {

    constructor() {
        console.log('constructor', 'appService');
        this.constructSomeObservable();
    }

    someObservable$:Observable <string[]>;

    constructSomeObservable() {
        this.someObservable$ = Observable.create(observer => {
                const eventSource = new EventSource('/interval-sse-observable');
                eventSource.onmessage = x => observer.next(JSON.parse(x.data));
                eventSource.onerror = x => observer.error(console.log('EventSource failed'));
                return () => {
                    eventSource.close();
                };
            })
            .startWith([])
            .scan((acc, value) => acc.concat(value));
    }
}

路由器或管道出了什么问题?

What I am getting wrong with the router or the pipe?

请参见github 此处上的示例项目.

See sample project on github here.

编辑:这是组件的修改版本:

edit: Here is the modified version of the component:

import {Component} from "angular2/core";
import {AppService} from "./app.services.ts";
import {Observable} from "rxjs/Rx";


@Component({
    selector: 'my-first',
    template: `
<div>
    <ul>
        <li *ngFor="#s of someObservable$ | async">
           a string: {{ s }}
        </li>
    </ul>
 </div>`
})
export class FirstComponent {

    someObservable$:Observable <string[]>;

    constructor(private appService:AppService) {
        console.log('constructor', 'first');
        this.someObservable$ = appService.someObservable$;
    }
}

模板中的数据未更新.是与两种/一种方式绑定吗?

The data is not updated in the template. Is it to do with two/one way binding?

推荐答案

我认为，与例如， setTimeout，SetInterval或xhr请求

I think angular zone doesn't patch events emitted from eventSource.onmessage unlike e.g. setTimeout, SetInterval or xhr request

来自 angular2-polyfills.js

/***/ function(module, exports, __webpack_require__) {

    /* WEBPACK VAR INJECTION */(function(global) {"use strict";
    __webpack_require__(1);
    var event_target_1 = __webpack_require__(2);
    var define_property_1 = __webpack_require__(4);
    var register_element_1 = __webpack_require__(5);
    var property_descriptor_1 = __webpack_require__(6);
    var utils_1 = __webpack_require__(3);
    var set = 'set';
    var clear = 'clear';
    var blockingMethods = ['alert', 'prompt', 'confirm'];
    var _global = typeof window == 'undefined' ? global : window;
    patchTimer(_global, set, clear, 'Timeout');
    patchTimer(_global, set, clear, 'Interval');
    patchTimer(_global, set, clear, 'Immediate');
    patchTimer(_global, 'request', 'cancelMacroTask', 'AnimationFrame');
    patchTimer(_global, 'mozRequest', 'mozCancel', 'AnimationFrame');
    patchTimer(_global, 'webkitRequest', 'webkitCancel', 'AnimationFrame');
    for (var i = 0; i < blockingMethods.length; i++) {
        var name = blockingMethods[i];
        utils_1.patchMethod(_global, name, function (delegate, symbol, name) {
            return function (s, args) {
                return Zone.current.run(delegate, _global, args, name);
            };
        });
    }
    event_target_1.eventTargetPatch(_global);
    property_descriptor_1.propertyDescriptorPatch(_global);
    utils_1.patchClass('MutationObserver');
    utils_1.patchClass('WebKitMutationObserver');
    utils_1.patchClass('FileReader');
    define_property_1.propertyPatch();
    register_element_1.registerElementPatch(_global);
    // Treat XMLHTTPRequest as a macrotask.
    patchXHR(_global);
    var XHR_TASK = utils_1.zoneSymbol('xhrTask');
    function patchXHR(window) {
        function findPendingTask(target) {
            var pendingTask = target[XHR_TASK];
            return pendingTask;
        }

因此，您需要将eventsource.onmessage的回调包装起来，例如:

Therefore you need to wrap your callback for eventsource.onmessage something like:

app.services.ts

import {Injectable, NgZone} from "angular2/core"; // <=== 1) Don't forget to import the NgZone class
import {Observable} from "rxjs/Rx";

@Injectable()
export class AppService {

  constructor(private zone: NgZone) { // <== 2) Don't forget also to inject zone in constructor
    console.log('constructor', 'appService');
    this.constructSomeObservable();
  }

  someObservable$: Observable<string[]>;

  constructSomeObservable() {
    this.someObservable$ = Observable.create(observer => {
      const eventSource = new EventSource('/interval-sse-observable');
      eventSource.onmessage = x => this.zone.run(() => observer.next(JSON.parse(x.data))); // <=== 3) Wrap onmessage event
      eventSource.onerror = x => observer.error(console.log('EventSource failed'));
      return () => {
        eventSource.close();
      };
    })
      .startWith([])
      .scan((acc, value) => acc.concat(value));
  }
}

这篇关于Angular 2异步管道无法自动渲染/更新可观察的数据的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！