[英]RxJS - How Subscriber is different from Observable and Subscription?
我一直試圖找到一個將Observable包裝到訂閱服務器中的示例,以監視異步調用的狀態,例如加載,完成或錯誤。 你能提供一個簡短的例子嗎?
不確定這是不是你的意思,但你可以像這樣包裝異步http調用
const httpStream = Observable.create(observer => {
fetch('http://server.com')
.then(response => response.json())
.then(data => {
observer.next(data); // if http call provides progress as well as completion
// these can all be pushed with observer.next()
observer.complete();
})
.catch(err => observer.error(err));
});
httpStream.subscribe(data => console.log(data));
當然,如果它實際上是你想要包裝你可以反而只是做
var result = Rx.Observable.fromPromise(fetch('http://myserver.com/'));
編輯:如果你正在使用角度HttpClient,那么就不需要包裝它,因為它已經是一個可觀察的。 要獲得進度更新以及最終響應,以下內容應該有效
const req = new HttpRequest('POST', 'http://api.server.com', body, {
reportProgress: true
});
this._http.request(req)
.filter((event) => event.type === HttpEventType.UploadProgress || event instanceof HttpResponse)
.map((event) => {
if (event.type === HttpEventType.UploadProgress) {
const percentDone = Math.round(100 * event.loaded / event.total);
return { type: 'uploadProgress', percentDone };
} else if (event instanceof HttpResponse) {
return { type: 'httpResponse', status: event.status };
}
})
.subscribe((response) => {
if (response.type === 'uploadProgress') {
console.log(`upload still in progress - percent done = ${response.percentDone}%`);
} else {
console.log(`upload completed - status = ${response.status}`);
}
});
事實上,如果您想知道所有請求都已完成,並且不需要每個請求的進度更新,而不是將請求推送到數組中,則更好的選擇可能是使用forkJoin - 類似於promise.all,一旦所有子可觀察量都已完成,你只能從observable得到一個輸出 - https://www.learnrxjs.io/operators/combination/forkjoin.html
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