[英]TypeError: promise.then is not a function
Using Rxjs v5, trying to run http.get requests in sequential order but getting error TypeError: promise.then is not a function
js code: 使用Rxjs v5,尝试按顺序运行http.get请求但得到错误TypeError: promise.then is not a function
js代码:
var http = require('http');
Rx.Observable
.from(data)
.pairwise()
.concatMap(a => {
var url = 'http://to/some/api?origins=' + a[0].lat + ',' + a[0].lng + '&destinations=' + a[1].lat + ',' + a[1].lng;
return Rx.Observable.fromPromise(http.get(url));
})
.subscribe(item => {
console.log(item);
});
The node http.get
method does not return a promise, see here 节点http.get
方法不返回promise,请参见此处
It actually uses a rather non-standard interface (at least I haven't really seen it before), so to get this working you need a small custom work-around instead ( note : this is a relatively naive implementation): 它实际上使用了一个相当非标准的界面(至少我以前没有真正看过它),所以要实现这个,你需要一个小的自定义解决方案( 注意 :这是一个相对天真的实现):
var http = require('http');
function observableGet(options) {
return new Rx.Observable(subscriber => {
var subscription = new Rx.Subscription();
//Create the request
var request = http.get(options, (res) => {
//Create a stream for the "end" event
var done = Rx.Observable.fromEvent(res, 'end');
//Create a stream for data events
var s1 = Rx.Observable.fromEvent(res, 'data')
//Take data events until all have been read
.takeUntil(done)
//Gather all the data events into a single object
.reduce((body, delta) => body + delta, '')
//Optional: Parse the resulting data object
.map(x => JSON.parse(x))
//Start the stream
.subscribe(subscriber);
//Register this stream for disposal
subscription.add(s1);
});
//Grab errors from the request and forward them to the error handler
//of subscriber
var s2 = Rx.Observable.fromEvent(request, 'error', (e) => { throw e; })
.subscribe(subscriber);
//Register for disposal
subscription.add(s2);
//Return the parent subscription
return subscription;
});
}
Then you can use it in place of http.get
然后你可以用它代替http.get
Rx.Observable
.from(data)
.pairwise()
.concatMap(a => {
var url = //...url;
return observableGet(url);
})
.subscribe(item => {
console.log(item);
});
Alternatively you could use a library that returns Promises
instead, which might make your life easier, ie request-promise 或者,您可以使用返回Promises
的库,这可能会让您的生活更轻松,即请求承诺
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