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使用 Rxjs v5,尝试按顺序运行 http.get 请求但出现错误 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);
});
最佳答案
Node http.get
方法不返回 promise ,参见 here
它实际上使用了一个相当不标准的界面(至少我以前没有真正见过它),所以要让它工作,你需要一个小的自定义解决方法(注意:这个是一个相对幼稚的实现):
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;
});
}
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);
});
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 request-promise
关于javascript - TypeError : promise. then is not a function,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/38879409/
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