Angular 5-使用XML响应获取HTTP

Question

Newby needs help with error. I am requesting data via a http get request. The data is in xml format. I need to convert it to json for use in my Angular app. When I run the following code I get a error in the console "TypeError this.http.get().map is not a function.

list() {
  return this.http.get(this.apiRoot).map(res => {
  let data;
  xml2js.parseString( res.toString, function (err, result) {
  console.dir(data); // Prints JSON object!
  data = result;       
  });
  return data;
  })
  .subscribe(data => { 
  console.log(data);              
  });  }

Thanks

Answer 1

您需要从rxjs导入可观察对象的运算符映射。

import { map } from 'rxjs/operators';

Answer 2

You need to import the rxjs map operator. With your existing code you can do:

import 'rxjs/add/operator/map';

You can also import the operator function itself. This is preferred. See: https://github.com/ReactiveX/rxjs/blob/master/doc/pipeable-operators.md

import { map } from 'rxjs/operators';

...
  return this.http.get(this.apiRoot).pipe(map(res => {

If you're using the deprecated HttpModule instead of HttpClient you'll have to do an additional step to get the response text:

.pipe(
  map(res => res.text()),

If you're using HttpClient you won't need to do this.

---

Finally, since you're using xml2js which does not support Promises or Observables you will have to wrap the call to .parseString to add it to the observable stream. Fortunately, RxJS provides a wrapper function that does this for you: http://reactivex.io/rxjs/class/es6/Observable.js~Observable.html#static-method-bindNodeCallback .

Here we use switcMap instead of map because bindNodeCallback returns an observable. switchMap will flatten it for us.

import { bindNodeCallback } from 'rxjs/observable/bindNodeCallback';
import { switchMap } from 'rxjs/operators';

function list() {
  return this.http
    .get(this.apiRoot)
    .pipe(switchMap(res => bindNodeCallback(xml2js.parseString)(res)))
    .subscribe(console.log);
}