"rxjs" observable.throw不是函数-Angular4 [英] "rxjs" observable.throw is not a function - Angular4

问题描述

我一直在学习Angular 4，直到我尝试在服务中实现捕获处理之前，一切都进行得很顺利.我正在尝试使用"rxjs"捕获和抛出，但是控制台中出现未定义的函数错误.

I've been learning Angular 4 and everything was going smoothly until I tried to implement catch handling in a service. I'm trying to use "rxjs" catch and throw but I've got an undefined function error in my console.

import { Injectable } from '@angular/core';
import { Http } from "@angular/http";
import { Observable } from 'rxjs/observable';
import 'rxjs/add/operator/catch';
import 'rxjs/add/observable/throw';
import { AppError } from "../app/common/app.error";
import { NotFoundError } from "../app/common/not-found-error";
import { BadInput } from "../app/common/bad-input";

@Injectable()
export class PostService {
  private url = "https://jsonplaceholder.typicode.com/posts";

  constructor(private http: Http) { }

 deletepost(post){
      // return this.http.delete(this.url + '/' + post.id)
      // Hard-coded id to test 404
      return this.http.delete(this.url + '/' + 93498)
        .catch((error: Response) => {
          console.log('error within catch is ' + Response)
          if(error.status === 404)
            return Observable.throw(new NotFoundError(error));

          return Observable.throw(new AppError(error));
        });
    }
}

这是错误消息:

TypeError: __WEBPACK_IMPORTED_MODULE_2_rxjs_observable__["Observable"].throw is not a function. 
(In '__WEBPACK_IMPORTED_MODULE_2_rxjs_observable__["Observable"].throw(new 
__WEBPACK_IMPORTED_MODULE_6__app_common_not_found_error__["a" /* NotFoundError 
*/](error))', 
'__WEBPACK_IMPORTED_MODULE_2_rxjs_observable__["Observable"].throw' is 
undefined) — post.service.ts:42

我的浏览器中也有此警告:

I also have this warning in my browser:

./~/rxjs/Observable.js
There are multiple modules with names that only differ in casing.
This can lead to unexpected behavior when compiling on a filesystem with other case-semantic.
Use equal casing. Compare these module identifiers:
* /Users/nickgowdy/Desktop/Angular2/angular4 source code/hello-world/node_modules/rxjs/Observable.js
    Used by 14 module(s), i. e.
    /Users/nickgowdy/Desktop/Angular2/angular4 source code/hello-world/node_modules/@angular/core/@angular/core.es5.js
* /Users/nickgowdy/Desktop/Angular2/angular4 source code/hello-world/node_modules/rxjs/observable.js
    Used by 1 module(s), i. e.
    /Users/nickgowdy/Desktop/Angular2/angular4 source code/hello-world/node_modules/@ngtools/webpack/src/index.js!/Users/nickgowdy/Desktop/Angular2/angular4 source code/hello-world/src/services/post.service.ts

推荐答案

错误There are multiple modules with names that only differ in casing.表示错误的导入与您尝试使用Observable的方式有关.

The error There are multiple modules with names that only differ in casing. is indicating the wrong import is being targeted with how you are trying to use Observable.

导入应以大写"O"表示，例如:

The import should be with a capital "O" like:

import { Observable } from 'rxjs/Observable';

这将导入单独的Observable运算符，该运算符将与创建的Observable上的catch或throw等运算符结合使用.

This will import the individual Observable operator, which be used in combination with operators such as catch or throw on created Observables.

import 'rxjs/add/operator/catch';
import 'rxjs/add/observable/throw';

要导入完整的Observable对象，您可以这样导入它:

To import the full Observable object you'd import it like this:

import { Observable } from 'rxjs/Rx'

更新:

对于RxJS(5.5+)的较新版本，例如map()和filter()的运算符可以用作

With newer versions of RxJS (5.5+) operators such as map() and filter() can used as pipeable operators in combination with pipe() rather than chaining. They are imported such as:

import { filter, map, catchError } from 'rxjs/operators';

请记住，诸如throw之类的术语是JavaScript中的保留字/关键字，因此RxJS throw运算符将导入为:

Keep in mind terms such as throw are reserved/key words in JavaScript so the RxJS throw operator is imported as:

import { _throw } from 'rxjs/observable/throw';

更新:

对于RxJS(6+)的较新版本，请使用以下命令:

For newer versions of RxJS (6+), use this:

import { throwError } from 'rxjs';

并抛出这样的错误:

if (error.status === 404)
    return throwError( new NotFoundError(error) )

这篇关于"rxjs" observable.throw不是函数-Angular4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！