输入'Observable<HttpEvent<>'不可分配给类型“Observable&lt;&gt;" [英] Type &#39;Observable&lt;HttpEvent&lt;&gt;&gt;&#39; is not assignable to type &#39;Observable&lt;&gt;&#39;

问题描述

我有这个代码片段:

SubmitTransaction(transNumber: string, transactionRequest: ITransactionRequestObj): Observable<TransactionResponse> {
    this.body =  JSON.stringify(transactionRequest);
    this.headers = new HttpHeaders().set('Content-Type', 'application/json');
    this.headers.append('Accept', 'application/json');
    this.options = new RequestOptions({headers: this.headers});
    return this.http.post<TransactionResponse>(this.baseUrl + '/transactions/' + transNumber + '/new',  this.body, this.options)
   .pipe(catchError((e) => this.errorHandler(e)));
  }

我所做的就是将我的项目从 Angular 5 升级到 Angular 6 并将 .catch((e) => this.errorHandler(e)); 更改为 .pipe(catchError((e) => this.errorHandler(e))); .但是，对于此特定方法，我收到以下 TypeScript 错误.

where all I did was upgrade my project from Angular 5 to Angular 6 and change .catch((e) => this.errorHandler(e)); to .pipe(catchError((e) => this.errorHandler(e))); . However, I am getting the following TypeScript error for this particular method.

错误:

[ts]
Type 'Observable<HttpEvent<TransactionResponse>>' is not assignable to type 'Observable<TransactionResponse>'.
  Type 'HttpEvent<TransactionResponse>' is not assignable to type 'TransactionResponse'.
    Type 'HttpSentEvent' is not assignable to type 'TransactionResponse'.
      Property '_transactionNumber' is missing in type 'HttpSentEvent'.

我不确定在这种情况下我应该做什么.上面的代码片段在 Angular 5 中工作.我需要做些什么才能为 Angular 6 修复它?

I'm not sure what I should do in this scenario. The code snippet above was working in Angular 5. What do I need to do to fix it for Angular 6?

errorHandler(error: HttpErrorResponse) {
      return throwError(error.message || 'Server Error');
  }

我注意到如果我不使用 HttpHeaders，它会起作用:

I have noticed if I don't use the HttpHeaders, it works:

SubmitTransaction(transNumber: string, transactionRequest: ITransactionRequestObj): Observable<TransactionResponse> {
    this.body =  JSON.stringify(transactionRequest);
    this.headers = new HttpHeaders().set('Content-Type', 'application/json');
    this.headers.append('Accept', 'application/json');
    this.options = new RequestOptions({headers: this.headers});
    return this.http.post<TransactionResponse>(this.baseUrl + '/transactions/' + transNumber + '/new',  transactionRequest)
    .pipe(catchError((e) => this.errorHandler(e)));
  }

但是，我可能需要使用 HttpHeaders...在这种情况下有什么解决方法?

However, I might need to use the HttpHeaders... what is the workaround in this scenario?

推荐答案

HttpHeaders 是一个不可变的数据结构.

HttpHeaders is an immutable data structure.

方法 append 返回 HttpHeaders 的一个新实例，而不是改变现有的实例，这意味着您需要对代码进行微小的更改.

The method append returns a new instance of HttpHeaders rather than mutating the existing one, meaning you'll need to make a tiny change in your code.

// old
this.headers.append('Accept', 'application/json')

// new
this.headers = this.headers.append('Accept', 'application/json')

更好的是，一次性完成:

Even better, just do it all at once:

this.headers = new HttpHeaders()
  .set('Content-Type', 'application/json')
  .set('Accept', 'application/json')

这篇关于输入'Observable<HttpEvent<>'不可分配给类型“Observable&lt;&gt;"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！