键入"Observable< HttpEvent<>>"不可分配给类型"Observable<>" [英] Type 'Observable<HttpEvent<>>' is not assignable to type 'Observable<>'

问题描述

我有以下代码段:

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应该做什么.上面的代码段在Angular 5中可用.我需要做些什么才能将其修复为Angular 6?

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');
  }

我已经注意到，如果我不使用HttpHeaders，它将起作用:

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，解决方法是什么?

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

推荐答案

HttpHeaders 是不可变的数据结构.

HttpHeaders is an immutable data structure.

方法 append 返回一个 HttpHeaders 的新实例，而不是对现有实例进行突变，这意味着您需要对代码进行一些细微更改.

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，一次完成所有操作:

Even better, just do it all at once:

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

这篇关于键入"Observable< HttpEvent<>>"不可分配给类型"Observable<>"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！