转换为函数时无法编译代码

Question

我有以下代码可以正常工作。

  public createData(data:Data):Observable<any>{
    console.log('contacting server at '+this.API_URL +this.NEW_DATA_URL +" with data "+data+ " with httpOptions "+httpOptions.withCredentials + ","+httpOptions.headers );

let newData = new Data(data)    
    let body = JSON.stringify(newQuestion); 
//I WANT TO MOVE THE CODE BELOW INTO A FUNCTION BUT AM GETTING COMPILATION ERROR
    this.loaderService.show();
    return this.http.post(this.NEW_QUESTION_URL,body,httpOptions)
      .pipe(tap(response => { 
        let httpEvent = <HttpEvent<any>>response;
        if(httpEvent.type === HttpEventType.Response)
        {
          console.log('response from backend service:', response);

          return result;
        }
        else {
          console.log("not an http response")
          return response;
        }
      })
      ,catchError(this.handleError)
        ,finalize(()=> this.loaderService.hide())); //error handler if Observable fails

  }

因为我可以重用部分代码，所以我想创建一个函数，但现在我遇到了编译错误。我无法找出错误所在。

新函数是

private sendMessage(url:string, body:any,httpOptions:any){
    this.loaderService.show();
    return this.http.post(url,body,httpOptions)
      .pipe(tap(response => { 

          let httpEvent = <HttpEvent<any>>response; //ERROR HERE - 'ArrayBuffer' cannot be converted to type 'HttpEvent<any>'.
          if(httpEvent.type === HttpEventType.Response)
          {
            console.log('response from backend service:', response);

            let result = <HttpResponse<any>>response;

            return result;
          }
          else {
            console.log("not an http response")
            return response;
          }
        })
        ,catchError(this.handleError)
        ,finalize(()=> this.loaderService.hide())); //error handler if Observable fails
    }

错误是 ERROR in src/app/web-to-backend-interface.service.ts(264,27): error TS2352: Type 'ArrayBuffer' cannot be converted to type 'HttpEvent<any>'. Type 'ArrayBuffer' is not comparable to type 'HttpUserEvent<any>'. Property 'type' is missing in type 'ArrayBuffer'.

http.post 有几个重载方法，其中之一是 return Observable - angular.io/api/common/http/HttpClient#post。如何让 Angular 使用 returns Observable<T> 的重载版本？我更改了代码并添加了 responseType:'json' 但这也不起作用

const httpOptions = {
  headers: new HttpHeaders({ 'Content-Type': 'application/json' }),
  withCredentials: true, 
observe: 'response' as 'response', 
  responseType: 'json' 
};


let observable:Observable<HttpEvent<any>> = this.http.post(url,body,httpOptions)
    return observable.pipe(tap((httpEvent:HttpEvent<any>) => {....}

我看到的错误是

ERROR in src/app/web-to-backend-interface.service.ts(80,71): error TS2345: Argument of type '{ headers: HttpHeaders; withCredentials: boolean; observe: "response"; responseType: string; }' is not assignable to parameter of type '{ headers?: HttpHeaders | { [header: string]: string | string[]; }; observe?: "body"; params?: Ht...'.
  Types of property 'observe' are incompatible.
    Type '"response"' is not assignable to type '"body"'.
src/app/web-to-backend-interface.service.ts(111,52): error TS2345: Argument of type '{ headers: HttpHeaders; withCredentials: boolean; observe: "response"; responseType: string; }' is not assignable to parameter of type '{ headers?: HttpHeaders | { [header: string]: string | string[]; }; observe?: "body"; params?: Ht...'.
  Types of property 'observe' are incompatible.
    Type '"response"' is not assignable to type '"body"'.
src/app/web-to-backend-interface.service.ts(195,73): error TS2345: Argument of type '{ headers: HttpHeaders; withCredentials: boolean; observe: "response"; responseType: string; }' is not assignable to parameter of type '{ headers?: HttpHeaders | { [header: string]: string | string[]; }; observe?: "body"; params?: Ht...'.
src/app/web-to-backend-interface.service.ts(215,72): error TS2345: Argument of type '{ headers: HttpHeaders; withCredentials: boolean; observe: "response"; responseType: string; }' is not assignable to parameter of type '{ headers?: HttpHeaders | { [header: string]: string | string[]; }; observe?: "body"; params?: Ht...'.
src/app/web-to-backend-interface.service.ts(250,54): error TS2345: Argument of type '{ headers: HttpHeaders; withCredentials: boolean; observe: "response"; responseType: string; }' is not assignable to parameter of type '{ headers?: HttpHeaders | { [header: string]: string | string[]; }; observe?: "body"; params?: Ht...'.
src/app/web-to-backend-interface.service.ts(290,9): error TS2322: Type 'Observable<ArrayBuffer>' is not assignable to type 'Observable<HttpEvent<any>>'.
  Type 'ArrayBuffer' is not assignable to type 'HttpEvent<any>'.
    Type 'ArrayBuffer' is not assignable to type 'HttpUserEvent<any>'.
      Property 'type' is missing in type 'ArrayBuffer'.
src/app/web-to-backend-interface.service.ts(296,59): error TS2552: Cannot find name 'response'. Did you mean 'Response'?

为什么为一个工作代码创建一个单独的函数会使其不可编译？我的错误是什么？

Answer 1

虽然我无法回答为什么你现在会收到 TS 错误，而你以前没有，但我可以建议你如何摆脱它（假设代码在你重构之前是有效的） .如果你在声明中给 response 一个类型，那么它不会得到你必须尝试映射的假定类型：

.pipe(tap((response: HttpEvent<any>) => { 

      let httpEvent = response; // No need for type-casting here anymore.

Answer 2

我能够解决它，但现在我的问题多于答案。如果有人能向我解释这种行为，我将不胜感激。

我正在使用以下 httpOptions 对象

const httpOptions = {
  headers: new HttpHeaders({ 'Content-Type': 'application/json' }),

withCredentials: true, 
observe: 'response' as 'response', 

};

在代码中的某些地方按如下方式使用它。

 return this.http.post(this.SIGNUP_USER_URL,body,httpOptions)

这有效。

然后我想到将 http.post 更改为函数 sendMessage （如问题中所述）并仅在一次地方替换它（记住我在几个地方使用 this.http.post地方所以想在一个地方开始尝试）。我注意到使用 httpOptions 使 post return Observable<ArrayBuffer>。

疑问 1 - 为什么？

然后我把httpOptions改成了

const httpOptions = {
  headers: new HttpHeaders({ 'Content-Type': 'application/json' }),

withCredentials: true, 
observe: 'response' as 'response', 
responseType:'json'  
};

它开始在我直接使用 http.post 的地方出现错误（没有 sendMessage。错误是

ERROR in src/app/web-to-backend-interface.service.ts(81,71): error TS2345: Argument of type '{ headers: HttpHeaders; withCredentials: boolean; observe: "response"; responseType: string; }' is not assignable to parameter of type '{ headers?: HttpHeaders | { [header: string]: string | string[]; }; observe?: "body"; params?: Ht...'.
  Types of property 'observe' are incompatible.
    Type '"response"' is not assignable to type '"body"'.
src/app/web-to-backend-interface.service.ts(112,52): error TS2345: Argument of type '{ headers: HttpHeaders; withCredentials: boolean; observe: "response"; responseType: string; }' is not assignable to parameter of type '{ headers?: HttpHeaders | { [header: string]: string | string[]; }; observe?: "body"; params?: Ht...'.
  Types of property 'observe' are incompatible.
    Type '"response"' is not assignable to type '"body"'.
src/app/web-to-backend-interface.service.ts(196,73): error TS2345: Argument of type '{ headers: HttpHeaders; withCredentials: boolean; observe: "response"; responseType: string; }' is not assignable to parameter of type '{ headers?: HttpHeaders | { [header: string]: string | string[]; }; observe?: "body"; params?: Ht...'.
src/app/web-to-backend-interface.service.ts(216,72): error TS2345: Argument of type '{ headers: HttpHeaders; withCredentials: boolean; observe: "response"; responseType: string; }' is not assignable to parameter of type '{ headers?: HttpHeaders | { [header: string]: string | string[]; }; observe?: "body"; params?: Ht...'.
src/app/web-to-backend-interface.service.ts(251,54): error TS2345: Argument of type '{ headers: HttpHeaders; withCredentials: boolean; observe: "response"; responseType: string; }' is not assignable to parameter of type '{ headers?: HttpHeaders | { [header: string]: string | string[]; }; observe?: "body"; params?: Ht...'.
src/app/web-to-backend-interface.service.ts(291,9): error TS2322: Type 'Observable<ArrayBuffer>' is not assignable to type 'Observable<HttpEvent<any>>'.
  Type 'ArrayBuffer' is not assignable to type 'HttpEvent<any>'.
    Type 'ArrayBuffer' is not assignable to type 'HttpUserEvent<any>'.
      Property 'type' is missing in type 'ArrayBuffer'.

所以我从 httpOptions 中删除了 responseType:'json' 并在我的 sendMessage 中的 this.http.post 中添加了一个显式对象！

private sendMessage(url:string, body:any,httpOptions){
  ...
    let observable:Observable<HttpEvent<any>> = this.http.post(url,body,{
          headers: new HttpHeaders({ 'Content-Type': 'application/json' }),
          withCredentials: true,
          observe: 'events',
          responseType: 'json'
        })
...
}

observe 和 responseType 之间似乎有关系。例如 observe=body 和 responseType=text 意味着 post 应该观察（查看）主体，将其解释为文本和 return 可观察。但我想知道为什么我就是不能改变 httpOptions

转换为函数时无法编译代码

unable to compile a code when converted into a function

typescript

angular6

rxjs6