问题
I'm using the new syntax to comply with RxJS 6 pipe(). Also using Angular 6. I have a service that handles http requests, and it pipes map and catchError to display a toast in case of connection error. Nevertheless, If I add catchError I get in console You provided 'undefined' where a stream was expected. You can provide an Observable, Promise, Array, or Iterable.
getDataHttpRequest(url, returnType) {
return this.http.get(url, this.getRequestOptions())
.pipe(
map((response) => {
if(response){
if (returnType === 'object') {
return response[0] == undefined ? response : response[0];
} else {
return response;
}
}
}),
catchError((error):any => {
if(error instanceof HttpErrorResponse && error.status === 0){
//no connection error(either user has no connection or the server is down)
this.toastr.error('Chequee su conexión e intente de nuevo en unos momentos. Contáctenos para reportar el problema a <a href="mailto:dev@info.com">dev@info.com</a>',"Error de Conexión",{tapToDismiss:true, disableTimeOut: true});
}
throwError(`Connection Error: ${error}`);
})
);
}
If I remove the catchError function the errors disappear in console, so that is the breaking piece of code. Any ideas on what could be wrong?
回答1:
The callback for catchError needs to return an Observable (it might throw an exception that will be converted to error as well I think).
catchError((error):any => {
if (whatever) {
...
return empty(); // just complete
}
return throwError(`Connection Error: ${error}`); // return another `error`
});
来源：https://stackoverflow.com/questions/50972811/rxjs-6-using-catcherror-gives-you-provided-undefined-where-a-stream-was-exp