Detecting a NULL Response from an Angular 5 RxJS Observable while Subscribing: A Guide

Question

Detecting a NULL Response from an Angular 5 RxJS Observable while Subscribing: A Guide

Using RxJS Observables within Angular

this.myService.getEmp(personEmpId).subscribe(
        result => {
            this.personName = result.person_name;
        },
        error => {
            console.log("EE:",error);
        }
    );

Is there a way to check if my subscription to this service returns a NULL result, indicating that no record was found?

I attempted to handle the error but it didn't trigger the console message.

Currently, I am encountering the following error:

ERROR TypeError: "result is null"

angular typescript rxjs observable

Answer 1

Answer №1

If you want to filter before subscribing to your service, you can add a filter like this:

// import the filter operator at the beginning of your source file
import { filter } from 'rxjs/operators'

this.myService.getEmp(personEmpId)
    .pipe(filter(result) => !!result)
    .subscribe(
        result => {
            this.personName = result.person_name;
        },
        error => {
            console.log("EE:",error);
        }
);

Additionally, if you need to handle cases where the webservice does not return any data, you can do so within the success callback:

this.myService.getEmp(personEmpId)
    .subscribe(
        result => {
            if (result) {
                this.personName = result.person_name;
            } else {
                // handle the scenario when there is no data returned
            }
        },
        error => {
            console.log("EE:",error);
        }
);

Answer 2

If you want to filter before subscribing to your service, you can add a filter like this:

// import the filter operator at the beginning of your source file
import { filter } from 'rxjs/operators'

this.myService.getEmp(personEmpId)
    .pipe(filter(result) => !!result)
    .subscribe(
        result => {
            this.personName = result.person_name;
        },
        error => {
            console.log("EE:",error);
        }
);

Additionally, if you need to handle cases where the webservice does not return any data, you can do so within the success callback:

this.myService.getEmp(personEmpId)
    .subscribe(
        result => {
            if (result) {
                this.personName = result.person_name;
            } else {
                // handle the scenario when there is no data returned
            }
        },
        error => {
            console.log("EE:",error);
        }
);

Answer 3

Answer №2

If you want to remove any NULL results from the output, simply utilize the filter function.

this.userService.getUser(userID).filter(user => user !== null).subscribe..

By implementing this filter, the subscriber will only receive values that are not NULL.

Answer 4

If you want to remove any NULL results from the output, simply utilize the filter function.

this.userService.getUser(userID).filter(user => user !== null).subscribe..

By implementing this filter, the subscriber will only receive values that are not NULL.

Answer 5

Answer №3

If the method you are using returns NULL (indicating no records found), this is not an error but a valid response. In this case, the error callback will not be executed. Instead, you should handle this specific scenario within the success callback.

this.myService.getEmp(personEmpId).subscribe(
    result => {
        if(result){ 
           this.personName = result.person_name;
        }
        else {
           //log or display message indicating no data was found
        }
    },
    error => {
        console.log("EE:",error);
    }
);

Answer 6

If the method you are using returns NULL (indicating no records found), this is not an error but a valid response. In this case, the error callback will not be executed. Instead, you should handle this specific scenario within the success callback.

this.myService.getEmp(personEmpId).subscribe(
    result => {
        if(result){ 
           this.personName = result.person_name;
        }
        else {
           //log or display message indicating no data was found
        }
    },
    error => {
        console.log("EE:",error);
    }
);

Answer 7

Answer №4

Give this a shot.

this.myService.retrieveEmployeeDetails(personEmpId).subscribe(
        response => {
            if(response){
                 this.personName = response.employee_name;
            }
            else{
              //handle error here
            }
        },
        err => {
            console.log("Error Encountered:",err);
        }
    );

Answer 8

Give this a shot.

this.myService.retrieveEmployeeDetails(personEmpId).subscribe(
        response => {
            if(response){
                 this.personName = response.employee_name;
            }
            else{
              //handle error here
            }
        },
        err => {
            console.log("Error Encountered:",err);
        }
    );

Detecting a NULL Response from an Angular 5 RxJS Observable while Subscribing: A Guide

Answer №1

Answer №2

Answer №3

Answer №4

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