Receiving undefined when subscribing data to an observable in Angular

Currently, I am facing an issue in my Angular project where subscribing the data to an observable is returning undefined. I have a service method in place that retrieves data from an HTTP request.

public fetchData(): Observable<Data[]> {
const url = `${this.apiUrl}/data`;

   return this.httpClient.get<ResponseData>(url).pipe(
      map(response => response._embedded.data)

   );
}

In addition, there is a component method that fetches the data from the service and assigns it to an "array".

  getData() {

  // fetching data from the service
  this.dataService.fetchData().subscribe(
    data => {
      this.array = data;


    }
  );

}

There is another method within the same file that relies on the "array".

processData(){
    console.log(this.array)
}

Ultimately, there is a main method that calls both of the aforementioned methods.

 executeMethods(){
    getData();
    processData();
}

The issue arises when calling the componentMethod() first, resulting in an "undefined" value for the array. One potential solution suggests placing the processData() function inside getData() during data subscription. However, due to the need for a loop, this approach is not preferred as it may delay processing time.

Answer №1

Make sure to invoke your secondMethod within the subscribe function but after the data has been processed.

Due to its asynchronous nature, calling it prematurely will result in an undefined value because it needs to wait for the data retrieval process to complete before proceeding to the next step.

If you call it too soon, there is a risk of the second method running before the completion of the first, causing unexpected results.

Answer №2

It seems like there may be some confusion in this section of your query:

"However, I am hesitant to go that route because implementing a loop could result in extended processing time"

Can you provide more insight into the specific loop you are referring to? Understanding this constraint might shed light on the root issue at hand...

Based on the details you shared, one potential approach could involve:

fetchData() {
  // Fetch data from the server
  return this.apiService.getData().pipe(
    map(response => {
      this.dataArray = response;
    })
  );
}

handleData(){
    fetchData().subscribe(() => {
        processData();
    })
}

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