Adding items to an array in Angular using the subscribe method

In my Angular application, I have an empty array defined as follows:

  users: any = [];

Within the ngOnInit lifecycle hook, I make a service call to fetch data and store it in the users array like so:

  ngOnInit() {

    //Fetching data from a JSON endpoint
    this.httpClient.get('https://api.myjson.com/bins/n5p2m').subscribe((response: any) => {
      console.log("response", response.data);
      response.data.forEach(element => {
        //Pushing the element data into the users array
        this.users.push(element);
      });
    })

    //Attempting to log the complete array after pushing elements from the service response data
    console.log("users array", this.users);
    //However, it shows an empty array at this point
  }

I am facing an issue where the data is not available in

console.log("users array", this.users);
due to delays caused by the service call.

My goal is to populate this.users with data that can be accessed outside of the service call and within the ngOnInit function.

To illustrate the problem, I have created a working example on StackBlitz: https://stackblitz.com/edit/angular-q3yphw

Please refer to the console logs for the current results.

The current output in

console.log("users array", this.users);
is an empty array [].

My desired outcome when logging

console.log("users array", this.users);
both inside and outside of the service call in ngOnInit is as follows:

[
{"id":1,"value":"User One"},
{"id":2,"value":"User Two"},
{"id":3,"value":"User Three"}
]

As a newcomer to Angular, I would appreciate guidance on achieving the expected result.

Answer №1

Shared a Stackblitz Demo

If you wish to modify the data received from the HTTP Client response, you can do so by using RxJS operators. When you subscribe to the final value after applying these methods within the pipe, it will be directly rendered on your template.

this.httpClient
  .get('https://api.myjson.com/bins/n5p2m')
  .pipe(
    map(response => response.data),
    tap(users => console.log("users array", users))    // users array [Object, Object, Object]
  )
  .subscribe(users => this.users = users);

If you prefer not to use RxJS Operators, you can still manipulate the data after subscribing to the final value and manually perform any necessary adjustments

There's no need for a .forEach() loop to store the array of objects as Angular already handles it for you. Simply assign it like

this.users = response.data to store an Array of Objects [Object, Object, Object]

this.httpClient
  .get('https://api.myjson.com/bins/n5p2m')
  .subscribe(response => this.users = response.data);  // The response data will be stored directly in an array of objects.

https://i.sstatic.net/1TWZP.png

Answer №2

Storing data in an array without using a loop is possible.

ngOnInit() {

  // Retrieving data from a JSON source
  this.httpClient.get('https://api.myjson.com/bins/n5p2m').subscribe((response: any) => {      
    this.users.push(...response.data)
    console.log("users array", this.users);  
  })            
}

Answer №3

When working with Angular, handling asynchronous operations like http get requests can be done using Promises and Observables. If you're looking to learn more about this concept, a good starting point is available here: Promise vs Observable

One way to approach this is by wrapping the http get request in a method that returns an Observable. By subscribing to this method and waiting for it to return a result, you can ensure the log statement only executes once the data is available.

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