Is there a way to access the result variable outside of the lambda function?

Question

Is there a way to access the result variable outside of the lambda function?

My goal is to retrieve data from an external API using Typescript. Below is the function I have written:

export class BarChartcomponent implements OnInit{
  public chart: any;
  data: any = [];
  
  constructor(private service:PostService) { }

  ngOnInit(): void {

    this.service.getPosts().subscribe(response => {
     this.data = response;
    });
    
    this.createChart();
  };
}

I am encountering an issue where the "data" variable appears as "undefined" when trying to use it for further data manipulation outside the subscribe function. I understand that this is a scope error, but I am unsure of how to resolve it.

javascript angularjs typescript

Answer 1

Answer №1

There are two methods to handle data retrieval: 1: Utilize promises and the 'then' function to track when data is received 2: Invoke your method within the subscribe function

Answer 2

There are two methods to handle data retrieval: 1: Utilize promises and the 'then' function to track when data is received 2: Invoke your method within the subscribe function

Answer 3

Answer №2

If myData is only accessible asynchronously, you can handle it using a promise:

ngOnInit(): void {
  this.myData = new Promise(function(resolve, reject) {
    this.service.fetchData().subscribe(response => {
      resolve(response);
    });
  }.bind(this));
  this.displayInfo(); // this method cannot access myData yet
}

Instead of directly using myData in a synchronous function:

someOperation() {
  console.log(this.myData);
}

You need to await its value inside an asynchronous function:

async someOperation() {
  console.log(await this.myData);
}

Keep in mind that by making the someOperation asynchronous, any return value must also be awaited. Once asynchronous operations are introduced, they cannot be avoided.

Answer 4

If myData is only accessible asynchronously, you can handle it using a promise:

ngOnInit(): void {
  this.myData = new Promise(function(resolve, reject) {
    this.service.fetchData().subscribe(response => {
      resolve(response);
    });
  }.bind(this));
  this.displayInfo(); // this method cannot access myData yet
}

Instead of directly using myData in a synchronous function:

someOperation() {
  console.log(this.myData);
}

You need to await its value inside an asynchronous function:

async someOperation() {
  console.log(await this.myData);
}

Keep in mind that by making the someOperation asynchronous, any return value must also be awaited. Once asynchronous operations are introduced, they cannot be avoided.

Is there a way to access the result variable outside of the lambda function?

Answer №1

Answer №2

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