Exploring ways to retrieve a function-scoped variable from within an Angular subscribe function

Question

Exploring ways to retrieve a function-scoped variable from within an Angular subscribe function

Here's the scenario: I have a simple question regarding an Angular component. Inside this component, there is a function structured like this:


somethingCollection: TypeSomething[]
...
public deleteSomething(something: TypeSomething): void {
    // something variable is within this scope
    this.someAPI.deleteSomething(something.id).subscribe( (res) => {
       // need to update this.somethingCollection here
       // but unable to access 'something' in outer scope
    }
}

It's clear that for updating this.somethingCollection, we require 'something.id'. However, once inside the subscribe method, I lose access to it.

Is there anyone who can guide me on how to retain access to function scoped variables within the subscribe method?

angular typescript scope

Answer 1

Answer №1

When dealing with overlapping function problems, it is crucial to prevent the loss of the value of this by storing references to the parent function's this using the scope chain.

By using aliases such as self, context, $this, or any other variable name when assigning the value of this to it, the reference remains fixed similar to a regular variable.

somethingCollection: TypeSomething[]
...
public deleteSomething(something: TypeSomething): void {
    let self = this;
    this.someAPI.deleteSomething(something.id).subscribe( (res) => {
       self.somethingCollection // access somethingCollection....
       // this.somethingCollection is undefined
    }
}

Answer 2

When dealing with overlapping function problems, it is crucial to prevent the loss of the value of this by storing references to the parent function's this using the scope chain.

By using aliases such as self, context, $this, or any other variable name when assigning the value of this to it, the reference remains fixed similar to a regular variable.

somethingCollection: TypeSomething[]
...
public deleteSomething(something: TypeSomething): void {
    let self = this;
    this.someAPI.deleteSomething(something.id).subscribe( (res) => {
       self.somethingCollection // access somethingCollection....
       // this.somethingCollection is undefined
    }
}

Answer 3

Answer №2

That statement is not accurate

export class AppComponent implements OnInit  {
  name = 'Angular ' + VERSION.major;
  constructor(private dataService:DataService){}


  public removeItem(item: any): void {
    console.log(item)
    this.dataService.getData(item.id).subscribe( (res) => {
      console.log(item,this.name,res)
    })
  }
  ngOnInit()
  {
    this.removeItem({id:3})
  }

}

view a demo on stackblitz

Answer 4

That statement is not accurate

export class AppComponent implements OnInit  {
  name = 'Angular ' + VERSION.major;
  constructor(private dataService:DataService){}


  public removeItem(item: any): void {
    console.log(item)
    this.dataService.getData(item.id).subscribe( (res) => {
      console.log(item,this.name,res)
    })
  }
  ngOnInit()
  {
    this.removeItem({id:3})
  }

}

view a demo on stackblitz

Exploring ways to retrieve a function-scoped variable from within an Angular subscribe function

Answer №1

Answer №2

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