Enhance Tuple in Angular Component Properties

Question

Enhance Tuple in Angular Component Properties

When using React, state variables can be created like this:

const SomeComponent = ({ someProp }) => {
  const [value, setValue] = useState<boolean>(false);
}

I wonder if there is a similar way to achieve the spread of a tuple within an Angular component's members.

For instance:

@Directive({
  selector: '[appDirective]'
})
export class AppDirective {
  [value, observable] = createState<boolean>(false);
}

The issue here is that [value, observable] is not valid syntax. While replacing it with

a = createState<boolean>(false)

does work, I'm interested in finding a method to expand the tuple into two separate member variables of the directive. It's worth noting that createState returns

[BehaviorSubject<T>, Observable<T>]

.

angular typescript tuples

Answer 1

Answer №1

It looks like the best alternative to your attempted code would be:

export class AppDirective {
  state = createNewState<boolean>(false);
  val = state[1];
  subj = state[0];
}

However, it seems that you are utilizing an obscure library which may hinder your development process. Angular offers a more convenient two-way binding feature that you should consider using instead:

val = 'onlyValue, Nothing else needed';

component.html:

<input type="text" [(ngModel)]="val">

Answer 2

It looks like the best alternative to your attempted code would be:

export class AppDirective {
  state = createNewState<boolean>(false);
  val = state[1];
  subj = state[0];
}

However, it seems that you are utilizing an obscure library which may hinder your development process. Angular offers a more convenient two-way binding feature that you should consider using instead:

val = 'onlyValue, Nothing else needed';

component.html:

<input type="text" [(ngModel)]="val">

Answer 3

Answer №2

When it comes to comparing function implementation and class definition, they are like apples and oranges. If you want to include destructuring for your class properties, you can achieve this by incorporating it within a function inside the class, as demonstrated below:

function initializeState<T>(initialState: T): [BehaviorSubject<T>, Observable<T>] {
  const state = new BehaviorSubject<T>(initialState);
  return [state, state.asObservable()];
}

export class AppComponent implements OnInit {
  value!: BehaviorSubject<boolean>;
  observable!: Observable<boolean>;

  ngOnInit(): void {
    [this.value, this.observable] = initializeState<boolean>(false);
    const [value, observable] = initializeState(false);
  }
}

Answer 4

When it comes to comparing function implementation and class definition, they are like apples and oranges. If you want to include destructuring for your class properties, you can achieve this by incorporating it within a function inside the class, as demonstrated below:

function initializeState<T>(initialState: T): [BehaviorSubject<T>, Observable<T>] {
  const state = new BehaviorSubject<T>(initialState);
  return [state, state.asObservable()];
}

export class AppComponent implements OnInit {
  value!: BehaviorSubject<boolean>;
  observable!: Observable<boolean>;

  ngOnInit(): void {
    [this.value, this.observable] = initializeState<boolean>(false);
    const [value, observable] = initializeState(false);
  }
}

Enhance Tuple in Angular Component Properties

Answer №1

Answer №2

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