How to make sure that the / ngOnInit constructor is executed before calling functions from the class?

Question

I have a class that, when initialized, retrieves data from the service and populates one of its properties, which is an array. The same class has a function that sorts, filters, and returns this array. When I instantiate an object of this class and call this function, I realized that it is called before its constructor, and the ngOnInit () functions are executed (possibly because I use the async content from the Observables returned by the service). How can I guarantee that the constructor and init are fully executed before any function of my class is called from the outside?

    export class BaseChoice implements PickAppraiser, OnInit {
weight = 0;
options = new Array<PickQuality>();

constructor(private championService: ChampionService) {}

ngOnInit() {
    // Iterates through the list of champions adding them to the current object
    this.championService.getChampions()
        .subscribe(champions => {
            // Iterates through the list of champions adding them to the current object
            Object.keys(champions).map(key => this.options.push(new PickQuality(champions[key], 0)))
        })
}

choose(n?: number): PickQuality[] {
    var sorted = this.options.sort((a, b) => a.score - b.score);
    return sorted;
}

}

I also tried to do something like

    choose(n?: number): PickQuality[] {
    // Iterates through the list of champions adding them to the current object
    this.championService.getChampions()
        .subscribe(champions => {
            // Iterates through the list of champions adding them to the current object
            Object.keys(champions).map(key => this.options.push(new PickQuality(champions[key], 0)))
            this.reevaluate(this.options);

            var sorted = this.options.sort((a, b) => a.score - b.score);
            var chosen;
            if(n) chosen = sorted.slice(1, n);
            else chosen = sorted.slice(1, 2);
            return chosen;
        });
}

async select(), , , .

Answer 1

, , . , , angular .

, - :

export class BaseChoice implements PickAppraiser, OnInit {
    weight = 0;
    options$: Observable<PickQuality>;
    champions$ : Observable<Champion>;

    constructor(private championService: ChampionService) {}

    ngOnInit() {
        this.champions$ = this
            .championService.getChampions();

        this.options$ = this.champions$.map((champion, index) => {
          return new PickQuality(champion, 0)))
      })
    }
}

, *ngFor="let option in options$ | async), , choose(), , - , , - .

, , championClicked$, .

, Observer (), , | async, .

, RxJS, angular 2.

Answer 2

options options = new Array<PickQuality>();, ?

choose(n?: number): PickQuality[] {
    if (this.options && this.options.length !== 0) {
       var sorted = this.options.sort((a, b) => a.score - b.score);
       return sorted;
    } else {
       /* do something else if options is empty */
    }
}

--- ---

, :

export class BaseChoice implements PickAppraiser, OnInit {
weight = 0;
options = new Subject<PickQuality[]>();

constructor(private championService: ChampionService) {}

ngOnInit() {
    this.championService.getChampions()
        .subscribe(champions => {
            Let arr = [];
            Object.keys(champions).map(key => arr.push(new PickQuality(champions[key], 0)));
             this.options.next(arr);
        })
}

choose(n?: number): PickQuality[] {
    return this.options.take(1).sort((a, b) => a.score - b.score);
}
}

Answer 3

select (n) , * ngIf = " . , " ", undefined, . - :

options: PickQuality[];

select (n) , , Observable Promise.