从函数的派生类访问基本成员

Question

I have created Angular2 + Typescript project. I have there alot of tables so I want to have something like base component for that.

There is my base component:

export abstract class ManagementComponent<T> implements BaseComponent {

    protected selectedItem: T;

    protected items: Array<T>;

}

Now there is my child component. I would like to get all items from http and then assign it into base class

export class CompetencesComponent extends ManagementComponent<Competence> implements OnInit {

    thisField: string;

    constructor(private service: CompetencesService) {
        super();

    }

    ngOnInit(): void {
        this.getCompetences();
    }

    private getCompetences() {
        this.service.getCompetences().subscribe(function (competences: Array<Competence>) {
            this.thisField // ok
            this.items  // not ok            
        })
    }
}

Any idea how I can access base fields from subscribe methods?

Answer 1

Currently I'd expect that you wouldn't be able to reference either thisField or items , because you should be losing the this context inside your subscription function.

You can switch to an arrow function to retain context:

this.service.getCompetences().subscribe((competences: Array<Competence>) => { ... }

Answer 2

You can set list of competencies to parent class as follow:

    private getCompetences() {
            var self = this;
            this.service.getCompetences().subscribe(function (competences: Array<Competence>) {
                this.thisField // ok
                self.items =  competences; // not ok          
            })
        }

The reason you are unable to access items property through this binding is the scope. Inside callback this binding is bound to something else and you loose the context.