call derived class method inside base generic class

[MasoudBimar]

i have a base generic component and i want to call derived method from base class that return data that belongs to derived class.

i cant define it static in abstract class!

so the problem is, when i create new instance of derived class with {} as TDomain inside base generic class, its empty and method return null ref error !

Base Entity is like this:

export abstract class BaseEntity
{
abstract getColumns():string[];
}

My Model is Like this:

export class Person extends BaseEntity 
{
getColumns() { return ["Id", "Name"]; }
 }

I have a generic base component:

    @Component({
      selector: 'base-component',
      templateUrl: './base.component.html',
      styleUrls: ['./base.component.css']
    })
    export class BaseComponent<TDomain  extends BaseEntity,TService extends DataService > 
implements OnInit {
    data:any[];
    
      constructor() {
      }
    
      ExportToExcel(): void {
        //must create an instance of derived class
        //then call getcolumns method of it
         ### let obj = {} as TDomain; // but its empty  doesnt work
        ### ExcelService.export(obj.getcolumns(this.data));
    
      }
        }

and derived component:

    @Component({
      selector: 'Derived-Cmp',
      templateUrl: './derived.component.html',
      styleUrls: ['./derived.component.css']
    })
    export class DerivedComponent extends  BaseCrudComponent<Person,PersonService> 
implements OnInit {
    
      //ExportToExcel Method called form html 
    
    }

How Should i call derived class method from base generic class?
(in BaseComponent i want to call getcolumns on TDomain )

[dragomirtitian]

I think Stack Overflow is a better forum for this type of question, you might actually find good answers to this question over there.

To create an instance of TDomain you need to pass the constructor of TDomain to the base class:

export abstract class BaseEntity {
    abstract getColumns(): string[];
}

export class Person extends BaseEntity {
    getColumns() { return ["Id", "Name"]; }
}
export class BaseComponent<TDomain extends BaseEntity> {
    data: any[];

    constructor(public ctor: new () => TDomain) {
    }

    ExportToExcel(): void {
        let obj = new this.ctor(); // create instance using the constructor
        obj.getColumns(); /// call method
    }
}

export class DerivedComponent extends BaseComponent<Person> {
    constructor() {
        super(Person)
    }
}

[RyanCavanaugh]

It looks like this is a question rather than a bug report. This issue tracker is for tracking bugs and active work on TypeScript itself, rather than a general forum for programmers using TypeScript to get help or ask questions.

You can ask questions on sites like Stack Overflow. We are not able to provide one-on-one support on the issue tracker. Please read the issue template carefully - it has important information on what kinds of reports can be acted on here, as well as links to useful TypeScript resources. Thanks!