Initialized dynamically created object with default values - Using Generics and Interfaces

Question

I need to initialize initial value of 'gDetailDS' object. I cannot create classes instead of interfaces and interfaces don't allow me to set default values.

I have tried using map or other functions to resolve the issue but could not get success. Using map, get the error "_this.gDetailDS.map is not a function".

export interface InterfaceA{
    sysSeq: number;
    code: string;
    isUpdate: boolean;
    version: number;
}

export interface InterfaceB{
    sysSeq: number;
    name: string;
    isReserved: boolean;
    isPublic: boolean;
    version: number;
 }


export class DetailComponent<T> extends CoreComponent {
    gDetailDS: any;
    constructor(){
        this.gDetailDS =  <T> new Object; 
    }

}

I want to get default values specially for booleans. for instance, after executing this below line,

this.gDetailDS =  <InterfaceB> new Object;

I should have an object of type InterfaceB with default sets for

this.gDetailDS.isReserved has default value "false";
this.gDetailDS.isPublic  has default value "false";

Your help would be much appreciated.

Rauks · Accepted Answer · 2019-02-08 14:17:07Z

1

Once transpiled to Javascript, your DetailComponent<T> has no information about the T. So you can not use it directly to get an instance of T.

But, if you can add parameters to your DetailComponent constructor, a solution to your problem would be:

export class DetailComponent<T> extends CoreComponent {
  gDetailDS: T;
  constructor(newInstance: new () => T){
      this.gDetailDS = new newInstance(); 
  }

}

class InterfaceAImpl implements InterfaceA {
  sysSeq: number;
  code: string;
  isUpdate: boolean;
  version: number;
};

var detailComponent: DetailComponent<InterfaceA> = new DetailComponent<InterfaceA>(InterfaceAImpl);

edited Feb 8, 2019 at 14:17

answered Feb 8, 2019 at 14:01

Rauks

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4 Comments

TAB Over a year ago

How could I set default value for isUpdate? Another point is that, I dont want to create a class for an interface.

Rauks Over a year ago

Like types, interfaces have no existance once the code is transpiled into javascript: Playground

TAB Over a year ago

Thats I know buddy, interface does not exist after transpilation. But before transpiling, how could we initialize our interface value.

Rauks Over a year ago

You can maybe have a look at the issue below: How to use interface and default parameters together? I'm not sure we can achieve having default values for interfaces properties without using classes directly (a class that implements the interface) or indirectly (like using a factory that build objects that are the type of your interface).

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