JQ.TypeScript.PnPJS.CustomObjectsOriginal.ts

import { Item, ODataEntity } from "sp-pnp-js";

export class MyItem extends Item {
    public static Fields = ["Id", "Title", "Category", "Quantity"];

    public Id: number;
    public Title: string;
    public Category: string;
    public Quantity: number;

    // override get to enfore select for our fields to always optimize
    // but allow it to be overridden by any supplied values
    public get(): Promise<MyItem> {
        // use apply and call to manipulate the request into the form we want
        // if another select isn't in place, let's default to only ever getting our fields.
        const query = this._query.getKeys().indexOf("$select") > -1 ? this : this.select.apply(this, MyItem.Fields);
        // call the base get, but in our case pass the appropriate ODataEntity def so we are returning
        // a MyItem instance
        return super.get.call(query, ODataEntity(MyItem), arguments[1] || {});
    }
}