Typescript: Static methods unable to access private properties in constructor

Question

Trying to make a static function give access to a property xdate, which was initialized in the constructor (in typescript 1.5.3).

this.xdate is accessible in all other instance methods. it remains inaccessible in the static method.

Q. Is there anyway I can make this.xdate accessible in the static method?

Below is my code:-

class vehicle{
  constructor(private xdate = new Date()){}

  vroom(){    console.log(this.xdate);  }
  static staticvroom(){ console.log(this.xdate);} //Warning: Property 'xdate' does not exist on type 'typeof vehicle'.


}//vehicle ends

let v1 = new vehicle;
v1.vroom(); //works

vehicle.staticvroom(); //undefined

/* this is how i executed it:- 
D:\js\Ang2\proj2\myforms\tsc_cRAP>tsc 7_.ts
7_.ts(18,42): error TS2339: Property 'xdate' does not exist on type 'typeof vehicle'.

D:\js\Ang2\proj2\myforms\tsc_cRAP>node 7_.js
2017-06-23T09:17:41.365Z
undefined

*/

Any pointers would be of great help. (If this is a repeated question, apologies in advance)

/* UglyHack#1: since static methods are available even before the instance of an object, I created a tmp obj. within staticvroom(){} and it worked.

static staticvroom(){ 
  console.log((new vehicle).xdate); 
}

Not sure the performance issues on this.

*/

You cannot. Since this inside static members refers to the class itself instead of the class instance. — Saravana
– Saravana, Commented Jun 23, 2017 at 9:29
I can create a new obj. within the static method and then access it using the obj variable. this worked for me: ` static staticvroom(){ let x = new vehicle; console.log(x.xdate); } ` — Plankton
– Plankton, Commented Jun 23, 2017 at 10:13
That's a horrible design, and it's extremely error prone. — Nitzan Tomer
– Nitzan Tomer, Commented Jun 23, 2017 at 10:20
Can you explain why is it horrible? I can set the object to null and delete all references to it towards the end in staticvroom(). static methods are accessible even before an instance is created; just might use that functionality, i thought. though i know its ugly, but i dont see any performance issues. — Plankton
– Plankton, Commented Jun 23, 2017 at 10:27
Static methods can not access any non-static parts of that class' instances by design. It seems like you should either not have that method static or not have xdate as a non-static field. However, we cannot be sure of this unless you improve your question with your main intents. — E_net4
– E_net4, Commented Jun 23, 2017 at 10:32

9me · Accepted Answer · 2020-09-09 10:13:59Z

4

You need to pass instance as parameter

class Vehicle {
  constructor(private xdate = new Date()) {}
  vroom(){
    console.log(this.xdate);
  }
  static staticVar: Date = new Date();
  static staticvroom(vehicle: Vehicle) {
    console.log(vehicle.xdate);
    console.log(this.staticVar); // You can even access static vars with this
  }


}// vehicle ends

let v1 = new Vehicle;
v1.vroom(); // works

Vehicle.staticvroom(v1);

edited Sep 9, 2020 at 10:13

answered Mar 25, 2020 at 9:54

9me

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