export interface MyInterface {
  position?: any;
  test?: any;
}

class Doff implements MyInterface { // <-- ERROR 1
  constructor() {
    // for the example it is direct assignment, 
    // here is a loop that reads the fields and adds them 1 to 1
    
    const field = "position" as keyof MyInterface;
    
    this[field] = true; // <<-- ERROR 2
  }
  
  public four = 4;
}
console.log("OBJ >> ", new Doff());

/* 
> ERROR 1
Type 'Doff' has no properties in common with type 'MyInterface'


> ERROR 2
Element implicitly has an 'any' type because expression
 of type 'keyof MyInterface' can't be used to index type 'Doff'.
  Property 'position' does not exist on type 'Doff'.

*/