Get return value of a function using notifySubscribers

问题

I got two different view models and I need to call a function in one view model from other. To acheive this i try to use ko.subscribable()

 var postbox=new ko.subscribable();// global variable 

EmployeeViewModel

  postbox.subscribe(function (showAlert) {
            return that.ValidateEmployees(showAlert);
        }, that, 'ValidateEmps');

  that.ValidateEmployees=function(){

  //validation logic
   return true/false;
  }

TaxCalculatorViewModel

var isEmpValid = postbox.notifySubscribers(true, "ValidateEmps");
 if (!isEmpValid ) {
  return false;
 }

The prioblem is I am always getting isEmpValid=undefined instead of getting the return value of ValidateEmployees

How to get the return value of a function when we pass using notifySubscribers?

来源：https://stackoverflow.com/questions/28828242/get-return-value-of-a-function-using-notifysubscribers