Add callback to angularjs service method

Question

Is there any way of adding a callback method to a function that calls service in a function i am calling multiple service methods and i want to a set a callback method to that function. I tried this but no luck

$scope.MyFunction() = function()
{
    //Multiple Service calls
    $scope.callService1 = service.CallService1() //returns true on success
    $scope.callService2 = service.CallService2() //returns true on success
    $scope.callService3= service.CallService3() //returns true on success

    if($scope.callService1  && $scope.callService2 && $scope.callService3)
    {
        $scope.CallbackMethod ();
    }
}

$scope.CallbackMethod = function()
{
    alert('CallbackMethod')
}

I tried this one too but its not in sync as the service calls takes some time.

$scope.MyFunction() = function(CallbackMethod)
{
    //Refer Above Code
} 

CallService service Method is something simple like

$http.post('/InstStrategy/ReadAll').then(function (response) {
    return true
});

Answer 1

Assuming that CallService1, CallService2 and CallService3 are async methods, they should return a deferred promise. For example:

this.CallService1 = function() {
  // Once the result is available resolve the promise.
  return $http.post('/InstStrategy/ReadAll').then(function(response) {
    return true;
  });
}

Now, it's time to define your function:

$scope.MyFunction = function(callback) {
  var callService1 = service.CallService1(),
      callService2 = service.CallService2(),
      callService3 = service.CallService3();

  // We want to wait for all these three methods to complete.
  $q.all([callService1, callService2, callService3])
    .then(function(results)) {
          // Results is an array containing the results of each of your service calls.
          var allTrue = true;
          angular.forEach(results, function(result) {
            if (!result) allTrue = false;
          });

          // If all the service calls where true, perform our callback.
          if (allTrue) callback();
    });
};

Note that the allTrue check is not really necessary, since the promises are systematically resolved with true.