Can someone else fix my problem? Please

My dearest friends,

Please I am facing the System.NullReferenceException in Program.cs. It says that "EventManager.NoArgumentInvoker.get returned null" how should I suppose to do? Please, can someone can else fix my exception. Any help will be very very appreciated. Please fix my error.

This is the code of Program.cs:

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using UnityEngine;
namespace ProgrammingAssignment3
{
///
/// Programming Assignment 3
///
class Program
{
// test case to run
static int testCaseNumber;
// debug log messages
static List<string> logMessages = new List<string>();
///
/// Tests the Programming Assignment 3 classes
///
/// command-line args
static void Main(string[] args)
{
// listen for Unity debug log events
UnityEngine.Debug.LogEvent.AddListener(HandleLogEvent);
// create Invoker and Listener
Invoker invoker = new Invoker();
Listener listener = new Listener();
// Awake is always called before Start
invoker.Awake();
// loop while there's more input
string input = Console.ReadLine();
while (input[0] != 'q')
{
// extract test case number from string
GetInputValueFromString(input);
// execute selected test case
switch (testCaseNumber)
{
case 1:
// invoker added to event manager first for no argument event
InitializeTestCase(invoker, listener);
EventManager.NoArgumentInvoker.InvokeNoArgumentEvent();
if (logMessages[0] == "MessageEvent" &&
logMessages.Count == 1)
{
Console.WriteLine("Passed");
}
else
{
Console.WriteLine("FAILED");
}
break;
case 2:
logMessages.Clear();
EventManager.ClearInvokersAndListeners();
// listener added to event manager first for no argument event
listener.Start();
invoker.Start();
EventManager.NoArgumentInvoker.InvokeNoArgumentEvent();
if (logMessages[0] == "MessageEvent" &&
logMessages.Count == 1)
{
Console.WriteLine("Passed");
}
else
{
Console.WriteLine("FAILED");
}
break;
case 3:
// invoker added to event manager first for one argument event
InitializeTestCase(invoker, listener);
EventManager.IntArgumentInvoker.InvokeOneArgumentEvent(-1);
if (logMessages[0] == "CountMessageEvent: -1" &&
logMessages.Count == 1)
{
Console.WriteLine("Passed");
}
else
{
Console.WriteLine("FAILED");
}
break;
case 4:
logMessages.Clear();
EventManager.ClearInvokersAndListeners();
// listener added to event manager first for one argument event
listener.Start();
invoker.Start();
EventManager.IntArgumentInvoker.InvokeOneArgumentEvent(-1);
if (logMessages[0] == "CountMessageEvent: -1" &&
logMessages.Count == 1)
{
Console.WriteLine("Passed");
}
else
{
Console.WriteLine("FAILED");
}
break;
case 5:
InitializeTestCase(invoker, listener);
// invoke no argument event directly through invoker
invoker.InvokeNoArgumentEvent();
if (logMessages[0] == "MessageEvent" &&
logMessages.Count == 1)
{
Console.WriteLine("Passed");
}
else
{
Console.WriteLine("FAILED");
}
break;
case 6:
InitializeTestCase(invoker, listener);
// invoke one argument event directly through invoker
invoker.InvokeOneArgumentEvent(-1);
if (logMessages[0] == "CountMessageEvent: -1" &&
logMessages.Count == 1)
{
Console.WriteLine("Passed");
}
else
{
Console.WriteLine("FAILED");
}
break;
case 7:
InitializeTestCase(invoker, listener);
// invoke multiple no argument events directly through invoker
invoker.InvokeNoArgumentEvent();
invoker.InvokeNoArgumentEvent();
invoker.InvokeNoArgumentEvent();
if (logMessages[0] == "MessageEvent" &&
logMessages[1] == "MessageEvent" &&
logMessages[2] == "MessageEvent" &&
logMessages.Count == 3)
{
Console.WriteLine("Passed");
}
else
{
Console.WriteLine("FAILED");
}
break;
case 8:
InitializeTestCase(invoker, listener);
// invoke multiple one argument events directly through invoker
invoker.InvokeOneArgumentEvent(1);
invoker.InvokeOneArgumentEvent(2);
invoker.InvokeOneArgumentEvent(3);
if (logMessages[0] == "CountMessageEvent: 1" &&
logMessages[1] == "CountMessageEvent: 2" &&
logMessages[2] == "CountMessageEvent: 3" &&
logMessages.Count == 3)
{
Console.WriteLine("Passed");
}
else
{
Console.WriteLine("FAILED");
}
break;
case 9:
InitializeTestCase(invoker, listener);
// invoke combination of events directly through invoker
invoker.InvokeOneArgumentEvent(1);
invoker.InvokeNoArgumentEvent();
invoker.InvokeOneArgumentEvent(3);
if (logMessages[0] == "CountMessageEvent: 1" &&
logMessages[1] == "MessageEvent" &&
logMessages[2] == "CountMessageEvent: 3" &&
logMessages.Count == 3)
{
Console.WriteLine("Passed");
}
else
{
Console.WriteLine("FAILED");
}
break;
case 10:
InitializeTestCase(invoker, listener);
// invoke multiple one argument events directly through invoker
invoker.InvokeNoArgumentEvent();
invoker.InvokeOneArgumentEvent(2);
invoker.InvokeNoArgumentEvent();
if (logMessages[0] == "MessageEvent" &&
logMessages[1] == "CountMessageEvent: 2" &&
logMessages[2] == "MessageEvent" &&
logMessages.Count == 3)
{
Console.WriteLine("Passed");
}
else
{
Console.WriteLine("FAILED");
}
break;
}
input = Console.ReadLine();
}
}
///
/// Extracts the test case number from the given input string
///
/// input string
static void GetInputValueFromString(string input)
{
testCaseNumber = int.Parse(input);
}
///
/// Handles the log event from the Debug mock
///
/// message to log
static void HandleLogEvent(string message)
{
logMessages.Add(message);
}
///
/// Initializes test case
///
static void InitializeTestCase(Invoker invoker, Listener listener)
{
logMessages.Clear();
EventManager.ClearInvokersAndListeners();
invoker.Start();
listener.Start();
}
}
}

This is the CountMessageEvent.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using UnityEngine.Events;
namespace ProgrammingAssignment3
{
public class CountMessageEvent : UnityEvent <int>
{
}
}

This is the listener.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
///
/// An event listener
///
public class Listener : MonoBehaviour
{
///
/// Use this for initialization
///
public void Start()
{
// add your code here
Invoker invoker = new Invoker();
invoker.AddNoArgumentListener(HandleMessageEvent);
invoker.AddOneArgumentListener(HandleCountMessageEvent);
}
///
/// Handles the no argument event
///
void HandleMessageEvent()
{
print("MessageEvent");
}
///
/// Handles the one argument event
///
/// number
void HandleCountMessageEvent(int number)
{
print("CountMessageEvent: " + number);
}
}

This is the Invoker.cs

using ProgrammingAssignment3;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.Events;
///
/// An event invoker
///
public class Invoker : MonoBehaviour
{
// add your fields for your message event support here
Timer MessageTimer;
MessageEvent messageEvent;
// add your fields for your count message event support here
int count;
Timer CountMessageTimer;
CountMessageEvent countMessageEvent = new CountMessageEvent();
///
/// Awake is called before Start
///
public void Awake()
{
// add your code here
messageEvent = new MessageEvent();
}
///
/// Use this for initialization
///
public void Start()
{
// add your code here
MessageTimer = gameObject.AddComponent();
MessageTimer.Duration = 1;
MessageTimer.Run();
}
///
/// Update is called once per frame
///
void Update()
{
// add your code here
if (MessageTimer.Finished)
{
messageEvent.Invoke();
MessageTimer.Run();
}
}
///
/// Adds the given listener to the no argument event
///
/// listener
public void AddNoArgumentListener(UnityAction listener)
{
// add your code here to add the given listener for
// the message event
//MessageEvent messageEvent = new MessageEvent();
messageEvent = new MessageEvent();
messageEvent.AddListener(listener);
}
///
/// Adds the given listener to the one argument event
///
/// listener
public void AddOneArgumentListener(UnityAction<int> listener)
{
// add your code here to add the given listener for
// the count message event
countMessageEvent.AddListener(listener);
}
///
/// Removes the given listener to the no argument event
///
/// listener
public void RemoveNoArgumentListener(UnityAction listener)
{
// add your code here to remove the given listener from the
// message event
messageEvent.RemoveListener(listener);
}
///
/// Removes the given listener to the one argument event
///
/// listener
public void RemoveOneArgumentListener(UnityAction<int> listener)
{
// add your code here to remove the given listener from the
// count message event
countMessageEvent.RemoveListener(listener);
}
///
/// Invokes the no argument event
///
/// NOTE: We need this public method for the autograder to work
///
public void InvokeNoArgumentEvent()
{
// add your code here to invoke the message event
messageEvent.Invoke();
}
///
/// Invokes the one argument event
///
/// NOTE: We need this public method for the autograder to work
///
/// argument to use for the Invoke
public void InvokeOneArgumentEvent(int argument)
{
// add your code here to invoke the count message event
// with the given argument
countMessageEvent.Invoke(argument);
}
}

This is the EventManager.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.Events;
///
/// The event manager
///
public static class EventManager
{
// DON'T change the fields, properties, or ClearInvokersAndListeners
// method; if you do, you'll break the autograder!
// All your work in this class is in the last 4 methods
#region Fields
// no argument event support
static Invoker noArgumentInvoker;
static UnityAction noArgumentListener;
// int argument event support
static Invoker intArgumentInvoker;
static UnityAction<int> intArgumentListener;
#endregion
#region Properties (for autograder use only)
///
/// Gets the no argument invoker
///
public static Invoker NoArgumentInvoker
{
get { return noArgumentInvoker; }
}
///
/// Gets the no argument listener
///
public static UnityAction NoArgumentListener
{
get { return noArgumentListener; }
}
///
/// Gets the int argument invoker
///
public static Invoker IntArgumentInvoker
{
get { return intArgumentInvoker; }
}
///
/// Gets the int argument listener
///
public static UnityAction<int> IntArgumentListener
{
get { return intArgumentListener; }
}
#endregion
#region Public methods
///
/// Clears all the invokers and listeners from the event manager.
///
/// Note: We need this functionality so the autograder can start with
/// a "clean" event manager at the start of each test case
///
public static void ClearInvokersAndListeners()
{
// no argument invoker and listener
if (noArgumentInvoker != null)
{
if (noArgumentListener != null)
{
noArgumentInvoker.RemoveNoArgumentListener(noArgumentListener);
noArgumentListener = null;
}
noArgumentInvoker = null;
}
// int argument invoker and listener
if (intArgumentInvoker != null)
{
if (intArgumentListener != null)
{
intArgumentInvoker.RemoveOneArgumentListener(intArgumentListener);
intArgumentListener = null;
}
intArgumentInvoker = null;
}
}
///
/// Adds the invoker for the no argument event
///
/// invoker
public static void AddNoArgumentInvoker(Invoker invoker)
{
// add your code here
noArgumentInvoker = invoker;
}
///
/// Adds the listener for the no argument event
///
/// listener
public static void AddNoArgumentListener(UnityAction listener)
{
// add your code here
listener= noArgumentListener;
}
///
/// Adds the invoker for the int argument event
///
/// invoker
public static void AddIntArgumentInvoker(Invoker invoker)
{
// add your code here
invoker= intArgumentInvoker;
}
///
/// Adds the listener for the int argument event
///
/// listener
public static void AddIntArgumentListener(UnityAction<int> listener)
{
// add your code here
intArgumentListener = listener;
}
#endregion
}

This is the code of MessageEvent.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using UnityEngine.Events;
namespace ProgrammingAssignment3
{
public class MessageEvent : UnityEvent
{
}
}

After implementing that, I faced this exception...

Please fix my error hurry. My work will be dued in Aug 3. Please help and fix my error and I will appreciate for your fix...

I also uploaded the zip file to see my full code...

6 Replies

Know the answer? Post it — somebody with the same question will find it here.

Koustubh W6y ago
Hey! Did you pass the test?? I'm taking the same course and I'm struggling to find the answer to this assignment! Could you please let me see your scripts? Thank You!!
+1
Ashutosh Gupta6y ago
it seems you are missing call of Eventmanager.AddNoArgumentListener to register listener.
+3
Salman Beg6y ago
EventManager.NoArgumentInvoker.InvokeNoArgumentEvent(); this methods null and you can check by putting debugger. Thanks.
+3
Kaung Htet Kyaw6y ago
Oh I forgot. This is the Unity Game coding.
+4
Kaung Htet Kyaw6y ago
Yes. Salman. But I want to know where is this happening... Can you explain me, please?
+4
Salman Beg6y ago
Hi.
The error is saying, Object reference not set to an instance of an object which means in that particular line it is getting null value and you need to check by debugging why it is getting null.
Check this link it may help you,

https://www.youtube.com/watch?v=GwtevbSLuXQ

Thanks.
+3