Boo: Object reference not set to an instance of an object

Questions & Answers
1

Hey Guys, I tried to use multidimensional arrays in boo and it just threw this error:

NullReferenceException: Object reference not set to an instance of an object
    GameScript.buildGrid () (at Assets/Scripts/GameScript.boo:28)
    GameScript.OnGUI () (at Assets/Scripts/GameScript.boo:40)

Here’s my Code:

import UnityEngine

public class Card (System.Object):
	isFaceUp as bool  = false
	isMatched as bool = false
	public img = "robot"


class GameScript (MonoBehaviour):
	cols as int = 4
	rows as int = 4
	totalCards as int = cols * rows
	matchesNeededToWin as int = totalCards * 0.5
	mathesMade as int = 0
	cardW as int = 100
	cardH as int = 100
	aCards as List
	aGrid as (Card, 2)
	aCardsFlipped as List
	playerCanClick as bool
	playerHasWon as bool = false
	
	def buildGrid():
		GUILayout.BeginVertical()
		for i in range(rows):
			GUILayout.BeginHorizontal()
			for j in range(cols):
				card = aGrid[i,j]
				if (GUILayout.Button(Resources.Load(card.img), GUILayout.Width(cardW))):
					Debug.Log(card.img)
					
	def Start ():
		playerCanClick = true
		for i in range(rows):
			for j in range(cols):
				aGrid[i,j] = Card()
	
	def OnGUI ():
		GUILayout.BeginArea (Rect (0,0,Screen.width,Screen.height))
		//buildGrid()
		GUILayout.EndArea()

Thanks in advance!

2

You made the size of 2 for aGrid of type Card.

aGrid as (Card, 2)

Your rows and cols are 4 each.

 cols as int = 4
 rows as int = 4

The for loop is using range(4) for both rows and cols.

for i in range(rows):
  GUILayout.BeginHorizontal()
    for j in range(cols):
      card = aGrid[i,j]

aGrid doesn’t have the range you’re looking for.

disclaimer: haven’t touched boo in years.