Total noob here. This is my first c# attempt, its a console application that simulates a drinking game called 'Left Right Center'. In the console I receive the following:
CONSOLE
Unhandled Exception: System.NullReferenceException: Object reference not set to an instance of an object
at LeftRightCenter.MainClass.Main (System.String[] args) [0x00038] in /Users/apple/Projects/LearningC/LearningC/Main.cs:80
[ERROR] FATAL UNHANDLED EXCEPTION: System.NullReferenceException: Object reference not set to an instance of an object
at LeftRightCenter.MainClass.Main (System.String[] args) [0x00038] in /Users/apple/Projects/LearningC/LearningC/Main.cs:80
C#
using System;
namespace LeftRightCenter
{
class Player
{
//fields
private int _quarters = 4;
public int Quarters {
get{ return _quarters; }
set{ _quarters += value; }
}
public Player (string name)
{
}
}
class Dice
{
Random random = new Random();
public int Roll ()
{
random = new Random ();
int diceSide;
diceSide = random.Next (0, 6);
diceSide = (diceSide > 2) ? 3 : diceSide;
return diceSide;
}
}
class MainClass
{
static int activePlayer = 0;
static int theCup = 0;
static Player[] thePlayers = {
new Player ("Jessica"),
new Player ("Isaac"),
new Player ("Ed"),
new Player ("Bella"),
new Player ("Elisa"),
new Player ("Fake RedHead"),
new Player ("Linda"),
new Player ("MJ"),
new Player ("Irene"),
new Player("Devin")
};
static Dice[] theDice = new Dice[2];
private static void MoveQuarter (int direction)
{
int numberOfPlayers = thePlayers.Length - 1;
switch (direction) {
case 0:
thePlayers [activePlayer].Quarters = -1;
theCup++;
break;
case 1:
thePlayers [activePlayer].Quarters = -1;
int leftPlayer = (activePlayer == 0) ? numberOfPlayers : activePlayer - 1;
thePlayers [leftPlayer].Quarters = +1;
break;
case 2:
thePlayers [activePlayer].Quarters = -1;
int rightPlayer = (activePlayer == numberOfPlayers) ? 0 : activePlayer + 1;
thePlayers [rightPlayer].Quarters = +1;
break;
}
}
public static void Main (string[] args)
{
int cupEndPoint = thePlayers.Length * 4 - 1;
while (theCup < cupEndPoint) {
foreach (Dice rattle in theDice) {
if (thePlayers [activePlayer].Quarters > 0) {
MoveQuarter (rattle.Roll ()); // this line seems to be the problem
}
}
Console.WriteLine ("{0} Quarters In the Cup", theCup);
}
}
}
}
I have no idea what the problem is or why, and my googling have proven more use confusing than helpful.
For those who are curious, I have little experiment working now
http://pastebin.com/jxCCW2cd
This line
static Dice[] theDice = new Dice[2];
declares an array that allows the storage of 2 objects of the Dice class, but each value in this array is still null.
You need to create a Dice on each slot of the array before using it in the foreach loop inside the Main method.
theDice[0] = new Dice();
theDice[1] = new Dice();
if you stop the debugger on the line
MoveQuarter (rattle.Roll ());
you will see that the rattle Dice is null.
EDIT: Looking at your code I have found a problematic situations
In the Roll method, you recreate the Random generator and this is no good for randomness. (See the accepted answer in this question)
Last, theDice array could be created and initialized in the same way you already do for thePlayers array
static Dice[] theDice = new Dice[2] {new Dice(), new Dice()};
This is a complete revision of your Dice class
class Dice
{
private static Random random;
public Dice()
{
// create the static random generator only on the first instance
if(random == null) random = new Random();
}
public int Roll ()
{
int diceSide;
diceSide = random.Next (1, 7);
diceSide = (diceSide > 2) ? 3 : diceSide;
return diceSide;
}
}
Related
I'm working on an assignment, where I have to make an application where you can throw 1-4 dice. The results are then added to a list.
However, if any of them is a 6, that one isn't added to the list, instead 2 additional dice are thrown.
As long as a die returns a 6, 2 more dice have to be thrown, until no die returns a 6.
Does anyone here know how to solve this? My programming skills are really basic, and I haven't used them much since last year.
for (int i = 0; i < qty; i++)
{
int diceNr = RollDice(random);
dicelist.Add(diceNr);
Console.WriteLine(diceNr);
if (diceNr == 6)
{
dicelist.Remove(diceNr);
Console.WriteLine("You got a six, that means you get 2 extra throws!");
for (int x = 0; x < 2; x++)
{
diceNr = RollDice(random);
dicelist.Add(diceNr);
}
You can try using a while loop as follows:
int i = quantity; #initialize a variable to your maximum number of throws
while(i > 0){ #until you have throws yet
i--; #this is the equivalent of one throw
int diceNr = RollDice(random);
dicelist.Add(diceNr);
Console.WriteLine(diceNr);
if(diceNr == 6){
Console.WriteLine("You got a six, that means you get 2 extra throws!");
i = i + 2; #add your bonus throws
}
}
You can use a while loop that exits once you are out of rolls. If you roll a six, add two more to the remaining quantity otherwise add the rolled value to the list.
int qty = 6;
// decrement remaining quantity each iteration
// until zero rolls remain
while(qty-- > 0)
{
int diceNr = RollDice(random);
Console.WriteLine(diceNr);
if (diceNr == 6)
{
// rolled six, add two more rolls
Console.WriteLine("You got a six, that means you get 2 extra throws!");
qty += 2;
}
else
{
// not six, add to list
dicelist.Add(diceNr);
}
}
// output all the non-six values
var allRolls = string.Join(",", diceList);
Console.WriteLine("All rolls: " + allRolls);
You could also do this with recursion (though I don't recommend it for this problem):
private static void Play(List<int> diceList, Random random, int rolls)
{
// base case, no rolls remain
if (rolls == 0)
return;
int diceNr = RollDice(random);
Console.WriteLine(diceNr);
if (diceNr == 6)
{
Console.WriteLine("You got a six, that means you get 2 extra throws!");
// add one to rolls since we are "reusing" this slot
// adding two would give us one more roll than we really want
rolls++
}
else
{
diceList.Add(diceNr);
// decrement rolls by one
rolls--;
}
// recursively call Play with updated roll count
// which is either original + 1 OR original - 1
Play(diceList, random, rolls);
}
private static int RollDice(Random r)
{
return r.Next(1, 7);
}
public static void Main()
{
var diceList = new List<int>();
var random = new Random();
int qty = 6;
Play(diceList, random, qty);
// output all the non-six values
var allRolls = string.Join(",", diceList);
Console.WriteLine("All rolls: " + allRolls);
}
My (readable) solution would look like:
class Program
{
static void Main(string[] args)
{
var game = new Game(4);
game.Play();
}
}
public class Game
{
private readonly int _noOfDices;
private readonly List<int> _result;
private readonly Random _random = new Random();
public Game(int noOfDices)
{
_noOfDices = noOfDices;
_result = new List<int>();
}
public void RollDice()
{
var no = _random.Next(1, 7);
if (no == 6)
{
RollDice();
RollDice();
}
else
{
_result.Add(no);
}
}
public void Play()
{
for (var i = 1; i <= _noOfDices; i++)
{
RollDice();
}
Console.WriteLine($"Output: {string.Join(',',_result)}");
}
}
Output:
I am trying to make a program that I Believe has to make use of recursion. In short: create a program that will throw a Dice. If it lands on a 6, two Dices are created and rolled, and so on until no more 6 are rolled.
The problem is not creating a new or true random object, but the recursive Dices.
The recursion method looks like this:
public static int Recursion(int a)
{
Random m = new Random();
if (a < 6)
{
return a;
}
else
{
a = m.Next(1, 7);
return Recursion(a) * 2;
}
}
Possibly something like this?
public static int Roll() {
return Roll(new Random(), 1);
}
public static int Roll(Random random, int diceCount) {
int sum = 0;
for (int dice = 1; dice <= diceCount; ++dice) {
int rolled = random.Next(1, 7);
if (rolled == 6) {
sum += Roll(random, 2)
}
else
{
sum += rolled;
}
}
return sum;
}
So, first I roll one die/dice. If it is not 6, then I accept its value as the result. If it is six, then I remove that die/dice, and replace it with two other I roll. Then, for each of the new ones I follow the same rule, until all the dice on the table is rolled and none of them is 6. Now I sum all the value of dice. This is what this recursive algorithm does. Note, that - however it has infinitely low chance - you can play this until the end of times, since there is always chance of rolling 6, so you can possibly roll only 6's until you die.
You can make it more object oriented by creating a dice object:
using System;
using System.Collections.Generic;
class Dices
{
public class Dice
{
private static Random roler = new Random();
private int roledNumber;
public int Role()
{
roledNumber = roler.Next(6) + 1 ;
return roledNumber;
}
public int Number
{
get { return roledNumber; }
}
}
static void Main(string[] args)
{
List<Dice> allDices = new List<Dice>();
Dice firstDice = new Dice();
allDices.Add(firstDice);
if (firstDice.Role() == 6) createDices(allDices);
}
static void createDices(List<Dice> dices)
{
Dice first = new Dice();
dices.Add(first);
if (first.Role() == 6) createDices(dices);
Dice second = new Dice();
dices.Add(second);
if (second.Role() == 6) createDices(dices);
}
}
I have an Gameobject that contains several prefabs, As in the picture below
public SimpleSpriteSequence birds;
Randomizer setBirds;
setBirds = new Randomizer(birds.sprites);
int index = setBirds.getRandom();
birds.setCurrentSpriteIndex(index);
In the image below we see the population of the array
Invoke("Interface", 1f);
Now with the help of the random I get a random bird from the array. But the problem is that the bird can be repeated. All I want is that at least 6 times in a row when the Invoke("Interface", 1f); function does not repeat the bird.So in principle I have to do so 6 times the bird does not repeat itself. To be a random of these birds but 6 times to be different birds. No I know if I explained it properly, but I hope you understand the idea.
Here is code but it is written in console application since i do not have your code and it is writen with custom class of Birds but you will adapt it to your code. If you need help with it i will help you.
class Birds
{
public int birdID;
public string birdName;
//public Sprite birdSprite;
}
class Program
{
static Random rnd = new Random();
static Birds[] birds = new Birds[10];
static int nBirdsSpawned = 0;
static List<int> spawnedBirds = new List<int>();
static void Main(string[] args)
{
//Database of my birds ;)
birds[0] = new Birds();
birds[1] = new Birds();
birds[2] = new Birds();
birds[3] = new Birds();
birds[4] = new Birds();
birds[5] = new Birds();
birds[6] = new Birds();
birds[7] = new Birds();
birds[8] = new Birds();
birds[9] = new Birds();
birds[0].birdID = 0;
birds[0].birdName = "Bird 1";
birds[1].birdID = 1;
birds[1].birdName = "Bird 2";
birds[2].birdID = 2;
birds[2].birdName = "Bird 3";
birds[3].birdID = 3;
birds[3].birdName = "Bird 4";
birds[4].birdID = 4;
birds[4].birdName = "Bird 5";
birds[5].birdID = 5;
birds[5].birdName = "Bird 6";
birds[6].birdID = 6;
birds[6].birdName = "Bird 7";
birds[7].birdID = 7;
birds[7].birdName = "Bird 8";
birds[8].birdID = 8;
birds[8].birdName = "Bird 9";
birds[9].birdID = 9;
birds[9].birdName = "Bird 10";
int i = 0;
while (i < 100)
{
RandomSpawn();
i++;
}
Console.Write("Finished");
Console.ReadKey();
}
static void CheckForBirdSpawn(int birdID)
{
if (nBirdsSpawned <= 6)
{
if (!spawnedBirds.Contains(birdID))
{
spawnedBirds.Add(birdID);
SpawnBird(birdID);
}
else
{
Console.WriteLine("Bird " + birds[birdID].birdName + " is already spawned!");
}
}
else
{
SpawnBird(birdID);
}
}
static void SpawnBird(int birdID)
{
Console.WriteLine(birds[birdID].birdName);
nBirdsSpawned++;
}
static void RandomSpawn()
{
int r = rnd.Next(0, 10);
CheckForBirdSpawn(r);
}
}
Until first 6 birds are spawned it check if bird is already spawned and if it is it doesn't allow it's spawning. After 6 birds are spawned it allows every bird to be spawned.
Here is output in console app:
I know this is a mainly code reply but how about you try something a little like this?
Populate a list of the bird indexes.
Pick a random index within that list.
Decrease all already spawned birds' Values.
If any reach zero, re-add the birds index into the availableBird list.
Spawn the bird, while adding it's index as Key and the amount of spawning delay needed until it can be spawned again as the Value.
Remove the birds index from the list.
Do the spawn whenever necessary, this will spawn every frame since it is found in a Coroutine which has an infinite while loop.
using UnityEngine;
using System.Collections;
using System.Collections.Generic;
public class burd : MonoBehaviour {
public bool spawning;
private System.Random rnd = new System.Random();
private Dictionary<int, int> spawnedBurdies = new Dictionary<int, int>();
private List<int> availableBurdies = new List<int>();
// Use this for initialization
void Start () {
for (int index = 0; index < 10; index++)
{
availableBurdies.Add(index);
}
StartCoroutine(SpawnBurdies());
}
private IEnumerator SpawnBurdies()
{
while (true)
{
if (spawning)
{
int burdIndex = rnd.Next(availableBurdies.Count);
spawnBurd(availableBurdies[burdIndex]);
availableBurdies.RemoveAt(burdIndex);
}
yield return new WaitForFixedUpdate();
}
}
private void spawnBurd(int burdIndex)
{
Debug.Log("Spawned burd #" + burdIndex);
List<int> burdieKeys = new List<int>();
foreach (var burdie in spawnedBurdies) { burdieKeys.Add(burdie.Key); }
foreach (var burdieKey in burdieKeys)
{
spawnedBurdies[burdieKey]--;
if(spawnedBurdies[burdieKey] <= 0)
{
spawnedBurdies.Remove(burdieKey);
availableBurdies.Add(burdieKey);
}
}
spawnedBurdies.Add(burdIndex, 6);
}
}
This solution would save you from attempting to spawn birds that can't be spawned; but if there are less birds than the minimum spawns to wait for, an Argument out of range error would be thrown.
I am having a bit of a problem figuring out how to randomly get an object out of a list that wasn't picked on the last update of a script. When this randomly instantiated object is spawned and reaches a certain y value, it will set itself to inactive. So when this object is not active, it will go through an array and pick another object at random. However, I do not want to include the previous active object.
example: blue ball was first active. Moves on the Y axis. Becomes inactive. Next object spawn should have no chance of being a blue ball. Any ideas and help will be greatly appreciated.
My code is below
using UnityEngine;
using System.Collections;
using System.Collections.Generic;
public class ballGeneratorShooter : MonoBehaviour
{
private int ballSelector;
private TagNumber theTagNumber;
public ObjectPooler[] theObjectballPools;//In my inspector, I have 5 prefab gameObjects attached
List<ObjectPooler> changingBalls;
public bool changeBalls;
public GameObject currentBall;
public GameObject newBall;
// Use this for initialization
void Start()
{
changingBalls = new List<ObjectPooler>();
currentBall = newBall;
}
// Update is called once per frame
void Update()
{
if (newBall == null)
{
ballSelector = Random.Range(0, theObjectballPools.Length);
newBall = theObjectballPools[ballSelector].GetPooledObject();
newBall.transform.position = transform.position;
newBall.transform.rotation = transform.rotation;
newBall.SetActive(true);
}
if (newBall.activeInHierarchy == false)
{
if (changeBalls)
{
for (int i = 0; i < theObjectballPools.Length; i++)
{
if (theObjectballPools[i].GetPooledObject().GetComponent<TagNumber>().tag != currentBall.GetComponent<TagNumber>().tag)
{
changingBalls.Add(theObjectballPools[i]);
}
//changingballs.Add(theObjectballPools[i]);
}
ballSelector = Random.Range(0, changingBalls.Count);
newBall = theObjectballPools[ballSelector].GetPooledObject();
Debug.Log(changingBalls.Count);
newBall.transform.position = transform.position;
newBall.transform.rotation = transform.rotation;
newBall.SetActive(true);
currentBall = newBall;
changeBalls = false;
changingBalls.Clear();
}
}
}
}
You need to store the random number to variable (lastRandomNum) each time you generate a random number. Now, use the function below that can generate a random number with exclusion.
int RandomWithExclusion(int min, int max, int exclusion)
{
var result = UnityEngine.Random.Range(min, max - 1);
return (result < exclusion) ? result : result + 1;
}
You pass in 0 to min, then theObjectballPools.Length or changingBalls.Count to the max, then finally, lastRandomNum value to the exclusion parameter.
You also need a boolean variable to determine if this is the first run. If this is the first run, use the Unity's Random.Range function then set the firstRun to false. If it is not the firstRun, use the RandomWithExclusion function from this answer and pass in the lastRandomNum value to exclude it. Also, store the generated random number to the lastRandomNum variable to be used next frame.
Below is a simplified version of what I said above. You have to incorporate that to your code.
GameObject[] yourItem = null;
bool firstRun = true;
int lastRandomNum = 0;
void Update()
{
if (firstRun)
{
firstRun = false;
//First run, use Random.Range
lastRandomNum = UnityEngine.Random.Range(0, yourItem.Length);
}
else
{
//Not First run, use RandomWithExclusion
lastRandomNum = RandomWithExclusion(0, yourItem.Length, lastRandomNum);
}
//Do something with the lastRandomNum value below
newBall = theObjectballPools[lastRandomNum].GetPooledObject();
}
int RandomWithExclusion(int min, int max, int exclusion)
{
var result = UnityEngine.Random.Range(min, max - 1);
return (result < exclusion) ? result : result + 1;
}
Try linq :
public class Ball
{
public static List<Ball> balls = new List<Ball>();
public int value { get; set; }
public Boolean active { get; set; }
public Ball() {}
public Ball(int size)
{
// initial class
Random rand = new Random();
for (int i = 0; i < size; i++)
{
balls.Add(new Ball(){ value = rand.Next(), active = false});
}
}
public Ball GetRandom()
{
Random rand = new Random();
Ball randomBall = balls.Where(x => x.active == false).Select((x) => new { value = x, randX = rand.Next() }).OrderBy(x => x.randX).FirstOrDefault().value;
randomBall.active = true;
return randomBall;
}
}
Hi I coded this OneAtRandom() extension method:
public static class GenericIListExtensions
{
public static T OneAtRandom<T>(this IList<T> list)
{
list.ThrowIfNull("list");
if (list.Count == 0)
throw new ArgumentException("OneAtRandom() cannot be called on 'list' with 0 elements");
int randomIdx = new Random().Next(list.Count);
return list[randomIdx];
}
}
Testing it using this unit test fails:
[Test]
public void ShouldNotAlwaysReturnTheSameValueIfOneAtRandomCalledOnListOfLengthTwo()
{
int SomeStatisticallyUnlikelyNumberOf = 100;
IList<string> list = new List<string>() { FirstString, SecondString };
bool firstStringFound = false;
bool secondStringFound = false;
SomeStatisticallyUnlikelyNumberOf.Times(() =>
{
string theString = list.OneAtRandom();
if (theString == FirstString) firstStringFound = true;
if (theString == SecondString) secondStringFound = true;
});
Assert.That(firstStringFound && secondStringFound);
}
It seems that int randomIdx = new Random().Next(list.Count);is generating the same number 100 times in a row, I think possibly because the seed is based on the time?
How can I get this to work properly?
Thanks :)
You shouldn't be calling new Random()for every iteration because it causes it to be reseeded and generate the same sequence of numbers again. Create one Random object at the start of your application and pass it into your function as a parameter.
public static class GenericIListExtensions
{
public static T OneAtRandom<T>(this IList<T> list, Random random)
{
list.ThrowIfNull("list");
if (list.Count == 0)
throw new ArgumentException("OneAtRandom() cannot be called on 'list' with 0 elements");
int randomIdx = random.Next(list.Count);
return list[randomIdx];
}
}
This also has the advantage of making your code more testable as you can pass in a Random that is seeded to a value of your choice so that your tests are repeatable.
No; it's generating the same number 100 times because you're not seeding the generator.
Move the "new Random()" to the constructor or a static var, and use the generated object.
You could use a seed based on the current time to create the instance of Random. A sample on MSDN uses the following code:
int randomInstancesToCreate = 4;
Random[] randomEngines = new Random[randomInstancesToCreate];
for (int ctr = 0; ctr < randomInstancesToCreate; ctr++)
{
randomEngines[ctr] = new Random(unchecked((int) (DateTime.Now.Ticks >> ctr)));
}