I want to create instance of a class not constructor in c#

Question

I need to call and instance of the class ControlledTank to access the GetPlayer method which I will complete later. However, when I try to create an instance it's using the constructor not the class.

public class ControlledTank
{
 private float Tangle;
 public ControlledTank(Player player, int tankX, int tankY, Game game)
 {
 Tangle = 0;
 //throw new NotImplementedException();
 }
 public Player GetPlayer()
 {
 throw new NotImplementedException();
 }
}

I don't have the values to parse into the constructor either so I just get errors.

The result I get

• rbm: add empty constructor? make the GetPlayer static?
• Pseudorandom: try create constructor with empty parameter. like this public ControlledTank() { }
• David: "it's using the constructor not the class" - What does that even mean? What were you expecting to happen? Why? A constructor is used to construct an instance of a class. Your constructor expects parameters. You are not supplying those parameters. Hence the error.
• MakePeaceGreatAgain: How do you expect to create an instance of a class when you don´t have the information needed to do so? That is you do not invoke the constructor and provide the parameters. When calling a constructor - and this is what you have to do in order to create an instance - needs some parameters you have to provide those unless there is another parameterless constructor.
• Igor: Learning to program by trial and error is no way to go about it. Constructors and constructor overloads is something you learn in the very beginning of almost any language (that supports it) and is considered fundamental / basic knowledge. Pick up a book or follow some tutorials but do not try to learn the basics by trial/error, that is just a recipe for frustration for you and everyone else involved.

Answer 1

Your constructor expects 4 parameters:

public ControlledTank(Player player, int tankX, int tankY, Game game)
{
 //...
}

You're passing it 0 parameters:

new ControlledTank()

Hence the error. So you have two options. Either pass the parameters needed by the constructor, or also add a constructor with the parameters (or lack thereof) which you need. For example:

public ControlledTank()
{
 Tangle = 0;
}

Note: A class can have multiple constructors. A class can also have a default constructor with 0 parameters (and no internal logic), but only if no other constructor is specified.

Answer 2

The error is right in front of you, you can't pass no parameters to constructor that must have parameters. Here is your options, you can decide what you want according to task in front of you:

Add default constructor:

public ControlledTank(){}

or make your constructor parameters with default values:

public ControlledTank(Player player = null, int tankX = 0, int tankY = 0, Game game = null){}

"it's using the constructor not the class" makes no sense. If you want to call constructor when you are accessing class by putting . operator after class name, you need to have static constructor (they are always parameterless):

static ControlledTank() {}

But it's useful, when you are want to initialize some static fields in it.

• Zohar Peled: Adding a parameter-less constructor might not be a good advice. Some of the parameters passed in the already existing constructor might be mandatory (I would guess that a ControlledTank can't be created outside of a game, so creating one without passing the game to it might not be the correct way to handle this situation).
• SᴇM: I understand that, I just want to give him an idea, what options do he have, so he can, according to his task, make his code working.

Answer 3

A constructor expects parameters to construct the class, and you're not providing parameters.

To fix this, you just need an empty default constructor:

public ControlledTank(){}

Answer 4

You need to write an empty constructor as well if you need to use it like this. The constructor is used to build the instance of the class:

public ControlledTank()
{
 Tangle = 0;
 player = new Player();
 tankX = 0;
 tankY = 0;
 game = new Game();
}