C#: How do you make a 2D game object jump?

Questions & Answers
1

I looked up a tutorial on youtube, and got this code from it:

using System.Collections;
using UnityEngine;

public class JumpScript : MonoBehaviour {

public float jumpHeight;
public bool isJumping = false;

void Start () {
	
}

// Update is called once per frame
void Update () {

	if(Input.GetKeyDown (KeyCode.Space)){ 

		if(isJumping == false)
		{
		Rigidbody2D.AddForce(Vector2.up * jumpHeight);
			isJumping = true;
		}

		}

		void OnCollisionEnter2D(Collision col)* †

	if(col.GameObject.tag == "ground")
	{
			IsJumping = false;
	}
}

}††
However, it keeps giving me errors. Does anyone know what to do?
List of errors:
*"Keyword ‘void’ cannot be used in this context
†“Unexpected symbol (', expecting ,‘, ;', or =’”
††Unexpected symbol `}’

2

you have a method (OnCollisionEnter2D) within the body of another method (Update), and a few other typos.

Here :

public class JumpScript : MonoBehaviour
{
    public float jumpHeight;
    private bool isJumping = false; // this doesn't need to be public
    private RigidBody2D _rigidBody2D;

    private void Awake ()
    {
        _rigidBody2D = GetComponent<RigidBody2D>();
    }
    private void Update ()
    {
        if (Input.GetKeyDown (KeyCode.Space) && !isJumping) // both conditions can be in the same branch
        { 
            _rigidBody2D.AddForce(Vector2.up * jumpHeight); // you need a reference to the RigidBody2D component
            isJumping = true;
         }
     }

    private void OnCollisionEnter2D (Collision col)
    {
        if (col.gameObject.tag == "ground") // GameObject is a type, gameObject is the property
        {
            isJumping = false;
        }
    }
 }
3

Just looking at it there, maybe this is your problem

         void OnCollisionEnter2D(Collision col) {
     if(col.GameObject.tag == "ground")
     {
             IsJumping = false;
     }
 }

instead of

         void OnCollisionEnter2D(Collision col)* †
     if(col.GameObject.tag == "ground")
     {
             IsJumping = false;
     }
 }
4

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class fghfgdf : MonoBehaviour
{
public GameObject platform;
public Rigidbody2D rb;

public bool isJumping = false;

public float jumpPower;
void Start()
{
    
}

// Update is called once per frame
void Update()
{
    if (Input.GetKeyDown (KeyCode.Space))
    {
        if (isJumping == false)
        {
            rb.AddForce(Vector2.up * jumpPower);
            isJumping = true;
        }
    }
}

void OnCollisionEnter2D(Collision2D col)
{
    if (platform.tag == "ground")
    {
        isJumping = false;
    }
}

},using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Jump : MonoBehaviour
{
public GameObject platform;
public Rigidbody2D rb;

public bool isJumping = false;

public float jumpPower;
void Start()
{
    
}

// Update is called once per frame
void Update()
{
    if (Input.GetKeyDown (KeyCode.Space))
    {
        if (isJumping == false)
        {
            rb.AddForce(Vector2.up * jumpPower);
            isJumping = true;
        }
    }
}

void OnCollisionEnter2D(Collision2D col)
{
    if (platform.tag == "ground")
    {
        isJumping = false;
    }
}

}