Input action maps in Unity - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output when reading a button press?

Consider this Unity C# code snippet using the new Input System. What will be printed when the button is pressed?

Unity

using UnityEngine;
using UnityEngine.InputSystem;

public class TestInput : MonoBehaviour
{
    public InputAction action;

    void OnEnable()
    {
        action.Enable();
        action.performed += ctx => Debug.Log("Button pressed");
    }

    void OnDisable()
    {
        action.Disable();
    }
}

A Button pressed is printed continuously every frame

B An error occurs because action is not initialized

C Nothing is printed unless the action is enabled and the button is pressed

D Button pressed is printed once when the script starts

💡 Hint

Think about when the performed event triggers and what enabling the action does.

The performed callback runs only when the input action is triggered (button pressed). The action must be enabled to listen for input. So nothing prints until the button is pressed while enabled.

🧠 Conceptual

intermediate

Which InputAction type is best for continuous movement?

In Unity's Input System, which InputAction type should you use to get smooth, continuous movement input like from a joystick or WASD keys?

A Value

B Button

C PassThrough

D Toggle

💡 Hint

Continuous movement needs a value that changes over time, not just a press or release.

The Value type action returns a continuous value (like a Vector2) representing joystick or keyboard axis input, perfect for smooth movement.

🔧 Debug

advanced

Why does this InputAction not trigger?

Given this code, why does the performed callback never run?

Unity

public class PlayerInput : MonoBehaviour
{
    public InputAction jumpAction;

    void Start()
    {
        jumpAction.performed += ctx => Debug.Log("Jump!");
    }

    void OnEnable()
    {
        // jumpAction.Enable();
    }

    void OnDisable()
    {
        jumpAction.Disable();
    }
}

A The jumpAction variable is null and causes a NullReferenceException

B The callback is added too late in Start(), it should be in Awake()

C The performed event only triggers on release, not press

D The action is never enabled, so it does not listen for input

💡 Hint

Check if the action is enabled anywhere.

The action must be enabled to listen for input. Since jumpAction.Enable() is commented out, the action never listens and the callback never runs.

📝 Syntax

advanced

Identify the syntax error in this InputAction callback setup

Which option contains the correct syntax to subscribe to an InputAction's performed event?

Unity

InputAction action = new InputAction();

A action.performed = ctx => Debug.Log("Action performed");

B action.performed += (InputAction.CallbackContext context) => { Debug.Log("Action performed"); };

C action.performed += context => Debug.Log("Action performed");

D action.performed += delegate { Debug.Log("Action performed"); };

💡 Hint

Remember how to add event handlers in C# with lambda or delegate syntax.

Option B uses the correct lambda syntax with explicit parameter type and braces. Option B tries to assign instead of add. Option B uses delegate without parameters, which is invalid for this event.

🚀 Application

expert

How to read a Vector2 from an InputAction and use it for movement?

You have an InputAction named moveAction set to type Value with a Vector2 binding. How do you read its value inside Update() to move a character?

Unity

public class PlayerController : MonoBehaviour
{
    public InputAction moveAction;
    public float speed = 5f;

    void OnEnable() => moveAction.Enable();
    void OnDisable() => moveAction.Disable();

    void Update()
    {
        // Fill in the code here
    }
}

A

Vector2 input = moveAction.ReadValue<Vector2>();
transform.Translate(input * speed * Time.deltaTime);

B

Vector2 input = moveAction.Read<Vector2>();
transform.position += input * speed;

C

Vector2 input = moveAction.value<Vector2>();
transform.Translate(input * speed);

D

Vector2 input = moveAction.Get<Vector2>();
transform.position += input * speed * Time.deltaTime;

💡 Hint

Look for the correct method to read the current value of an InputAction.

The method ReadValue<T>() reads the current value of the InputAction. Then multiplying by speed and deltaTime moves the character smoothly.