Debug.Log for debugging in Unity - Mini Project: Build & Apply

Debug.Log for debugging

📖 Scenario: You are creating a simple Unity script to track the player's score during a game. You want to see the score updates in the Unity Console to make sure your code works correctly.

🎯 Goal: Build a Unity C# script that uses Debug.Log to print the player's score updates to the Console for easy debugging.

📋 What You'll Learn

Create an integer variable called score and set it to 0

Create an integer variable called pointsToAdd and set it to 10

Add pointsToAdd to score

Use Debug.Log to print the message "Score updated: " followed by the current score

💡 Why This Matters

🌍 Real World

Game developers use Debug.Log to check values and program flow while building games in Unity.

💼 Career

Knowing how to debug with Debug.Log is a basic but essential skill for Unity developers to find and fix issues quickly.

1

Create the initial score variable

Create an integer variable called score and set it to 0 inside the Start() method.

Unity

using UnityEngine;

public class ScoreTracker : MonoBehaviour
{
    void Start()
    {
        // Create an integer variable called score and set it to 0
        
    }
}

Hint

Use int score = 0; inside the Start() method.

2

Add points to add variable

Inside the Start() method, create an integer variable called pointsToAdd and set it to 10.

Unity

using UnityEngine;

public class ScoreTracker : MonoBehaviour
{
    void Start()
    {
        int score = 0;
        // Create an integer variable called pointsToAdd and set it to 10
        
    }
}

Hint

Use int pointsToAdd = 10; inside the Start() method.

3

Add points to the score

Inside the Start() method, add pointsToAdd to score using the += operator.

Unity

using UnityEngine;

public class ScoreTracker : MonoBehaviour
{
    void Start()
    {
        int score = 0;
        int pointsToAdd = 10;
        // Add pointsToAdd to score
        
    }
}

Hint

Use score += pointsToAdd; to add points.

4

Print the updated score with Debug.Log

Use Debug.Log inside the Start() method to print the message "Score updated: " followed by the current score.

Unity

using UnityEngine;

public class ScoreTracker : MonoBehaviour
{
    void Start()
    {
        int score = 0;
        int pointsToAdd = 10;
        score += pointsToAdd;
        // Use Debug.Log to print "Score updated: " plus the score
        
    }
}

Hint

Use Debug.Log("Score updated: " + score); to print the message.

Practice

1. What is the main purpose of Debug.Log in Unity?

easy

A. To create new game objects

B. To save game data to a file

C. To change the color of objects

D. To print messages to the Console for debugging

Solution

1. Step 1: Understand Debug.Log function

   Debug.Log is used to print messages to the Unity Console, helping developers see what is happening in the game.

2. Step 2: Identify the purpose from options

   Only To print messages to the Console for debugging describes printing messages for debugging, which matches Debug.Log's purpose.

3. Final Answer:

   To print messages to the Console for debugging -> Option D

4. Quick Check:

   Debug.Log prints messages = B [OK]

Hint: Debug.Log shows messages in Console to check game status [OK]

Common Mistakes:

• Thinking Debug.Log creates or changes objects
• Confusing Debug.Log with saving or loading data
• Assuming Debug.Log changes game visuals

2. Which of the following is the correct way to print the message "Hello World" using Debug.Log in Unity?

easy

A. Debug.Log(Hello World);

B. Debug.Log("Hello World");

C. Debug.Log['Hello World'];

D. Debug.Log{Hello World};

Solution

1. Step 1: Check correct syntax for Debug.Log

   Debug.Log requires a string inside parentheses and double quotes for text, like Debug.Log("text").

2. Step 2: Identify correct option

   Debug.Log("Hello World"); uses parentheses and double quotes correctly. Other options have wrong syntax like missing quotes or wrong brackets.

3. Final Answer:

   Debug.Log("Hello World"); -> Option B

4. Quick Check:

   Correct syntax uses parentheses and quotes = D [OK]

Hint: Use parentheses and double quotes for strings in Debug.Log [OK]

Common Mistakes:

• Forgetting quotes around text
• Using square or curly brackets instead of parentheses
• Missing semicolon at the end

3. What will be printed in the Console when this code runs?

int score = 10;
Debug.Log("Score: " + score);

medium

A. Score: 10

B. Score: score

C. 10

D. Score + score

Solution

1. Step 1: Understand string concatenation in Debug.Log

   The code combines the string "Score: " with the integer variable score using +, which converts the number to text.

2. Step 2: Determine the output message

   The output will be the text "Score: " followed by the value 10, so the Console shows "Score: 10".

3. Final Answer:

   Score: 10 -> Option A

4. Quick Check:

   String + int converts int to string = A [OK]

Hint: Adding string + number prints combined text in Console [OK]

Common Mistakes:

• Expecting variable name printed instead of value
• Forgetting + operator for concatenation
• Confusing output with just number or variable name

4. What is wrong with this code snippet?

int score = 10;
Debug.Log("Player score is: " + score)

medium

A. Debug.Log cannot print variables

B. score variable is not declared

C. Missing semicolon at the end

D. Quotes are missing around the string

Solution

1. Step 1: Check syntax of Debug.Log statement

   The statement is missing a semicolon at the end, which is required in C#.

2. Step 2: Verify other parts

   The string has quotes, score variable is declared above, and Debug.Log can print variables. The syntax error is the missing semicolon.

3. Final Answer:

   Missing semicolon at the end -> Option C

4. Quick Check:

   Statements need semicolon ; at end = A [OK]

Hint: Always end Debug.Log lines with a semicolon ; [OK]

Common Mistakes:

• Ignoring missing semicolon errors
• Assuming Debug.Log can't print variables
• Confusing string quotes with missing quotes

5. You want to debug a player's health value inside the Update() method. Which code correctly prints the health variable every frame?

hard

A. void Update() { Debug.Log(health); }

B. void Update() { Debug.Log("health"); }

C. void Update() { Debug.Log(health + health); }

D. void Update() { Debug.Log(health); Debug.Log(); }

Solution

1. Step 1: Understand how to print variable value

   To print the value of health, pass it directly to Debug.Log. void Update() { Debug.Log(health); } does this correctly.

2. Step 2: Check other options for correctness

   void Update() { Debug.Log("health"); } prints the word "health" literally, not the variable value. void Update() { Debug.Log(health + health); } incorrectly adds health to itself (doubling the numeric value). void Update() { Debug.Log(health); Debug.Log(); } calls Debug.Log() without arguments, causing error.

3. Final Answer:

   void Update() { Debug.Log(health); } -> Option A

4. Quick Check:

   Pass variable directly to Debug.Log to print value = C [OK]

Hint: Pass variable directly to Debug.Log to see its value [OK]

Common Mistakes:

• Printing variable name as string instead of value
• Calling Debug.Log without arguments
• Unnecessary string concatenation