File-based save system in Unity - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Unity C# code saving a player's score?

Consider this Unity C# code that saves a player's score to a file and then reads it back. What will be printed in the console?

Unity

using System.IO;
using UnityEngine;

public class SaveLoadExample : MonoBehaviour
{
    void Start()
    {
        string path = Application.persistentDataPath + "/score.txt";
        File.WriteAllText(path, "150");
        string scoreText = File.ReadAllText(path);
        Debug.Log($"Score loaded: {scoreText}");
    }
}

A Score loaded: 150

B Score loaded: 0

C FileNotFoundException

D Score loaded: null

💡 Hint

Think about what File.WriteAllText and File.ReadAllText do.

The code writes the string "150" to the file, then reads it back and prints it. So the output is "Score loaded: 150".

🧠 Conceptual

intermediate

Which file path is best for saving game data in Unity?

In Unity, where should you save persistent game data to ensure it works on all platforms?

A Application.persistentDataPath

B Application.streamingAssetsPath

C Application.dataPath

D Application.temporaryCachePath

💡 Hint

Look for the path meant for permanent data storage.

Application.persistentDataPath is the recommended location for saving files that should persist between app sessions on all platforms.

🔧 Debug

advanced

Why does this Unity save code throw an exception?

Look at this code snippet that tries to save player data. Why does it throw an exception?

Unity

using System.IO;
using UnityEngine;

public class SaveDebug : MonoBehaviour
{
    void SaveScore(int score)
    {
        string path = Application.persistentDataPath + "/save.txt";
        FileStream fs = new FileStream(path, FileMode.Open);
        StreamWriter writer = new StreamWriter(fs);
        writer.Write(score);
        writer.Close();
        fs.Close();
    }
}

A FileStream needs FileAccess.ReadWrite specified

B StreamWriter.Write cannot write integers

C Application.persistentDataPath is read-only

D FileMode.Open throws exception if file does not exist

💡 Hint

Check what happens if the file is missing when opening with FileMode.Open.

FileMode.Open requires the file to exist. If it doesn't, an exception is thrown. Use FileMode.Create or FileMode.OpenOrCreate to avoid this.

📝 Syntax

advanced

Which option correctly serializes and saves a PlayerData object to JSON in Unity?

Given a PlayerData class, which code snippet correctly saves it as JSON to a file?

Unity

public class PlayerData
{
    public int level;
    public float health;
}

A

string json = JsonUtility.FromJson(playerData);
File.WriteAllText(path, json);

B

string json = JsonUtility.ToJson(playerData);
File.ReadAllText(path, json);

C

string json = JsonUtility.ToJson(playerData);
File.WriteAllText(path, json);

D

string json = JsonUtility.ToString(playerData);
File.WriteAllText(path, json);

💡 Hint

Remember the method to convert an object to JSON is ToJson.

JsonUtility.ToJson converts an object to a JSON string. Then File.WriteAllText saves it to a file. Other options misuse methods or use wrong functions.

🚀 Application

expert

How many files are created after running this Unity save system code?

This code saves multiple player profiles to separate files. How many files will be created after running it?

Unity

using System.IO;
using UnityEngine;

public class MultiSave : MonoBehaviour
{
    void SaveProfiles()
    {
        for (int i = 0; i < 3; i++)
        {
            string path = Application.persistentDataPath + $"/player_{i}.json";
            string json = JsonUtility.ToJson(new PlayerData { level = i, health = 100f });
            File.WriteAllText(path, json);
        }
    }
}

public class PlayerData
{
    public int level;
    public float health;
}

A 1

B 3

C 0

D 4

💡 Hint

Count how many times File.WriteAllText is called with different file names.

The loop runs 3 times, each time creating a file named player_0.json, player_1.json, and player_2.json. So 3 files are created.