Save slot management in Unity - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this save slot check?

Consider this Unity C# code snippet that checks if a save slot is empty or not. What will be printed to the console?

Unity

string slotKey = "SaveSlot1";
if (PlayerPrefs.HasKey(slotKey))
{
    Debug.Log("Slot occupied");
}
else
{
    Debug.Log("Slot empty");
}

A Slot occupied

B Slot empty

C No output

D Runtime error

💡 Hint

Think about what PlayerPrefs.HasKey returns if the key does not exist.

Since the key "SaveSlot1" is not set, PlayerPrefs.HasKey returns false, so "Slot empty" is printed.

❓ Predict Output

intermediate

What does this code print after saving data?

This code saves a player's score in slot 2 and then reads it back. What will be printed?

Unity

int slot = 2;
string key = $"SaveSlot{slot}_Score";
PlayerPrefs.SetInt(key, 150);
int score = PlayerPrefs.GetInt(key, 0);
Debug.Log(score);

A 150

B null

C 0

D Runtime error

💡 Hint

Remember that SetInt stores the value and GetInt retrieves it.

The score 150 is saved with the key "SaveSlot2_Score" and then retrieved, so 150 is printed.

🔧 Debug

advanced

Why does this save slot loading code fail?

Look at this code that tries to load a player's name from a save slot. It throws a NullReferenceException. Why?

Unity

string slotKey = "SaveSlot3_Name";
string playerName = PlayerPrefs.GetString(slotKey, null);
int nameLength = playerName.Length;
Debug.Log(nameLength);

A PlayerPrefs.GetString returns null if key missing, causing NullReferenceException on Length

B PlayerPrefs.GetString throws exception if key missing

C The variable slotKey is not initialized

D playerName is empty string, so Length is zero, no exception

💡 Hint

What happens if you call GetString with a key that does not exist?

PlayerPrefs.GetString(slotKey, null) returns null if the key does not exist, causing a NullReferenceException when accessing .Length.

📝 Syntax

advanced

Which option correctly saves and loads a boolean in a save slot?

Unity's PlayerPrefs does not have a direct method for booleans. Which code correctly saves and loads a boolean value?

A

PlayerPrefs.SetFloat("SaveSlot1_Completed", completed ? 1.0f : 0.0f);
bool completed = PlayerPrefs.GetFloat("SaveSlot1_Completed") == 1.0f;

B

PlayerPrefs.SetBool("SaveSlot1_Completed", completed);
bool completed = PlayerPrefs.GetBool("SaveSlot1_Completed");

C

PlayerPrefs.SetString("SaveSlot1_Completed", completed.ToString());
bool completed = bool.Parse(PlayerPrefs.GetString("SaveSlot1_Completed"));

D

PlayerPrefs.SetInt("SaveSlot1_Completed", completed ? 1 : 0);
bool completed = PlayerPrefs.GetInt("SaveSlot1_Completed") == 1;

💡 Hint

PlayerPrefs supports int, float, and string but not bool directly.

Option D uses int 1 and 0 to represent true and false, which is the common pattern in Unity. Options B and C use non-existent methods or parsing that can fail. Option D uses float which is less common and can cause precision issues.

🚀 Application

expert

How many save slots are created by this code?

This code saves player data for multiple slots. How many distinct save slots are created?

Unity

for (int i = 0; i < 3; i++)
{
    PlayerPrefs.SetInt($"Slot{i}_Level", i + 1);
    PlayerPrefs.SetString($"Slot{i}_Name", $"Player{i}");
}

int count = 0;
for (int i = 0; i < 5; i++)
{
    if (PlayerPrefs.HasKey($"Slot{i}_Level"))
        count++;
}
Debug.Log(count);

A 0

B 5

C 3

D 2

💡 Hint

Check how many keys are set and how many are checked.

The first loop sets keys for slots 0, 1, and 2 only. The second loop checks slots 0 to 4. Only slots 0, 1, and 2 have keys, so count is 3.