Lobby and matchmaking basics in Unity - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a new lobby with a maximum of 4 players.

Unity

var options = new CreateLobbyOptions { MaxPlayers = [1] };
LobbyService.Instance.CreateLobbyAsync("MyLobby", options);

Drag options to blanks, or click blank then click option'

A2

B4

C8

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Setting MaxPlayers to 1 limits the lobby to only one player.

Using a number larger than intended can cause unexpected behavior.

The maximum number of players is set to 4 to allow up to 4 players in the lobby.

2fill in blank

medium

Complete the code to join a lobby by its ID.

Unity

var lobby = await LobbyService.Instance.JoinLobbyByIdAsync([1]);

Drag options to blanks, or click blank then click option'

A"gameMode"

B"lobbyName"

C"playerName"

D"12345"

Attempts:

3 left

💡 Hint

Common Mistakes

Using the lobby name instead of the lobby ID.

Passing player or game mode strings instead of the lobby ID.

You need to provide the lobby ID as a string to join the correct lobby.

3fill in blank

hard

Fix the error in the code to properly list all available lobbies.

Unity

var lobbyList = await LobbyService.Instance.[1]();

Drag options to blanks, or click blank then click option'

AListLobbiesAsync

BRetrieveLobbies

CFetchLobbies

DGetAllLobbiesAsync

Attempts:

3 left

💡 Hint

Common Mistakes

Using a method name that does not exist in the LobbyService API.

Forgetting the 'Async' suffix for asynchronous methods.

The correct method to list all lobbies is ListLobbiesAsync.

4fill in blank

hard

Fill both blanks to create a lobby and set it to be private.

Unity

var options = new CreateLobbyOptions { [1] = 6, [2] = true };
await LobbyService.Instance.CreateLobbyAsync("PrivateLobby", options);

Drag options to blanks, or click blank then click option'

AMaxPlayers

BIsPrivate

CIsPublic

DPlayerCount

Attempts:

3 left

💡 Hint

Common Mistakes

Using IsPublic instead of IsPrivate.

Confusing PlayerCount with MaxPlayers.

MaxPlayers sets the maximum players, and IsPrivate makes the lobby private.

5fill in blank

hard

Fill all three blanks to update the lobby's data with a new game mode and max players.

Unity

var updateOptions = new UpdateLobbyOptions {
    Data = new Dictionary<string, DataObject> {
        { "GameMode", new DataObject(DataObject.VisibilityOptions.Public, [1]) }
    },
    [2] = [3]
};
await LobbyService.Instance.UpdateLobbyAsync(lobby.Id, updateOptions);

Drag options to blanks, or click blank then click option'

A"Deathmatch"

BMaxPlayers

C8

D"CaptureTheFlag"

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong game mode string.

Mixing up the property names for max players.

The game mode is set to "Deathmatch", MaxPlayers is updated to 8.

Practice

1. What is the main purpose of a lobby in Unity multiplayer games?

easy

A. To let players wait and prepare before the game starts

B. To automatically find and connect players

C. To render 3D graphics for the game

D. To save player progress locally

Solution

1. Step 1: Understand the role of a lobby

   A lobby is a waiting area where players gather before the game begins.

2. Step 2: Differentiate from matchmaking

   Matchmaking is the process of finding and connecting players automatically, not the lobby itself.

3. Final Answer:

   To let players wait and prepare before the game starts -> Option A

4. Quick Check:

   Lobby = waiting area before game [OK]

Hint: Lobbies are for waiting; matchmaking is for finding players [OK]

Common Mistakes:

• Confusing lobby with matchmaking
• Thinking lobby handles graphics
• Assuming lobby saves progress

2. Which of the following is the correct way to override a lobby method in Unity C#?

easy

A. public override void OnPlayerJoined() {}

B. override public void OnPlayerJoined() {}

C. public void OnPlayerJoined() override {}

D. void override OnPlayerJoined() {}

Solution

1. Step 1: Recall C# override syntax

   In C#, the correct syntax places 'override' before the return type.

2. Step 2: Check each option

   public override void OnPlayerJoined() {} uses 'public override void MethodName()' which is correct syntax.

3. Final Answer:

   public override void OnPlayerJoined() {} -> Option A

4. Quick Check:

   Override keyword before return type [OK]

Hint: In C#, 'override' comes before the return type [OK]

Common Mistakes:

• Placing override after method name
• Omitting override keyword
• Wrong order of keywords

3. Given this code snippet in a Unity lobby script:

public override void OnPlayerJoined(Player player) {
    Debug.Log($"Player {player.Name} joined.");
    if (Players.Count >= 4) {
        StartGame();
    }
}

What happens when the 4th player joins?

medium

A. The lobby closes without starting the game

B. Nothing happens until manually started

C. The game starts automatically

D. An error occurs because Players.Count is undefined

Solution

1. Step 1: Analyze the OnPlayerJoined method

   When a player joins, it logs their name and checks if Players.Count is 4 or more.

2. Step 2: Understand the condition

   If Players.Count is 4 or more, StartGame() is called, starting the game automatically.

3. Final Answer:

   The game starts automatically -> Option C

4. Quick Check:

   Players.Count >= 4 triggers StartGame() [OK]

Hint: Check conditions that trigger StartGame() call [OK]

Common Mistakes:

• Assuming manual start needed
• Thinking Players.Count is undefined
• Confusing lobby closing with game start

4. Identify the error in this matchmaking code snippet:

public void Matchmake() {
    var match = Matchmaker.CreateMatch();
    match.OnPlayerJoined += OnPlayerJoined;
    match.Start();
}

void OnPlayerJoined(Player player) {
    Debug.Log("Player joined: " + player.Name);
}

medium

A. Start() method does not exist on match object

B. Event subscription syntax is incorrect

C. OnPlayerJoined method must be public to subscribe

D. Matchmaker.CreateMatch() might return null and is not checked

Solution

1. Step 1: Review event subscription

   The syntax 'match.OnPlayerJoined += OnPlayerJoined;' is correct for subscribing to events.

2. Step 2: Check for null safety

   Matchmaker.CreateMatch() might return null if no match is found, but code does not check for null before using match.

3. Final Answer:

   Matchmaker.CreateMatch() might return null and is not checked -> Option D

4. Quick Check:

   Always check for null after CreateMatch() [OK]

Hint: Always check if CreateMatch() returns null before use [OK]

Common Mistakes:

• Assuming event subscription syntax is wrong
• Ignoring null checks
• Assuming Start() method is missing

5. You want to create a lobby that only starts the game when all players are ready. Which approach is best in Unity matchmaking?

hard

A. Call StartGame() immediately when the first player joins

B. Override OnPlayerJoined to check a 'ready' flag on each player before calling StartGame()

C. Use a timer to start the game after 30 seconds regardless of players

D. Disable matchmaking and start game manually from UI

Solution

1. Step 1: Understand the requirement

   The game should start only when all players are ready, not just when they join.

2. Step 2: Choose the best method

   Overriding OnPlayerJoined to check each player's 'ready' status before starting the game ensures all are prepared.

3. Final Answer:

   Override OnPlayerJoined to check a 'ready' flag on each player before calling StartGame() -> Option B

4. Quick Check:

   Check readiness before starting game [OK]

Hint: Check all players' ready flags before starting game [OK]

Common Mistakes:

• Starting game too early
• Ignoring player readiness
• Disabling matchmaking unnecessarily