Game States

Part of the Building Real Games section of Coddy's Unity journey. Lesson 14 of 56.

A game is in one state at a time: waiting for the player, running, or over. Two bools such as isPlaying and isOver can both end up true by mistake, and a string such as "Playng" compiles and never matches. C# has a type for a fixed list of choices, the enum. This crossing light uses one:

public enum Signal { Red, Yellow, Green }

public class Crossing : MonoBehaviour
{
    public Signal signal;

    void Update()
    {
        if (signal == Signal.Red && Input.GetMouseButtonDown(0))
        {
            signal = Signal.Green;
            Debug.Log("Walk!");
        }
    }

    public bool CanWalk()
    {
        return signal == Signal.Green;
    }
}

enum Signal { Red, Yellow, Green } makes a new type with exactly three values, written Signal.Red, Signal.Yellow and Signal.Green. A Signal field holds one of them at a time; you compare it with == and change it with =. A misspelled Signal.Gren is a compile error, so the mistake shows before you press Play.

The enum is declared outside the class, so every script can use Signal, and a pedestrian's script can ask crossing.CanWalk(). A new enum field starts at the first value, here Red. In the Inspector a public enum field shows as a drop-down list of its values. Underneath, each value is a number counted from 0: (int)Signal.Green is 2.

Challenge

Easy

Cross the floor without touching the lava. The GameManager (a singleton) and the Lava script are there; give the game its states.

In GameManager.cs, above the class, declare an enum GameState with the values Ready, Playing and GameOver, in that order, and give GameManager a public GameState field named state. The game starts Ready.
While the game is Ready, Space starts it: the state becomes Playing and Go! is logged.
Lava calls HitLava(). While the game is Playing, that ends it: the state becomes GameOver and Game over is logged. Space never restarts a finished game.
In Player.cs, the arrows walk the player only while the state is Playing.

Press Play, try the arrows before Space, then walk into the lava, then Check.

Try it yourself

using UnityEngine;

// Declare the GameState enum here: Ready, Playing, GameOver

public class GameManager : MonoBehaviour
{
    public static GameManager Instance;
    // a public GameState field named state

    void Awake()
    {
        Instance = this;
    }

    void Update()
    {
        // While Ready, Space starts the game and logs Go!
    }

    public void HitLava()
    {
        // While Playing, the game is over: log Game over
    }
}