State machine
- Game Development course
- Advanced
- Lesson 41/71
- 4 min
Learn enemy states with a simple FSM.
Finite State Machine (FSM)
An FSM (Finite State Machine) is a streamlined pattern ensuring a character resides in strictly one state at any given moment (e.g., Patrol, Chase, Attack).
public enum EnemyState {
Patrol,
Chase,
Attack
}States are modeled using an enum, preventing contradictory concurrent states.
State Transitions and the switch Statement
Every frame, behavior matching the active state executes within a switch-case block. When triggers fire, the state variable is updated.
switch (currentState) {
case EnemyState.Patrol:
PatrolAlongWaypoints();
break;
case EnemyState.Chase:
agent.SetDestination(player.position);
break;
}For instance, when the player breaches proximity, setting currentState = EnemyState.Chase; launches pursuit.
Practice State machine transition
Define a Start method. Inside, declare string aktifDurum = "Chase"; and print "Dusman durumu: " + aktifDurum to the console.
Starter code
using UnityEngine;
public class FsmTester : MonoBehaviour
{
// Start icinde aktifDurum tanimla ve yazdir
}Sample solution
using UnityEngine;
public class FsmTester : MonoBehaviour
{
void Start()
{
string aktifDurum = "Chase";
Debug.Log("Dusman durumu: " + aktifDurum);
}
}Expected output
Dusman durumu: Chase
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 What is the architectural pattern called that transitions an enemy from Patrol to Chase upon spotting a player?
- Finite State Machine (FSM) Correct answer
- Audio Listener
- Shader Pipeline
- JSON Deserializer
Explanation: A Finite State Machine (FSM) manages transitions between discrete states based on sensory conditions.
2 Enemy states enum declaration
public enum EnemyState { ____, Chase, Attack }public enum EnemyState { Patrol, Chase, Attack }Explanation: The 'Patrol' label is used to designate the default scouting state of an enemy.
3 FSM state concepts
| Term | Meaning |
|---|---|
Patrol |
Patrolling along a predefined path |
Chase |
Pursuing the player as a target |
Attack |
Dealing damage when player is in range |
FSM |
Machine selecting behavior by state |