Reactive Programming for Game Developers: An Introduction

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If you are a game developer and haven’t heard of reactive programming yet, drop your business and read this article. I am not kidding.

Don't be distracted by kittens. Read about reactive programming!

So I got your attention?

Excellent! I will do my best not to lose him.

What is Reactive Programming?

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 using UnityEngine;
 using UnityEngine.UI;
 
 public class Player : MonoBehaviour {
   public int health = 100;
   public Text scoreLabel;
 
   public void ApplyDamage(int damage) {
     health -= damage;
     scoreLabel.text = health.ToString();
   }
 }
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

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using UnityEngine;
 using UnityEngine.UI;
 
 public class Player : MonoBehaviour {
   public int health = 100;
   public Text scoreLabel;
 
   public void ApplyDamage(int damage) {
     health -= damage;
     scoreLabel.text = health.ToString();
   }
 }
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

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 using UnityEngine;
 using UnityEngine.UI;
 using UniRx;
 
 public class Player : MonoBehaviour {
   public ReactiveProperty<int> health 
     = new ReactiveProperty<int>(100);
 
   public void ApplyDamage(int damage) {
     health.Value -= damage;
   }
 }
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

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using UnityEngine;
 using UnityEngine.UI;
 using UniRx;
 
 public class UiPresenter : MonoBehaviour {
   public Player player;
 
   public Text scoreLabel;
 
   void Start() {
     player.health.SubscribeToText(scoreLabel);
   }
 }
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

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all_balls_in_order = Observable.Merge(h1, h2, h3, h4, h5, h6);
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

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all_balls_delayed = Observable.Merge(
  h1.Delay(
    TimeSpan.FromSeconds(1)
  ), 
  h2.Delay(
    TimeSpan.FromSeconds(2)
  ), 
  h3.Delay(
    TimeSpan.FromSeconds(3)
  ), 
  h4.Delay(
    TimeSpan.FromSeconds(3)
  ), 
  h5.Delay(
    TimeSpan.FromSeconds(2)
  ), 
  h6.Delay(
    TimeSpan.FromSeconds(1)
  )
);
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

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using UnityEngine;
 using UnityEngine.UI;
 using UniRx;
 
 public class UiPresenter : MonoBehaviour {
   public Player player;
 
   public Text scoreLabel;
 
   void Start() {
     player.health
       .Select(health => string.Format("Health: {0}", health))
       .Subscribe(text => scoreLabel.text = text);
   }
 }
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

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using UnityEngine;
 using UnityEngine.UI;
 using UniRx;
 
 public class UiPresenter : MonoBehaviour {
   public Player player;
 
   public Text scoreLabel;
   public Animator animator;
 
   void Start() {
     player.health
       .Select(health => string.Format("Health: {0}", health))
       .Do(x => animator.Play("Flash"))
       .Subscribe(text => scoreLabel.text = text);
   }
 }
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

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using UnityEngine;
 using UnityEngine.UI;
 using UniRx;
 
 public class UiPresenter : MonoBehaviour {
   public ReactiveProperty<Player> player 
     = new ReactiveProperty<Player>();
 
   public Text scoreLabel;
   public Animator animator;
 
   void Start() {
     var playerHealth = this.player
       .Where(player => player != null)
       .Select(player => player.health);
 
     playerHealth
       .Select(health => string.Format("Health: {0}", health))
       .Do(x => animator.Play("Flash"))
       .Subscribe(text => scoreLabel.text = text);
   }
 }
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

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