Csharp
14 Apr 2019

Refactor If Statement By using Delegate

If statements will make the code looks very ugly, and violate the open closed principle. But we can use Delegate or (Finite State Machine)FSM to make it better.

In this post, I use simple Player's Movement States as an example.

1. Using If statement to implement Player Movement States

Code Example

public enum Movement
{
    Idle,Walk,Run,Jump
}

public class PlayerMovement : MonoBehaviour
{
    public Movement movement;

    void Update()
    {
        if(movement == Movement.Idle)
        {
            Debug.Log("Player is in Idle State");
        }else if(movement== Movement.Walk)
        {
            Debug.Log("Player is in Walk State");
        }
        else if (movement == Movement.Run)
        {
            Debug.Log("Player is in Run State");
        }
        else if (movement == Movement.Jump)
        {
            Debug.Log("Player is in Jump State");
        }
    }
}

2. Using Delegate to implement Player Movement States

Code Example

public enum Movement
{
     Idle,Walk,Run,Jump
}

public class PlayerMovement : MonoBehaviour
{
    public Movement movement;
    public delegate void MovementHandler();
    MovementHandler[] handler;

    void Start()
    {
        handler = new MovementHandler[] { Idle, Walk, Run, Jump };
    }

    void Update()
    {
        MovementHandler moveState = handler[(int)movement];
        moveState(); // call delegate
    }

    void Idle()
    {
        Debug.Log("Player is in Idle State");
    }
    void Walk()
    {
        Debug.Log("Player is in Walk State");
    }
    void Run()
    {
        Debug.Log("Player is in Run State");
    }
    void Jump()
    {
        Debug.Log("Player is in Jump State");
    }

}

End –Cheng Gu

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