[Behavioral Pattern] - Chain Of Responsibility

https://refactoring.guru/design-patterns/chain-of-responsibility

Chain of Responsibility

 

 

특정 메시지 혹은 이벤트 등을 관련 있는 모두에서 전달하며, 알아서 처리하게 하는 방식.

 

 

예제 

 - Dialog 등이 겹겹이 있을 때, device back button을 누를 때.

 - Dialog component 안에서 색 변경을 눌러 관련 컴포넌트의 변화를 만들 때. 

 

예제 코드 

public abstract class ABackButtonHandler
{
    protected ABackButtonHandler _nextHandler;

    public void SetNextHandler(ABackButtonHandler next)
    {
        _nextHandler = next;
    }
    public abstract void OnBackButtonPressed();
}

public class MessageDialog : ABackButtonHandler
{
    public override void OnBackButtonPressed()
    {
        if(_nextHandler != null)
        {
            _nextHandler.OnBackButtonPressed();
        }
        else
        {
            // DO OWN thing..   - close this dialog?
        }
    }
}

public class NormalDialog : ABackButtonHandler
{
    public override void OnBackButtonPressed()
    {
        if(_nextHandler != null)
        {
            _nextHandler.OnBackButtonPressed();
        }
        else
        {
            // DO OWN thing.. - close this dialog ?
        }
    }
}

public class MainView : ABackButtonHandler
{
    public override void OnBackButtonPressed()
    {
        if(_nextHandler != null)
        {
            _nextHandler.OnBackButtonPressed();
        }
        else
        {
            // DO OWN thing..   - show message? "Would you want to close the app?"
        }
    }
}




internal class ChainOfResponsibilityDemo
{
    public void Run()
    {
        MainView _view = new MainView();
        NormalDialog _dlg = new NormalDialog();
        MessageDialog _msgDlg = new MessageDialog();
        _view.SetNextHandler(_dlg);
        _dlg.SetNextHandler(_msgDlg);

        _view.OnBackButtonPressed();
    }
}