Returning from submethod from super

Question

I have something like this:

class SuperClass {
  public void onClick(){
    if(disabled) return;
  }
}

class SubClass extends SuperClass {
  public void onClick(){
    super.onClick();
    System.out.println("Clicked");
  }
}

This outputs "Clicked" every time I click the button.

I want the SubClass onClick() to not work if disabled is true and don't want to add an extra line in every SubClass. How can I do that?

@DrColossos In the super class. That's not the problem. The problem is that when i return from the method in the superclass, it only returns from the super method and not the method in the subclass. — usama8800, May 14 '14 at 11:59

score 3 · Answer 1 · answered May 14 '14 at 11:58

You should use the template method pattern

abstract class SuperClass {
  public void onClick(){
    if(!disabled) clickAction() ;
  }

  public abstract void clickAction();
}

class SubClass extends SuperClass {
  public void clickAction(){
    System.out.println("Clicked");
  }
}

score 2 · Answer 2 · answered May 14 '14 at 11:59

Maybe something like this:

class SuperClass {
  public void onClick(){
    if(disabled) return;
    processClick();
  }
  protected void processClick() {
  }
}

class SubClass extends SuperClass {
  protected void processClick(){
    super.processClick();
    System.out.println("Clicked");
  }
}

score 2 · Accepted Answer · answered May 14 '14 at 11:59

Delegate to another method:

class SuperClass {
  public void onClick(){
    if(!disabled) handleOnClick();
  }
  public void handleOnClick(){
  }
}

class SubClass extends SuperClass {
  public void handleOnClick(){
    System.out.println("Clicked");
  }
}

score 2 · Answer 4 · answered May 14 '14 at 11:59

you can't not this way anyway. The function call in the super object doesn't have any right to do anything to stop the method in the subclass from executing. What you're looking for is a TemplateMethodPattern pattern maybe. You could have something like this

 abstract class SuperClass {
  public void onClick(){
    if(disabled) return;
    doClick();
  }

  protected abstract void doClick();

}

class SubClass extends SuperClass {
  protected void doClick(){  
    System.out.println("Clicked");
  }
}

Returning from submethod from super

4 Answers4