Don't Pass Control Flags Downward

This is tip 6.2 from Thinking Forth.

Suppose we have the some code that looks like the following:

class Window {
  void setVisible(boolean show) {
    if (show) {
      // ... show the window
    } else {
      // ... hide the window
    }
  }
}

static void main(String... args) {
  var window = ...
  window.setVisible(true);
  // ... do something, then:
  window.setVisible(false);
}

We know exactly when the window should be shown/hidden at compile time, so the calls to setVisible(boolean) are asking the program to make pointless decisions at run time. It also makes the setVisible function trying to do two jobs, show and hide the window, which violates the single responsibility principle.

So it would be better to just spell out exactly what our intentions are:

class Window {
  void show() {}
  void hide() {}
}

static void main(String... args) {
  var window = ...
  window.show();
  // ... do something, then:
  window.hide();
}

2023-09-24