Question

I have been struggling with this error for more than two hours:

error: aggregate 'Ui::UpdaterProgress updaterProgress' has incomplete type and cannot be defined

I have a simple UI screen on Qt. Setting up with a dialog:

  #include <ui_UpdaterProgress.h>

  namespace Ui {
  class UpdaterProgress;
  }
  ....
  Ui::UpdaterProgress updaterProgress;
  QDialog updateProgressDialog;
  updaterProgress.setupUi(&updateProgressDialog);

It’s a simple UI with an icon, two labels, progress bar and a cancel button. Am I doing anything wrong here?

I get this error if I don’t do the forward declaration:

error: 'UpdaterProgress' is not a member of 'Ui'
error: expected `;' before 'updaterProgress'
error: 'updaterProgress' was not declared in this scope

Answer 1

Have you defined class UpdaterProgress in your ....???
Define your UpdaterProgress class before using it in Ui::UpdaterProgress updaterProgress;.
Prototyping itself cannot tell anything about the class, that’s why incomplete type error.