invalid use of incomplete type / forward decalration of 'class UI::file_ui'

Adham

I have two files:

module.h

#ifndef MODULE_H
#define MODULE_H

#include "parent_module.h"

class parent_module;

class module : public parent_module
{
public:
    module();

    ...

private:

    ...
};

#endif // MODULE_H

and module_ui.h

#ifndef MODULE_UI_H
#define MODULE_UI_H

#include ...

#include "../module.h"

namespace Ui {
class module_ui;
}

class module;

class module_ui : public QDialog, module
{
    Q_OBJECT

public:
   
   ...

private:

   ...
};

#endif // MODULE_UI_H

And this is the implementation for the ui header file: module_ui.cpp

#include "module_ui.h"
#include "ui_module_ui.h"

module_ui::module_ui(QWidget *parent) :
    QDialog(parent),
    ui(new Ui::module_ui) //error occurs here
{
    ui->setupUi(this); //and here
    ...
}

module_ui::~module_ui()
{
    qDebug() << "Module_UI destructor called";
    ...
    delete ui;  //and here (and basically everywhere ui is called)
}

Basically a parent/base class that is inheritted by child ui class. I have this same structure for many other files and it works fine. However when I added this set I keep getting the following errors:

..module_ui.cpp:28:16: error: invalid use of incomplete type 'class Ui::module_ui'
ui(new Ui::module_ui)
^~~~~~~~~~~~~~~~~~~

In file included from ..\module_ui.cpp:22:0:
..\module_ui.h:23:7: note: forward declaration of 'class Ui::module_ui'
class module_ui;
^~~~~~~~~~~~~~~~~~~

I have the all the files properly add in the .pro file (.cpp to SOURCES, .h to HEADERS, and .ui to FORMS)
I literally went back and followed the exact same structure as all the other files which are working fine. I've got no idea what I am missing here.

Help is appreciated.

SGaist

Hi,

Did you check that uic is properly run on that form ?

Adham

@SGaist said in invalid use of incomplete type / forward decalration of 'class UI::file_ui':

check

I just checked and it is not.. The ui_module_ui.h file generated has instances of module.h instead of module_ui.h.

class Ui_module //here it should be UI_module_ui
{
public:
    ...
    void setupUi(QDialog *module) //and here it should pass a pointer to module_ui
    {
     ... //all other instances are the same
    }

I can fix it manually but that would not solve the problem for anyone building from scratch. Any idea why that is happening? I believe I have the include statements the right way round

SGaist

I currently wonder if you using _ui in your designer based widget does not trigger some issue.

Try renaming it to something more meaningful without using _ui.

Adham

@SGaist renamed it and got the same issue. It shouldn't matter because I have like 20 other files named module_something_ui and they all work fine.

SGaist

Then with silly ideas: did you check whether you have a missing backslash in your .pro when listing that particular form ? If you do it one file per line that is.

Adham

@SGaist I'm pretty sure it'll be a silly one.
Yep. One file per line, backslash after every file

SGaist

Did you already nuke the build folder and rebuild from scratch ?

Adham

@SGaist I finally figured it out.

The module.h file was actually the ui file at first and then I created a child class module_ui.h that inherits from it and instantiates the actual QDialog. Soo, I changed everything up but forgot to change the class name in the .ui file.. Pretty silly

Anyways thanks for your help.

SGaist

@Adham said in invalid use of incomplete type / forward decalration of 'class UI::file_ui':

Pretty silly

So we were right ! :-D