No appropriate default constructor available

lfreeman6490

I am trying to build my QT application to no avail. The error I am getting is

C2512: "Ui:Pathloss": no appropriate default constructor available

Even though in my pathloss.h file I have this

#define PATHLOSS_H

#include <QWidget>

namespace Ui {
class Pathloss;
}

class Pathloss : public QWidget
{
    Q_OBJECT
    
public:
    Pathloss::Pathloss(QWidget *parent=NULL);
    ~Pathloss();

private:
    Ui::Pathloss *ui;
};

#endif // PATHLOSS_H

code_text

I am new to c++ and QT, but I believe that

public:
    Pathloss::Pathloss(QWidget *parent=NULL);

should be my default constructor, is that not correct?

KroMignon

@lfreeman6490 said in No appropriate default constructor available:

With this piece of code, you are defining a class called Pathloss in namespace Ui (full name is Ui::Pathloss)

namespace Ui {
class Pathloss;
}

With piece of code you a declaring class Pathloss without namespace:

class Pathloss : public QWidget
{
...
};

So they are 2 different classes.
If you want to declare the class outside the namespace, you have to give full class name:

class Ui::Pathloss : public QWidget
{
...
};

cf:

Kent-Dorfman

and what namespace owns Pathloss?...hint hint

KroMignon

@lfreeman6490 said in No appropriate default constructor available:

With this piece of code, you are defining a class called Pathloss in namespace Ui (full name is Ui::Pathloss)

namespace Ui {
class Pathloss;
}

With piece of code you a declaring class Pathloss without namespace:

class Pathloss : public QWidget
{
...
};

So they are 2 different classes.
If you want to declare the class outside the namespace, you have to give full class name:

class Ui::Pathloss : public QWidget
{
...
};

cf:

lfreeman6490

@KroMignon @Kent-Dorfman So I changed that, thank you very much, I fixed the other errors besides one. It's saying that

C2039: 'setupUi': is not a member of 'Ui::Pathloss'

I'm assuming that has something to do with me changing that name and finding where setupUi is at, thanks again to both of you. I really appreciate it

lfreeman6490

This post is deleted!

KroMignon

@lfreeman6490 said in No appropriate default constructor available:

QT is telling me to look in the declaration of Pathloss. When I build this with QMake it builds fine, but when I try to run it it throws the error

First, it is not Qt, it is Microsoft c++ compiler ;) (Error code C2039, looks like Microsoft compiler error code)

Then some basics:

Qt Creator (which is an IDE, like Microsoft Visual Studio), to edit/compile/run your code.
qmake is a build manager (like cmake, messon, etc.): running qmake will update your make file, but not compile the project

Sorry if I am rude, but your code looks very messy...
I cannot understand what you are trying to do, it don't make sense to me. So it is not simple to give you useful hints!

I think you are starting from a code example you have found somewhere in documentation or internet.
Go back to first version and try to understand how it works and then start to change it step by step.

lfreeman6490

@KroMignon This was handed to me the other day by someone else and I have been trying to build it. I don't have any c++ experience so that is probably why it seems messy

KroMignon

@lfreeman6490

I don't know anything about the software you are trying to build.
So I can only guess.
I am very sorry, my first answer was not correct. I was not take in account that you are using Qt UI Designer!

The Ui namespace is used by Qt Creator / UI Designer to group auto-generated Pathloss code in one namespace. It helps to differentiate between the ui class that is generated from designer ui file and the class that implements the functionality.

So the idea, is that you will have:

Ui::Pathloss which holds the UI as created with designer
Pathloss which is the QWidget which will build the widget, it will hold an instance of Ui::Pathloss to build the widget content

You can read this article to have more details about this: https://www.meetingcpp.com/blog/items/an-introduction-into-qt-part-ii.html

So you could better understand how it works, and how you have to make the modifications you want to do.