Qt, cannot instantiate an object in a window's constructor?

Question

How do I create an instance of an object in the constructor for a window? I am generating three errors just by declaring a pointer, named objects, in 'window.h' and instantiating it in 'window.cpp:' 'Window::Window(...){...objects = new objectHandler(1)}'

window.obj:-1: error: LNK2019: unresolved external symbol "public: __thiscall objectHandler::objectHandler(int)" (??0objectHandler@@QAE@H@Z) referenced in function "public: __thiscall Window::Window(class QWidget *)" (??0Window@@QAE@PAVQWidget@@@Z)
(file not found)

window.obj:-1: error: LNK2019: unresolved external symbol "public: __thiscall objectHandler::~objectHandler(void)" (??1objectHandler@@QAE@XZ) referenced in function "public: void * __thiscall objectHandler::`scalar deleting destructor'(unsigned int)" (??_GobjectHandler@@QAEPAXI@Z)
(file not found)

debug\Phursik.exe:-1: error: LNK1120: 2 unresolved externals

I looked up the errors and apparently they have to do with the functions being declared but not defined by the class. I am sure; however, that all functions declared in 'objectHandler.h' are defined in 'objectHandler.cpp' and Qt Creator even knows how to find one from the other. I am quite perplexed so thank you for your help in advance.

From window.cpp

Window::Window(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::Window)
{
...
    objects = new objectHandler(STEP_TIME_HOURS);
    ui->setupUi(this);
}

From window.h

namespace Ui {
class Window;
}

class Window : public QWidget
{
    Q_OBJECT

public:
    explicit Window(QWidget *parent = 0);
    ~Window();
...

From objecthandler.cpp

objectHandler::objectHandler(int stepTimeHours)
{
    this->stepTimeHours = stepTimeHours;
    head = nullptr;
    current = nullptr;
    tail = nullptr;
}

objectHandler::~objectHandler()
{
    current = head;
    if (current->next)
    {
        current = current->next;
        delete current->last;
    }
    else if (current)
        delete current;
}...

From objecthandler.h

class objectHandler
{
public:
    objectHandler(int stepTimeHours);
    ~objectHandler();
...
    largeBody *head, *current, *tail;
}

It looks like a mistake in the #includes. There is nothing special with instantiating objects inside a window's constructor. Do you use Q_OBJECT in your custom classes? — vsz
– vsz, Commented Jan 1, 2015 at 0:43
If you deliberately insert a syntax error (e.g. by typing in garbage characters) into either of those two functions (i.e. into objecthandler class's constructor or destructor), do you then get a syntax error when you rebuild your program? — Jeremy Friesner
– Jeremy Friesner, Commented Jan 1, 2015 at 4:20
"It looks like a mistake in the #includes. There is nothing special with instantiating objects inside a window's constructor. Do you use Q_OBJECT in your custom classes?" I added in redundancy and checked the includes so I don't know why it would be. I only use Q_OBJECT in my window class. "If you deliberately insert a syntax error (e.g. by typing in garbage characters) into either of those two functions (i.e. into objecthandler class's constructor or destructor), do you then get a syntax error when you rebuild your program?" I do not. — Gage Ervin
– Gage Ervin, Commented Jan 1, 2015 at 7:07
@user3732350 : could you post some of the more relevant code? For example, the header of your custom class, and at least the beginning of your cpp files? — vsz
– vsz, Commented Jan 1, 2015 at 12:28

Community · Accepted Answer · 2017-05-23 12:07:55Z

1

I solved it. The issue below is similar except QT Creator automagically added my '.h' files to the list in the .pro file. I just needed to delete the build folder and suddenly everything started working.

Why doesn't Qt Creator find included headers in included paths - even though qmake is able to find them

edited May 23, 2017 at 12:07

CommunityBot

11 silver badge

answered Jan 3, 2015 at 20:15

Gage Ervin

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