Cannot open include file " but I can create objects "

[Project try]

Hey guys I have a weird problem here , I can't include my header :

error: C1083: Cannot open include file: 'calculator.h': No such file or directory

this is the code from last night I was just trying to use it as a class " still unfinished " but I think even though it's unfinished it should run just fine , but it doesn't.

main:
@
#include <QApplication>
#include<calculator.h>

int main(int argc, char *argv[])
{
QApplication a(argc, argv);
calculator *dialog;
dialog->show();

return a.exec();

}

@

header:
@
#ifndef CALCULATOR_H
#define CALCULATOR_H
#include<QLabel>
#include<QHBoxLayout>
#include<QLineEdit>
#include<QIntValidator>
class calculator : QWidget
{

public:
calculator();

void convert();
void convert1();

private:
QLineEdit *edit;
QLineEdit *edit1;
QIntValidator *Valid;
QHBoxLayout *left;
QHBoxLayout *Main;

};

#endif // CALCULATOR_H
@

implement:

@

#include<calculator.h>
calculator::calculator()
{
edit = new QLineEdit;
edit1=new QLineEdit;

 left= new QHBoxLayout;
 Main=new QHBoxLayout;
    edit->setMaximumWidth(20);
    edit->setFixedWidth(20);
    edit->setValidator(Valid);
    edit1->setMaximumWidth(20);
    edit1->setFixedWidth(20);
    edit1->setValidator(Valid);
    left->addWidget(edit);
    left->addWidget(edit1);
    Main->addLayout(left);
    setLayout(Main);
   QObject:: connect(edit,SIGNAL(editingFinished()),this,SLOT(convert));
   QObject:: connect(edit1,SIGNAL(editingFinished()),this,SLOT(convert1));

}
void calculator::convert(){
QString numbertext=edit->text();
int x=numbertext.toInt();

}
void calculator::convert1(){
QString numbertext=edit1->text();
int y=numbertext.toInt();

}

@

project:

@
#-------------------------------------------------

Project created by QtCreator 2014-03-07T23:16:20

#-------------------------------------------------

QT += core gui
QT += widgets

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TARGET = untitled14
TEMPLATE = app

SOURCES += main.cpp
calculator.cpp

HEADERS +=
calculator.h

FORMS += mainwindow.ui
@

[Project try]

I can't seems to fix it , I deleted everything in the class to see " maybe the error is in the coding " but it still gives the same problem.

I'll try to create a new class and see if it works.

[Project try]

it works now , but when I use :

calculator *p=new calculator;

and i use show function it doesn't show ?

[SGaist]

Hi,

You are missing the base class initialization:

@
calculator::calculator(QWidget parent):
QWidget(parent)
{
//rest of the code
}
@

Also you currently have a memory leak in your application since you don't delete dialog once the application is finished.

[Project try]

Hey , thanks for your help in advance.

I have a problem now when I compile it doesn't show the window then says

The program has unexpectedly finished.

--

and I didn't understand your code what is :

@
QWidget{
//code ?
}

you mean I should put what I put in the constructor inside that QWIDGET braces ?

about the leak , lets just hope it runs first :D

[Project try]

oh yeah forgot about qwidget in the implement :D

[Project try]

Still same problem :(

[Project try]

the code " I changed the project to solve the first problem so I named the class to another name "

imp:
@
#include "checkclass.h"

checkclass::checkclass(QWidget parent):
QWidget(){
edit = new QLineEdit;
edit1=new QLineEdit;

     left= new QHBoxLayout;
     Main=new QHBoxLayout;
        edit->setMaximumWidth(20);
        edit->setFixedWidth(20);
        edit->setValidator(Valid);
        edit1->setMaximumWidth(20);
        edit1->setFixedWidth(20);
        edit1->setValidator(Valid);
        QObject:: connect(edit,SIGNAL(editingFinished()),this,SLOT(convert));
               QObject:: connect(edit1,SIGNAL(editingFinished()),this,SLOT(convert1));
        left->addWidget(edit);
        left->addWidget(edit1);
        Main->addLayout(left);

        setLayout(Main);

}

void checkclass::convert(){
QString numbertext=edit->text();
int x=numbertext.toInt();

}
void checkclass::convert1(){
QString numbertext=edit1->text();
int y=numbertext.toInt();

}

@

header:
@
#ifndef CHECKCLASS_H
#define CHECKCLASS_H
#include<QLabel>
#include<QHBoxLayout>
#include<QLineEdit>
#include<QIntValidator>
#include<QWidget>
class checkclass : public QWidget
{
public:
checkclass(QWidget parent);

void convert();
    void convert1();
private:
    QLineEdit *edit;
    QLineEdit *edit1;
QIntValidator *Valid;
    QHBoxLayout *left;

    QHBoxLayout *Main;

};

#endif // CHECKCLASS_H
@

[SGaist]

Valid is not initialized

[Project try]

same problem :(

[Project try]

@SGaist , Hopefully you didn't go to sleep yet , I really need your help , because tomorrow I want to focus on studying for my mid term exam :D

[Project try]

The problem happens only when I use show function like for example:

myclass *A;
A->show();

it crashes , when I don't use show() my program runs just fine in the backround.

[JKSH]

[quote author="Project try" date="1394235877"]The problem happens only when I use show function like for example:

myclass *A;
A->show();

it crashes , when I don't use show() my program runs just fine in the backround.[/quote]Like SGaist said, you didn't initialize your pointer. A does not point to a valid object yet, so it will cause problems if you try to use it. It's not just show(), ANY function can cause a crash -- it might not crash immediately, but will crash some time later.

Call new to initialize your pointer. This is a very fundamental (and very important) concept of C++ by the way; if you are not familiar with it, I highly recommend reading a tutorial about pointers.

[Project try]

Thanks man ^^ , it worked

but can you please tell me why did we put : QWidget *parent in the arguments of the constructor ? even though we didn't send any argument but it was a default so what's the point ?

and since it didn't take any argument there's no need to delete that parent pointer ? , because I saw a lot of examples and most of them use it like I said but they didn't really explain why.

[Project try]

Good night , I need to sleep , thanks guys for helping me , and sorry for asking lots of question :(

[SGaist]

So that you can reuse your widget the same way you would a standard Qt widget.

Even if you don't reuse it somewhere else, it's good practice to keep a consistent code base. You never know who will use your code later

[JKSH]

Parent-child relationships have multiple uses in Qt. One of them is memory management. When a parent object is deleted, it will automatically delete its child objects. Thus, you should never store or delete the parent pointer.

[quote]
@
checkclass::checkclass(QWidget parent):
QWidget(){
...
@
[/quote]You have not made use of the parent pointer. Pass it to the QWidget constructor, and let Qt take care of things in the background:

@
checkclass::checkclass(QWidget parent):
QWidget(parent){
...
@