qstring.h no such file or directory error!

[wenn32]

hello i am trying to get this program work but it returns me error

QString.h no such file or directory error!

here is the code

#ifndef PUSHBUTTON_H
#define PUSHBUTTON_H
#include <QPushButton>
#include <QString> //here is where its showing error
 
class PushButton: public QPushButton
{
    Q_OBJECT
public:
    PushButton(QWidget* parent = 0): QPushButton(parent){}
    PushButton(const QString& text, QWidget* parent = 0) : QPushButton(text, parent){}
public slots:
    void updatenewvalues()
    {
        if(this->text() == "Don't click me!")
        {
            setText("Click me!");
            return;
        }
        setText("Don't click me!");
    }
};
#endif // PUSHBUTTON_H

#ifndef PUSHBUTTON_H
#define PUSHBUTTON_H
#include <QPushButton>
#include <QString> //here is where its showing error

class PushButton: public QPushButton
{
    Q_OBJECT
public:
    PushButton(QWidget* parent = 0): QPushButton(parent){}
    PushButton(const QString& text, QWidget* parent = 0) : QPushButton(text, parent){}
public slots:
    void updatenewvalues()
    {
        if(this->text() == "Don't click me!")
        {
            setText("Click me!");
            return;
        }
        setText("Don't click me!");
    }
};
#endif // PUSHBUTTON_H

To copy to clipboard, switch view to plain text mode 

int main(int argc, char* argv[])
{
    QApplication app(argc, argv);
    PushButton clickme("Click me!");
    clickme.resize(200, 30);
    clickme.setFont(QFont("Times", 18, QFont::Bold));
    QObject::connect(&clickme, SIGNAL(clicked()), &clickme, SLOT(updatenewvalues()));
    clickme.show();
    return app.exec();
}

int main(int argc, char* argv[])
{
    QApplication app(argc, argv);
    PushButton clickme("Click me!");
    clickme.resize(200, 30);
    clickme.setFont(QFont("Times", 18, QFont::Bold));
    QObject::connect(&clickme, SIGNAL(clicked()), &clickme, SLOT(updatenewvalues()));
    clickme.show();
    return app.exec();
}

To copy to clipboard, switch view to plain text mode 

Thanks!

[MasterBLB]

Hmm everything seems OK,moreover this #include QString isn't necessary.
What is not fully right done is the connection of the signal.Move it into constructor of your class.

Show us compilation output please.

[wenn32]

connection of the signal???due to mean like this

PushButton::PushButton()
{
  QObject::connect(&clickme, SIGNAL(clicked()), &clickme, SLOT(updatenewvalues()));
}

PushButton::PushButton()
{
  QObject::connect(&clickme, SIGNAL(clicked()), &clickme, SLOT(updatenewvalues()));
}

To copy to clipboard, switch view to plain text mode 

i am new to c++ but i can write few codes since i already have experience with c

[ChrisW67]

Sort of, use "this" in place of "&clickme" (which will not compile anyway). You have two possible constructors (neither is parameterless) so you need to be sure that the connection gets made regardless of which is called (or eliminate one if you will never use it).

[wenn32]

ok here is it i have rewritten everything from the beginning

#ifndef PUSHBUTTON_H
#define PUSHBUTTON_H
#include <QPushButton.h>
class pushbutton : class QPushButton
{
    Q_OBJECT
   pushbutton(const QString& text, QWidget* parent = 0) : QPushButton(text, parent)
    {
        QObject::connect(this,signal(clicked()),this,slot(change()));
    }
 
    public slots:
    void change()
    {
    if(this->text() == "Don't click me!")
    {
        setText("Click me!");
        return;
    }
        setText("Don't click me!");
    }
}
#endif

#ifndef PUSHBUTTON_H
#define PUSHBUTTON_H
#include <QPushButton.h>
class pushbutton : class QPushButton
{
    Q_OBJECT
   pushbutton(const QString& text, QWidget* parent = 0) : QPushButton(text, parent)
    {
        QObject::connect(this,signal(clicked()),this,slot(change()));
    }

    public slots:
    void change()
    {
    if(this->text() == "Don't click me!")
    {
        setText("Click me!");
        return;
    }
        setText("Don't click me!");
    }
}
#endif

To copy to clipboard, switch view to plain text mode 

#include <QApplication>
#include "pushbutton.h"
 
 
int main(int argc, char* argv[])
{
    QApplication app(argc, argv);
    pushbutton button = new pushbutton("Dont click me");
 
    button.show();
    return app.exec();
}

#include <QApplication>
#include "pushbutton.h"


int main(int argc, char* argv[])
{
    QApplication app(argc, argv);
    pushbutton button = new pushbutton("Dont click me");

    button.show();
    return app.exec();
}

To copy to clipboard, switch view to plain text mode 

these are the following errors that shows me

C:\Documents and Settings\t\My Documents\project\frontend\pushbutton.h|6|error: expected class-name before 'class'|
 
C:\Documents and Settings\t\My Documents\project\frontend\pushbutton.h|6|error: expected '{' before 'class'|
 
C:\Documents and Settings\t\My Documents\project\frontend\pushbutton.h|6|error: redefinition of 'class QPushButton'|
 
C:\Qt\2010.03\qt\include\QtGui\..\..\src\gui\widgets\qpushbutton.h|58|error: previous definition of 'class QPushButton'|
 
C:\Documents and Settings\t\My Documents\project\frontend\pushbutton.h|6|error: new types may not be defined in a return type|
 
C:\Documents and Settings\t\My Documents\project\frontend\pushbutton.h|6|note: (perhaps a semicolon is missing after the definition of '<type error>')|
 
C:\Documents and Settings\t\My Documents\project\frontend\main.cpp|5|error: two or more data types in declaration of 'main'|
 
||=== Build finished: 6 errors, 0 warnings ===|

C:\Documents and Settings\t\My Documents\project\frontend\pushbutton.h|6|error: expected class-name before 'class'|

C:\Documents and Settings\t\My Documents\project\frontend\pushbutton.h|6|error: expected '{' before 'class'|

C:\Documents and Settings\t\My Documents\project\frontend\pushbutton.h|6|error: redefinition of 'class QPushButton'|

C:\Qt\2010.03\qt\include\QtGui\..\..\src\gui\widgets\qpushbutton.h|58|error: previous definition of 'class QPushButton'|

C:\Documents and Settings\t\My Documents\project\frontend\pushbutton.h|6|error: new types may not be defined in a return type|

C:\Documents and Settings\t\My Documents\project\frontend\pushbutton.h|6|note: (perhaps a semicolon is missing after the definition of '<type error>')|

C:\Documents and Settings\t\My Documents\project\frontend\main.cpp|5|error: two or more data types in declaration of 'main'|

||=== Build finished: 6 errors, 0 warnings ===|

To copy to clipboard, switch view to plain text mode 

please help me Thanks!

[stampede]

You forgot the semicolon after class declaration.
edit: and your class' constructor is private now, add public: before definition of constructor

[wenn32]

ok thanks for the reply i have added the ';' after class declaration and public: to the constructor but still the problems occur

C:\Documents and Settings\t\My Documents\project\frontend\pushbutton.h|6|error: expected class-name before 'class'|
 
C:\Documents and Settings\t\My Documents\project\frontend\pushbutton.h|6|error: expected '{' before 'class'|
 
C:\Documents and Settings\t\My Documents\project\frontend\pushbutton.h|6|error: redefinition of 'class QPushButton'|
 
C:\Qt\2010.03\qt\include\QtGui\..\..\src\gui\widgets\qpushbutton.h|58|error: previous definition of 'class QPushButton'|
 
C:\Documents and Settings\t\My Documents\project\frontend\pushbutton.h|26|error: multiple types in one declaration|
 
C:\Documents and Settings\t\My Documents\project\frontend\main.cpp||In function 'int main(int, char**)':|
 
C:\Documents and Settings\t\My Documents\project\frontend\main.cpp|8|error: variable 'pushbutton button' has initializer but incomplete type|
 
C:\Documents and Settings\t\My Documents\project\frontend\main.cpp|8|error: invalid use of incomplete type 'class pushbutton'|
 
C:\Documents and Settings\t\My Documents\project\frontend\pushbutton.h|6|error: forward declaration of 'class pushbutton'|
 
||=== Build finished: 8 errors, 0 warnings ===|

C:\Documents and Settings\t\My Documents\project\frontend\pushbutton.h|6|error: expected class-name before 'class'|

C:\Documents and Settings\t\My Documents\project\frontend\pushbutton.h|6|error: expected '{' before 'class'|

C:\Documents and Settings\t\My Documents\project\frontend\pushbutton.h|6|error: redefinition of 'class QPushButton'|

C:\Qt\2010.03\qt\include\QtGui\..\..\src\gui\widgets\qpushbutton.h|58|error: previous definition of 'class QPushButton'|

C:\Documents and Settings\t\My Documents\project\frontend\pushbutton.h|26|error: multiple types in one declaration|

C:\Documents and Settings\t\My Documents\project\frontend\main.cpp||In function 'int main(int, char**)':|

C:\Documents and Settings\t\My Documents\project\frontend\main.cpp|8|error: variable 'pushbutton button' has initializer but incomplete type|

C:\Documents and Settings\t\My Documents\project\frontend\main.cpp|8|error: invalid use of incomplete type 'class pushbutton'|

C:\Documents and Settings\t\My Documents\project\frontend\pushbutton.h|6|error: forward declaration of 'class pushbutton'|

||=== Build finished: 8 errors, 0 warnings ===|

To copy to clipboard, switch view to plain text mode 

[stampede]

Inheritance requires the public, protected or private keywords, not class

class pushbutton : public /*private or protected, not class*/ QPushButton
{
    Q_OBJECT
   pushbutton(const QString& text, QWidget* parent = 0) : QPushButton(text, parent)
    {
        QObject::connect(this,signal(clicked()),this,slot(change()));
    }
 ...

class pushbutton : public /*private or protected, not class*/ QPushButton
{
    Q_OBJECT
   pushbutton(const QString& text, QWidget* parent = 0) : QPushButton(text, parent)
    {
        QObject::connect(this,signal(clicked()),this,slot(change()));
    }
 ...

To copy to clipboard, switch view to plain text mode 

Better start with good C++ book before programming with Qt.

[wenn32]

its showing error in this code

pushbutton(const QString& text, QWidget* parent = 0) : QPushButton(text, parent)
    {
        QObject::connect(this,SIGNAL(clicked()),this,SLOT(change()));
    }

pushbutton(const QString& text, QWidget* parent = 0) : QPushButton(text, parent)
    {
        QObject::connect(this,SIGNAL(clicked()),this,SLOT(change()));
    }

To copy to clipboard, switch view to plain text mode 

its showing error in this part

obj\Debug\main.o||In function `pushbutton':|
 
C:\Documents and Settings\t\My Documents\project\frontend\pushbutton.h|11|undefined reference to `vtable for pushbutton'|
 
C:\Documents and Settings\t\My Documents\project\frontend\pushbutton.h|11|undefined reference to `vtable for pushbutton'|
||=== Build finished: 2 errors, 0 warnings ===|

obj\Debug\main.o||In function `pushbutton':|

C:\Documents and Settings\t\My Documents\project\frontend\pushbutton.h|11|undefined reference to `vtable for pushbutton'|

C:\Documents and Settings\t\My Documents\project\frontend\pushbutton.h|11|undefined reference to `vtable for pushbutton'|
||=== Build finished: 2 errors, 0 warnings ===|

To copy to clipboard, switch view to plain text mode 

i know that its basic c++ but i am more into C if i get this signal and slot part correct then i will be rolling :-)

[stampede]

Is the class header on the list of HEADERS in .pro file ? Check if you have moc_pushbutton.cpp somewhere in the build directories. I think the header is not moc'ed, so you get undefined references, make sure its in the list of HEADERS and run qmake/make again.
Btw. you don't have to use QObject:: for connections, pushbutton class is derived from QObject, so you can simply call connect(...).

[wenn32]

Is the class header on the list of HEADERS in .pro file ? Check if you have moc_pushbutton.cpp somewhere in the build directories. I think the header is not moc'ed, so you get undefined references, make sure its in the list of HEADERS and run qmake/make again.
Btw. you don't have to use QObject:: for connections, pushbutton class is derived from QObject, so you can simply call connect(...).

i am using code blocks IDE and i didn't find any .pro file in the project folder.so should i create a .pro file to get rid of the error??

[tbscope]

pushbutton button = new pushbutton("Dont click me");

pushbutton button = new pushbutton("Dont click me");

To copy to clipboard, switch view to plain text mode 

Better start with learning C++ first. It is an absolute must for using Qt.

It is either:

pushbutton *button = new pushbutton("...");

pushbutton *button = new pushbutton("...");

To copy to clipboard, switch view to plain text mode 

or

pushbutton button("...");

pushbutton button("...");

To copy to clipboard, switch view to plain text mode