[Solved] Using C++ class in projects
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No, I don't use namespaces either in my header file or in my cpp file.
I want to make it as easy as it can be done.
So, this is the content of my Useful file:
#include "useful.h"This is my header:
@#ifndef USEFUL_H
#define USEFUL_H#include <QWidget>
class Useful : public QWidget
{
Q_OBJECT
public:
explicit Useful(QWidget *parent = 0);
double sqr(double x);signals:
public slots:
};#endif // USEFUL_H@
and my cpp
@#include "useful.h"Useful::Useful(QWidget *parent) :
QWidget(parent)
{
}double sqr(double x)
{
return(x * x);
}@So, I just have the sqr function to simplify this thread.
I want to use sqr(4) instead of Useful.sqr(4) in my main/mainwindow cpp.
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As you are wrapping your function inside a class you'll need to call it by using that class. If you only want your function to be inside the namespace you don't need a class, but only wrap this function inside the namespace.
useful.h:
@
namespace useful{
double sqr(double x)
}
@useful.cpp:
@
double useful::sqr(double x)
{
return (x*x);
}
@In your main code you may now use either
@
using namespace useful;
...
double foo = sqr(2.0);
...
@or
@
...
double foo = useful::sqr(2.0);
...
@If you wrap your function inside a class that's inside a namespace it works the same regarding the namespace usage, but you'll have to instantiate a class for calling the function or declare the function to be static.
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Thanks for the fast answer!
Do I have to set the namespace's name to "useful", i.e. lowercase ?
or should this be
@namespace Useful { ...@
?And does the whole class useful (class Useful : public QWidget) in the header file be wrapped with "namespace ..." or what do I actually have to wrap with the namespace?
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It does not matter if your namespace is lower or upper case. I wrote it in lower case because I prefer coding conventions where upper case is only applied to classes and namespaces are lower case so you'll if you are using a static class function or a namespace function.
If you are encapsulating your function inside a class (called Useful) that's inside a namespace you'll have to do something like:
@
using namespace MyNamespace;// if the function is not static
Useful u;
double d = u.sqrt(2.0);// if the function is static
double d = Useful::sqrt(2.0);
@If you're not using namespace :
@
// function is non-static
MyNamespace::Useful u;
double d = u.sqrt(2.0);// function is static
double d = MyNamespace::Useful::sqrt(2.0);
@ -
Actually, I want to use namespace to avoid using these long codes to call a simple function like my sqr one.
Is there nothing simple so that I can easily call my function with
@sqr(1.234);@ ?And you can refer to my code posted "here":http://qt-project.org/forums/viewreply/83941/.
btw: I think line 8 should be
@double d = Useful::sqr(2.0);@ ? -
Ok, but what to write in the corresponding files in addition ?
The code as is provided by you is clear but not sufficient to be placed in a file.
Sorry, I have no idea what to add. -
Wel, let me give a tested example coding :)
useful.h:
@
#ifndef USEFUL_H
#define USEFUL_Hnamespace useful{
double power(double d);
}#endif // USEFUL_H
@
useful.cpp:
@
#include "useful.h"double useful::power(double d)
{
return (d*d);
}
@main.cpp:
@
#include "useful.h"
#include <iostream>using namespace useful;
int main(int argc, char *argv[])
{
std::cout << "power: " << power(2.0) << std::endl;
return 0;
}
@This code uses the namespace useful that is defined in useful.h to call the function useful::power(double d) and prints the result to the default output.
Hope this helps you somewhat more.
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Thank you, this is great.
It was exactly what I was looking for. Now I will extend this code with really useful functions and some structs I want to access to from other projects easily ;)