Using Enumeration in C++

Enumeration in C++ is a user defined type that contains a set of constant values. An enumeration consists of an identifier and a list of types. Every type in an enumeration corresponds to a constant value. Default value for the first type is integer 0 and the next one gets the integer value 1. But an enumeration type can have a value other than default integer 0. Therefore an enum type can be casted to integer.

Following sample project created by qt creator and contains following files:

1- UsingEnumeration.pro
2- device.h
3- device.cpp
4- main.cpp

UsingEnumeration.pro file contains project configuration.

TEMPLATE = app
CONFIG += console
CONFIG -= app_bundle
CONFIG -= qt
SOURCES += main.cpp \
    device.cpp
HEADERS += \
    device.h

device.h header file contains definition for Device class and Status enumeration.

#ifndef DEVICE_H
#define DEVICE_H

namespace UsingEnumsSample
{

enum Status {
    IDLE = 0,
    ACTIVE = 1,
    DEAD = 2
};

class Device
{
public:

    Device();
    void setStatus(Status pStatus);
    Status getStatus();

private:
    Status status;
};

}

#endif // DEVICE_H

device.cpp file contains implementation for Device class. setDevice method accepts an enumerator and assigns the passed value to Device class private enumeration member.

#include "device.h"

namespace UsingEnumsSample
{

Device::Device()
{
}

void Device::setStatus(Status pStatus)
{
    status = pStatus;
}

Status Device::getStatus()
{
    return status;
}

}

main.cpp method creates a Device instance and calls its setStatus and getStatus methods to set the Status value to the private Status enumeration member.

#include <iostream>
#include "device.h"

using namespace std;
using namespace UsingEnumsSample;

int main()
{
    Device device;
    device.setStatus(ACTIVE);
    cout << device.getStatus() << endl;
    device.setStatus(IDLE);
    cout << device.getStatus() << endl;
    return 0;
}

When the main method is executed, values of the Status member is displayed on the terminal which are consequently 1 and 0 as the program runs.

boost::array of std::string items in Qt Creator

boost::array is a template class which enables it to be able to be declared for different type of items. There exists an array as a member inside boost:array template class declaration so boost:array also acts a C-array wrapper with fixed number of items inside it.

Following sample project created by qt creator and contains following files:

1- BoostArrayOfStrings.pro
2- main.cpp

BoostArrayOfStrings.pro file contains project configuration.

TEMPLATE = app
CONFIG += console

SOURCES += main.cpp

INCLUDEPATH += /home/tufan/boost_1_55_0

Boost header files and libraries are located under the directory : /home/tufan/boost_1_55_0

main.cpp file contains main method.

#include <boost/array.hpp>
#include <string.h>

using namespace std;

int main()
{
    typedef boost::array<string,3> boostArray;
    boostArray stringArray;

    stringArray[0] = "FirstStringMember";
    stringArray.at(1) = "SecondStringMember";
    stringArray.at(2) = "ThirdStringMember";

    // some common container operations
    cout << "size:     " << stringArray.size() << endl;
    cout << "empty:    " << boolalpha << stringArray.empty() << endl;
    cout << "front:    " << stringArray.front() << endl;
    cout << "back:     " << stringArray.back() << endl;
    cout << "elements:    " << endl;

    for(boostArray::iterator iter(stringArray.begin()); iter != stringArray.end(); ++iter)
    {
        cout << *iter << endl;
    }

    return 0;
}

boost array contains 3 string items. Members of the array are initialized by using array subscript operator and at() function.

size:     3
empty:    false
front:    FirstStringMember
back:     ThirdStringMember
elements:  
FirstStringMember
SecondStringMember
ThirdStringMember

boost::array of Integers in Qt Creator

boost::array provides C-style array declaration and usage with constant number of items inside it. When only static-constant sized arrays are required, then boost::array comes with a better memory management solution than std::vector.

After including boost libraries into a Qt Creator C++ project, it becomes easy to use boost::array type of members in your programs.

boost/array.hpp file contains boost::array type.

As the boost::array documentation indicates boost::array is the STL compliant container wrapper for arrays of constant size.

Following sample project created by qt creator and contains following files:
1- BoostArrayOfIntegers.pro
2- main.cpp

BoostArrayOfIntegers.pro file contains project configuration.

TEMPLATE = app
CONFIG += console

SOURCES += main.cpp

INCLUDEPATH += /home/tufan/boost_1_55_0

I have installed the boost library to the directory         :  /home/tufan/boost_1_55_0
and boost/array.hpp file is located at                           :  /home/tufan/boost_1_55_0/boost/array.hpp

so qt creator does not complain about path related errors.

There is also another installed boost library which contains an older version of boost libraries  at directory : /usr/include/boost

In BoostArrayOfIntegers.pro file I have stated that I will use the boost library from specific location and qt creator selected the library from : /home/tufan/boost_1_55_0

main.cpp file contains main method.

#include <boost/array.hpp>

using namespace std;

int main()
{
    typedef boost::array<int, 4> intArrayType;
    intArrayType myArray = {{1,2,3,4}};
    std::cout << "boost intArray content :" << "\n";
    for( intArrayType::const_iterator iterator = myArray.begin(),
         iteratorEnd = myArray.end();
         iterator != iteratorEnd; ++iterator )
    {
        cout << *iterator << endl;
    }

    return 0;
}

boost::array is initialized with 4 integer members in curly braces. I used an iterator to traverse the integer members of the boost::array.

When the project is executed the following terminal output is generated :

boost intArray content :
1
2
3
4