THECODEPROGRAM

Let's begin.

In here we are going to use Template programming. So if you have no idea of Template programming firstly take a look at below article. https://thecodeprogram.com/explanation-of-template-programing-in-c---and-qt

In C# I used Dictionary class for this purpose very much. So I will use the Dictionary word since here.

Firstly we need to create a Header file and name it What you want. I here named this header file as QDictionary. Here we did not created cpp file because we can not access the private variables directly. One of our articles I will talk about PIMPL design patter to access them in C++.

In this header file we will create a template class and its private and public sections. Then I will implement required methods and variables in this class.

• I declared them as TKey and TValue. And I have created two vectors in this class to store these datas. One of these Vectors will keep the keys and the other one will keep the Values at same index.
• We will implement methods to get datas with specified indexes. Also we will be able to get datas at same keys.
• Then we will implements the removing method with key data.
• Also we are going to implement methods to werite all values and keys in our dictionary class.

Below you can see our template class property and method structure.

qdictionary.h

#include <QVector>
#include <QString>
#include <QDebug>


template <typename TKey, typename TValue> class QDictionary
{

private:
    TKey  key;
    TValue  value;
    unsigned int size =0;

    QVector<TKey> * arrKeys = new QVector<TKey>(1);
    QVector<TValue> * arrValues = new QVector<TValue>(1);

    QString controlKeyOutput(TKey k){
        std::string t = typeid(TKey).name();
        if(t == "int" ) return QString::number(k);
        //else if(t == "class QString" ) return k;
        else return "";
    }

    //I have no ideo why it is returning 7QString.
    //it was returning class QString at QT 5.8
    QString controlValueOutput(TValue v){
        std::string t = typeid(TValue).name();
        if(QString::fromStdString(t).indexOf("QString") > -1) return v;
        else return "";
    }


public:
    QDictionary();

    void add(TKey k, TValue v){
        arrKeys->append(k);
        arrValues->append(v);
        size++;

        //prepare for next adding
        arrKeys->resize(size+1);
        arrKeys->resize(size+1);
    }

    TValue getWithkey(TKey k){
        int index = arrKeys->indexOf(k);
        return arrValues->at(index);
    }


    void removeFromIndex(int i){
        arrKeys->remove(i);
        arrValues->remove(i);
        size--;

        //prepare for next adding
        arrKeys->resize(size-1);
        arrKeys->resize(size-1);
    }

    void removeFromKey(TKey k){
        int index = arrKeys->indexOf(k);
        removeFromIndex(index);
    }

    void removeFromValue(TValue v){
        int index = arrValues->indexOf(v);
        removeFromIndex(index);
    }

    int getSize(){ return size; }

    QString getPairAtKey(TKey k){

        qDebug() << "TValue türü : " << typeid(TValue).name() << Qt::endl;

        int index = arrKeys->indexOf(k);
        QString rK =  controlKeyOutput( arrKeys->at(index) ) ;
        QString rV =  controlValueOutput( arrValues->at(index) );
        return rK + "=" + rV;
    }

    QString getAllValues(){
        QString output = "";
        for(unsigned int i=0; i<arrValues->size(); i++){
            output += controlValueOutput(arrValues->at(i)) + "\n";
        }
        return output;
    }
};

add(TKey k, TValue v) method:

    void add(TKey k, TValue v){
        arrKeys->append(k);
        arrValues->append(v);
        size++;

        //prepare for next adding
        arrKeys->resize(size+1);
        arrKeys->resize(size+1);
    }

we will get data wusing key with getWithkey(TKey k) method.

    TValue getWithkey(TKey k){
        int index = arrKeys->indexOf(k);
        return arrValues->at(index);
    }

we will use removeFromIndex(int i) and removeFromKey(TKey k) methods to remove datas from Dictionary.

    void removeFromIndex(int i){
        arrKeys->remove(i);
        arrValues->remove(i);
        size--;

        //prepare for next adding
        arrKeys->resize(size-1);
        arrKeys->resize(size-1);
    }

    void removeFromKey(TKey k){
        int index = arrKeys->indexOf(k);
        removeFromIndex(index);
    }

Also we can get data types of variables with typeid.

    QString controlKeyOutput(TKey k){
        std::string t = typeid(TKey).name();
        if(t == "int" ) return QString::number(k);
        //else if(t == "class QString" ) return k;
        else return "";
    }

    QString controlValueOutput(TValue v){
        std::string t = typeid(TValue).name();
        if(t == "class QString" ) return v;
        else return "";
    }

Until here out methods are ready. Now, It is time to test our QDictionary.

At my UI class

• First I will initialize a Dictionary template class with int and QString data types.
• Then I will add some datas in it.
• Then I will get size of Dictionary.
• Then I will get all datas of Dictionary.
• Then I will get some specific datas with via index and key.
• Last I will remove some datas from my Dictionary.

mainwindow.cpp

QString res = "";

    Dictionary<int, QString> *dict = new Dictionary<int, QString>();
    dict->add(1,"Burak");
    dict->add(2,"Hamdi");
    dict->add(3,"Tufan");
    dict->add(4,"The");
    dict->add(5,"Code");
    dict->add(6,"Program");

    res += "Added some values to dictionary with keys...\n";
    res += "Dictionary Size : " + QString::number( dict->getSize() ) + " \n";

    res += dict->getAllValues();

    res +=  QStringLiteral("Value with key 3 : %1. \n").arg( dict->getWithkey(3) ) ;
    res +=  QStringLiteral("Value with key 5 : %1. \n\n").arg( dict->getWithkey(5) ) ;

    dict->removeFromKey(1);

    res += "Removed data on Key 1...\n";
    res += "Dictionary Size : " + QString::number( dict->getSize() ) + " \n";
    res +=  QStringLiteral("Value with key 2 : %1. \n").arg( dict->getWithkey(2) ) ;

    res += dict->getAllValues();

    res += "Key-Value pair at key 4 -> " + dict->getPairAtKey(4);

    ui->plainTextEdit->setPlainText(res);

That is all in this article.

You can reach the source code of example on Github via below link.
https://github.com/thecodeprogram/Dictionary-Impl.-With-Template-in-Qt-C-

Burak Hamdi TUFAN