From Forum Nokia Wiki

ID	...	Creation date	12 January 2009
Platform	S60 3rd Edition FP1, S60 3rd Edition FP2, S60 5th Edition	Tested on devices	Emulator
Category	Qt for Symbian	Subcategory	Application

Keywords (APIs, classes, methods, functions): QHash,QMap

Overview

This code snippet demonstrates how to create a Dictionary in Qt for S60. The QHash class is a template class that provides a hash-table-based dictionary. It stores (key, value) pairs and provides very fast lookup of the value associated with a key.

QHash provides very similar functionality to QMap. Both are used to create a dictionary.

Preconditions

• Download and Install latest version Qt for Symbian - Installation packages which has links on how to install the latest version

Various Function of QHash class

• Returns the value associated with the key.

QHash<QString, int> hash;

• To look up a value, use operator[]() or value():

int num1 = hash["thirteen"];
int num2 = hash.value("thirteen");

• Normally, a QHash allows only one value per key. If you call insert() with a key that already exists in the QHash, the previous value is erased. For example:

hash.insert("plenty", 100);
hash.insert("plenty", 2000);
// hash.value("plenty") == 2000

Source File

#include <QHash>
#include <QLabel>
#include <QtGui>
#include <QApplication>
#include <QString>
#include <QHBoxLayout>
#include <QWidget>
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QHash<QString, int> hash;
    QWidget win;
    QHBoxLayout *layout = new QHBoxLayout;
    hash["one"] = 1;
    hash["three"] = 3;
    hash["seven"] = 7;
    hash.insert("twelve", 12);
    QLabel *label1=new QLabel;
    int num2=2;
    int num1 = hash.value("one");
    if (hash.contains("three"))         // Checks in the hash table, Return the value if it exist
         num2 = hash.value("three");
    int num3 = hash["seven"];
    int x = hash.value("thirty", 30);    // If "thirty" is not there in a hash table than assign 30 to x.
    QString str1;
    str1.setNum(num1);
    label1->setText(str1);
    layout->addWidget(label1);
    win.setLayout(layout);
    win.show();
    return a.exec();
}

Similar is with QMap

QHash provides very similar functionality to QMap. The differences are:

• QHash provides faster lookups than QMap. (See Algorithmic Complexity for details.)
• When iterating over a QMap, the items are always sorted by key. With QHash, the items are arbitrarily ordered.
• The key type of a QMap must provide operator<(). The key type of a QHash must provide operator==() and a global qHash(Key) function.

Source code

#include "Qdict.h"
 
#include <QtGui>
#include <QApplication>
#include <QHash>
#include<QMap>
#include <QLabel>
#include <QString>
#include <QHBoxLayout>
#include <QWidget>
 
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QMap<QString, int> map;
       QWidget win;
       QHBoxLayout *layout = new QHBoxLayout;
       map["one"] = 1;
       map["three"] = 3;
       map["seven"] = 7;
       map.insert("twelve", 12);
       QLabel *label1=new QLabel;
       int num2=2;
       int num1 = map.value("one");
       if (map.contains("three"))         // Checks in the hash table, Return the value if it exist
            num2 = map.value("three");
       int num3 = map["seven"];
       int x = map.value("thirty", 30);    // If "thirty" is not there in a hash table than assign 30 to x.
       QString str1;
       str1.setNum(num1);
       label1->setText(str1);
       layout->addWidget(label1);
       win.setLayout(layout);
       win.show();
 
    return a.exec();
}