What is Qt?

Qt is a cross-platform application and UI framework. Using Qt, you can write applications once and deploy them across desktop, mobile and embedded operating systems without rewriting the source code.

Qt is a complete C++ application development framework, which includes a class library and tools for cross-platform development and internationalization.

Qt supports the development of cross platform GUI applications with its “write once, compile anywhere” approach. Using a single source tree and a simple recompilation, applications can be written for Windows 98 to XP and Vista, Mac OS X,S60,Linux, Solaris, HP-UX, and many other versions of Unix with X11. Qt applications can also be compiled to run on embedded Linux and Windows CE platforms.

Qt is available under various licenses.If you want to build commercial applications,you must buy a commercial Qt license; if you want to build open source programs, you can use the open source (GPL) edition.

Qt Faqs

1) What is Qt?

2) Signals and Slots?

3) meta object system

4) Widgets

5) Events

6) Actions

Symbian Internals

1) Introduction

2) Symbian Data Types

3) Descriptors

4) Arrays

5) Leaves

6) Cleanup stack

7) Two phase construction

8) Active objects

9) Client/Server

C++:: Constructors and Destructors

Constructor

Constructors in C++ are special member functions of a class. A Constructor is a function that initilizes the members of object.There can be any number of overloaded constructors inside a class.The Constructor is automatically called whenever an object is created or dynamically allocated using "new" operator.

If no constructor is supplied then a default one is created by the compiler without any parameters.If you supply a constructor with parameters then default will NOT be created.

Some Points about Constructor:

-- Constructors have the same name as the class.

-- Constructors do not return any values.

-- Constructors are invoked first when a class is initialized. Any initializations for the class members,memory allocations are done at the constructor.

-- Constructors are never virtual.

Ex:

Class Sample{

public:

Sample(){ ..}

};

Destructor

Destructors in C++ also have the same name,except that they are preceded by a '~' operator. The destructors are called when the object of a class goes out of scope.The main use of destructors is to release dynamic allocated memory.Destructors are used to free memory,release resources and to perform other cleanup.If the destructor is not declared inside a class,the compiler automatically create a default one.

If the constructor/destructor is declared as private,then the class cannot be instantiated.

Ex:

~Sample()

.

C++ Basics

Class

Objects

Constructors and Destructors

Memory Management

Inline

Static

Overloading

Polymorphisam

Virtual Functions

Inheritance

Friend

Templates

Singleton

STL

C++:Singleton Class

Definition:

A class whose number of instances that can be instantiated is limited to one is called a singleton class. Thus, at any given time only one instance can exist, no more.

Can you give me an example, where it is used?

The singleton design pattern is used whenever the design requires only one instance of a class. Some examples:

• Application classes. There should only be one application class. (Note: Please bear in mind, MFC class 'CWinApp' is not implemented as a singleton class)
• Logger classes. For logging purposes of an application there is usually one logger instance required.