Introduction to C++: Part 1 PDF are explicit versions of the

Lecture-3

o A class can have more than one constructor. Destructor o Called when an object is cleaned up (goes out of scope) o One class can have only one destructor.

Characteristic of Member Function

Destructor can be virtual but constructors cannot. 5.Only one destructor can be defined in the class. The destructors not have any argument. 6. The destructor

Introduction to Classes (Chapter 13.1 – 13.12)

in the class can have different properties than object: an instance of a class in the same ... Only one destructor per class

Chapter-9 CONSTRUCTORS AND DESTRUCTORS

It is sometimes convenient if an object can initialize itself when it is first created without the need A class can have more than one constructor.

Faculty of Diploma Studies – 695

Only functions of the class can access the data of the class and they 36 Which class allows only one object to be created? A. Nuclear Family Class.

UNIT 4 CONSTRUCTORS AND DESTRUCTORS

If a class has constructor each object of that class will be initialized. 1) Constructor can take arguments but destructor didn't.

Electronic Science C and C++ Programming 32. Constructors and

A class cannot have more than one destructor. It takes no arguments and no return types can be specified for it not even void. It is called automatically by

Introduction to C++: Part 1

are explicit versions of the default C++ constructors and destructors. ? Every class has them – if you don't define them then empty ones that do nothing will

Object Oriented Programming Using C++

A derived class can be defined by specifying its relationship with the base Multiple inheritance: A new class is derived from more than one base class ...

Introduction to C++: Part 1

Bother references and pointers can be used to refer to objects in memory Classes can contain members ... Only one destructor per class is allowed!

Introduction to C++: Part 3

Tutorial Outline: Part 3

Defining Classes

Class inheritance

Public, private, and protected access

Virtual functions

A first C++ class

Open project Basic_Rectangle.

A C++ class consists of 2 files: a header file (.h) and a source file (.cpp) The header file contains the definitions for the types and names of members, methods, and how the class relates to other classes (if it does). The source file contains the code that implements the functionality of the class Sometimes there is a header file for a class but no source file.

Using Eclipse

An IDE is very useful for setting up code that follows patterns and configuring the build system to compile them. This saves time and effort for the programmer. Right-click on the Basic_Rectangleproject and choose NewAEClass

Give it the name

Rectangleand click

the Finish button.

Open the new files

Rectangle.hand

Rectangle.cpp

Rectangle.h

keyword

Class name

Curly brace

and a semi-colon.

Access

control

Default declared methods

Rectangle();

A constructor. Called when an object of this class is created.

~Rectangle();

A destructor. Called when an object of this class is removed from memory, i.e. destroyed.

Ignore the virtualkeyword for now.

Rectangle.cpp

Header file included

Class_name:: pattern indicates

the method declared in the header is being implemented in code here.

Methods are otherwise regular

functions with arguments () and matched curly braces {}.

A Rectangle class should store a

length and a width. supply an Area() method to compute its own area.

Edit the header file to look like the

code to the right.

Encapsulation

Bundling the data and area calculation for a rectangle into a single class is an example of the concept of encapsulation.

The code for the two methods is needed

Right-click in the Rectangle.h

window and choose

SourceAEImplementMethods

Click Select Allthen click OK.

Fill in the methods

Member variables can be accessed as though they were passed to the method.

Methods can also call each other.

Fill in the Area() method and then write your own ScaledArea

Step 1: add some comments.

Step 2: add some code.

Using the new class

Open Basic_Rectangle.cpp

Add an include statement for

the new Rectangle.h

Create a Rectangle object

and call its methods.

Special methods

There are several methods that deal with creating and destroying objects.

These include:

Constructorscalled when an object is created. Can have many defined per class. Destructorone per class, called when an object is destroyed Copycalled when an object is created by copying an existing object Movea feature of C++11 that is used in certain circumstances to avoid copies.

Construction and Destruction

The constructoris called when an

object is created.

This is used to initialize an object:

Load values into member variables

Open files

Connect to hardware, databases,

networks, etc.

The destructoris called when an

object goes out of scope.

Example:

Object c1 is created when the

program reaches the first line of the function, and destroyed when the program leaves the function. voidfunction(){

ClassOnec1 ;

The rTobject is created in memory.

When it is created its constructoris called to do any necessary initialization.

The constructor can take any number of

arguments like any other function but it cannotreturn any values.

What if there are multiple constructors?

The compiler follows standard function overload rules.Note the constructor has no return type!

A second constructor

rectangle.h classRectangle public:

Rectangle();

Rectangle(constfloatwidth,

constfloatlength); /* etc*/ rectangle.cpp #include "rectangle.h³ /* C++11 style */

Rectangle::Rectangle(constfloatwidth,

constfloatlength): m_width(width), m_length(length) /* extra code could go here */ Adding a second constructor is similar to overloading a function. Here the modern C++11 style is used to set the member values this is called a member initialization list

Member Initialization Lists

Syntax:

MyClass(intA,OtherClass&B,floatC):

m_A(A), m_B(B), m_C(C){ /* other code can go here */

Colon goes here

Members assigned

and separated with commas. The order

Additional code can be

added in the code block.

And now use both constructors

Both constructors are now used.

The new constructor initializes the

values when the object is created.

Constructors are used to:

Initialize members

Open files

Connect to databases

Etc.

#include usingnamespacestd; #include "Rectangle.h³ intmain(intargc, char** argv)

Rectangle rT;

rT.m_width=1.0; rT.m_length=2.0; cout<Rectangle rT_2(2.0,2.0); cout<Default values

C++11 added the ability to define default

values in headers in an intuitive way.

Pre-C++11 default values would have been

coded into constructors. If members with default values get their value set in constructor than the default value is ignored. classRectangle { public:

Rectangle();

Rectangle(constfloatwidth,

constfloatlength) ;

Rectangle(constRectangle&orig);

virtual~Rectangle(); floatm_length= 0.0 ; floatm_width= 0.0 ; floatArea(); floatScaledArea(constfloatscale); private:

Default constructors and destructors

The two methods created by Eclipse automatically are explicit versions of the defaultC++ constructors and destructors.

Every class has them

empty ones that do nothing will be created for you by the compiler. delete it with the deletekeyword. Also in the header file you can use the defaultkeyword if you like to be clear that you are using the default. classFoo { public:

Foo()=delete;

// Another constructor // mustbe defined!

Foo(intx);

classBar { public:

Bar()=default;

Custom constructors and destructors

You must define your own constructor when you want to initialize an object with arguments.quotesdbs_dbs21.pdfusesText_27

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[PDF] Introduction to C++: Part 1 are explicit versions of the

Introduction to C++: Part 3

Tutorial Outline: Part 3

Defining Classes

Class inheritance

Public, private, and protected access

Virtual functions

A first C++ class

Open project Basic_Rectangle.

Using Eclipse

Give it the name

Rectangleand click

Open the new files

Rectangle.hand

Rectangle.cpp

Rectangle.h

Class name

Curly brace

Curly brace

Access

Default declared methods

Rectangle();

~Rectangle();

Ignore the virtualkeyword for now.

Rectangle.cpp

Header file included

Class_name:: pattern indicates

Methods are otherwise regular

A Rectangle class should store a

Edit the header file to look like the

Encapsulation

The code for the two methods is needed

Right-click in the Rectangle.h

SourceAEImplementMethods

Click Select Allthen click OK.

Fill in the methods

Methods can also call each other.

Step 1: add some comments.

Step 2: add some code.

Using the new class

Open Basic_Rectangle.cpp

Add an include statement for

Create a Rectangle object

Special methods

These include:

Construction and Destruction

The constructoris called when an

This is used to initialize an object:

Load values into member variables

Open files

Connect to hardware, databases,

The destructoris called when an

Example:

Object c1 is created when the

ClassOnec1 ;

The rTobject is created in memory.

The constructor can take any number of

What if there are multiple constructors?

A second constructor

Rectangle();

Rectangle(constfloatwidth,

Rectangle::Rectangle(constfloatwidth,

Member Initialization Lists

Syntax:

MyClass(intA,OtherClass&B,floatC):

Colon goes here

Members assigned

Additional code can be

And now use both constructors

Both constructors are now used.

The new constructor initializes the

Constructors are used to:

Initialize members

Open files

Connect to databases

Etc.

Rectangle rT;

C++11 added the ability to define default

Pre-C++11 default values would have been

Rectangle();

Defining Classes

Class inheritance

Public, private, and protected access

Virtual functions

Open project Basic_Rectangle.

Give it the name

Open the new files

Rectangle();

~Rectangle();

Ignore the virtualkeyword for now.

A Rectangle class should store a

Edit the header file to look like the

Right-click in the Rectangle.h

Click Select Allthen click OK.

Methods can also call each other.

Step 1: add some comments.

Step 2: add some code.

Open Basic_Rectangle.cpp

Add an include statement for

Create a Rectangle object

These include:

The constructoris called when an

This is used to initialize an object:

Load values into member variables

Open files

Connect to hardware, databases,

The destructoris called when an

Example:

Object c1 is created when the

The rTobject is created in memory.

The constructor can take any number of

What if there are multiple constructors?

Syntax:

Both constructors are now used.

Constructors are used to:

Initialize members

Open files

Connect to databases

Etc.

C++11 added the ability to define default

Pre-C++11 default values would have been

Every class has them