C++ language constructs with Objects and Classes

Namespace

Collection of related names or identifiers (functions, class, variables). Helps to separate identifiers from similar identifiers in other namespaces or global namespaces. It beings with keyword namespace. std is a namespace whose members are used in the program. Its members are cout, cin, endl, etc.

Overloading

Creation of two or more members with the same name but different in parameters.

Function Overloading

Having two function with the same name but different in parameters. Increases readability of the program because no need to use different names for the same action.

int add(int x, int y) {
	return x+y;
}
 
int add(int x, int y, int z){
	return x+y+z;
}

Operator Overloading

Operator is overloaded to provide special meaning to the user defined data type. It can be used to perform different operation on the same operand.

return_type class_name :: operator op(argument_list) {
//funtion body
}

Inline functions

When we make an inline function, compiler places a copy of the code of that function at each point, where the function is called at compile time.

It saves memory space. If changes were made to the inline function, the entire function needs to be recompiled again.

inline return_type function_name(parameters) {
	//function code
}

Default Argument

Used when we provide no argument or few argument while calling a function.

void temp(int = 13, float = 6.9);
 
int main() {
	...
	temp();
	...
}
 
void temp(int i, float f) { //takes the default value declared above 13 & 6.9
	//code
}

Introduction to Class and object

Class

It is a user defined data type that has members and functions.

class Student {
	public:
		int id;
		string name;
		string address;
}

Object

It is an entity that has state and behavior. State means data and behavior means functionality.

Stduent s1; //creating an object of Student

Access Specifiers

It defines the scope (who can access) of the attributes and methods of a class.

Private

members cannot be accessed outside the class.

Public

member are accessible outside the class.

Protected

members can be accessed outside the class however, they can only be accessed by the inherited class.

Member Functions

It can accessed within the class definition or separately using scope resolution operator.

Types:

1. Simple Function
2. Static Function
3. Const Function
4. Inline Function
5. Friend Function

Constructors

Constructor is a special type of function whose name should be same as the class name. It is invoked when the object is created and doesn’t have any return type.

Types

1. Default Constructor: doesn’t take any parameters, used to initialize data members with real values.
2. Parameterized Constructor: contains parameters (or arguments) in the constructor definition and declaration.
3. Copy Constructor: member function that initialize an object using another object in the same class.

Constructor Overloading

Constructors with the same name but different parameters (or arguments).

Destructor

It destroys the class objects created by constructors preceded by the ~ symbol.

class Customer
	{
	public:
	    Customer();
	    ~Customer();
	};

Dynamic memory allocation for objects and object array

Memory allocation can be done in two ways: Static Allocation or Compile-time allocation and Dynamic Allocation or Run-time allocation.

Memory allocation is divided into two parts:

1. Stack: All memory declared inside a function will take up memory from it.
2. Heap: Used to allocate memory dynamically when program runs.

New Operator

It denotes the request for memory allocation on the free store.

int *p = new int;

Delete Operator

Releases the allocated memory.

For Arrays

char* pvalue = NULL; //request memory for the variable
pvalue = new char[20];

this Pointer

It refers to the current instance of the class. It is used to pass current objects as parameters to another object.

Applications

1. Return Object
2. Method Chaining
3. Distinguished Data Members

Static Data Member and Static Function

Static Data Member

Declared using the static keywords, only visible within the class. Only one copy of static data member in the class, even if there are many class objects.

	static data_type data_member_name;

Static Function

Declared using the static keyword. Can be used to access static data members and can be called without creating an object of it.

Constant Member Functions and Constant Objects

Declared using the constant keyword. Constant member function can only read or retrieve the data members of the calling class without modifying them.

Specifies the function is a read only function and doesn’t modify the object for the given class.

Friend Function and Friend Classes

Friend Function

Function declared using the friend keyword that can access private, protected and public members of a class.

Friend Class

Declared using friend keyword to have access to private, protected and public members of other class. Allowing to extend storage and access its parts while maintaining encapsulation.

References

1. Inline Functions in C++ - GeeksforGeeks (opens in a new tab)