abstract class in c 2b 2b

1#include <iostream>
2#include  <string>
3//Pure virtual function or inteface allows us to define a function in a base class that doesn't have an implementation or definition in the base class and force sub classes to implement that function
4//Pure virtual function is also called an interface in other languages
5class Entity {
6public:
7	//virtual std::string GetName() { return "Entity"; }//This is a function that is just virtual .Overriding this function in sub class is optional we can instantiate subcllass without overriding  or implementing this function
8	
9	//Below is an example a Pure Virtual Function
10	//It is an unimplemented function ant it forces the  sub class to implement it and define it
11	//You will not be able to instantiate sub class without implementing or defining the function in sub class
12	virtual std::string GetName() = 0; 
13  //the pure virtual function must have virtual written at the beginning and =0 at the end
14 //This function cannot contain any definition in base class,it is just a declaration
15};
16class Player :public Entity {
17	std::string m_name;
18
19public:
20	Player(const std::string& name)
21		:m_name(name)
22	{};
23	void Print() { std::cout << "This is Sub class" << std::endl; };
24	std::string GetName()override { return m_name; };//Pure virtual functions is implemented here in this sub class
25};
26
27int main()
28{
29	//Entity a;//We can't do this because class Entity contains function that is unimplemented
30	Player x("Jacob");//This will work because we have implemented or defined the function in this sub class
31	std::cin.get();
32}

1#include <iostream>
2#include  <string>
3//Pure virtual function  or inteface allows us to define a function in a base class that doesn't have an implementation or definition in the base class and force sub classes to implement that function
4//Pure virtual function is also called an interface in other languages
5class Entity {
6public:
7	//virtual std::string GetName() { return "Entity"; }//This is a function that is just virtual .Overriding this function in sub class is optional we can instantiate subcllass without overriding  or implementing this function
8	
9	//Below is an example a Pure Virtual Function
10	//It is an unimplemented function ant it forces the  sub class to implement it and define it
11	//You will not be able to instantiate sub class without implementing or defining the function in sub class
12	virtual std::string GetName() = 0; 
13  //the pure virtual function must have virtual written at the beginning and =0 at the end
14 //This function cannot contain any definition in base class,it is just a declaration
15};
16class Player :public Entity {
17	std::string m_name;
18
19public:
20	Player(const std::string& name)
21		:m_name(name)
22	{};
23	void Print() { std::cout << "This is Sub class" << std::endl; };
24	std::string GetName()override { return m_name; };//Pure virtual functions is implemented here in this sub class
25};
26void PrintName(Entity* entity) {
27
28	std::cout << entity->GetName() << std::endl;
29}
30int main()
31{
32	//Entity a;//We can't do this because class Entity contains function that is unimplemented
33	Player x("Jacob");//This will work because we have implemented or defined the function in this sub class
34	std::cin.get();
35}

1//Code by Soumyadeep Ghosh 
2//insta : @soumyadepp
3//linked in : https://www.linkedin.com/in/soumyadeep-ghosh-90a1951b6/
4#include <bits/stdc++.h>
5
6using namespace std;
7
8class person
9{
10  string p_id;
11  public:
12  virtual void get_info()=0; //declaring person as abstract class
13  virtual void show()=0;
14};
15
16class student:public person
17{
18  string name;
19  int roll_no;
20  public:
21  /*overriding the pure virtual function declared in base class otherwise
22    this class will become an abstract one and then objects cannot be created
23    for the same*/
24    void get_info()
25    {
26      cout<<"Enter name of the student "<<endl;
27      cin>>name;
28      cout<<"Enter roll number of the student "<<endl;
29      cin>>roll_no;
30    }
31   void show()
32   {
33     cout<<"Name : "<<name<<" Roll number: "<<roll_no<<endl;
34   }
35};
36
37int main()
38{
39  person *p;
40  p=new student;
41  p->get_info();
42  p->show();
43  return 0;
44}
45

1struct Abstract {
2    virtual void f() = 0; // pure virtual
3}; // "Abstract" is abstract
4 
5struct Concrete : Abstract {
6    void f() override {} // non-pure virtual
7    virtual void g();     // non-pure virtual
8}; // "Concrete" is non-abstract
9 
10struct Abstract2 : Concrete {
11    void g() override = 0; // pure virtual overrider
12}; // "Abstract2" is abstract
13 
14int main()
15{
16    // Abstract a; // Error: abstract class
17    Concrete b; // OK
18    Abstract& a = b; // OK to reference abstract base
19    a.f(); // virtual dispatch to Concrete::f()
20    // Abstract2 a2; // Error: abstract class (final overrider of g() is pure)
21}

1struct Abstract
2{
3     virtual ~Abstract() = 0;
4};
5
6Abstract::~Abstract() {}
7
8struct Valid: public Abstract
9{
10        // Notice you don't need to actually overide the base
11        // classes pure virtual method as it has a default
12};
13
14
15int main()
16{
17    // Abstract        a;  // This line fails to compile as Abstract is abstract
18    Valid           v;  // This compiles fine.
19}