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  1. #include <iostream>
  2.  
  3. class A{
  4. 	int var;
  5. 	virtual void foo() = 0;
  6. public:
  7. 	void bar();
  8. };
  9.  
  10. class B : public A{
  11. public:
  12. 	int var; // This is usually not a good practice (violates Liskov's principle)
  13. 	void foo();
  14. };
  15.  
  16. void A::bar(){
  17. 	std::cout << var << std::endl; // This will output an uninitialized A var!
  18. }
  19.  
  20. void B::foo(){
  21. 	var = 42; // B's var hides A's var so this only sets the derived one's
  22. }
  23.  
  24. void func(){
  25. 	B myObj;
  26. 	myObj.foo(); // No polymorphic behavior here, B::foo is called
  27. 	myObj.bar(); // the same, but A::bar is called since B doesn't define one
  28. }
  29.  
  30. class A2{
  31. 	virtual void foo() = 0;
  32. public:
  33. 	int var;
  34. 	void bar() {
  35. 		std::cout << var;
  36. 	}
  37. };
  38.  
  39. class B2 : public A2{
  40. public:
  41. 	void foo() {
  42. 		var = 42; // Sets the common A2::var variable
  43. 	};
  44. };
  45.  
  46. void func2(){
  47. 	B2 myObj;
  48. 	myObj.foo();
  49. 	myObj.bar();
  50. }
  51.  
  52. int main() {
  53. 	func();
  54. 	func2();
  55. }
Success #stdin #stdout 0s 3340KB
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134514939
42
https://ideone.com/M1AwY7
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
public

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