Conversion from Derived** to Base**

by

It’s basically the same reason why a bowl of bananas is not a bowl of fruits. If a bowl of bananas were a bowl of fruits, you could put an apple into the bowl, and it would no longer be a bowl of bananas.

As long as you only inspect the bowl, the conversion is harmless. But as soon as you start modifying it, the conversion becomes unsafe. This is the key point to bear in mind. (This is the precise reason why the immutable Scala collections actually allow the conversion, but the mutable collections prohibit it.)

Same with your example. If there was a conversion from Derived** to Base**, you could put a pointer to an apple were the type system promised only a pointer to a banana could exist. Boom!

More Related Contents:

  1. What are the differences between a pointer variable and a reference variable in C++?
  2. When should static_cast, dynamic_cast, const_cast and reinterpret_cast be used?
  3. What is a smart pointer and when should I use one?
  4. What is object slicing?
  5. How do I use arrays in C++?
  6. What is the difference between const int*, const int * const, and int const *?
  7. Why do I have to access template base class members through the this pointer?
  8. How to pass objects to functions in C++?
  9. What is the difference between public, private, and protected inheritance in C++?
  10. C++ delete – It deletes my objects but I can still access the data?
  11. Pointer to class data member “::*”
  12. Why should I use a pointer rather than the object itself?
  13. Function with same name but different signature in derived class
  14. Which kind of pointer do I use when?
  15. Why does the use of ‘new’ cause memory leaks?
  16. What is the point of function pointers?
  17. Why is ‘this’ a pointer and not a reference?
  18. What are the differences between a pointer variable and a reference variable?
  19. Conversion of pointer-to-pointer between derived and base classes?
  20. What’s the meaning of * and & when applied to variable names?
  21. Why do we actually need Private or Protected inheritance in C++?
  22. Do all pointers have the same size in C++?
  23. Function with same name but different signature in derived class not found
  24. C++ Access derived class member from base class pointer
  25. Copying derived entities using only base class pointers, (without exhaustive testing!) – C++
  26. What does ‘dereferencing’ a pointer mean in C/C++?
  27. Can I use if (pointer) instead of if (pointer != NULL)?
  28. Trouble with inheritance of operator= in C++
  29. C++11 virtual destructors and auto generation of move special functions
  30. What does slicing mean in C++?

Leave a Comment