pimpl c++

PIMPL stands for "Pointer to Implementation" and is a design pattern used in C++ to hide the implementation details of a class from its users. This pattern is also known as the "Compiler Firewall" or "Opaque Pointer" pattern.

The steps to implement the PIMPL pattern in C++ are as follows:

1. Create a class header file (.h) that contains the public interface of the class. This header file should only include the necessary declarations and should not expose the implementation details.

2. Create a separate implementation file (.cpp) that contains the private implementation details of the class. This file should include the necessary headers and should define the member functions of the class.

3. In the header file, declare a private data member of type "struct Impl;" This is the opaque pointer that will be used to point to the implementation details.

4. In the implementation file, define the "struct Impl" and include all the private members and functions that make up the implementation of the class.

5. In the constructor of the class, allocate memory for the opaque pointer using the "new" operator. This memory will be managed by the class and will be deallocated in the destructor.

6. In the constructor, initialize the opaque pointer by creating an instance of the "struct Impl" using "new" operator. This will create the actual implementation object.

7. In the destructor, deallocate the memory for the opaque pointer using the "delete" operator.

8. Implement the member functions of the class by using the "->" operator to access the implementation details through the opaque pointer.

By using the PIMPL pattern, the implementation details of the class are hidden from the users, allowing for better encapsulation and separation of concerns. Additionally, this pattern helps in reducing compilation dependencies, as changes made to the implementation file do not require recompilation of the client code.