Why Use the PIMPL Idiom with Public Methods in the Implementation Class?

Why Utilize the PIMPL Idiom?

The Pointer to Implementation (PIMPL) idiom shields implementation details and data from library users. When employing this idiom, it is common practice to define public methods in the PIMPL class rather than the public class. This poses the question: why not directly implement the methods in the public class?

Consider the following PIMPL implementation:

#include "cat.h"

#include "cat_impl.h"

Cat::Cat() {
    cat_ = new CatImpl;
}

Cat::~Cat() {
    delete cat_;
}

Cat::Purr(){ cat_->Purr(); }

In this example, the public class Cat acts as a "facade" for the PIMPL class CatImpl, which holds the actual implementation of the Purr() method. The PIMPL idiom offers several advantages:

• Decouples Interface from Implementation: By separating the interface (public class) from the implementation (PIMPL class), changes to the implementation do not require recompilation of client code that uses the interface.
• Hides Internal Details: The PIMPL idiom conceals implementation details, protecting them from unauthorized access and modification.
• Promotes Encapsulation: By keeping implementation details private, the PIMPL idiom enhances encapsulation and prevents accidental misuse of internal state.
• Supports Code Reuse: The PIMPL class can be used across multiple library versions, allowing for easy code reuse and maintenance.

Therefore, using the PIMPL idiom with public methods defined in the PIMPL class provides the benefits of decoupling, concealment, encapsulation, and code reuse, making it a valuable idiom for developing flexible and maintainable software libraries.

The above is the detailed content of Why Use the PIMPL Idiom with Public Methods in the Implementation Class?. For more information, please follow other related articles on the PHP Chinese website!