What are the Advantages of Using Private Virtual Methods in C ?

Virtual Private Methods in C

Have you encountered a C class with a private virtual method? This intriguing coding practice can offer significant advantages in certain scenarios.

Advantage of Private Virtual Methods

According to Herb Sutter, a renowned C expert, declaring a virtual method as private benefits the code in the following ways:

• Customization Flexibility: Derived classes can override the private virtual method to adapt its behavior without exposing the method directly for external access (as in protected methods).
• Modularity: Private virtual methods enhance encapsulation by confining their accessibility to the class that defines them, allowing the base class to encapsulate the underlying implementation.

Practical Example

Consider the HTMLDocument class in the C project you mentioned:

<code class="cpp">class HTMLDocument : public Document, public CachedResourceClient {
private:
    virtual bool childAllowed(Node*);
    virtual PassRefPtr<Element> createElement(const AtomicString& tagName, ExceptionCode&);
};</code>

The private virtual methods childAllowed and createElement provide customization points for derived classes without exposing these methods externally. This allows subclasses to specialize the document handling behavior without modifying the base class implementation directly.

Conclusion

Private virtual methods in C strike a balance between customization and encapsulation. By limiting their visibility to the defining class, they empower derived classes to tailor specific aspects of a base class's behavior without compromising the overall modularity and flexibility of the design.

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