Book Image

Hands-On Design Patterns with C++ (Second Edition) - Second Edition

By : Fedor G. Pikus
5 (1)
Book Image

Hands-On Design Patterns with C++ (Second Edition) - Second Edition

5 (1)
By: Fedor G. Pikus

Overview of this book

C++ is a general-purpose programming language designed for efficiency, performance, and flexibility. Design patterns are commonly accepted solutions to well-recognized design problems. In essence, they are a library of reusable components, only for software architecture, and not for a concrete implementation. This book helps you focus on the design patterns that naturally adapt to your needs, and on the patterns that uniquely benefit from the features of C++. Armed with the knowledge of these patterns, you’ll spend less time searching for solutions to common problems and tackle challenges with the solutions developed from experience. You’ll also explore that design patterns are a concise and efficient way to communicate, as patterns are a familiar and recognizable solution to a specific problem and can convey a considerable amount of information with a single line of code. By the end of this book, you’ll have a deep understanding of how to use design patterns to write maintainable, robust, and reusable software.
Table of Contents (26 chapters)
1
Part 1: Getting Started with C++ Features and Concepts
5
Part 2: Common C++ Idioms
10
Part 3: C++ Design Patterns
18
Part 4: Advanced C++ Design Patterns

Friends and templates

Both classes and functions in C++ can be templates, and we can have several different combinations - a class template can grant friendship to a non-template function if its parameter types don’t depend on the template parameters; this is not a particularly interesting case, and certainly does not solve any of the problems we’re dealing with now. When the friend function needs to operate on the template parameter types, making the right friends becomes trickier.

Friends of template classes

Let’s start by making our C class into a template:

template <typename T> class C {
  T x_;
  public:
  C(T x) : x_(x) {}
};

We still want to add objects of type C and print them out. We have already considered reasons why the former is better accomplished with a non-member function, and the latter cannot be done in any other way. These reasons remain valid for class templates as well.

No problem - we can...