Data Member Initialization in Modern C++
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Data Member Initialization in Modern C++

Constructors, Destructors, Non-static Data Member Initialization, Inline Variables, Designated Initializers, and More Modern C++ Features. A not-only-beginner approach.

About the Book

Throughout this book, you will learn practical options to initialize data members in Modern C++. More specifically, this text teaches various types of constructors, non-static data member initialization, inline variables, designated initializers, and more. Additionally, you’ll see the changes and new techniques from C++11 to C++20 and lots of examples to round out your understanding.

The goal of this book is to equip you with the following knowledge:

  • The basic rules of data members and constructors.
  • Essential information about copy constructors, move constructors and destructors.
  • How to efficiently initialize non-static data members using C++11 features like non-static data member initialization, inheriting, and delegating constructors.
  • How to streamline working with static data members with inline variables from C++17.
  • How to work with container-like member, non-copyable data members like `const` data members or move-able only data members.
  • Aggregates and Designated initializers from C++20.

The book contains 15 chapters in the following structure:

  • Chapters 1 to 5 create a foundation for the rest of the book. They cover constructors, destructors, and the basics of data members.
  • Chapter 6 shows a use case for passing strings into constructors.
  • Chapter 7 is a short quiz on constructors. You can check your knowledge from the first "part" of the book.
  • Chapter 8 describes Non-static Data Member Initialization (NSDMI), a powerful feature from C++11 that improves how we work with data members.
  • Chapter 9 serves as a practical summary for NSDMI, where you can solve a few exercises.
  • Chapter 10 discusses how to initialize container-like data members.
  • (In progress) Chapter 11 contains information about non-regular data members and how to handle them in a class. You'll learn about `const` data members, `unique_ptr` as a data member and references.
  • Chapter 12 shows how `inline` variables from C++17 work.
  • Chapter 13 moves to C++20 and describes Designated Initializers, a handy feature based on similar thing from the C language.
  • Chapter 14 it's the summary chapter with a demo that gathers most of the features described in the book.
  • Chapter 15 is the final quiz with seven questions ranging from constructors to designated initializers.

Most sections are completed, but I'm still working on filling two chapters and polishing the quality.

Who is this book for?

The book is intended for beginner/intermediate C++ programmers who want to learn how to work with static and non-static class data members in Modern C++ (from C++11 to C++20).

You should know at least some of the basics of creating and using custom classes.

This text is also helpful for experienced programmers who know older C++ standards and want to move into C++17/C++20

About the Author

Bartłomiej Filipek
Bartłomiej Filipek

Bartłomiej (Bartek) Filipek is a C++ software developer with more than 12 years of professional experience. In 2010 he graduated from Jagiellonian University in Cracow, Poland with a Masters Degree in Computer Science.

Bartek currently works at Xara, where he develops features for advanced document editors. He also has experience with desktop graphics applications, game development, large-scale systems for aviation, writing graphics drivers and even biofeedback. In the past, Bartek has also taught programming (mostly game and graphics programming courses) at local universities in Cracow.

Since 2011 Bartek has been regularly blogging at and Initially, the topics revolved around graphics programming, but now the blog focuses on core C++. He's also a co-organiser of the C++ User Group in Cracow. You can hear Bartek in one @CppCast episode where he talks about C++17, blogging and text processing.

Since October 2018, Bartek has been a C++ Expert for the Polish National Body which works directly with ISO/IEC JTC 1/SC 22 (C++ Standardisation Committee).

In the same month, Bartek was awarded his first MVP title for the years 2019/2020 by Microsoft.

In his spare time, he loves assembling Lego models with his little son.

See his blog at

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Reader Testimonials

Jonathan Boccara
Jonathan Boccara


A new thorough and practical book from Bartek that will take you by the hand and give you an in-depth understanding of a core aspect of C++. The book starts with simple examples and then guides you through various aspects of constructors, and different kinds of data members. I like that it addresses the latest features of C++, including C++20.

Andreas Fertig
Andreas Fertig

Data Member Initialization in Modern C++ gives you an excellent overview of how to initialize class members. I like the practical examples, detailed overview, and discussions of various techniques for custom types design.

Table of Contents

  • About the Book
    • Why should you read this book?
    • Learning objectives
    • The structure of the book
    • Who is this book for?
    • Prerequisites
    • Reader feedback & errata
    • Example code
    • Code license
    • Formatting
    • Special sections
  • About the Author
  • Acknowledgements
  • Revision History
  • 1. Simple Types and Data Members
    • Basics
    • Setting values to zero
    • Initialization with aggregates
    • Default data member initialization
    • Summary
  • 2. Classes and Initialization With Constructors
    • A simple class type
    • Basics of constructors
    • Body of a constructor
    • Adding constructors to DataPacket
    • Compiler-generated default constructors
    • Explicit constructors
    • Difference between direct and copy initialization
    • Using explicit for strong types
    • Constructor summary
  • 3. Copy and Move Constructors
    • Copy constructor
    • Move constructor
    • Distinguishing from assignment
    • Adding debug logging to constructors
    • Copy and swap idiom
    • Trivial classes and user-provided default constructors
  • 4. Delegating and Inheriting Constructors
    • Delegating constructors
    • Limitations
    • Inheritance
    • Inheriting constructors
  • 5. Destructors
    • Basics
    • Objects allocated on the heap
    • Destructors and data members
    • Virtual destructors and polymorphism
    • Partially created objects
    • A compiler-generated destructor
    • Summary and use cases
  • 6. A Use Case - Best Way to Initialize string Data Members
  • 7. Quiz on Special Member Functions
  • 8. Non-Static Data Member Initialization
    • How it works
    • Investigation
    • Experiments
    • Other forms of NSDMI
    • Copy constructor and NSDMI
    • Move constructor and NSDMI
    • C++14 changes
    • C++20 changes
    • Limitations of NSDMI
    • NSDMI: Advantages and Disadvantages
    • NSDMI summary
  • 9. NSDMI: Exercises
    • The first exercise
    • The second exercise
  • 10. Containers as Data Members
    • The basics
    • Using std::initializer list
    • Example implementation
    • More options (advanced)
    • Summary
  • 11. Non-regular Data Members
    • Constant non-static data members
    • References as data members
    • Pointers as data members
    • Moveable-only data members
    • Summary
  • 12. Inline Variables in C++17
    • About static data members
    • Motivation for inline variables
    • Exercise for inline variables
    • Global inline variables
    • Constexpr and inline variables
  • 13. Aggregates and Designated Initializers in C++20
    • Aggregates in C++20
    • The basics of Designated Initializers
    • Rules
    • Advantages of designated initialization
    • Examples
    • Summary
  • 14. Summary of Class Data Members
    • The summary example
    • Compiler support
  • 15. The Final Quiz
  • Appendix A - Quiz and Exercises Answers
    • The quiz after Inheriting Constructors
    • The final quiz
    • Solution to the first coding problem
    • Solution to the second coding problem
    • Solution to the third coding problem
  • References
  • Notes

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