What .NET Developers Must Know about C++ Classes: Listing 6

Initializer lists used in structs and user-defined containers.

#include <iostream>
#include <string>
#include <sstream>
#include <initializer_list>
#include <algorithm>
#include <vector>

using namespace std;

// unless specified otherwise, everything in a struct gets public access:
struct Person {
  string firstName, lastName;
  // concatenates first and last name, with a space in between
  string getFullName() {
    stringstream ss;
    ss << firstName << ' ' << lastName;
    return ss.str();

// a common functionality for a list of Person. Not instantiable.
class AbstractPersonList {
// Pure virtual function that pushes elements to the list
  virtual void push_back(Person p) = 0;
// reusable function to be called by derived constructors. It fills the list with the
// STL initializer_list of Person received as parameter
  inline void initStorage(initializer_list<Person> personList) {
    // this is a C++11 notation known as a range-based for loop.
    // Iterates over the parameter, pushing every Person element to the list
    for (Person p : personList)

// Person list implementation over an STL vector
class VectorPersonList : public AbstractPersonList {
  vector<Person> storage_;
  inline void push_back(Person p) { storage_.push_back(p); }
// Initializer-list constructor.
  VectorPersonList(initializer_list<Person> personList) {

  inline vector<Person>::iterator begin() { return storage_.begin(); }
  inline vector<Person>::iterator end() { return storage_.end(); }

// Person list implementation over a primitive array Person[]
class ArrayPersonList : public AbstractPersonList {
  size_t size_;
  Person* storage_;
  inline void push_back(Person p) {
    static size_t index = 0;
    storage_[index++] = p;
// Initializer-list constructor.
  ArrayPersonList(initializer_list<Person> personList) :
          size_{personList.size()}, storage_{nullptr} {
    if (size_>0) {
      // allocates storage space based on the initializer list size
      storage_ = new Person[size_];
  // A destructor is needed to release any memory allocated at construction
  ~ArrayPersonList() {
    if (storage_!=nullptr)
      delete[] storage_;

  Person* begin() { return storage_; }
  Person* end() { return storage_ + size_; }

int main() {
  // C++03 scope of initializer-lists: structs and classes. Notice that the
  // assignment ('=' sign) is optional.
  Person moe = { "Moe", "Howard" }, larry = { "Larry", "Fine" },
      shemp{ "Shemp", "Howard" }, curly{ "Curly", "Howard" };
  // In C# this is equivalent to:
  // Person moe = new Person { firstName = “Moe”, lastName = “Howard” };

  // C++11 initializer-list enhancement: array-like notation that initializes
  // the list calling the type initializer-list constructor
  VectorPersonList vpl = { moe, larry, shemp };
  ArrayPersonList apl = { moe, curly, larry };
  // In C#, if the type implements IEnumerable, this is equivalent to:
  // ArrayPersonList apl = new ArrayPersonList { moe, curly, larry };

  // range-based for loop over the vector-based list
  // Prints:
  // Hello Moe Howard!
  // Hello Larry Fine!
  // Hello Shemp Howard!
  for (Person p : vpl)
    cout << "Hello " << p.getFullName() << '!' << endl;

  // range-based for loop over the array-based list
  // Prints:
  // Hello Moe Howard!
  // Hello Curly Howard!
  // Hello Larry Fine!
  for (Person p : apl)
    cout << "Hello " << p.getFullName() << '!' << endl;

About the Author

Diego Dagum is a software architect and developer with more than 20 years of experience. He can be reached at [email protected]

comments powered by Disqus


  • Python in VS Code Adds Data Viewer for Debugging

    The January 2021 update to the Python Extension for Visual Studio Code is out with a short list of new features headed by a data viewer used while debugging.

  • GitHub Ships Enterprise Server 3.0 Release Candidate

    It's described as "the biggest ever change to Enterprise Server," with improvements to Actions, Packages, mobile, security and more.

  • Attacks on .NET Apps Grow in Number, Severity, Says Security Firm

    .NET apps were found to have more serious vulnerabilities and suffer more attacks last year, according to data gathered by Contrast Labs.

  • Microsoft Opens Up Old Win32 APIs to C# and Rust, More Languages to Come

    Microsoft is opening up old Win32 APIs long used for 32-bit Windows programming, letting coders use languages of their choice instead of the default C/C++ option.

Upcoming Events