How do I initialize a member array with an initializer_list?

by

You can use a variadic template constructor instead of an initializer list constructor:

struct foo { 
    int x[2]; 
    template <typename... T> 
    foo(T... ts) : x{ts...} { // note the use of brace-init-list
    } 
};

int main() {
    foo f1(1,2);   // OK
    foo f2{1,2};   // Also OK
    foo f3(42);    // OK; x[1] zero-initialized
    foo f4(1,2,3); // Error: too many initializers
    foo f5(3.14);  // Error: narrowing conversion not allowed
    foo f6("foo"); // Error: no conversion from const char* to int
}

EDIT: If you can live without constness, another way would be to skip initialization and fill the array in the function body:

struct foo {
    int x[2]; // or std::array<int, 2> x;
    foo(std::initializer_list<int> il) {
       std::copy(il.begin(), il.end(), x);
       // or std::copy(il.begin(), il.end(), x.begin());
       // or x.fill(il.begin());
    }
}

This way, though, you lose the compile-time bounds checking that the former solution provides.

More Related Contents:

  1. How to construct std::array object with initializer list? [duplicate]
  2. C++: Using for loop I need to take infinite values of a point using arrays. How can I take values of point [ ] until 2 points of are equal
  3. Invalid operands to binary expression while implementing vector [closed]
  4. How do I take values from text file and input into a 2D array? c++
  5. Can I list-initialize a vector of move-only type?
  6. initializer_list and move semantics
  7. Does “int size = 10;” yield a constant expression?
  8. Initializer lists and RHS of operators
  9. initializer_list and template type deduction
  10. Initializing a member array in constructor initializer
  11. When to use the brace-enclosed initializer?
  12. C++11: Correct std::array initialization?
  13. Brace-enclosed initializer list constructor
  14. Order of evaluation of elements in list-initialization
  15. Why does ‘std::vector b{2};’ create a 1-element vector, and not a 2-element one?
  16. Why doesn’t my template accept an initializer list
  17. How does the range-based for work for plain arrays?
  18. Now that we have std::array what uses are left for C-style arrays?
  19. Range-based for loop on a dynamic array?
  20. what is the best modern c++ approach to construct and manipulate a 2d array [closed]
  21. Is int arr[ ] valid C++?
  22. C++11 initializer list fails – but only on lists of length 2
  23. too many initializers for ‘int [0]’ c++
  24. How does std::end know the end of an array?
  25. Why can’t I initialize a reference in an initializer list with uniform initialization?
  26. Range-based for with brace-initializer over non-const values?
  27. Interfacing C++11 array with Cython
  28. What would a std::map extended initializer list look like?
  29. Initialization difference with or without curly braces in C++
  30. Which greedy initializer-list examples are lurking in the Standard Library?

Leave a Comment