`std::initializer_list`: Brace Initialization, Implementor’s View¶

`std::initializer_list`¶

Used to implement brace initialization of custom datatypes, like std::vector

std::vector<int> ints{1, 2, 3};
std::vector<std::pair<int, std::string>> pairs{ {1, "one"}, {2, "two"} };

When the compiler sees elements in braces, it creates a std::initializer_list<T> of those elements (deducing whatever types are necessary)
Very lightweight ⟶ no copy
Shallow wrapper around compiler-specific internals

Direct Usage ¶

Works like any container datatype …

#include <initializer_list>

std::initializer_list<point> points { {1, 2}, {3, 4} };
for (auto p: points)
    do_something_with(p);

Custom Class That Supports Brace Initialization ¶

struct point
{
    int x, y;
};

class PointCloud
{
public:
    PointCloud(std::initializer_list<point> points) : _points(points) {}
private:
    std::vector<point> _points;
};

PointCloud cloud{ {1, 2}, {2, 3} };