A default-initialized dynamic::variable has no value. No value is represented with the dynamic::nullable type.

We can query if the variable has a certain type with the dynamic::variable::is<T>() member function. We can also examine if the variable has no value by comparing it with dynamic::null.

// Create an empty variable
dynamic::variable data;
assert(data.is<dynamic::nullable>());
assert(data == dynamic::null);

If we assign a boolean value to the above variable then the variable changes into a boolean type.

// Change into boolean
data = true;
assert(data.is<bool>());
assert(data == true);

We can even change it into an array by assigning an initializer list to it.

// Change into array
data = { 1, 20, 300 };
assert(data.is<dynamic::array>());
assert(data.size() == 3);
assert(data[0] == 1);
assert(data[1] == 20);
assert(data[2] == 300);

Finally, we will change our variable into an associative array.

// Change into associative array
data =
  {
    { "alpha", null },             // nullable
    { "bravo", true },             // boolean
    { "charlie", 2 },              // integer
    { "delta", 3.0 },              // floating-point number
    { "echo", "blue" },            // string
    { "foxtrot", { 1, 2, 3 } },    // nested array of integers
    { "golf", { { "level", 2 } } } // nested associative array
  };
assert(data.is<dynamic::map>());
assert(data.size() == 7);