std::expected<T,E>::swap - cppreference.com (original) (raw)
| Primary template | ||
|---|---|---|
| constexpr void swap( expected& other ) noexcept(/* see below */); | (1) | (since C++23) |
| void partial specialization | ||
| constexpr void swap( expected& other ) noexcept(/* see below */); | (2) | (since C++23) |
Swaps the contents with those of other.
- The contained values are swapped as follows:
| Value of has_value() | Value of other.has_value() | |
|---|---|---|
| true | false | |
| true | using std::swap;swap(val, rhs.val); | see below |
| false | other.swap(*this); | using std::swap;swap(unex, rhs.unex); |
[edit] Parameters
| other | - | the expected object to exchange the contents with |
|---|
[edit] Exceptions
[edit] Example
#include #include #include using Ex = std::expected<std::string, int>; void show(const Ex& ex1, const Ex& ex2, std::string_view term = "\n") { for (int i{}; i != 2; ++i) { std::cout << (i ? "ex2" : "ex1"); if (const Ex& ex = (i ? ex2 : ex1); ex.has_value()) std::cout << ".value() = " << *ex << " "; else std::cout << ".error() = " << ex.error() << " "; } std::cout << term; } int main() { Ex ex1("\N{CAT FACE}"); Ex ex2{"\N{GREEN HEART}"}; show(ex1, ex2, "after ex1.swap(ex2):\n"); ex1.swap(ex2); show(ex1, ex2, "\n\n"); ex2 = std::unexpected(13); show(ex1, ex2, "after ex1.swap(ex2):\n"); ex1.swap(ex2); show(ex1, ex2, "\n\n"); ex2 = std::unexpected(37); show(ex1, ex2, "after ex1.swap(ex2):\n"); ex1.swap(ex2); show(ex1, ex2); }
Output:
ex1.value() = 🐱 ex2.value() = 💚 after ex1.swap(ex2): ex1.value() = 💚 ex2.value() = 🐱 ex1.value() = 💚 ex2.error() = 13 after ex1.swap(ex2): ex1.error() = 13 ex2.value() = 💚 ex1.error() = 13 ex2.error() = 37 after ex1.swap(ex2): ex1.error() = 37 ex2.error() = 13