Tuesday Coding Tip 03 - Structured bindings

Question

Tuesday coding tips are super short posts about various tidbits mainly from C++, but also from other programming languages I use. You can also follow the #TuesdayCodingTips hashtag on Mastodon and Linkedin.

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Since C++17, we can use “structured bindings”. These allow you to perform tuple, array, or even structure unpacking. Such unpacking is commonly helpful when iterating over maps, so you don’t have to define an alias for key and value manually. It is equally useful when a function returns a tuple.

// Iterating over key-value pairs
auto myMap = std::unordered_map<std::string, int>{ /* ... */ };
for (auto&& [key, value] : myMap)
{ /* ... */ }

// Tuple unpacking
auto&& [index, quantity, name] = std::tuple{10, 30, "a"};

// Struct member aliasing
struct S {
    int veryLongAndDescriptiveName;
    std::string anotherVeryWordyName;
};

auto&& [index2, name2] = S{}; // s is of type S

// Array unpacking
auto&& [first, second, third] = std::array{1, 2, 3};

Unpacking struct members and arrays is just a cherry on top. You won’t use it much, but it is there should you ever need it!