Structured bindings were introduced in C++17 as a way to decompose objects into their constituent elements. They have proven to be a powerful feature for working with complex types and making code more readable. In C++20, structured bindings were further enhanced to be used directly in if statements, offering even more flexibility and expressiveness.

Let’s take a closer look at how structured bindings can be leveraged in if statements to improve code readability and eliminate the need for temporary variables.

The Old Way

Before the introduction of structured bindings in if statements, you would need to create temporary variables to hold the decomposed values if you wanted to use them in an if condition. Here’s an example:

std::map<int, std::string> myMap;
// ...

auto it = myMap.find(42);
if (it != myMap.end()) {
    int key = it->first;
    std::string value = it->second;

    // Use key and value...
}

In the code snippet above, we had to create key and value variables to store the decomposed values of the std::map iterator. This approach introduces unnecessary clutter and makes the code less concise.

The New Way

Thanks to the enhanced structured bindings in C++20, we can directly use the decomposed values in the if statement itself. This eliminates the need for temporary variables and simplifies the code. Here’s the updated version of the previous example:

std::map<int, std::string> myMap;
// ...

if (auto [it, inserted] = myMap.try_emplace(42, "Hello"); !inserted) {
    int key = it->first;
    std::string value = it->second;

    // Use key and value...
}

In the revised code above, the structured binding [it, inserted] is used directly in the if statement. The try_emplace function returns a pair of values, and we can now directly extract and use those values within the if condition itself. This not only reduces the verbosity but also makes the intent of the code clearer.

By integrating structured bindings into if statements, C++20 allows us to write more concise and expressive code. The improved syntax provides a natural way to access decomposed values without creating unnecessary temporary variables.

#Cpp #StructuredBindings