22b4470f2a
Update all links to C++ Core Guidelines to `e49158a`.
Refresh done using the following script and some manual edits:
db76e34e74/personal/fred-tingaud/rspec/refresh-cppcoreguidelines.py
When re-using this script, be mindful that:
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Co-authored-by: Marco Borgeaud <marco.borgeaud@sonarsource.com>
67 lines
2.0 KiB
Plaintext
67 lines
2.0 KiB
Plaintext
== Why is this an issue?
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{cpp}17 introduced structured binding, a syntax that initializes multiple entities by elements or members of an object. It is handy to emulate several return values from a function.
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Suppose you have a function that returns a pair:
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[source,cpp]
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----
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std::pair<std::string, std::string> getPair();
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----
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Structured binding allows you to bind the members of the ``++std::pair++`` class directly to new names:
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[source,cpp]
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----
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auto [firstName, lastName] = getPair();
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----
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The names ``++firstName++`` and ``++lastName++`` are called structured bindings. As you can see, structured binding makes the code more readable as it allows binding values to names that carry information about their purpose.
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Structured binding works with:
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* Raw arrays, by binding a name to each element
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* Any type that has a tuple-like API
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* Classes and structures where all non-static data members are publicly accessible
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This rule will detect places where ``++std::pair++`` and ``++std::tuple++`` can be effortlessly replaced by a structured binding.
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=== Noncompliant code example
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[source,cpp,diff-id=1,diff-type=noncompliant]
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----
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void printingMap(const std::map<int, std::string>& map) {
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for (const auto& elem : map) { // Noncompliant
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std::cout << elem.first << ": " << elem.second << "\n";
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}
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}
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----
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=== Compliant solution
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[source,cpp,diff-id=1,diff-type=compliant]
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----
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void printingMap(const std::map<int, std::string>& map) {
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for (const auto& [key, value] : map) { // Compliant
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std::cout << key << ": " << value << "\n";
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}
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}
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----
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== Resources
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=== Documentation
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* {cpp} reference - https://en.cppreference.com/w/cpp/language/structured_binding[Structured binding declaration]
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=== External coding guidelines
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* {cpp} Core Guidelines - https://github.com/isocpp/CppCoreGuidelines/blob/e49158a/CppCoreGuidelines.md#f21-to-return-multiple-out-values-prefer-returning-a-struct-or-tuple[F.21: To return multiple "out" values, prefer returning a struct or tuple]
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