Structured Binding (C++17)

One-Liner

A single line of syntax that destructures elements of a tuple, pair, struct, or array into separate variables simultaneously, eliminating std::tie and per-field access.

Header

None (language feature)

Core API Cheat Sheet

Binding Form	Syntax	Description
By value	auto [x, y] = ...;	Copies elements to new variables
Lvalue reference	auto& [x, y] = ...;	Binds to references of the original object
Read-only reference	const auto& [x, y] = ...;	Const reference, avoids copying
Forwarding reference	auto&& [x, y] = ...;	Perfect forwarding semantics
Array destructuring	int arr[3]; auto& [x, y, z] = arr;	Binds to array elements (count must match)
Pair destructuring	auto& [key, val] = pair;	Binds to first/second of a pair
Tuple destructuring	auto& [a, b] = tuple;	Binds to tuple-like elements
Struct destructuring	auto& [x, y] = struct_obj;	Binds to public data members (declaration order)

Minimal Example

#include <iostream>
#include <tuple>

int main() {
    // 1. Pair destructuring
    std::pair<int, int> coord{10, 20};
    auto& [x, y] = coord; // Bind by reference
    x = 30;               // Modifies coord.first

    // 2. Struct destructuring
    struct Sensor { int id; float value; };
    Sensor s{1, 3.14f};
    auto [id, val] = s;   // Bind by value (copy)

    // 3. Array destructuring
    int data[3] = {1, 2, 3};
    auto& [a, b, c] = data;

    std::cout << x << ", " << y << "\n"; // 30, 20
}

Embedded Applicability: High

• Pure compile-time syntactic sugar with zero runtime overhead; generated code is equivalent to manual field access.
• Simplifies unpacking of multi-field structures like register sets or sensor data, improving readability.
• Use const auto& to avoid copying, ideal for read-only access to hardware-mapped structs.
• C++17 is fully supported in mainstream embedded toolchains (GCC 7+, ARM Clang 6+).

Compiler Support

GCC	Clang	MSVC
7	4.0	19.1

See Also

• Tutorial: Structured Bindings
• cppreference: Structured binding declaration

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部分内容参考自 cppreference.com，采用 CC-BY-SA 4.0 许可