C++ function call reflection technology: parameter passing and dynamic access of return values

C Function call reflection technology allows dynamically obtaining function parameter and return value information at runtime. Use the typeid(decltype(...)) and decltype(...) expressions to obtain parameter and return value type information. Through reflection, we can dynamically call functions and select specific functions based on runtime input, enabling flexible and scalable code.

C Function call reflection technology: parameter transfer and dynamic access of return values

Function call reflection is a kind of function call reflection at runtime Powerful techniques for obtaining and manipulating function information. By leveraging the C compiler's metadata information, we can dynamically access a function's parameters, return values, and type information, enabling highly flexible and extensible code.

Parameter passing

To obtain the parameter information of the function, you can use typeid(decltype(...)) to obtain the type of the parameter type information. `cpp
// Get the type information of function parameters

include db98ac07aedf84c58d65e6e9066fbbc5

class MyClass {
public:

void Function(int a, double b, std::string c) {
    // ...
}

};

int main() {

using namespace std;
auto p = &MyClass::Function;

// 获取参数类型
cout << typeid(decltype(p)).name() << endl;  // MyClass::Function(int, double, std::string)

}

**返回值**

要获取函数的返回值类型信息，可以使用 `decltype(...)` 表达式：

// Get the type information of the function return value

include da44d27d277691559b830f97ca0443e6

class MyClass {
public:

int Function() {
    // ...
}

};

int main() {

using namespace std;
auto p = &MyClass::Function;

// 获取返回值类型
cout << typeid(decltype(p())).name() << endl;  // int

}

**实战案例：动态函数调用**

假设我们有一个包含一系列以不同方式接受参数并生成不同类型结果的函数的类 `MyFunctions`。我们可以使用函数调用反射来动态地调用这些函数，并根据运行时的输入选择特定的函数：

// Dynamically call functions

include ce38e4109220e7a6cf9498a8a1bd07be

include da2c3d4ec9d0ede5770d8970d3e75edc

class MyFunctions {
public:

int Sum(int a, int b) {
    return a + b;
}

double Divide(double a, double b) {
    return a / b;
}

};

int main() {

using namespace std;
MyFunctions functions;

// 获取函数指针
auto sumPtr = &MyFunctions::Sum;
auto dividePtr = &MyFunctions::Divide;

// 根据输入动态选择函数
function<double(double, double)> func;
if (choice == "sum") {
    func = function<double(double, double)>(sumPtr);
} else if (choice == "divide") {
    func = function<double(double, double)>(dividePtr);
}

// 调用动态选择后的函数
double result = func(10.0, 5.0);
cout << result << endl;  // 输出：2.0

}

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