C++模板类型安全 静态检查机制解析

std::vector<int>

MyContainer<std::string>

int

T

template <typename T>
void processNumber(T value) {
    static_assert(std::is_arithmetic<T>::value, "Error: T must be an arithmetic type!");
    // ... 对数值类型进行操作
}

#include <concepts> // C++20

template <std::integral T> // T 必须是整数类型
void processIntegral(T value) {
    // ...
}

template <typename T>
concept MyPrintable = requires(T a) { // 定义一个概念：类型T必须可被输出到流
    { std::cout << a } -> std::same_as<std::ostream&>;
};

template <MyPrintable T>
void print(T value) {
    std::cout << value << std::endl;
}

#include <type_traits> // for std::enable_if, std::is_integral

// SFINAE 示例：只有当 T 是整数类型时，这个函数才会被考虑
template <typename T>
typename std::enable_if<std::is_integral<T>::value, void>::type
printValue(T value) {
    std::cout << "Integral value: " << value << std::endl;
}

// SFINAE 示例：当 T 是浮点类型时
template <typename T>
typename std::enable_if<std::is_floating_point<T>::value, void>::type
printValue(T value) {
    std::cout << "Floating point value: " << value << std::endl;
}

<type_traits>

std::is_same

std::is_pointer

std::has_member

template <typename T>
class MySmartPointer {
    static_assert(std::is_default_constructible<T>::value, "T must be default constructible for MySmartPointer!");
    // ...
};

template <MyConcept T>

#include <concepts> // C++20

template <typename T>
concept Sortable = std::totally_ordered<T>; // T 必须是全序可比较的

template <Sortable T>
void sortMyVector(std::vector<T>& vec) {
    std::sort(vec.begin(), vec.end());
}

std::is_base_of

// C++11/14 SFINAE 结合 Type Traits 示例
template <typename T>
typename std::enable_if<std::is_base_of<BaseClass, T>::value, void>::type
processDerived(T& obj) {
    // ... 对 BaseClass 的派生类进行操作
}

template <typename T>
typename std::enable_if<!std::is_base_of<BaseClass, T>::value, void>::type
processDerived(T& obj) {
    // ... 对非 BaseClass 派生类进行操作
    std::cout << "Warning: Not a derived class of BaseClass." << std::endl;
}

if constexpr

template <typename T>
void printInfo(T value) {
    if constexpr (std::is_pointer<T>::value) {
        std::cout << "This is a pointer: " << value << " pointing to " << *value << std::endl;
    } else if constexpr (std::is_integral<T>::value) {
        std::cout << "This is an integral number: " << value << std::endl;
    } else {
        std::cout << "Unknown type, value: " << value << std::endl;
    }
}