boost::any

boost::any 是一个非常灵活的类型安全容器，可以存储任意类型的值，是实现“泛型容器”或“动态类型”的重要工具。

#include <boost/any.hpp>
#include <iostream>
#include <vector>
#include <string>
#include <typeinfo>

// 1. 存储任意类型的值
boost::any a = 42;           // int
a = std::string("hello");    // string
a = 3.14;                    // double
a = true;                    // bool

// 2. 静态转换（不安全，类型错误时返回 nullptr）
boost::any a = 100;
int* p = boost::any_cast<int>(&a); // 获取指针
if (p) {
    std::cout << "Value: " << *p << std::endl;
}

std::string* sp = boost::any_cast<std::string>(&a);
if (!sp) {
    std::cout << "不是 string 类型" << std::endl;
}

// 3. 动态转换（类型错误时抛出 boost::bad_any_cast）
try {
    int value = boost::any_cast<int>(a);        // 成功
    std::string s = boost::any_cast<std::string>(a); // 抛出异常
} catch (const boost::bad_any_cast& e) {
    std::cout << "类型转换失败: " << e.what() << std::endl;
}

#include <map>
#include <boost/any.hpp>

class Properties {
private:
    std::map<std::string, boost::any> data_;

public:
    template<typename T>
    void set(const std::string& key, const T& value) {
        data_[key] = value;
    }

    template<typename T>
    T get(const std::string& key) const {
        auto it = data_.find(key);
        if (it == data_.end()) {
            throw std::runtime_error("Key not found: " + key);
        }
        return boost::any_cast<T>(it->second);
    }

    template<typename T>
    bool is_type(const std::string& key) const {
        auto it = data_.find(key);
        if (it == data_.end()) return false;
        return it->second.type() == typeid(T);
    }

    bool has_key(const std::string& key) const {
        return data_.find(key) != data_.end();
    }
};

// 使用示例
void example_properties() {
    Properties props;
    props.set("name", std::string("Alice"));
    props.set("age", 30);
    props.set("salary", 75000.50);
    props.set("active", true);

    std::cout << "Name: " << props.get<std::string>("name") << std::endl;
    std::cout << "Age: " << props.get<int>("age") << std::endl;
    std::cout << "Salary: " << props.get<double>("salary") << std::endl;

    std::cout << "Has 'email'? " << (props.has_key("email") ? "yes" : "no") << std::endl;

    std::cout << "Is 'age' an int? " << (props.is_type<int>("age") ? "yes" : "no") << std::endl;
}