问DI容器的C++中的单例模式

EN

#include <iostream>

//-----------------------------------------------------------------------------
// create an abstract baseclass (closest thing C++ has to an interface)
struct data_itf
{
    virtual int get_value1() const = 0;
    virtual ~data_itf() = default;

protected:
    data_itf() = default;
};

//-----------------------------------------------------------------------------
// two injectable instance types

struct test_data_container :
    public data_itf
{
    int get_value1() const override
    {
        return 0;
    }

    ~test_data_container()
    {
        std::cout << "test_data_container deleted";
    }
};

struct production_data_container :
    public data_itf
{
    int get_value1() const override
    {
        return 42;
    }

    ~production_data_container()
    {
        std::cout << "production_data_container deleted";
    }

};

//-----------------------------------------------------------------------------
// meyers threadsafe singleton to get to instances implementing
// interface to be injected.
// 

data_itf& get_test_data()
{
    static test_data_container test_data;
    return test_data;
}

data_itf& get_production_data()
{
    static production_data_container production_data;
    return production_data;
}

//-----------------------------------------------------------------------------
// object that needs data
class my_object_t
{
public:
    explicit my_object_t(const data_itf& data) :
        m_data{ data }
    {
    }

    ~my_object_t()
    {
        std::cout << "my_object deleted";
    }

    void function()
    {
        std::cout << m_data.get_value1() << "\n";
    }

private:
    const data_itf& m_data;
};

//-----------------------------------------------------------------------------

int main()
{
    auto& data = get_production_data();
    my_object_t object{ data };

    object.function();

    return 0;
}