问C++模板类静态成员初始化

EN

#include <iostream>

template<typename T1, typename T2>
class TemplateClass
{
protected:
    T1 t1;
    static T2 t2;

public:
    TemplateClass ();
};

template<typename T1, typename T2>
TemplateClass<T1, T2>::TemplateClass ()
{
    TemplateClass<T1, T2>::t2.initialize (10);
}

class T1Sample
{
private:
    int i;

public:
    T1Sample () : i (1) {};
    int get_i () { return i; };
};

class T2Sample
{
private:
    int i;

public:
    T2Sample () : i (0) {};
    void initialize (int x) { i = x; };
    int get_i () { return i; };
};

class DerivedClass : TemplateClass<T1Sample, T2Sample>
{
private:
    int z;

public:
    DerivedClass () { z = t1.get_i () + TemplateClass<T1Sample, T2Sample>::t2.get_i (); };
    int get_z () { return z; };
};

int main ()
{
    DerivedClass d;
    std::cout << d.get_z () << std::endl;
}