模板类静态数据成员初始化的部分模板特化 [英] Partial template specialization for initialization of static data members of template classes

问题描述

对于特定参数，如何以不同的方式初始化模板类的静态数据成员?

How would one initialize static data members of a template class differently for particular parameters?

我知道模板与其他类型的类不同，只有在项目中使用的才会被实例化.我可以为不同的参数列出许多不同的初始化，并让编译器使用合适的方法吗?

I understand that templates are different than other kinds of classes and only what is used in the project ever gets instantiated. Can I list a number of different initializations for different parameters and have the compiler use whichever is appropriate?

例如，以下是否有效，如果无效，正确的方法是什么?:

For example, does the following work, and if not what is the correct way to do this? :

template<class T>
class someClass
{
   static T someData;
   // other data, functions, etc...
};

template<class T>
T someClass::someData = T.getValue();

template<>
int someClass<int>::someData = 5;

template<>
double someClass<double>::someData = 5.0;

// etc...

推荐答案

应该可以.您可能需要将这些放入 .c 文件而不是标题中.

Should work. You may need to put these into the .c file instead of the header.

int someClass<int>::someData = 5;
double someClass<double>::someData = 5.0;

这里还有一个工作部分模板特化，初始化静态数据成员:

Here is also a working partial template specialization with initialization of static data members:

// .h
template <class T, bool O>
struct Foo {
    T *d_ptr;
    static short id;
    Foo(T *ptr) : d_ptr(ptr) { }
};
template <class T>
struct Foo<T, true> {
    T *d_ptr;
    static short id;
    Foo(T *ptr) : d_ptr(ptr) { }
};
template<class T, bool O>
short Foo<T, O>::id = 0;
template<class T>
short Foo<T, true>::id = 1;

//.cpp
int main(int argc, char *argv[])
{
    Foo<int, true> ft(0);
    Foo<int, false> ff(0);
    cout << ft.id << " " << ff.id << endl;
}

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