Providing Explicit Specialisations for Non-Template Members of Class Template

class-members-expl-spec.cc

// Tested with Clang 3.4, GCC 4.8.2.

#include <iostream>
#include <string>


template<typename T> class Foo {
public:
    std::string Method();
    static std::string StaticMethod();
    static const std::string StaticData;
    enum class Enum;
    struct InnerStruct{ static const std::string StaticData; };  
};

template<typename T> std::string Foo<T>::Method() {
    return "std::string Foo<T>::Method() - primary template.";
}

template<> std::string Foo<char>::Method() {
    return "std::string Foo<T>::Method() - "
        "explicit specialisation for <char>.";
}

template<typename T> std::string Foo<T>::StaticMethod() {
    return "std::string Foo<T>::StaticMethod() - primary template.";
}

template<> std::string Foo<char>::StaticMethod() {
    return "std::string Foo<char>::StaticMethod() - "
        "explicit specialisation for <char>.";
}   

template<typename T> const std::string Foo<T>::StaticData{
    "std::string Foo<T>::StaticData - primary template." };

template<> const std::string Foo<char>::StaticData{
    "std::string Foo<char>::StaticData - "
    "explicit specialisation for <char>." };

template<typename T> enum class Foo<T>::Enum { Primary = 0 };

template<> enum class Foo<char>::Enum { Specialised = 1 };

template<typename T> const std::string Foo<T>::InnerStruct::StaticData{
    "std::string Foo<T>::InnerStruct::StaticData - primary template." };

template<> struct Foo<char>::InnerStruct{
    static const std::string StaticData; };
const std::string Foo<char>::InnerStruct::StaticData{
    "std::string Foo<char>::InnerStruct::StaticData - "
    "explicit specialisation for <char>." };


int main() {
    // Member function.
    std::cout << Foo<int>().Method() << std::endl;
    std::cout << Foo<char>().Method() << std::endl;

    // Static member function.  
    std::cout << Foo<int>::StaticMethod() << std::endl;
    std::cout << Foo<char>::StaticMethod() << std::endl;

    // Static data member.  
    std::cout << Foo<int>::StaticData << std::endl;
    std::cout << Foo<char>::StaticData << std::endl;

    // Member enumeration.  
    std::cout << static_cast<int>(Foo<int>::Enum::Primary) << std::endl;
    std::cout << static_cast<int>(Foo<char>::Enum::Specialised) << std::endl;

    // Member class.  
    std::cout << Foo<int>::InnerStruct::StaticData << std::endl;
    std::cout << Foo<char>::InnerStruct::StaticData << std::endl;
}

See the article.