CODEWITHSUNDEEP
c++classc++11templates
ark0f
ark0f

Reputation: 35

C++ use inner enum for class template

template <Type T>
class Socket {
public:
    enum class Type {
        TCP,
        UDP
    };
    ...
}

How I can use enum Type for class template? I want to use it as Socket::Type::UDP and etc. I try declare enum class Socket::Type before Socket but it doesn't work.

Upvotes: 3

Views: 394

Answers (1)

Qaz
Qaz

Reputation: 61920

Each Socket<...> has a different Type enum. Apart from the separate enum types, one reason it isn't possible to use Socket::Type is that a specialization of Socket could not even include the enum, or make Type something other than an enum.

You have two main options:

  1. Use a separate class/namespace named closely:

    class Sockets {
public:
    enum class Type { ... };
};

template<Sockets::Type T>
class Socket { ... };

Socket<Sockets::Type::TCP> s;

  2. Use a separate enum type:

    enum class SocketType { ... };

template<SocketType T>
class Socket { ... };

Socket<SocketType::TCP> s;

Alternatively, don't template Socket. You'll surely end up with a bunch of if (T == TCP) { ... } else { ... }. It would likely be better to cleanly separate the common parts and use two different implementations for TCP and UDP.

Upvotes: 3

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