避免在专用模板中的代码重复 [英] Avoiding code duplication in a specialized template

问题描述

我想有两个类似的模板，一个有一个参数，另一个有2个参数：

I want to have two similar templates, one with 1 parameter and other with 2 parameters:

template<typename T1, typename T2=void>
struct foo {
  T1 m_t1;
  T2 m_t2;
  foo(T1 t1, T2 t2) : m_t1(t1), m_t2(t2) {}
  T1 t1() { return m_t1; }
  T2 t2() { return m_t2; }
};

template<typename T1>
struct foo<T1,void> {
  T1 m_t1;
  foo(T1 t1) : m_t1(t1) {}
  T1 t1() { return m_t1; }
};

注意所有T1相关的东西的代码重复。如何避免这种情况？

Notice the code duplication for all the T1-related stuff. How can I avoid this?

推荐答案

唯一的解决方案是在基类中尽可能多的代码。例如：

The only solution to this is to have as much code as possible in a base class. For example:

template<typename T1>
struct foo_base {
    T1 m_t1;
    explicit foo_base(T1 t1) : m_t1(t1) {}
    T1 t1() const { return m_t1; }
};

template<typename T1, typename T2=void>
struct foo : foo_base<T1> {
    T2 m_t2;
    foo(T1 t1, T2 t2) : foo_base<T1>(t1), m_t2(t2) {}
    T2 t2() const { return m_t2; }
};

template<typename T1>
struct foo<T1,void> : foo_base<T1> {
    explicit foo(T1 t1) : foo_base<T1>(t1) {}
};

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