Question

假设我有一系列带有私有构造函数的类，必须通过专用New(...)静态函数分配，如下所示：

class Foo {
public:
  static Foo* New();
private:
  Foo() {}
};

class Bar {
public:
  static Bar* New(int a, int b);
private:
  Bar() {}
};

我想编写一个模板类，以通用的方式调用它们的New(...)静态函数：

template<class T, typename... Args>
class Test {
public:
  static Test<T> Make(Args&&... args) {
    return Test<T>(T::New(std::forward<Args>(args)...));
  }

private:
  inline Test(T* object) : m_object(object) {}

  T* m_object;
};

所以我可以这样做：

auto foo = Test<Foo>::Make();
auto bar = Test<Bar>::Make(1, 2);

没有参数的Foo案例有效，但不是Bar案例。 Clang说，它希望New()不带参数，好像参数没有正确转发一样。我做错了什么？

更新：在尝试拨打Buffer时，Clang和我的Test<Buffer>::Make(1000)课程发生了真实的错误：

Buffer.hpp:25:29: note: candidate function template not viable: requires single argument 'string', but no arguments were provided
    inline static BufferRef New(const char (&string)[N]) {  // For literal strings
                            ^
Buffer.hpp:16:29: note: candidate function not viable: requires single argument 'length', but no arguments were provided
    inline static BufferRef New(size_t length) {
                            ^
Buffer.hpp:29:29: note: candidate function not viable: requires at least argument 'string', but no arguments were provided
    inline static BufferRef New(const char* string, bool copy = true) {
                            ^
Buffer.hpp:33:29: note: candidate function not viable: requires at least argument 'string', but no arguments were provided
    inline static BufferRef New(const std::string& string, bool copy = true) {
                            ^
Buffer.hpp:20:29: note: candidate function not viable: requires at least 2 arguments, but 0 were provided
    inline static BufferRef New(void* bytes, size_t length, bool copy = true) {

Answer 1

我想通了 - 可变参数模板参数＆＃34;显然＆＃34;需要在静态函数上，而不是类本身：

template<class T>
class Test {
public:
  template<typename... Args>
  static Test<T> Make(Args&&... args) {
    return Test<T>(T::New(std::forward<Args>(args)...));
  }

private:
  inline Test(T* object) : m_object(object) {}

  T* m_object;
};

在转发参数时，在模板中的参数类上调用静态函数

1 个答案: