我想为作为模板参数传递的每种类型创建实现 print()
方法的模板类。
类似的东西:
class Interface
{
public:
virtual ~Interface() = default;
virtual void print(int) = 0;
virtual void print(double) = 0;
};
X x<int, double, Interface>;
X 类
具有公共(public)方法 void print()
并且它有效。
完整代码如下:
#include <iostream>
#include <type_traits>
struct Printer
{
void print(int i) {std::cout << i << std::endl; }
void print(double d) {std::cout << d << std::endl; }
};
class Interface
{
public:
virtual ~Interface() = default;
virtual void print(int) = 0;
virtual void print(double) = 0;
};
template <typename... Args>
class X;
template <typename Interface>
class X<Interface> : public Interface
{
static_assert(std::is_abstract<Interface>::value, "Last argument should be an interface");
public:
X(Printer printer) {}
using Interface::print;
};
template <typename Arg, typename... Args>
class X<Arg, Args...> : public X<Args...>
{
using Parent = X<Args...>;
public:
using Parent::print;
X(Printer printer_): Parent(printer), printer{printer_} {}
void print(Arg arg) override { printer.print(arg); }
private:
Printer printer;
};
int main()
{
Printer printer;
X<double, int, Interface> x(printer);
x.print(5);
}
如您所见,class X
使用 Printer
类,但问题是我想将 Printer
作为模板参数...
这可能吗?如何做到这一点?
最佳答案
As you see class X uses Printer class but the problem is that I would like to have Printer as a template parameter...
Is it possible? How to do that?
抱歉,但是...我没有看到问题(Story Teller 建议进行了极大的简化:在地面案例中放置一个 Printer
对象)
template <typename...>
class X;
template <typename Printer, typename Interface>
class X<Printer, Interface> : public Interface
{
static_assert(std::is_abstract<Interface>::value,
"Last argument should be an interface");
public:
X (Printer p0) : printer{p0}
{ }
using Interface::print; // why?
protected:
Printer printer;
};
template <typename Printer, typename Arg, typename... Args>
class X<Printer, Arg, Args...> : public X<Printer, Args...>
{
using Parent = X<Printer, Args...>;
public:
using Parent::print;
using Parent::printer;
X(Printer printer_): Parent{printer_} {}
void print(Arg arg) override { printer.print(arg); }
};
// ....
X<Printer, double, int, Interface> x(printer);
题外话:注意:你正在使用未初始化的printer
X(Printer printer_): Parent(printer), printer{printer_} {}
我想你应该写 Parent(printer_)
关于c++ - 模板类使用参数包时如何传递其他模板参数?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/58712888/