c ++模板元编程:如何创建和迭代"typedef"类型的列表.在模板类中. [英] c++ template metaprogramming: how to create and iterate over list of types that are "typedefs" in template class.

问题描述

我的代码是一个工厂，它根据模板参数中的类型创建对象.我想将其扩展为类型列表".

My code is a factory that creates objects based on types from template parameters. I want to extend this to a "list of" types.

这就是我所拥有的: Algo1 定义了类型 indata . FASSubscriberFactory :: Create() 返回指向 FASSubscriber< Algo1 :: indata，..> 的指针.看到这里:

This is what I have: Algo1 defines a type indata. FASSubscriberFactory::Create() returns a pointer to FASSubscriber<Algo1::indata,..> . See here:

struct Algo1  
{
    typedef DataType1 indata;
}

template <class T, class FEED = T::indata, class PROC = typename ProcessorFactory<T>::ptype>
struct FASSubscriberFactory
{
    typedef FASSubscriber<typename PROC , typename FEED > fftype;

    static fftype * Create()
    {
        return new fftype(FASConfig::Data2Feed<FEED>::name, ProcessorFactory<T>::Create());
    }
}

void main() 
{
    auto myFASSubscriber4Algo1 FASSubscriberFactory<Algo1>::Create();
}

这就是我想要的: Algo1 定义typedefs indata 的列表. FASSubscriberFactory :: CreateList() 返回指向 FASSubscriber< Algo1 :: indata，..> 列表的指针em> foreach 键入 Algo1:indata .请参见下面的伪代码中的注释.

This is what I want: Algo1 defines a list of typedefs indata. FASSubscriberFactory::CreateList() returns a pointer to a list of FASSubscriber<Algo1::indata,..> foreach type in Algo1:indata. See //comments in pseudocode below.

struct Algo1 
{
    //Want to define a list of types
    typedef std::list<types> indata = { DataType1, DateType2 }
}

template <class T, class FEEDs = T::indata, class PROC = typename ProcessorFactory<T>::ptype>
struct FASSubscriberFactory
{
    //want to create a list FASSubscribers from list of types T::indata
    typedef list<FASSubscriber<PROC, FEEDs::type> listoffftypes 
    static lisoftypes * CreateList()
    {
        listoffftypes mylot();

        //for each type in FEEDs - want to lopp around list of types
        foreach(feedtype in FEEDs )
        {
            mylot.push(Create<feedtype>());
        }
        return mylot; 
    }

    template <class FEED>
    static fftype * Create()
    {
        typedef FASSubscriber<typename PROC , typename FEED > fftype;

        return new fftype(FASConfig::Data2Feed<FEED>::name, ProcessorFactory<T>::Create());
    }
}

void main() 
{
    auto myListOfFASSubscriber4Algo1 FASSubscriberFactory<Algo1>::Create();
}

我真正想要的是一种定义和迭代在模板参数类中定义的类型列表"的方法.看了一下A. Alexa的TYPELISTS，但是我没有看到任何循环.

All I really want is a way to define and iterate over a "typelist" which is defined in the template argument class. Took a look at A. Alexa's TYPELISTS, but I didnt see any loops.

谢谢j

推荐答案

我有各种各样的模板，而C ++ 11的 std :: tuple 是您想要的，尽管我不是完全确定我了解您的要求.

I have a feeling variadic templates and std::tuple from C++11 is what you want, although I'm not exactly sure I understand what you're asking.

// returns a tuple of pointers created by a Create for each type in the parameter pack
template<typename... TS>
static std::tuple<TS*...> CreateList() {
    return { Create<TS>()... };
}

请不要用普通的C ++代码来描述模板的元图形化；这很令人困惑.

Please don't describe template metapogramming in terms of normal C++ code; it is confusing.

例如，如果您这样称呼它:

For instance if you called it like this:

FASSubscriberFactory</* stuff */>::CreateList<int, float, foo, bar>()

本质上是这样做的:

static std::tuple<int*, float*, foo*, bar*> CreateList() {
    return { Create<int>(), Create<float>(), Create<foo>(), Create<bar>() };
}

这篇关于c ++模板元编程:如何创建和迭代"typedef"类型的列表.在模板类中.的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！