Jump to content
  • Advertisement
Sign in to follow this  

[C++] Traits and Template Specialization

This topic is 3038 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

Recommended Posts

I am trying to create a number fo traits templates to package up
the following information:

* Type (a class or struct)
* Container
* A name for the collection

So far the following works ok:

extern char const NoneStr[] = "NONE";

template < typename T, typename CONT = void, const char* TagName = NoneStr >
struct MyTraits
typedef T ElementType;
typedef CONT ContainerType;
static const char* GetTag() { return TagName; }

This can then be specialised as follows:

extern char const StructOneStr[] = "StructOneName";

struct MyTraits<Struct1>
: MyTraits<SimpleOne, std::vector<StructOne>, StructOneStr > {};

extern char const StructTwoStr[] = "StructTwoName";

struct MyTraits<Struct2>
: MyTraits<SimpleTwo, std::deque<StructTwo>, StructTwoStr > {};

These traits can then be used in programs in the following way:
Note: this function uses boost serialization to write a collection to an xml file,
the Traits template is used to provide a nicer tag than the auto-generated one

template <typename T>
void SerializeToXmlFile( const MyTraits<T>::ContainerType& data,
const string& filename )
ofstream ofs(filename);
boost::archive::xml_oarchive oa(ofs);
oa & boost::serialization::make_nvp( MyTraits<T>::GetTag(), data);

For maps things are not write so straight forwards:

extern char const mapStr[] = "MapName";
typedef std::pair< string, long > MyMapData_t;

struct MyTraits<MyMapData_t> : MyTraits< MyMapData_t,
std::map< MyMapData_t::first_type,
MyMapData_t::second_type >,
MapStr > {};

Ideally I would like to find a way of writing a template such that
if T is of type std::pair the container is automatically set to a
map type. Unfortunately I have been unable to come up with the
correct syntax (is this possible using partial template specialization).

Share this post

Link to post
Share on other sites
Try this:

template <typename T>
struct ConvPairToMap
typedef T in_type;
template <typename A, typename B>
struct ConvPairToMap<std::pair<A,B> >
typedef std::map<A,B> in_type;

ConvPairToMap<int>::in_type a = 5;
ConvPairToMap<std::pair<int,double> >::in_type b = std::map<int,double>();

Share this post

Link to post
Share on other sites
Sign in to follow this  

  • Advertisement

Important Information

By using GameDev.net, you agree to our community Guidelines, Terms of Use, and Privacy Policy.

GameDev.net is your game development community. Create an account for your GameDev Portfolio and participate in the largest developer community in the games industry.

Sign me up!