Is it possible to map int(enum) to type

Question

lets say I have this simplified example:
I have some code that does serialization and deserialization of a class... first byte is enum that encodes class type(they all inherit from same base).. eg.

    Color* c;
    auto classType == read_byte(buffer);
    switch (classType)
    case eBlue:
    {
       c = new Blue(buffer);
    }
    case eGray:
    {
       c = new Gray(buffer)
    }

//...

is there any way to have a map from enum to type so I can replace switch

c = new enum2Type(buffer);

edit ofc I would never use raw ptr IRL.:)

std::map<TheEnumType, std::function<Color*(TheBufferType)>? — juanchopanza
– juanchopanza, Commented May 22, 2013 at 12:04
Also look at the "Related" links, e.g. stackoverflow.com/questions/4968691/… and stackoverflow.com/questions/4995378/… — Alexey Kukanov
– Alexey Kukanov, Commented May 22, 2013 at 12:27

Andriy Tylychko · Accepted Answer · 2013-05-22 12:49:30Z

3

template<typename T>
T* makeColor(Buffer const& buffer)
{
    return new T(buffer);
}

...

std::map<ColerEnum, Color* (*)(Buffer const&)> m;
m[grayEnum] = makeColor<Gray>;

...

Color* c = m[typeByte](buffer);

answered May 22, 2013 at 12:49

Andriy Tylychko

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Comments

juanchopanza · Accepted Answer · 2013-05-22 13:55:08Z

1

You could replace your switch case by a map or array of functors with a buffer parameter, returning a (smart) pointer to Color:

enum EnumType { blueEnum, grayEnum };
struct Buffer { .... };
struct Color { .... };

template <typename T>
Color* make_stuff(const Buffer& b) { return new T(b); }

then

#include <functional>
#include <map>
...

// if you are sure enum values start at 0 and increase withoug jumps, 
// you could use a plain array
std::map<EnumType, std::function<Color*(const Buffer&)>> m;

m[grayEnum] = make_stuff<Gray>;
m[blueEnum] = make_stuff<Blue>;

Color* c = m.at(classType);

edited May 22, 2013 at 13:55

answered May 22, 2013 at 12:14

juanchopanza

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1 Comment

juanchopanza Over a year ago

@NoSenseEtAl You can save some of the duplication by using a function template.

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