Question

I have a map, where string representing the name of attribute and the second value representing the type, which this attribute should have.

map.insert(make_pair("X", iDatatype::iUint));
map.insert(make_pair("Y", iDatatype::iUint));
map.insert(make_pair("RADIANT", iDatatype::iFloat));

where iDatatype is just enumeration of all possible types.

 typedef enum
{
    iUnknown    = 0,
    iByte   = 1,
    iChar       = 2,
    iUChar      = 3,
    iShort      = 4.....

} iDatatype;

If the program gets the command to create, for example, “RADIANT” than it look at the map, find the iDatatype value (iter->second) and go to switch case.

 switch (iter->second) {
           case iDatatype::iUint:
           uint value = ......
            // You gotta do what you gonna do
            break;
              } .......

In Switch case, the function, which depends on type of attribute, will be called.

This code works. But I am not sure, if it the best solution to map string with the types.
And the problem that I don’t know what should I look for? Could you recommend what methods or techniques are commonly used for such purpose? Thank you a lot.

Answer 1

Unless you need the map for some other reference, another approach will be:

if(command == "X" || command == "Y") // make sure command is std::string
                                     // or use strcmp
{
    // create uint
}
else if(command == "RADIANT")
{
    // create float
}

However I’m not sure how much faster this will be than using a map, because a map uses binary search while this uses iterative search.
If you want to gain the boost of binary search while no need for another enum you can use a map of functions:

std::map<std::string, std::function<void()> map;
map.insert(make_pair("X", &create_uint));
map.insert(make_pair("Y", &create_uint));
map.insert(make_pair("RADIANT", &create_float));

and later call it like:

std::string key = "X";
map[key]();

you can also pass parameters to it like:

void create_uint(std::string param) { /* ... */ }

std::map<std::string, std::function<void(std::string)> map;
map.insert(make_pair("X", &create_uint));

std::string key = "X";
std::string param = "XYZ";
map[key](param);