Map and Functor :: STL

[kuphryn]

Hi.

How do you define a functor that handles elements in an STL map? For example:

std::map<int, char *> testMap;

char *testChar = new char[10];
_strcpy(testChar, "November");

testMap.insert(std::pair<int, char *>(0, testChar));

...

// Now I want to deallocate all values in testMap.

std::for_each(testMap.begin(), testMap.end(), DeleteValue());

How do you define DeleteValue functor that handles elements in an STL map?

Thanks,
Kuphryn

[proxima centaur]

You want a function object.

You have to define a "parenthesis" operator.

so you would do something like:

struct delete_value
{
    bool operator() ( int value )
    {
         // do stuff...
       return true; // or false
    }
};

I've only defined functors for evaluating lower_than operations on "custom" objects... I dunno about deleting...

See this page for more info:

http://www.ccd.bnl.gov/bcf/cluster/p...g/fun_0476.htm

[kuphryn]

Christian of CodeProject mentioned that the iterator returns a pair object. For example:

class DeleteValue 
{
   public:
      void operator()(std::pair<int, char *> pairObject)
      {
         // How do you use the pairObject?
      }
};

How do you identify with a pair object?

Kuphryn

[Paul McKenzie]

Originally posted by kuphryn
Christian of CodeProject mentioned that the iterator returns a pair object. For example:

class DeleteValue 
{
   public:
      void operator()(std::pair<int, char *> pairObject)
      {
         // How do you use the pairObject?
      }
};

How do you identify with a pair object?

Kuphryn

pairObject.first -- This is the int
pairObject.second -- This is the char *

Regards,

Paul McKenzie

[kuphryn]

Nice! Thanks.

Here is one answer by JoaquÃ*n M López Muñoz of CodeProject.

class DeleteValue : public std::unary_function<std::pair<int const,char *>&, void>
{
   public: 
      void operator()(std::pair<int const,char *> &pairObject)
      {
         delete [] pairObject.second;
      } 
};

Kuphryn