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I want to perform in place modification to a std::map while iterating over it
#include <string>
#include <map>
struct EmployeeKey
{
    std::string name;
    int amount;
    int age;
};

struct EmployeeDetail
{
    std::string dept;
    int section;
    int salary;
};

bool compareByNameAge(const std::string& name,
                      const int& age,
                      const EmployeeKey& key )
{
    return name > key.name && age > key.age;
}

typedef std::map<EmployeeKey, EmployeeDetail> EmployeeMap;

int main()
{
    EmployeeMap eMap;
    // insert entries to the map
    int age = 10;
    std::string name = "John";

    EmployeeMap transformMap;
    foreach( iter, eMap )
    {
        if ( compareByNameAge(name, age, iter->first) )
        {
            //**This is what i want to avoid.......
            // take a copy of the data modified
            // push it in a new map.
            EmployeeDetail det = iter->second;
            det.salary = 1000;
            transformMap[iter->first] = det;
        }
    }

    //** Also, i need to avoid too...
    // do the cpy of the modified values
    // from the transform map to the
    // original map
    foreach( iter1, transformMap )
        eMap[iter1->first] = iter1->second;
}

foreach( iter, eMap )
   {
       if ( compareByNameAge(name, age, iter->first) )
       {
           iter->second.salary = 1000;
       }
   }

foreach(iter, eMap)
{
   if (compareByNameAge(name, age, iter->first))
     iter->second.salary = 1000;
}

EmployeeDetail& det = iter->second;
det.salary = 1000;

EmployeeDetail& det = iter->second;   // notice new '&' character.
det.salary = 1000;   // modifies the 'EmployeeDetail' object in-place.

it->second.salary = 1000;

class SalaryUpdater
{
public:
    SalaryUpdater(const std::string& name, int age) : name_(name), age_(age) { }

    void operator()(EmployeeMap::value_type& item)
    {
        if(compareByNameAge(name_, age_, item.first))
        {
            item.second.salary = 1000;
        }
    }

private:
    std::string name_;
    int age_;
};

int main()
{
    EmployeeMap eMap;
    // insert entries to the map

    std::for_each(eMap.begin(), eMap.end(), SalaryUpdater("John", 10));
}

for (auto& pair : eMap )
  if (pair.first.name == "Rob")
    pair.second.salary *= 1000;

for(EmployeeMap::iterator it = eMap.begin(); it != eMap.end(); ++it)
  if(pair.first.name == "Rob")
    pair.second.hours /= 2;