Consider the following code :
std::map <string,string> myMap;
myMap.insert(std::make_pair("first_key" , "no_value" ));
myMap.insert(std::make_pair("first_key" , "first_value" ));
myMap.insert(std::make_pair("second_key" , "second_value" ));
typedef map<string, string>::const_iterator MapIterator;
for (MapIterator iter = myMap.begin(); iter != myMap.end(); iter++)
{
cout << "Key: " << iter->first << endl << "Values:" << iter->second << endl;
}
The output is :
Key: first_key
Values:no_value
Key: second_key
Values:second_value
Meaning is that the second assignment :
myMap.insert(std::make_pair("first_key" , "first_value" ));
didn't take place .
How can I make a pair , only if the key is not already listed , and if is listed - change its value ?
Is there any generic method of std::map ?
Add a condition before insert
if (myMap.find("first_key") == myMap.end()) {
myMap.insert(std::make_pair("first_key" , "first_value" ));
}
else {
myMap["first_key"] = "first_value";
}