CODEWITHSUNDEEP
c++templatesdictionarystl
user2235747
user2235747

Reputation: 395

inserting " " key into map

While inserting key, value pair into a map, What will be the behavior if the key is " " and corresponding that value is present. for example 

std::map<std::string, std::string> map1;
std::string key = "";
std::string value = "xyz";

map1.insert(std::pair<std::string, std::string>(key, value));

And what is the best way to handle this scenario?

Upvotes: 1

Views: 4844

Answers (1)

juanchopanza
juanchopanza

Reputation: 227608

std::string does not have a special state or value "null". A string initialized with "" is just an empty string, but it is still a string like any other. When using it as a key, std::map::insert will do what it always does: insert the element only if no element with the same key already exists.

Note that you can check whether the insert succeeded using the second member of the return value:

auto res = map1.insert(std::pair<std::string, std::string>(key, value));
std::cout << std::boolalpha;
std::cout << "Success? " << res.second << '\n'; // Success? true

// try again (and fail)
auto res = map1.insert(std::pair<std::string, std::string>(key, value));
std::cout << "Success? " << res.second << '\n'; // Success? false

Upvotes: 8

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