Thread: [Newbie] C++ call by reference question

Hello!

I have typedefs like the following:

Code:

typedef std::set<std::string>TBookKey;
typedef std::vector<bookObjs>TBookValues;
typedef std::map<bookKey, bookValues> TBookMap;

And, member variable declaration:

Code:

private:
TBookMap bookMap;

** Question **
Is it possible to create an API to obtain:
The pointer or reference to the TBookKey (set), and TBookValues (vector) of the a specific pair from the bookMap? (Not a copy of them)

I think, if I define the API signature such as:

Code:

// iterate through BookMap to get the actual Key/Value reference of specified pair.

void
GetBookMapPair(const int bookID, TBookKey& key, TBookValues& value);

The caller will always get a copy of TBookKey and TBookValues of the specified (bookID) pair, but not the pointer/reference of the Key/Value. Because that the operator= of set/vector is overloaded to make a copy. Is it correct? Any suggestions/comments?

may tks!

Originally Posted by grumpy

No, you're not correct.

The function GetBookMapPair() accepts two argum,ents (key and value) by reference. Those arguments are not copied.

I *think* what he's asking about is to get a reference to the actual object in the set or vector, given the ID number of ... I'm not sure what. (In other words, can you force a set or a vector to give you a reference to an object that it contains, rather than a copy of it?)

On the other hand, I'm not sure why we have a map from a set of strings to a vector of bookObjs in the first place, so there is quite a mystery.