Re: map (associative array) loses values?

"Jim Langston" <>
Tue, 11 Sep 2007 12:35:21 -0700
"BobR" <> wrote in message

<> wrote in message...

On Sep 11, 5:59 pm, Kai-Uwe Bux <> wrote:

ah, ok. <string, int> works like a charm! :)

I'm using new, because I need the table somewhere else. The try/catch
is in my main, while the function resides in the SearchText class. The
delete statements are there, I just didn't post them ;)

Ofcourse I'm just a c++ newbie (this is my first program actually), so
what would you do different?

An alternative to Jim's suggestion:

// pass by non-const reference.
void SearchText::countWords( std::map<std::string, int> &map ){
    map["aap"] = 1;
    map["noot"] = 2;

    std::cout << map["aap"] << std::endl;
    std::cout << map["noot"] << std::endl;

// int main(){
  try {

     std::map<std::string, int> MyMap;

     SearchText text("test.txt");
     text.countWords( MyMap );
     std::cout << MyMap["aap"] << std::endl;
     std::cout << MyMap["noot"] << std::endl;
  catch( int ex) {
     cout << "Could not open file." << endl;
// return 0;
// } // main()

Sorry, I didn't test that. Post back if you have trouble ( I may have
something. <G>).

There are a lot of alternatives to mine and Bob's suggestion. In fact, if I
was designing this class myself I would totally encapsulate the map inside
the class and main would only get to it via functions. Depending on what it
would be for something like (untested code)

class SearchText
   SearchText( const std::string& FileName );
   int Value( const std::string& key ) const;
   int CountWords();
   std::map<std::string, int> Data_;

SearchText::SearchText( const std::string& FileName )
   // Open file and load Data_

int Value( const std::string& Key ) const
   if ( Data_.find( Key ) != Data_.end() )
      return Data_[Key];
      return 0;

int CountWords()
   // Return whatever it is this is trying to count

I am a strong believe in data encapsulation in classes, and try to always
prevent giving points or references to my internal classes data. Anything
you need the map for in mian you can encapsulate. Even encapsulate
operator[] if you wish.

int SearchText::operator[]( const std::string& Key )
   return Value( Key );

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