Re: initialize reference

From:

Carl Barron <cbarron413@adelphia.net>

Newsgroups:

comp.lang.c++.moderated

Date:

25 Jul 2006 07:50:04 -0400

Message-ID:

<250720060323230825%cbarron413@adelphia.net>

In article <1153777669.706631.247520@75g2000cwc.googlegroups.com>, jean
<jean.shu@gmail.com> wrote:

Hi,

I have the following code. Basically, I want to insert to different map
depends on m_bDefaultTag . I know I need to initialize updateTags. But
how? Is there a way to achieve my goal? Thanks.

class tag_entry
{
string m_name;
int value;
}

void MyFunc()
{
            std::map<std::string, tag_entry >& customTags =
GetCustomTags();
            std::map<std::string, tag_entry >& defineTags =
GetDefineTags();
            std::map<std::string, tag_entry >& updateTags;

            if( m_bDefaultTag ) {
                  updateTags = defineTags;
            }
            else {
                  updateTags = customTags;
            }
            customTags.insert( mapElement );
}

use the ternary ? : operator like this.
   void MyFunc()
   {
      std::map<std::string,tag_entry> &customTags = GetCustomTags();
      std::map<std::string,tag_entry> &defineTags = GetDefineTags();
      std::map<std::string,tag_entry> &updateTags =
         m_bDefaultTag ?
            defineTags :
            customTags;
   }

    or use a pointer instead of a reference until which map to use is
determined and then create the reference by dereferencing the pointer.

   void MyFunc()
   {
      std::map<std::string,tag_entry> &customTags = GetCustomTags();
      std::map<std::string,tag_entry> &defineTags = GetDefineTags();
      std::map<std::string,tag_entry> *p;
      if(m_bDefaultTag)
         p = &defineTags;
      else
         p = &customTags;
      std::map<std::string,tag_entry> &uptadeTags = *p;
   }

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