asked on

c++; map interator; detecting when a find() returns an invalid iterator

I've got a map<string,string> as part of a class and am writing a function to delete one of the map items, based on the key name. Once I obtain the iterator - through a find() - I tell it to erase it from the map. Works great if it finds a match. If it doesn't find a match, VS2005 pops up an errors "debug assertion failed!".

I've looked online and cannot find anything which dictates how to test an iterator for a NULL/invalid value. I finally discovered a solution which IMHO seems rather clunky... but it does the job.

if(iter._Ptr->_Isnil) { return; } // exit method if invalid iterator

I find it difficult to believe this is the proper way to test for an invalid iterator. Is there a better way? The full 'delete' method is listed below.

Oh and I suppose I should mention, this is a cross-platform app, so g++ 4.1.2 will also need to be able to compile it.

void deleteItem(string key) {
    map<string,string>::iterator i = this->_Items->find(key);
    if(i._Ptr->_Isnil) { return; }
    this->_Items->erase(i);
  }

Open in new window

ASKER CERTIFIED SOLUTION

LordOfPorts

membership

This solution is only available to members.

To access this solution, you must be a member of Experts Exchange.

Start Free Trial

wktang83

void deleteItem(string key) {
    map<string,string>::iterator i = this->_Items->find(key);
    if(i._Ptr == this->_Items->end()) { return; }
    this->_Items->erase(i);
  }

Open in new window

BaconU

ASKER

Ah, yes... I should have known. I mistakenly assumed that the end() was only to be used in conjunction with begin().

This is a much nicer solution! Thanks LordOfPorts!

BaconU

ASKER

wktang83, according to my tests, you don't need the ._Ptr when testing again end().