iterate vector, remove certain items as I go

Question

I have a std::vector m_vPaths; I will iterate this vector and call ::DeleteFile(strPath) as I go. If I successfully delete the file, I will remove it from the vector. My question is can I get around having to use two vectors? Is there different data structure that might be better suited for what I need to do?

example: using iterators almost does what I want, but problem is once you erase using an iterator, all iterators become invalid.

 std::vector<std::string> iter = m_vPaths.begin();     for( ; iter != m_vPaths.end(); iter++) {         std::string strPath = *iter;         if(::DeleteFile(strPath.c_str())) {             m_vPaths.erase(iter);                    //Now my interators are invalid because I used erase,                 //but I want to continue deleteing the files remaining in my vector.             }     } 

I can use two vectors and I will no longer have a problem, but is there a better, more efficient method of doing what I'm trying to do?

btw, incase it is unclear, m_vPaths is declared like this (in my class):

std::vector<std::string> m_vPaths; 

Answer 1

The erase() method returns a new (valid) iterator that points to the next element after the deleted one. You can use this iterator to continue with the loop:

std::vector<std::string>::iterator iter; for (iter = m_vPaths.begin(); iter != m_vPaths.end(); ) {     if (::DeleteFile(iter->c_str()))         iter = m_vPaths.erase(iter);     else         ++iter; } 

Answer 2

Check out std::remove_if:

#include <algorithm> // for remove_if #include <functional> // for unary_function  struct delete_file : public std::unary_function<const std::string&, bool>  {     bool operator()(const std::string& strPath) const     {         return ::DeleteFile(strPath.c_str());     } }  m_vPaths.erase(std::remove_if(m_vPaths.begin(), m_vPaths.end(), delete_file()),                 m_vPaths.end()); 

Use a std::list to stop the invalid iterators problem, though you lose random access. (And cache performance, in general)

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For the record, the way you would implement your code would be:

typedef std::vector<std::string> string_vector; typedef std::vector<std::string>::iterator string_vector_iterator;  string_vector_iterator iter = m_vPaths.begin(); while (iter != m_vPaths.end()) {     if(::DeleteFile(iter->c_str()))     {         // erase returns the new iterator         iter = m_vPaths.erase(iter);     }     else     {         ++iter;     } } 

But you should use std::remove_if (reinventing the wheel is bad).