Std::map inside the erase (iterator) call attention to detail

Method One:

[CPP]  View plain copy std::map<std::string, std::string > maptest;   bool  TestVal (const std::string & val);      ......   std::map<std: : String, std::string >::iterator it = maptest.begin ();   while (it !=  maptest.end ())    {            if (TestVal ( It->second))             {                     it =  Maptest.erase (IT);            }             else                     it++;  }   ...........   In this way, through the STD:: The erase method of the map, after releasing it, returns a pointer to the next element to get the latest iterator

Method Two:

[CPP]  View plain copy std::map<std::string, std::string > maptest;   bool  TestVal (const std::string & val);      ......   std::map<std: : String, std::string >::iterator it = maptest.begin ();   while (it !=  maptest.end ())    {            if (TestVal ( It->second))             {                    maptest.erase (it++);             }             else                     it++;  }   ...........   This method utilizes the features of Post + +, This time to execute Maptest.eraSE (it++); This statement is divided into three processes

1. Assign value of it to a temporary variable as a parameter variable passed to erase

2. Because parameter processing takes precedence over function calls, the next step is to perform the it++ operation, where it now points to the next address.

3, and then call the Erase function, release the first step to delete the value of it to remove the temporary variable refers to the location.

If only maptest.erase (it); When this statement is executed, it is an illegal pointer, and if you do it again, it will go wrong.

To sum up, the movement of ITER needs attention when it comes to erase.

from:http://blog.csdn.net/lmh12506/article/details/9167653

Note: I have encountered such a mistake before, but when I see it again, I forget to look at other people's posts.