c++ - 在迭代 map 时向/从 map 添加/删除元素是否安全

Question

在迭代 map 时，向 map 添加/删除元素是否安全？请看下面的伪代码:

       //Pseudo Code
       //test is a global variable
       map<int, CustomClass*> test;
       test[Index1] = new CustomClass;
       test[Index2] = new CustomClass;
       test[Index3] = new CustomClass;

       ... 
       //Iterating the map
       map<int, CustomClass*>::iterator itor;
       itor = test.begin();
       while(itor != test.end())
       {
            if (itor->first == IndexToRemove)
            {
                   //below function will remove 
                   //element from the map
                   RemoveFromMap(IndexToRemove);
            } 

            if (NeedAddNewElement())
            {
                   //below function will add
                   // an element to the map
                   AddNewElement(IndexToAdd);
            }

            itor++;
       }

       //Remove a mapping from map
       void RemoveFromMap(int index)
       {
            map<int, CustomClass*>::iterator itor;
            itor = test.begin();
            while(itor != test.end())
            {
                 if (itor->first == index)
                 {
                      test.erase(itor);
                      break;
                 }

                 itor++;
             }
        }

       //add new mapping to map
       void AddNewElement(int index)
       {
            //chech if index exists
            if (test.find(index) == test.end())          
             {           
                    test[index] = new CustomClass;           
             }
       }

Answer 1

在遍历容器并删除元素时，迭代器指向的迭代器本身变得无效!

因此:

iterator = container.erase(iterator)

获取下一个有效的迭代器。