Erasing element in a vector while iterating using swap-and-pop

Question

I want to erase certain elements while iterating a vector, but the below code results in a "vector iterator not incrementable" assertion failure.

for(auto iter=vec.begin(); iter!=vec.end(); ++iter) 
{     
    if((*iter).isDead())
    {        
        std::swap(*iter, vec.back());//swap with the back       
        vec.pop_back();     //erase the element
    } 
} 

What is wrong with this code?

Answer 1

You should increment the iterator only if you don't remove any element at that iteration:

for(auto iter=vec.begin(); iter!=vec.end();) 
{     
    if((*iter).isDead())
    {        
        std::swap(*iter, vec.back());//swap with the back       
        vec.pop_back();     //erase the element
    } 
    else
        ++iter;
}

Or even better, replace the whole loop with remove_if:

vec.erase(std::remove_if(vec.begin(), vec.end(),
    std::bind(&ValueType::isDead, _1)), vec.end());