Question

I have the next problem:
I created the structure:

struct Series : vector<Candle>
{ 
 Security Sec;
 int LookFor;
 int TF;
 int Corrector;
 string ID;
 int line;
 Series(){};
 Series (int _lookfor);
 void Update();  
};

Constructor:

Series::Series (int _lookfor)
{
 LookFor=_lookfor;
 for (int i = 1; i<=LookFor; i++)
  {
    Candle cantype = Candle(i);
    push_back(cantype);
  }
}

So, then we call this construcor it fills object by candle-values. LookFor – is a number of candles in the vector-series.
After initialization i want update this serie (if there is more new candle, i want delete last one and insert new on the begining of vector-serie)

void Series::Update()
{
if (size()==LookFor)
{
        if (newer(cantype,c1))
        {
          Candle cantype = Candle(1);
          Candle c1 = at(0);
          pop_back();
          emplace(begin(),cantype);
        }
}

I need to initialize a vector of these series:

vector vec;
vec.push_back(Series(3));

And constructor does its job, everithing is fine.
But then i update them:

for (size_t x =0; x<=size()-1;x++) vec[x].Update();

I have a problem: it cann’t save changes in vector. In Update method everithing is fine, it inserts needed candle in itself, but then method is ended – the state of vector (each element of vec) has no changes. In method we see changes, but after it vector become after constructor-like, the state still the same.
Tell me, please, what am I doing wrong?

Answer 1

• As others already mentioned, do not derive from these containers (could cause nasty errors like missing dtor calls and memory leaks, no virtual destructor is present in these containers). Instead, add the vector as a member or leave it as is, if you do private inheritance.

• You may use the iterator interface for such containers:

for(std::vector<Series>::iterator sIt = vec.begin();sIt != vec.end();++sIt) sIt->Update();

• For your task, consider using a deque or a list as a circular buffer instead of the vector for the Candles. It would perform better for insertions and therefore allows you to use push_front() instead of emplace() or insert().
  Alternatively, you could hold an index of the vector element just past the last element (which should be the first) and just assign the new candle, et voilà, you’ve got a dense circular buffer.
  There are implementations of such circular buffers, for example the one of boost:
  http://www.boost.org/doc/libs/1_52_0/libs/circular_buffer/doc/circular_buffer.html

Despite logic issues, which could prevent the modification in certain states, I can’t see, why your code doesn’t work at all, at least not when I went through the snippets you posted.