vector<int> - missing type specifier - visual-c++

Question

This is the header of a class I am working on in Visual C++ Express 2010:
/* custom class header to communicate with LynxMotion robot arm */
#include <vector>
using namespace System;
using namespace System::IO::Ports;
public ref class LynxRobotArm
{
public:
LynxRobotArm();
~LynxRobotArm();
void connectToSerialPort(String^ portName, int baudRate);
void disconnectFromSerialPort();
void setCurrentPosition(int channel, int position);
int getCurrentPosition(int channel);
void moveToPosition(int channel, int position);
private:
void initConnection();
SerialPort^ serialPort;
array<String^> ^serialPortNames;
String^ portName;
int baudRate;
vector<int> currentPosition;
};
Everything worked fine until I changed the last line int currentPosition to vector<int> currentPosition. If I try to compile / debug now, I get these error messages:
error C2143: syntax error : missing ';' before '<'
error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
error C2238: unexpected token(s) preceding ';'
I checked MSDN for some more info on these error codes, but I cannot figure out what is wrong with the code. Any ideas?

Answer 1

vector is template defined within std namespace, thus you should write std::vector<int> instead of vector<int>.
Alternatively you could write using namespace std; at the beginning of this file, but note that this is considered bad practice since it could cause some of names of your classes to become ambiguous.

Answer 2

You are using vector. Vector is contained with the namespace std. Namespaces encapsulate the normal scope of a variable/class. You cannot access elements within a namespace without resolving the scope somehow. There are 3 main ways to go about this:
#include <vector>
using namespace std;
You don't generally want to use this one, it will create issues because it allows you to see ANY function/class contained in the namespace std. This is bound to cause naming collisions.
Next way is:
#include <vector>
using std::vector;
This way is a little better. It makes vector visible to anything in the file or any file that includes said file. It is perhaps completely harmless in a .cpp file, because you shouldn't be including .cpp files anyways. And you should know what symbols you're or not. In the scenario of a .h/.hpp file, you may still not want to use this. Any file that has your .hpp file included their source code will see class vector as the name definition. This could be bad for users of your code, because they may not be expecting that symbol to be defined. In the case of an hpp file, you should always use the following:
#include <vector>
class myClass{
private:
std::vector myVector;
};
Using namespaces this way guarantees that it will only be visible exactly where the symbol is used, and nowhere else. This is the only way I'd use it in a .hpp file.