Parsing array of an object in a library constructor

Question

I am trying to develop an Arduino library that consists out of two classes. I want 'WayPointStack' to store an array of 'WPCommand', but I can't get it to work.

WayPointStack.h

#ifndef WayPointStack_h
#define WayPointStack_h
#include "Arduino.h"
#include "WPCommand.h"
class WayPointStack
{
 public:
 WayPointStack();
 WayPointStack(WPCommand* wp);
 WPCommand GetNextWP();
 WPCommand GetWP(int i);
 void AddWP(int target, int time);
 int SetWPPointer(int i);
 int GetLength();
 private:
 WPCommand* _wp;
 int pointer;
 int length;
};
#endif

WPCommand.h

#ifndef WPCommand_h
#define WPCommand_h
#include "Arduino.h"
class WPCommand
{
 public:
 WPCommand(int target, int time );
 WPCommand();
 int GetTarget();
 int GetTime();
 int LEFT;
 int RIGHT;
 int FORWARD;
 int BACKWARD;
 int STOP;
 int END;
 private:
 int _target;
 int _time;
};
#endif

Parts of WaypointStack.cpp

#include "Arduino.h"
#include "WayPointStack.h"
#include "WPCommand.h"
#define arrSize 100
WayPointStack::WayPointStack()
{
 _wp = new WPCommand[arrSize]; // should be enough, heap blabla
 length = 0;
 pointer = 0;
}
WayPointStack::WayPointStack(WPCommand[] wp)
{
 _wp = new WPCommand[arrSize]; // should be enough, heap blabla
 for (int i = 0; i < sizeof(wp), i++){
 _wp[i] = wp[i];
 }
 length = sizeof(wp);
 pointer = 0;
}

I'm pretty sure I'm doing something wrong with the pointers, but I don't know how to fix it. The first two errors are

WayPointStack.cpp:24:42: error: expected ',' or '...' before 'wp'
WayPointStack::WayPointStack(WPCommand[] wp)

and

WayPointStack.cpp:27:29: error: 'wp' was not declared in this scope
for (int i = 0; i < sizeof(wp), i++){

I obviously have to use a pointer. This is all I know, so far. Has someone an idea?

• Mikael Patel: Arduino is not Java it is based on C++. Check the syntax for array/vectors and passing parameters by reference. Also check who to determine the number of elements in a vector. Sizeof() is the number of bytes.

Answer 1

This is a C++, not Arduino question and should be asked on Stack Overflow.

In C/C++ the [] must be on variable name, not on type. WPCommand wp[] (it is the same as WPCommand* wp).

sizeof return size in bytes, not element count. send length as parameter

Dynamic memory allocation in MCU is not a good thing. You can have in WayPointStack

WPCommand _wp[arrSize] 

• Kruspe: Thank you. It reduced the error amount dramatically.