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?

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. — Mikael Patel
– Mikael Patel, Commented Mar 27, 2019 at 7:10

Juraj · Accepted Answer · 2019-03-27 05:02:10Z

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]

answered Mar 27, 2019 at 5:02

Juraj♦

18.3k4 gold badges32 silver badges50 bronze badges

Thank you. It reduced the error amount dramatically.

Kruspe
– Kruspe

2019-03-27 09:57:02 +00:00
Commented Mar 27, 2019 at 9:57

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