Initialize a "Matrix" object in my own library?

Question

So, I'm trying to make a custom library to drive a 8x8 Bi-Color LED Matrix from 2 MAX7219's that incorporates two "Matrix" objects from the "Matrix" library and I cannot, for the life of me, figure out how to initialize them in my class. Can someone help me? By the way, I have been programming for 8 years, and consequently have a decent knowledge of the topic! Here is my current code:

header file

#include "Arduino.h"
#include "Matrix.h"
#include "Sprite.h"
class ZackBiColorMatrix{
 public:
 ZackBiColorMatrix(byte dataR, byte loadR, byte clockR, byte dataG, byte loadG, byte clockG);
 Matrix r;
 Matrix g;
 void setLED(byte col, byte row, byte val, char color);
 void writeSprite(byte x, byte y, Sprite sp, char color);
 private:
 byte redData;
 byte redLoad;
 byte redClock;
 byte greenData;
 byte greenLoad;
 byte greenClock;
};

and the .cpp file:

#include "Arduino.h"
#include "Sprite.h"
#include "Matrix.h"
#include "ZackBiColorMatrix.h"
ZackBiColorMatrix::ZackBiColorMatrix (byte dataR, byte loadR, byte clockR, byte dataG, byte loadG, byte clockG) {
 redData = dataR;
 redLoad = loadR;
 redClock = clockR;
 greenData = dataG;
 greenLoad = loadG;
 greenClock = clockG;
 r = Matrix (redData, redClock, redLoad);
 g = Matrix (greenData, greenClock, greenLoad);
}
void ZackBiColorMatrix::setLED (byte col, byte row, byte val, char color) {
 if (color == 'g') {
 g.write (col, row, val);
 }
 else if (color == 'r') {
 r.write (col, row, val);
 }
}
void ZackBiColorMatrix::writeSprite (byte x, byte y, Sprite sp, char color) {
 if (color == 'g') {
 g.write (x, y, sp);
 }
 else if (color == 'r') {
 r.write (x, y, sp);
 }
}

Also, I use the Eclipse Arduino IDE if that matters.

• Kingsley: What you have in your constructor is perfectly valid C++, and it will initialise the member variables.

Answer 1

This is a C++ question actually.

In C++, you initialize class members in the class constructor definition by using a "member intialization list" as follows for your example:

ZackBiColorMatrix::ZackBiColorMatrix (byte dataR, byte loadR, byte clockR, byte dataG, byte loadG, byte clockG)
: r(dataR, clockR, loadR),
 g(dataG, clockG, loadG) {
 ... Additional initialization here
}

This is a special C++ construct (note the colon : after the constructor declaration but before its implementation).

Also note that, in your example, I think you don't need to declare redData, redLoad, redClock, greenData, greenLoad, greenClock, sicne they are not being used once your 2 Matrix fields have been initialized.

Hence you could simplify your class further, I think.

• Ricardo: Hey @ZackElec, if the answer helped you, please consider accepting it. You can do it by clicking the checkmark on the left-hand side of the question, just below the up/down vote arrows and the question vote count. Once you get 15 reputation points, you can also upvote the question. Thanks!!