teaching machines

CS 330 Lecture 25 – Concrete Classes in C++

April 6, 2015 by Chris Johnson. Filed under cs330, lectures, spring 2015.

Agenda

• what ?s
• classes in C++
• namespaces
• RAII
• references
• overloading builtin operators
• I/O of custom types

Code

Image.h

#ifndef IMAGE_H
#define IMAGE_H

#include <string>

namespace cs330 {
  class Image {
    public:
      Image(int width, int height);
      Image(std::string path);
      ~Image();

    private:
      int width;
      int height;
      unsigned char *pixels;
  };
}

#endif

Image.cpp

#include "Image.h"

namespace cs330 {

Image::Image(int width, int height) :
  width(width),
  height(height) {
  // The Java way:
  /* this->width = width; */
  /* this->height = height; */
  pixels = new unsigned char[width * height];
}

Image::Image(std::string path) {
  ifstream in(path.c_str());
  std::string wasted;
  // read p2
  in >> wasted;
  // read width
  in >> this->width;
  // read height
  in >> this->height;
  // read max
  int max;
  in >> max;
  // read all pixels
  in.close();
}

Image::~Image() {
  delete[] pixels;
}

}

main.cpp

#include <iostream>
#include "Image.h"

/* using namespace cs330; */
/* using cs330::Image; */

int main(int argc, char **argv) {
  /* Image img = Image(512, 256); */
  cs330::Image img(512, 256);
  cs330::Image *img2 = new Image(3000, 256);

  // img's destructor automatically called for us
  // img2's destructor awaits our future delete
  //   delete img2;
  return 0;
}

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