How to Implement Implicit Conversion to Iterable<T>?

I have a BufferedImage for which I wish to implement an Iterable so that I may iterate over all the pixels.

data class Pixel(val point: Point, val color: Color)

fun BufferedImage.iterable(): Iterable<Pixel> {
  return object: Iterable<Pixel> {
  override fun iterator(): Iterator<Pixel> {
           return iterator()

fun BufferedImage.iterator(): Iterator<Pixel> {
  return object : Iterator<Pixel> {
  var currentX = 0
  var currentY = 0

  &nbsp;&nbsp;override fun hasNext(): Boolean {

           return currentY != getHeight()

  &nbsp;&nbsp;override fun next(): Pixel {

           val point = Point(currentX, currentY)
           val color = Color(getRGB(currentX, currentY))

           if (currentX == getWidth() - 1) {
           currentX = 0
           currentY += 1
           } else {
           currentX += 1

           return Pixel(point, color)

This code let's me write

for (pixel in image) { doStuff(pixel) }


image.iterator().map { doStuff(it) } image.iterable().map { doStuff(it) }

But I can't directly write { doStuff(it) }

Why not? I feel like I'm missing only one more piece and then everything will work as intended.

Kotlin does not support implicit conversions, in fact, this is something we are strongly against. The best we can offer for your case is explicitly calling some method/property before calling map(), e.g.: {...}


val Iterable<Pixel>   get() = ...

1 Like

Small addition, recently something changed and keyword operator is now required for declaration of function iterator() to use it implicitly in for cycles.

operator fun BufferedImage.iterator(): Iterator