Using "next" in an "iterator" and getting type mismatch error - scala

Question

I am writing my code in Scala and need to have a loop over a vector of points in an image but getting type mismatch error!. I can understand why I have the error but I don't know how to solve it. here is my code:
val output= new Mat (image.rows, image.cols,CV_8UC3,new Scalar(0, 0, 0))
val it = Iterator(vect1)
var vect3=new Array[Byte](3)
vect3(0)=0
vect3(1)=255.toByte
vect3(2)=0
var e= new Point(0,0)
while(it.hasNext){
e = it.next();
output.put(e.x.toInt,e.y.toInt,vect3)
}
and I am getting this error:
...
type mismatch;
found : scala.collection.mutable.ArrayBuffer[org.opencv.core.Point]
required: org.opencv.core.Point[
e = it.next()

Answer 1

By doing val it = Iterator(vect1), you are creating an iterator that iterates on vect1 itself, and not on vect1's elements. Thankfully, you don't need to create an iterator for that, because it already exists :
val vect1 = ArrayBuffer(1, 2, 3)
// vect1: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(1, 2, 3)
val it = vect1.iterator
// it: Iterator[Int] = non-empty iterator
while (it.hasNext) {
println(it.next)
}
// 1
// 2
// 3
// res0: Unit = ()
Note that, according to the Scala API documentation, ArrayBuffer inherits from IterableLike. IterableLike basically means that a collection is iterable, so it makes sense that it defines a method which returns an iterator.
By the way, you can also avoid directly accessing the iterator entirely, using either the foreach method or a for comprehension, because IterableLike also defines the foreachmethod:
// foreach
vect1.foreach(p => output.put(p.x.toInt, p.y.toInt, vect3))
// for comprehension
for (p <- vect1) {
output.put(p.x.toInt, p.y.toInt, vect3)
}
Using the foreach method or the for comprehension is strictly equivalent: the compiler translates for comprehensions to one or more method calls; in this case, a call to foreach.