Iterating through a collection

In order to implement a collection, we must provide a way to access each element in the collection, which can be accomplished using the int index value shown in the following code. We will implement a first in, first out (FIFO) order queue. We will provide a way to store the elements using a slice data structure. Lastly, we will implement a Next() method to provide a way to traverse the elements in the collection.

In the following code, we define an interface for the Iterator object. It has one method, Next(), which will return the next element in the collection and a Boolean flag to indicate whether it's OK to continue iterating:

type CarIterator interface {
     Next() (value string, ok bool)
}
const INVALID_INT_VAL = -1
const INVALID_STRING_VAL = ""

Next, we define a collection object that has two properties: an int index used to access the current element and a slice of strings, that is, the actual data in the collection:

type Collection struct {
       index...