Iterator pattern

README.md

@@ -111,6 +111,9 @@ Without violating encapsulation, capture and externalize an object's internal st
 ### Interpretor
 Given a language, define a representation for its grammar along with an interpreter that uses the representation to interpret sentences in the language.
 
+### Iterator (Cursor)
+Provide a way to access the elements of an aggregate object sequentially without exposing its underlying representation.
+
 ### Command
 Encapsulate a request as an object, thereby letting you parametrize clients with different requests, and support undoable operations.
 

behavioral/iterator/iterator.go

@@ -0,0 +1,82 @@
+package main
+
+import (
+	"fmt"
+)
+
+//Iterator object should implement this interface
+type Iterator interface {
+	First()
+	Next() bool
+	Done() bool
+	CurrentItem() interface{}
+}
+
+//A list object should implement Iterable interface in order to be a iterable list
+type Iterable interface {
+	CreateIterator() Iterator
+}
+
+//Iterator object
+type ListIterator struct {
+	data  []string
+	index int
+}
+
+func (i *ListIterator) Done() bool {
+	return i.index >= len(i.data)
+}
+
+func (i *ListIterator) CurrentItem() interface{} {
+	return i.data[i.index]
+}
+
+func (i *ListIterator) First() {
+	i.index = 0
+}
+
+func (i *ListIterator) Next() bool {
+	i.index++
+	if i.Done() {
+		return false
+	}
+	return true
+}
+
+//Actual a basic list object.I don't use abstraction here.
+type List struct {
+	data []string
+}
+
+func (l *List) Append(str string) {
+	l.data = append(l.data, str)
+}
+
+func (l *List) Count() int {
+	return len(l.data)
+}
+
+func (l *List) CreateIterator() Iterator {
+	listIterator := &ListIterator{data: l.data, index: -1}
+	return listIterator
+}
+
+//Basic testing....
+
+func main() {
+	lst := &List{data: make([]string, 0)}
+	lst.Append("A")
+	lst.Append("B")
+	lst.Append("C")
+	lst.Append("D")
+	lst.Append("E")
+
+	//time to iterate...
+	lstIterator := lst.CreateIterator()
+	for lstIterator.Next() {
+		fmt.Println("-", lstIterator.CurrentItem())
+	}
+
+	lstIterator.First()
+	fmt.Println("First:", lstIterator.CurrentItem())
+}