Merge pull request #21 from bvwells/iterator

Implement iterator design pattern #12

Author: bvwells

README.md

@@ -64,7 +64,7 @@ Name       | Description                               | Status
 [`Chain of Responsibility`](./behavioral/chain_of_responsibility.go) | Avoid coupling the sender of a request to its receiver by giving more than one object a chance to handle the request. Chain the receiving objects and pass the request along the chain until an object handles it. | Implemented
 [`Command`](./behavioral/command.go) | Encapsulate a request as an object, thereby allowing for the parameterization of clients with different requests, and the queuing or logging of requests. It also allows for the support of undoable operations. | Implemented
 [`Interpreter`](./behavioral/interpreter.go) | Given a language, define a representation for its grammar along with an interpreter that uses the representation to interpret sentences in the language. |
-[`Iterator`](./behavioral/iterator.go) | Provide a way to access the elements of an aggregate object sequentially without exposing its underlying representation. |
+[`Iterator`](./behavioral/iterator.go) | Provide a way to access the elements of an aggregate object sequentially without exposing its underlying representation. | Implemented
 [`Mediator`](./behavioral/mediator.go) | Define an object that encapsulates how a set of objects interact. Mediator promotes loose coupling by keeping objects from referring to each other explicitly, and it allows their interaction to vary independently. |
 [`Memento`](./behavioral/memento.go) | Without violating encapsulation, capture and externalize an object's internal state allowing the object to be restored to this state later. |
 [`Observer`](./behavioral/observer.go) | Define a one-to-many dependency between objects where a state change in one object results in all its dependents being notified and updated automatically. | Implemented

behavioral/iterator.go

@@ -1 +1,48 @@
 package behavioral
+
+// Iterator is an interface for an iterator.
+type Iterator interface {
+
+	// Index returns the index of the current iterator.
+	Index() int
+
+	// Value returns the current value of the iterator.
+	Value() interface{}
+
+	// HasNext returns whether another next element exists.
+	HasNext() bool
+
+	// Next increments the iterator to point to the next element.
+	Next()
+}
+
+// ArrayIterator is an iterator which iterates over an array.
+type ArrayIterator struct {
+	array []interface{}
+	index int
+}
+
+// Index returns the index of the current iterator.
+func (i *ArrayIterator) Index() int {
+	return i.index
+}
+
+// Value returns the current value of the iterator.
+func (i *ArrayIterator) Value() interface{} {
+	return i.array[i.index]
+}
+
+// HasNext returns whether another next element exists.
+func (i *ArrayIterator) HasNext() bool {
+	if i.index+1 == len(i.array) {
+		return false
+	}
+	return true
+}
+
+// Next increments the iterator to point to the next element.
+func (i *ArrayIterator) Next() {
+	if i.HasNext() {
+		i.index++
+	}
+}

behavioral/iterator_test.go

@@ -0,0 +1,19 @@
+package behavioral
+
+import (
+	"testing"
+)
+
+func TestIterator(t *testing.T) {
+
+	array := []interface{}{10.0, 20.0, 30.0, 40.0, 50.0}
+
+	iterator := ArrayIterator{array, 0}
+
+	for it := iterator; iterator.HasNext(); iterator.Next() {
+		index, value := it.Index(), it.Value().(float64)
+		if value != array[index] {
+			t.Errorf("Expected array value to equal %v, but recieved %v", array[index], value)
+		}
+	}
+}