From 4f6f5032606ce2c53a3af9b3b5c2b73a03fa9913 Mon Sep 17 00:00:00 2001
From: Edward <crazybber@outlook.com>
Date: Sun, 3 May 2020 19:33:03 +0800
Subject: [PATCH] add two iterator patterns examples

---
 .../book_iterator/book_iterator.go            | 91 +++++++++++++++++++
 .../book_iterator/book_iterator_test.go       | 22 +++++
 .../04_iterator/person_iterator/iterator.go   | 72 +++++++++++++++
 .../person_iterator/iterator_test.go          | 18 ++++
 4 files changed, 203 insertions(+)
 create mode 100644 behavior/04_iterator/book_iterator/book_iterator.go
 create mode 100644 behavior/04_iterator/book_iterator/book_iterator_test.go
 create mode 100644 behavior/04_iterator/person_iterator/iterator.go
 create mode 100644 behavior/04_iterator/person_iterator/iterator_test.go

diff --git a/behavior/04_iterator/book_iterator/book_iterator.go b/behavior/04_iterator/book_iterator/book_iterator.go
new file mode 100644
index 0000000..7ffb0ff
--- /dev/null
+++ b/behavior/04_iterator/book_iterator/book_iterator.go
@@ -0,0 +1,91 @@
+// Package iterator is an example of the Iterator Pattern.
+package iterator
+
+// Iterator provides a iterator interface.
+type Iterator interface {
+	Index() int
+	Value() interface{}
+	Has() bool
+	Next()
+	Prev()
+	Reset()
+	End()
+}
+
+// Aggregate provides a collection interface.
+type Aggregate interface {
+	Iterator() Iterator
+}
+
+// BookIterator implements the Iterator interface.
+type BookIterator struct {
+	shelf    *BookShelf
+	index    int
+	internal int
+}
+
+// Index returns current index
+func (i *BookIterator) Index() int {
+	return i.index
+}
+
+// Value returns current value
+func (i *BookIterator) Value() interface{} {
+	return i.shelf.Books[i.index]
+}
+
+// Has implementation.
+func (i *BookIterator) Has() bool {
+	if i.internal < 0 || i.internal >= len(i.shelf.Books) {
+		return false
+	}
+	return true
+}
+
+// Next goes to the next item.
+func (i *BookIterator) Next() {
+	i.internal++
+	if i.Has() {
+		i.index++
+	}
+}
+
+// Prev goes to the previous item.
+func (i *BookIterator) Prev() {
+	i.internal--
+	if i.Has() {
+		i.index--
+	}
+}
+
+// Reset resets iterator.
+func (i *BookIterator) Reset() {
+	i.index = 0
+	i.internal = 0
+}
+
+// End goes to the last item.
+func (i *BookIterator) End() {
+	i.index = len(i.shelf.Books) - 1
+	i.internal = i.index
+}
+
+// BookShelf implements the Aggregate interface.
+type BookShelf struct {
+	Books []*Book
+}
+
+// Iterator creates and returns the iterator over the collection.
+func (b *BookShelf) Iterator() Iterator {
+	return &BookIterator{shelf: b}
+}
+
+// Add adds an item to the collection.
+func (b *BookShelf) Add(book *Book) {
+	b.Books = append(b.Books, book)
+}
+
+// Book implements a item of the collection.
+type Book struct {
+	Name string
+}
diff --git a/behavior/04_iterator/book_iterator/book_iterator_test.go b/behavior/04_iterator/book_iterator/book_iterator_test.go
new file mode 100644
index 0000000..636db76
--- /dev/null
+++ b/behavior/04_iterator/book_iterator/book_iterator_test.go
@@ -0,0 +1,22 @@
+// Package iterator is an example of the Iterator Pattern.
+package iterator
+
+import "testing"
+
+func TestIterator(t *testing.T) {
+
+	shelf := new(BookShelf)
+
+	books := []string{"A", "B", "C", "D", "E", "F"}
+
+	for _, book := range books {
+		shelf.Add(&Book{Name: book})
+	}
+
+	for iterator := shelf.Iterator(); iterator.Has(); iterator.Next() {
+		index, value := iterator.Index(), iterator.Value().(*Book)
+		if value.Name != books[index] {
+			t.Errorf("Expect Book.Name to %s, but %s", books[index], value.Name)
+		}
+	}
+}
diff --git a/behavior/04_iterator/person_iterator/iterator.go b/behavior/04_iterator/person_iterator/iterator.go
new file mode 100644
index 0000000..13a3eae
--- /dev/null
+++ b/behavior/04_iterator/person_iterator/iterator.go
@@ -0,0 +1,72 @@
+package iterator
+
+import "fmt"
+
+/*
+	设计思想：
+		1. Iterator结构体
+			实现Next()  HasNext()方法
+		2. Container容器
+			容器实现添加 移除Visitor 和
+*/
+//创建迭代器
+type Iterator struct {
+	index int
+	Container
+}
+
+func (i *Iterator) Next() Visitor {
+	fmt.Println(i.index)
+	visitor := i.list[i.index]
+	i.index += 1
+	return visitor
+}
+
+func (i *Iterator) HasNext() bool {
+	if i.index >= len(i.list) {
+		return false
+	}
+	return true
+}
+
+//创建容器
+type Container struct {
+	list []Visitor
+}
+
+func (c *Container) Add(visitor Visitor) {
+	c.list = append(c.list, visitor)
+}
+
+func (c *Container) Remove(index int) {
+	if index < 0 || index > len(c.list) {
+		return
+	}
+	c.list = append(c.list[:index], c.list[index+1:]...)
+}
+
+//创建Visitor接口
+type Visitor interface {
+	Visit()
+}
+
+//创建具体的visitor对象
+type Teacher struct{}
+
+type Analysis struct{}
+
+func (t *Teacher) Visit() {
+	fmt.Println("this is teacher visitor")
+}
+
+func (a *Analysis) Visit() {
+	fmt.Println("this is analysis visitor")
+}
+
+//工厂方法创建迭代器
+func NewIterator() *Iterator {
+	return &Iterator{
+		index:     0,
+		Container: Container{},
+	}
+}
diff --git a/behavior/04_iterator/person_iterator/iterator_test.go b/behavior/04_iterator/person_iterator/iterator_test.go
new file mode 100644
index 0000000..add615b
--- /dev/null
+++ b/behavior/04_iterator/person_iterator/iterator_test.go
@@ -0,0 +1,18 @@
+package iterator
+
+import "testing"
+
+func TestIterator_Next(t *testing.T) {
+	teacher := new(Teacher)
+	analysis := new(Analysis)
+	//迭代器
+	iterator := NewIterator()
+	iterator.Add(teacher)
+	iterator.Add(analysis)
+	if len(iterator.list) != 2 {
+		t.Error("期望的count is 2")
+	}
+	for iterator.HasNext() {
+		iterator.Next().Visit()
+	}
+}