当前位置： 首页 > news >正文

第十七章：遍历万象，步步为营——Iterator的迭代艺术

news 2025/10/7 6:27:09

第十七章：遍历万象，步步为营——Iterator的迭代艺术

风云再起，迭代游侠登场

在Template Method展示完他那精妙的模板艺术后，Iterator动作流畅、步履轻盈地走出。他的步伐如同行云流水，仿佛能够轻松穿越任何复杂的数据结构。

"Template Method兄的算法骨架确实精妙，"Iterator优雅地说道，“但在集合遍历和元素访问方面，需要更加统一和优雅的方式。诸位请看——”

Iterator身形一晃，瞬间在几个不同的数据结构间穿梭：“我的迭代器模式，专为解决集合遍历的统一访问问题而生！我提供一种方法顺序访问一个聚合对象中的各个元素，而又不暴露其内部表示！”

架构老人眼中闪过赞许之色：“善！Iterator，就请你为大家展示这迭代艺术的精妙所在。”

迭代器模式的核心要义

Iterator面向众人，开始阐述他的武学真谛：

“在我的迭代器模式中，主要包含四个核心角色：”

“Iterator（迭代器）：定义访问和遍历元素的接口。”

“ConcreteIterator（具体迭代器）：实现迭代器接口，跟踪遍历的当前位置。”

“Aggregate（聚合）：定义创建相应迭代器对象的接口。”

“ConcreteAggregate（具体聚合）：实现创建相应迭代器的接口，返回具体迭代器的实例。”

"其精妙之处在于，"Iterator继续道，“我将集合的遍历行为抽象出来，使得客户端无需了解集合的内部结构。这样，我们可以用相同的方式遍历不同的集合，甚至支持多种遍历方式！”

C++实战：多媒体库管理系统

"且让我以一个多媒体库管理系统为例，展示迭代器模式的实战应用。"Iterator说着，手中凝聚出一道道代码流光。

基础框架搭建

首先，Iterator定义了迭代器接口：

#include <iostream>
#include <vector>
#include <string>
#include <memory>
#include <algorithm>
#include <map>
#include <iomanip>
#include <sstream>
#include <random>
#include <thread>
#include <chrono>
#include <list>
#include <set>// 迭代器接口
template<typename T>
class Iterator {
public:virtual ~Iterator() = default;// 重置到第一个元素virtual void first() = 0;// 移动到下一个元素virtual void next() = 0;// 检查是否还有更多元素virtual bool isDone() const = 0;// 获取当前元素virtual T currentItem() const = 0;// 获取当前位置virtual int currentPosition() const = 0;// 便利方法：遍历所有元素virtual void traverse(std::function<void(const T&)> visitor) {for (first(); !isDone(); next()) {visitor(currentItem());}}
};// 聚合接口
template<typename T>
class Aggregate {
public:virtual ~Aggregate() = default;virtual std::unique_ptr<Iterator<T>> createIterator() = 0;virtual std::unique_ptr<Iterator<T>> createReverseIterator() = 0;virtual int size() const = 0;virtual bool isEmpty() const = 0;
};

具体聚合和迭代器实现

Iterator展示了各种数据结构的迭代器实现：

// 具体聚合：数组集合
template<typename T>
class ArrayCollection : public Aggregate<T> {
private:std::vector<T> items_;std::string name_;public:ArrayCollection(const std::string& name = "数组集合") : name_(name) {std::cout << "📚 创建数组集合: " << name_ << std::endl;}void add(const T& item) {items_.push_back(item);}T& operator[](int index) {return items_[index];}const T& operator[](int index) const {return items_[index];}std::unique_ptr<Iterator<T>> createIterator() override {return std::make_unique<ArrayIterator<T>>(this);}std::unique_ptr<Iterator<T>> createReverseIterator() override {return std::make_unique<ReverseArrayIterator<T>>(this);}int size() const override {return items_.size();}bool isEmpty() const override {return items_.empty();}std::string getName() const {return name_;}// 数组集合特有的方法void sort() {std::sort(items_.begin(), items_.end());std::cout << "🔢 对集合 " << name_ << " 进行排序" << std::endl;}void clear() {items_.clear();std::cout << "🧹 清空集合 " << name_ << std::endl;}private:// 具体迭代器：数组迭代器class ArrayIterator : public Iterator<T> {private:const ArrayCollection<T>* collection_;int currentIndex_;public:ArrayIterator(const ArrayCollection<T>* collection) : collection_(collection), currentIndex_(0) {std::cout << "   🔄 创建数组迭代器" << std::endl;}void first() override {currentIndex_ = 0;}void next() override {if (!isDone()) {currentIndex_++;}}bool isDone() const override {return currentIndex_ >= collection_->size();}T currentItem() const override {if (isDone()) {throw std::out_of_range("迭代器已到达末尾");}return (*collection_)[currentIndex_];}int currentPosition() const override {return currentIndex_;}};// 具体迭代器：反向数组迭代器class ReverseArrayIterator : public Iterator<T> {private:const ArrayCollection<T>* collection_;int currentIndex_;public:ReverseArrayIterator(const ArrayCollection<T>* collection) : collection_(collection), currentIndex_(collection->size() - 1) {std::cout << "   🔄 创建反向数组迭代器" << std::endl;}void first() override {currentIndex_ = collection_->size() - 1;}void next() override {if (!isDone()) {currentIndex_--;}}bool isDone() const override {return currentIndex_ < 0;}T currentItem() const override {if (isDone()) {throw std::out_of_range("迭代器已到达开头");}return (*collection_)[currentIndex_];}int currentPosition() const override {return currentIndex_;}};
};// 具体聚合：链表集合
template<typename T>
class LinkedListCollection : public Aggregate<T> {
private:std::list<T> items_;std::string name_;public:LinkedListCollection(const std::string& name = "链表集合") : name_(name) {std::cout << "🔗 创建链表集合: " << name_ << std::endl;}void add(const T& item) {items_.push_back(item);}void addFront(const T& item) {items_.push_front(item);}std::unique_ptr<Iterator<T>> createIterator() override {return std::make_unique<LinkedListIterator<T>>(this);}std::unique_ptr<Iterator<T>> createReverseIterator() override {return std::make_unique<ReverseLinkedListIterator<T>>(this);}int size() const override {return items_.size();}bool isEmpty() const override {return items_.empty();}std::string getName() const {return name_;}private:// 具体迭代器：链表迭代器class LinkedListIterator : public Iterator<T> {private:const LinkedListCollection<T>* collection_;typename std::list<T>::const_iterator current_;public:LinkedListIterator(const LinkedListCollection<T>* collection) : collection_(collection), current_(collection->items_.begin()) {std::cout << "   🔄 创建链表迭代器" << std::endl;}void first() override {current_ = collection_->items_.begin();}void next() override {if (!isDone()) {++current_;}}bool isDone() const override {return current_ == collection_->items_.end();}T currentItem() const override {if (isDone()) {throw std::out_of_range("迭代器已到达末尾");}return *current_;}int currentPosition() const override {// 链表没有索引，返回近似位置return std::distance(collection_->items_.begin(), current_);}};// 具体迭代器：反向链表迭代器class ReverseLinkedListIterator : public Iterator<T> {private:const LinkedListCollection<T>* collection_;typename std::list<T>::const_reverse_iterator current_;public:ReverseLinkedListIterator(const LinkedListCollection<T>* collection) : collection_(collection), current_(collection->items_.rbegin()) {std::cout << "   🔄 创建反向链表迭代器" << std::endl;}void first() override {current_ = collection_->items_.rbegin();}void next() override {if (!isDone()) {++current_;}}bool isDone() const override {return current_ == collection_->items_.rend();}T currentItem() const override {if (isDone()) {throw std::out_of_range("迭代器已到达开头");}return *current_;}int currentPosition() const override {// 反向位置计算return collection_->items_.size() - 1 - std::distance(collection_->items_.rbegin(), current_);}};
};// 具体聚合：集合（不允许重复）
template<typename T>
class SetCollection : public Aggregate<T> {
private:std::set<T> items_;std::string name_;public:SetCollection(const std::string& name = "集合") : name_(name) {std::cout << "🔄 创建集合: " << name_ << std::endl;}void add(const T& item) {items_.insert(item);}std::unique_ptr<Iterator<T>> createIterator() override {return std::make_unique<SetIterator<T>>(this);}std::unique_ptr<Iterator<T>> createReverseIterator() override {return std::make_unique<ReverseSetIterator<T>>(this);}int size() const override {return items_.size();}bool isEmpty() const override {return items_.empty();}std::string getName() const {return name_;}// 集合特有的方法bool contains(const T& item) const {return items_.find(item) != items_.end();}void remove(const T& item) {items_.erase(item);std::cout << "🗑️  从集合 " << name_ << " 中移除元素" << std::endl;}private:// 具体迭代器：集合迭代器class SetIterator : public Iterator<T> {private:const SetCollection<T>* collection_;typename std::set<T>::const_iterator current_;public:SetIterator(const SetCollection<T>* collection) : collection_(collection), current_(collection->items_.begin()) {std::cout << "   🔄 创建集合迭代器" << std::endl;}void first() override {current_ = collection_->items_.begin();}void next() override {if (!isDone()) {++current_;}}bool isDone() const override {return current_ == collection_->items_.end();}T currentItem() const override {if (isDone()) {throw std::out_of_range("迭代器已到达末尾");}return *current_;}int currentPosition() const override {return std::distance(collection_->items_.begin(), current_);}};// 具体迭代器：反向集合迭代器class ReverseSetIterator : public Iterator<T> {private:const SetCollection<T>* collection_;typename std::set<T>::const_reverse_iterator current_;public:ReverseSetIterator(const SetCollection<T>* collection) : collection_(collection), current_(collection->items_.rbegin()) {std::cout << "   🔄 创建反向集合迭代器" << std::endl;}void first() override {current_ = collection_->items_.rbegin();}void next() override {if (!isDone()) {++current_;}}bool isDone() const override {return current_ == collection_->items_.rend();}T currentItem() const override {if (isDone()) {throw std::out_of_range("迭代器已到达开头");}return *current_;}int currentPosition() const override {return collection_->items_.size() - 1 - std::distance(collection_->items_.rbegin(), current_);}};
};

UML 武功秘籍图

creates
creates
«interface»
Iterator<T>
+first() : void
+next() : void
+isDone() : bool
+currentItem() : T
+currentPosition() : int
+traverse(function<void(const T&)>) : void
«interface»
Aggregate<T>
+createIterator()
+createReverseIterator()
+size() : int
+isEmpty() : bool
ArrayCollection<T>
-vector<T> items_
-string name_
+add(T) : void
+operator[](int)
+createIterator()
+createReverseIterator()
+size() : int
+isEmpty() : bool
+sort() : void
+clear() : void
ArrayIterator<T>
-const ArrayCollection<T>* collection_
-int currentIndex_
+first() : void
+next() : void
+isDone() : bool
+currentItem() : T
+currentPosition() : int
LinkedListCollection<T>
-list<T> items_
-string name_
+add(T) : void
+addFront(T) : void
+createIterator()
+createReverseIterator()
+size() : int
+isEmpty() : bool
LinkedListIterator<T>
-const LinkedListCollection<T>* collection_
-list<T>::const_iterator current_
+first() : void
+next() : void
+isDone() : bool
+currentItem() : T
+currentPosition() : int

实战演练：高级迭代系统

Iterator继续展示更复杂的迭代器模式应用：

// 过滤迭代器：基于条件的元素过滤
template<typename T>
class FilterIterator : public Iterator<T> {
private:std::unique_ptr<Iterator<T>> baseIterator_;std::function<bool(const T&)> predicate_;T currentItem_;bool isValid_;public:FilterIterator(std::unique_ptr<Iterator<T>> baseIterator, std::function<bool(const T&)> predicate): baseIterator_(std::move(baseIterator)), predicate_(predicate) {std::cout << "🎯 创建过滤迭代器" << std::endl;findNextValid();}void first() override {baseIterator_->first();findNextValid();}void next() override {if (!isDone()) {baseIterator_->next();findNextValid();}}bool isDone() const override {return !isValid_;}T currentItem() const override {if (isDone()) {throw std::out_of_range("迭代器已到达末尾");}return currentItem_;}int currentPosition() const override {return baseIterator_->currentPosition();}private:void findNextValid() {isValid_ = false;while (!baseIterator_->isDone()) {T item = baseIterator_->currentItem();if (predicate_(item)) {currentItem_ = item;isValid_ = true;break;}baseIterator_->next();}}
};// 转换迭代器：对元素进行转换
template<typename T, typename U>
class TransformIterator : public Iterator<U> {
private:std::unique_ptr<Iterator<T>> baseIterator_;std::function<U(const T&)> transformer_;public:TransformIterator(std::unique_ptr<Iterator<T>> baseIterator, std::function<U(const T&)> transformer): baseIterator_(std::move(baseIterator)), transformer_(transformer) {std::cout << "🔄 创建转换迭代器" << std::endl;}void first() override {baseIterator_->first();}void next() override {baseIterator_->next();}bool isDone() const override {return baseIterator_->isDone();}U currentItem() const override {if (isDone()) {throw std::out_of_range("迭代器已到达末尾");}return transformer_(baseIterator_->currentItem());}int currentPosition() const override {return baseIterator_->currentPosition();}
};// 分页迭代器：支持分页遍历
template<typename T>
class PagedIterator : public Iterator<T> {
private:std::unique_ptr<Iterator<T>> baseIterator_;int pageSize_;int currentPage_;std::vector<T> currentPageItems_;int pageIndex_;public:PagedIterator(std::unique_ptr<Iterator<T>> baseIterator, int pageSize): baseIterator_(std::move(baseIterator)), pageSize_(pageSize), currentPage_(0), pageIndex_(0) {std::cout << "📄 创建分页迭代器，页大小: " << pageSize_ << std::endl;loadNextPage();}void first() override {baseIterator_->first();currentPage_ = 0;loadNextPage();}void next() override {if (!isDone()) {pageIndex_++;if (pageIndex_ >= currentPageItems_.size()) {loadNextPage();}}}bool isDone() const override {return currentPageItems_.empty();}T currentItem() const override {if (isDone()) {throw std::out_of_range("迭代器已到达末尾");}return currentPageItems_[pageIndex_];}int currentPosition() const override {return currentPage_ * pageSize_ + pageIndex_;}int getCurrentPage() const {return currentPage_;}int getPageCount() const {// 简化实现，实际需要知道总元素数return -1;}private:void loadNextPage() {currentPageItems_.clear();pageIndex_ = 0;int count = 0;while (!baseIterator_->isDone() && count < pageSize_) {currentPageItems_.push_back(baseIterator_->currentItem());baseIterator_->next();count++;}if (!currentPageItems_.empty()) {currentPage_++;std::cout << "   📖 加载第 " << currentPage_ << " 页，包含 " << currentPageItems_.size() << " 个元素" << std::endl;}}
};// 复合迭代器：合并多个迭代器
template<typename T>
class CompositeIterator : public Iterator<T> {
private:std::vector<std::unique_ptr<Iterator<T>>> iterators_;size_t currentIteratorIndex_;public:CompositeIterator() : currentIteratorIndex_(0) {std::cout << "🧩 创建复合迭代器" << std::endl;}void addIterator(std::unique_ptr<Iterator<T>> iterator) {iterators_.push_back(std::move(iterator));}void first() override {currentIteratorIndex_ = 0;for (auto& iterator : iterators_) {iterator->first();}}void next() override {if (isDone()) return;if (!iterators_[currentIteratorIndex_]->isDone()) {iterators_[currentIteratorIndex_]->next();}// 如果当前迭代器结束，移动到下一个while (currentIteratorIndex_ < iterators_.size() && iterators_[currentIteratorIndex_]->isDone()) {currentIteratorIndex_++;}}bool isDone() const override {return currentIteratorIndex_ >= iterators_.size();}T currentItem() const override {if (isDone()) {throw std::out_of_range("迭代器已到达末尾");}return iterators_[currentIteratorIndex_]->currentItem();}int currentPosition() const override {if (isDone()) {return -1;}int position = 0;for (size_t i = 0; i < currentIteratorIndex_; i++) {// 计算前面迭代器的总元素数（简化实现）position += 100; // 假设每个迭代器有100个元素}return position + iterators_[currentIteratorIndex_]->currentPosition();}size_t getCurrentSourceIndex() const {return currentIteratorIndex_;}
};

多媒体数据模型

// 多媒体文件类
class MediaFile {
private:std::string filename_;std::string type_; // "audio", "video", "image"int size_; // KBint duration_; // secondsint rating_; // 1-5public:MediaFile(const std::string& filename, const std::string& type, int size = 0, int duration = 0, int rating = 3): filename_(filename), type_(type), size_(size), duration_(duration), rating_(rating) {}std::string getFilename() const { return filename_; }std::string getType() const { return type_; }int getSize() const { return size_; }int getDuration() const { return duration_; }int getRating() const { return rating_; }void setRating(int rating) {rating_ = std::max(1, std::min(5, rating));}std::string toString() const {std::stringstream ss;ss << filename_ << " [" << type_ << ", " << size_ << "KB, " << duration_ << "s, 评分:" << rating_ << "/5]";return ss.str();}// 用于集合比较bool operator<(const MediaFile& other) const {return filename_ < other.filename_;}bool operator==(const MediaFile& other) const {return filename_ == other.filename_;}
};// 多媒体库类
class MediaLibrary {
private:ArrayCollection<MediaFile> audioFiles_;ArrayCollection<MediaFile> videoFiles_;ArrayCollection<MediaFile> imageFiles_;SetCollection<MediaFile> favoriteFiles_;public:MediaLibrary() : audioFiles_("音频文件"), videoFiles_("视频文件"), imageFiles_("图片文件"), favoriteFiles_("收藏文件") {std::cout << "🏛️  创建多媒体库" << std::endl;initializeSampleData();}void initializeSampleData() {// 添加示例数据audioFiles_.add(MediaFile("song1.mp3", "audio", 5120, 180, 4));audioFiles_.add(MediaFile("song2.mp3", "audio", 6144, 210, 5));audioFiles_.add(MediaFile("podcast1.mp3", "audio", 10240, 3600, 3));videoFiles_.add(MediaFile("movie1.mp4", "video", 1048576, 7200, 5));videoFiles_.add(MediaFile("clip1.mp4", "video", 51200, 180, 4));videoFiles_.add(MediaFile("documentary1.mp4", "video", 2097152, 5400, 4));imageFiles_.add(MediaFile("photo1.jpg", "image", 2048, 0, 3));imageFiles_.add(MediaFile("photo2.jpg", "image", 3072, 0, 5));imageFiles_.add(MediaFile("screenshot1.png", "image", 1024, 0, 2));// 添加一些收藏favoriteFiles_.add(MediaFile("song2.mp3", "audio", 6144, 210, 5));favoriteFiles_.add(MediaFile("movie1.mp4", "video", 1048576, 7200, 5));favoriteFiles_.add(MediaFile("photo2.jpg", "image", 3072, 0, 5));std::cout << "✅ 多媒体库初始化完成" << std::endl;}// 获取各种迭代器std::unique_ptr<Iterator<MediaFile>> getAllFilesIterator() {auto composite = std::make_unique<CompositeIterator<MediaFile>>();composite->addIterator(audioFiles_.createIterator());composite->addIterator(videoFiles_.createIterator());composite->addIterator(imageFiles_.createIterator());return composite;}std::unique_ptr<Iterator<MediaFile>> getAudioFilesIterator() {return audioFiles_.createIterator();}std::unique_ptr<Iterator<MediaFile>> getVideoFilesIterator() {return videoFiles_.createIterator();}std::unique_ptr<Iterator<MediaFile>> getImageFilesIterator() {return imageFiles_.createIterator();}std::unique_ptr<Iterator<MediaFile>> getFavoriteFilesIterator() {return favoriteFiles_.createIterator();}std::unique_ptr<Iterator<MediaFile>> getHighRatedFilesIterator(int minRating = 4) {auto allFiles = getAllFilesIterator();return std::make_unique<FilterIterator<MediaFile>>(std::move(allFiles),[minRating](const MediaFile& file) {return file.getRating() >= minRating;});}std::unique_ptr<Iterator<MediaFile>> getLargeFilesIterator(int minSizeKB = 10240) {auto allFiles = getAllFilesIterator();return std::make_unique<FilterIterator<MediaFile>>(std::move(allFiles),[minSizeKB](const MediaFile& file) {return file.getSize() >= minSizeKB;});}std::unique_ptr<Iterator<std::string>> getFilenamesIterator() {auto allFiles = getAllFilesIterator();return std::make_unique<TransformIterator<MediaFile, std::string>>(std::move(allFiles),[](const MediaFile& file) {return file.getFilename();});}std::unique_ptr<Iterator<MediaFile>> getPagedIterator(int pageSize = 2) {auto allFiles = getAllFilesIterator();return std::make_unique<PagedIterator<MediaFile>>(std::move(allFiles), pageSize);}// 统计信息void showLibraryStats() {std::cout << "\n📊 多媒体库统计信息:" << std::endl;std::cout << "   音频文件: " << audioFiles_.size() << " 个" << std::endl;std::cout << "   视频文件: " << videoFiles_.size() << " 个" << std::endl;std::cout << "   图片文件: " << imageFiles_.size() << " 个" << std::endl;std::cout << "   收藏文件: " << favoriteFiles_.size() << " 个" << std::endl;int totalSize = 0;auto iterator = getAllFilesIterator();iterator->traverse([&totalSize](const MediaFile& file) {totalSize += file.getSize();});std::cout << "   总大小: " << (totalSize / 1024.0) << " MB" << std::endl;}// 添加新文件void addMediaFile(const MediaFile& file) {if (file.getType() == "audio") {audioFiles_.add(file);} else if (file.getType() == "video") {videoFiles_.add(file);} else if (file.getType() == "image") {imageFiles_.add(file);}std::cout << "➕ 添加文件: " << file.getFilename() << std::endl;}// 添加到收藏void addToFavorites(const MediaFile& file) {favoriteFiles_.add(file);std::cout << "⭐ 添加到收藏: " << file.getFilename() << std::endl;}
};

完整测试代码

// 测试迭代器模式
void testIteratorPattern() {std::cout << "=== 迭代器模式测试开始 ===" << std::endl;// 创建数组集合并测试std::cout << "\n--- 数组集合测试 ---" << std::endl;ArrayCollection<int> numbers("数字集合");for (int i = 1; i <= 5; i++) {numbers.add(i * 10);}auto iterator = numbers.createIterator();std::cout << "正向遍历:" << std::endl;iterator->traverse([](const int& num) {std::cout << "   " << num << std::endl;});auto reverseIterator = numbers.createReverseIterator();std::cout << "反向遍历:" << std::endl;reverseIterator->traverse([](const int& num) {std::cout << "   " << num << std::endl;});// 创建链表集合并测试std::cout << "\n--- 链表集合测试 ---" << std::endl;LinkedListCollection<std::string> names("名字集合");names.add("张三");names.add("李四");names.add("王五");names.addFront("赵六"); // 添加到前面auto nameIterator = names.createIterator();std::cout << "名字遍历:" << std::endl;nameIterator->traverse([](const std::string& name) {std::cout << "   " << name << std::endl;});// 创建集合并测试std::cout << "\n--- 集合测试 ---" << std::endl;SetCollection<int> uniqueNumbers("唯一数字集合");uniqueNumbers.add(10);uniqueNumbers.add(20);uniqueNumbers.add(10); // 重复，不会被添加uniqueNumbers.add(30);auto setIterator = uniqueNumbers.createIterator();std::cout << "唯一数字遍历:" << std::endl;setIterator->traverse([](const int& num) {std::cout << "   " << num << std::endl;});std::cout << "\n=== 基础迭代器模式测试结束 ===" << std::endl;
}// 测试高级迭代器
void testAdvancedIterators() {std::cout << "\n=== 高级迭代器测试开始 ===" << std::endl;// 创建测试数据ArrayCollection<int> numbers("测试数字");for (int i = 1; i <= 10; i++) {numbers.add(i);}// 测试过滤迭代器std::cout << "\n--- 过滤迭代器测试 ---" << std::endl;auto baseIterator = numbers.createIterator();auto evenIterator = std::make_unique<FilterIterator<int>>(std::move(baseIterator),[](const int& num) { return num % 2 == 0; });std::cout << "偶数数字:" << std::endl;evenIterator->traverse([](const int& num) {std::cout << "   " << num << std::endl;});// 测试转换迭代器std::cout << "\n--- 转换迭代器测试 ---" << std::endl;baseIterator = numbers.createIterator();auto squaredIterator = std::make_unique<TransformIterator<int, int>>(std::move(baseIterator),[](const int& num) { return num * num; });std::cout << "数字平方:" << std::endl;squaredIterator->traverse([](const int& num) {std::cout << "   " << num << std::endl;});// 测试分页迭代器std::cout << "\n--- 分页迭代器测试 ---" << std::endl;baseIterator = numbers.createIterator();auto pagedIterator = std::make_unique<PagedIterator<int>>(std::move(baseIterator), 3);std::cout << "分页遍历:" << std::endl;pagedIterator->traverse([](const int& num) {std::cout << "   " << num << " (第" << dynamic_cast<PagedIterator<int>&>(*pagedIterator).getCurrentPage() << "页)" << std::endl;});// 测试复合迭代器std::cout << "\n--- 复合迭代器测试 ---" << std::endl;ArrayCollection<int> collection1("集合1");ArrayCollection<int> collection2("集合2");collection1.add(100);collection1.add(200);collection2.add(300);collection2.add(400);auto compositeIterator = std::make_unique<CompositeIterator<int>>();compositeIterator->addIterator(collection1.createIterator());compositeIterator->addIterator(collection2.createIterator());std::cout << "复合遍历:" << std::endl;compositeIterator->traverse([](const int& num) {std::cout << "   " << num << std::endl;});std::cout << "\n=== 高级迭代器测试结束 ===" << std::endl;
}// 测试多媒体库
void testMediaLibrary() {std::cout << "\n=== 多媒体库测试开始 ===" << std::endl;MediaLibrary library;// 显示库统计library.showLibraryStats();// 测试各种迭代器std::cout << "\n--- 所有文件遍历 ---" << std::endl;auto allIterator = library.getAllFilesIterator();allIterator->traverse([](const MediaFile& file) {std::cout << "   " << file.toString() << std::endl;});std::cout << "\n--- 高评分文件遍历 (评分>=4) ---" << std::endl;auto highRatedIterator = library.getHighRatedFilesIterator(4);highRatedIterator->traverse([](const MediaFile& file) {std::cout << "   " << file.toString() << std::endl;});std::cout << "\n--- 大文件遍历 (>=10MB) ---" << std::endl;auto largeFilesIterator = library.getLargeFilesIterator(10240);largeFilesIterator->traverse([](const MediaFile& file) {std::cout << "   " << file.toString() << std::endl;});std::cout << "\n--- 仅文件名遍历 ---" << std::endl;auto filenamesIterator = library.getFilenamesIterator();filenamesIterator->traverse([](const std::string& filename) {std::cout << "   " << filename << std::endl;});std::cout << "\n--- 分页遍历 (每页2个) ---" << std::endl;auto pagedIterator = library.getPagedIterator(2);pagedIterator->traverse([](const MediaFile& file) {std::cout << "   " << file.toString() << std::endl;});std::cout << "\n=== 多媒体库测试结束 ===" << std::endl;
}// 实战应用：智能媒体播放器
class SmartMediaPlayer {
private:MediaLibrary library_;std::vector<MediaFile> playHistory_;std::vector<MediaFile> playQueue_;public:SmartMediaPlayer() {std::cout << "🎵 创建智能媒体播放器" << std::endl;}void playAll() {std::cout << "\n🎶 播放所有媒体文件..." << std::endl;auto iterator = library_.getAllFilesIterator();iterator->traverse([this](const MediaFile& file) {playFile(file);});std::cout << "✅ 所有文件播放完成" << std::endl;}void playHighRated(int minRating = 4) {std::cout << "\n⭐ 播放高评分文件 (评分>=" << minRating << ")..." << std::endl;auto iterator = library_.getHighRatedFilesIterator(minRating);iterator->traverse([this](const MediaFile& file) {playFile(file);});}void playByType(const std::string& type) {std::cout << "\n🎯 播放类型: " << type << "..." << std::endl;std::unique_ptr<Iterator<MediaFile>> iterator;if (type == "audio") {iterator = library_.getAudioFilesIterator();} else if (type == "video") {iterator = library_.getVideoFilesIterator();} else if (type == "image") {iterator = library_.getImageFilesIterator();} else {std::cout << "❌ 未知媒体类型: " << type << std::endl;return;}iterator->traverse([this](const MediaFile& file) {playFile(file);});}void playFavorites() {std::cout << "\n❤️  播放收藏文件..." << std::endl;auto iterator = library_.getFavoriteFilesIterator();iterator->traverse([this](const MediaFile& file) {playFile(file);});}void createPlaylist(const std::string& name, std::function<bool(const MediaFile&)> criteria) {std::cout << "\n📝 创建播放列表: " << name << "..." << std::endl;auto allFiles = library_.getAllFilesIterator();auto playlistIterator = std::make_unique<FilterIterator<MediaFile>>(std::move(allFiles), criteria);int count = 0;playlistIterator->traverse([this, &count](const MediaFile& file) {playQueue_.push_back(file);count++;});std::cout << "✅ 播放列表 '" << name << "' 创建完成，包含 " << count << " 个文件" << std::endl;}void playQueue() {std::cout << "\n▶️  播放队列中的文件..." << std::endl;for (const auto& file : playQueue_) {playFile(file);}playQueue_.clear();}void showPlayHistory() {std::cout << "\n📜 播放历史 (" << playHistory_.size() << " 个文件):" << std::endl;for (const auto& file : playHistory_) {std::cout << "   " << file.toString() << std::endl;}}void runDemo() {std::cout << "\n🎮 运行智能媒体播放器演示..." << std::endl;std::cout << "==========================" << std::endl;// 显示库信息library_.showLibraryStats();// 播放各种内容playByType("audio");playHighRated(5);// 创建自定义播放列表createPlaylist("大型视频文件", [](const MediaFile& file) {return file.getType() == "video" && file.getSize() > 500000;});playQueue();// 显示播放历史showPlayHistory();}private:void playFile(const MediaFile& file) {std::cout << "   ▶️  播放: " << file.getFilename() << std::endl;// 模拟播放过程if (file.getType() == "audio" || file.getType() == "video") {std::cout << "      ⏱️  时长: " << file.getDuration() << "秒" << std::endl;std::this_thread::sleep_for(std::chrono::milliseconds(100));} else {std::cout << "      🖼️  显示图片" << std::endl;std::this_thread::sleep_for(std::chrono::milliseconds(50));}// 记录播放历史playHistory_.push_back(file);}
};// 高级应用：迭代器工具类
class IteratorUtils {
public:// 统计元素数量template<typename T>static int count(std::unique_ptr<Iterator<T>> iterator) {int count = 0;iterator->traverse([&count](const T&) { count++; });return count;}// 查找元素template<typename T>static std::optional<T> find(std::unique_ptr<Iterator<T>> iterator, std::function<bool(const T&)> predicate) {for (iterator->first(); !iterator->isDone(); iterator->next()) {if (predicate(iterator->currentItem())) {return iterator->currentItem();}}return std::nullopt;}// 转换为向量template<typename T>static std::vector<T> toVector(std::unique_ptr<Iterator<T>> iterator) {std::vector<T> result;iterator->traverse([&result](const T& item) {result.push_back(item);});return result;}// 应用函数到每个元素template<typename T>static void forEach(std::unique_ptr<Iterator<T>> iterator, std::function<void(const T&)> action) {iterator->traverse(action);}// 检查所有元素是否满足条件template<typename T>static bool allMatch(std::unique_ptr<Iterator<T>> iterator, std::function<bool(const T&)> predicate) {for (iterator->first(); !iterator->isDone(); iterator->next()) {if (!predicate(iterator->currentItem())) {return false;}}return true;}// 检查是否有元素满足条件template<typename T>static bool anyMatch(std::unique_ptr<Iterator<T>> iterator, std::function<bool(const T&)> predicate) {for (iterator->first(); !iterator->isDone(); iterator->next()) {if (predicate(iterator->currentItem())) {return true;}}return false;}
};int main() {std::cout << "🌈 设计模式武林大会 - 迭代器模式演示 🌈" << std::endl;std::cout << "=====================================" << std::endl;// 测试基础迭代器模式testIteratorPattern();// 测试高级迭代器testAdvancedIterators();// 测试多媒体库testMediaLibrary();// 运行智能媒体播放器演示std::cout << "\n=== 智能媒体播放器演示 ===" << std::endl;SmartMediaPlayer player;player.runDemo();// 测试迭代器工具类std::cout << "\n=== 迭代器工具类测试 ===" << std::endl;ArrayCollection<int> testCollection("测试工具类");for (int i = 1; i <= 5; i++) {testCollection.add(i);}auto testIterator = testCollection.createIterator();std::cout << "元素数量: " << IteratorUtils::count<int>(std::move(testIterator)) << std::endl;testIterator = testCollection.createIterator();auto found = IteratorUtils::find<int>(std::move(testIterator), [](int num) { return num > 3; });if (found) {std::cout << "找到元素: " << found.value() << std::endl;}std::cout << "\n🎉 迭代器模式演示全部完成!" << std::endl;return 0;
}

迭代器模式的武学心得

适用场景

  • 统一遍历接口：当需要为不同的聚合结构提供统一的遍历方式时
  • 隐藏内部结构：当不希望暴露聚合对象的内部表示时
  • 支持多种遍历：当需要支持多种遍历方式（正序、逆序、过滤等）时
  • 简化客户端代码：当希望简化客户端的遍历代码时

优点

  • 简化聚合接口：聚合对象不需要包含遍历代码
  • 支持多种遍历：可以轻松实现不同的遍历算法
  • 封装性良好：将遍历逻辑封装在迭代器中，不暴露聚合内部
  • 开闭原则：可以增加新的迭代器而不修改聚合类
  • 并行遍历：可以同时使用多个迭代器遍历同一聚合

缺点

  • 增加系统复杂度：每个聚合都需要对应的迭代器类
  • 可能降低性能：迭代器调用可能比直接访问稍慢
  • 修改聚合困难：如果在遍历过程中修改聚合，迭代器可能失效

武林高手的点评

Composite 赞叹道：“Iterator 兄的遍历统一确实精妙！能够如此优雅地处理各种数据结构的遍历，这在需要操作复杂集合的系统中确实无人能及。”

Visitor 也点头称赞：“Iterator 兄专注于元素的遍历访问，而我更关注对元素的操作。我们都涉及集合元素的处理，但关注点不同。”

Iterator 谦虚回应：“诸位过奖了。每个模式都有其适用场景。在需要统一遍历集合元素时，我的迭代器模式确实能发挥重要作用。但在需要对元素执行特定操作时，Visitor 兄的方法更加合适。”

下章预告

在Iterator展示完他那精妙的迭代艺术后，Chain of Responsibility 几位高手手挽手，连成一条长链走来。

“Iterator 兄的遍历统一确实精妙，但在请求处理和职责传递方面，需要更加灵活的链式处理方式。” Chain of Responsibility 为首者说道，“下一章，我们将展示如何通过责任链模式将请求的发送者与接收者解耦，让多个对象都有机会处理请求！”

架构老人满意地点头：“善！请求的链式处理确实是构建灵活系统的关键。下一章，就请 Chain of Responsibility 展示他的责任链艺术！”

欲知 Chain of Responsibility 如何通过责任链模式实现请求的灵活处理，且听下回分解！

http://www.dtcms.com/a/449565.html

相关文章：

  • 记一次vcenter server 无法同步主机的故障处理过程
  • 手搓20颗芯片｜专栏开篇：从0到1搭建芯片设计与UVM验证体系
  • 《 Linux 点滴漫谈： 三 》Linux 的骨架：文件系统与目录结构的完整图谱
  • 跨境自建站模板库存网站建设公司
  • 【Web安全】转义字符注入？转义也会失效的SQL注入
  • 虚拟机中建设iis网站网站推广洛阳
  • python+vue高校新生报到管理系统设计（源码+文档+调试+基础修改+答疑）
  • 中秋连连看小游戏开发完整教程
  • 产品图案设计网站一起做网店网站入驻收费
  • traffic-filter inbound acl 概念及题目
  • Python3 XML 解析
  • 驾驭涌现的艺术：自组织系统——解锁复杂世界的创新与适应力
  • 青岛做外贸网站建设西安网站建设培训中心
  • 【MES架构师与C#高级工程师（设备控制方向）两大职业路径的技术】
  • MySQL 8.0.26崩溃恢复全解析
  • 北京哪个网站最好湖南网络营销
  • 【Linux】MobaXterm 工具介绍
  • 2025-10-6学习笔记
  • 【面板数据】各国数字服务贸易进出口额数据集（2005-2023年）
  • dede怎么做商城网站个人网站免费制作平台
  • Oracle OCP认证考试题目详解082系列第57题
  • 嵌入式开发学习日志36——stm32之USART串口通信前述
  • Linux中capability权能管理的实现
  • Python 语法与注释详解
  • joomla 网站建设教程合肥网站推广公司
  • 介绍一个做美食的网站网店网站技术方案
  • 电源——BUCK电路设计实战
  • wordpress点击页面跳转通辽做网站通过seo来赚钱
  • Git 分支完整操作指南
  • 英伟达：人类反馈与可验证奖励相结合