【设计模式】迭代器模式

概念

行为模式

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类图

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代码

#include <iostream>
#include <vector>using namespace std;class Profile {
public:Profile (int index, string email) {id = index;content = email;}void GetId() {cout << "Id get! " << id << endl;}void GetEmail() {cout << "Email get! " << content << endl;}private:int id;string content;
};class ProfileIterator {
public:virtual ~ProfileIterator() = default;virtual Profile* GetNext() = 0;virtual bool HasMore() = 0;
};class SocialNetwork {
public:virtual ProfileIterator* CreateFriendsIterator(int profileId) = 0;virtual ProfileIterator* CreateCoworkersIterator(int profileId) = 0;
};class WeChat;
class WeChatIterator : public ProfileIterator {
public:WeChatIterator(WeChat* weChat, int profileId, const string& type) {this->weChat = weChat;this->profileId = profileId;this->type = type;};Profile* GetNext() override {if (HasMore()) {currentPosition++;return profiles[currentPosition - 1];}return nullptr;}bool HasMore() override {LazyInit();return currentPosition < profiles.size();}private:WeChat* weChat;int profileId;string type;int currentPosition{0};vector<Profile*> profiles;void LazyInit() {if (profiles.empty()) {cout << "WeChatIterator lazy init." << endl;profiles.emplace_back(new Profile(profileId, type));}}
};class WeChat : public SocialNetwork {
public:ProfileIterator* CreateFriendsIterator(int profileId) override {return new WeChatIterator(this, profileId, "friends");}ProfileIterator* CreateCoworkersIterator(int profileId) override {return new WeChatIterator(this, profileId, "coworkers");}
};class SocialSpammer {
public:static void Send(ProfileIterator* iterator, const string& message) {while (iterator->HasMore()) {auto profile = iterator->GetNext();profile->GetId();profile->GetEmail();}}
};int main(int argc, char *argv[]) {auto network = new WeChat();auto coworkerIter = network->CreateCoworkersIterator(0);auto friendIter = network->CreateFriendsIterator(1);SocialSpammer::Send(coworkerIter, "VIP MSG!");SocialSpammer::Send(friendIter, "JUNK MSG!");delete network;delete coworkerIter;delete friendIter;return 0;
}