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C++ 中介者模式详解

news 来源：原创 2025/5/13 5:39:00

循以下设计原则：

单一职责原则：将对象间的交互集中到中介者中
迪米特法则：减少对象间的直接通信
开闭原则：可以新增中介者而不修改现有组件

主要优点

降低耦合：减少对象间的直接依赖
集中控制：将交互逻辑集中到中介者
简化维护：交互关系更容易理解和修改
复用性：组件可以更容易地被复用

模式结构

主要组件

Mediator（中介者接口）
- 定义与各组件通信的接口
ConcreteMediator（具体中介者）
- 实现中介者接口
- 协调各组件之间的交互
- 知道所有组件及其用途
Component（组件）
- 每个组件都知道其中介者对象
- 组件间不直接通信，而是通过中介者

完整代码示例

#include <iostream>
#include <string>
#include <memory>
#include <vector>
#include <algorithm>// 前置声明
class Component;// ==================== 中介者接口 ====================
class Mediator {
public:virtual void notify(Component* sender, const std::string& event) const = 0;virtual ~Mediator() = default;
};// ==================== 组件基类 ====================
class Component {
protected:Mediator* mediator_;public:explicit Component(Mediator* mediator = nullptr) : mediator_(mediator) {}void setMediator(Mediator* mediator) {mediator_ = mediator;}virtual ~Component() = default;
};// ==================== 具体组件 ====================
class Button : public Component {std::string name_;public:explicit Button(const std::string& name, Mediator* mediator = nullptr): Component(mediator), name_(name) {}void click() {std::cout << name_ << " 被点击" << std::endl;if (mediator_) {mediator_->notify(this, "click");}}
};class TextBox : public Component {std::string text_;public:explicit TextBox(Mediator* mediator = nullptr) : Component(mediator) {}void setText(const std::string& text) {text_ = text;std::cout << "文本框内容设置为: " << text << std::endl;if (mediator_) {mediator_->notify(this, "text_changed");}}std::string getText() const { return text_; }
};class CheckBox : public Component {bool checked_ = false;public:explicit CheckBox(Mediator* mediator = nullptr) : Component(mediator) {}void check() {checked_ = !checked_;std::cout << "复选框状态: " << (checked_ ? "选中" : "未选中") << std::endl;if (mediator_) {mediator_->notify(this, checked_ ? "checked" : "unchecked");}}bool isChecked() const { return checked_; }
};// ==================== 具体中介者 ====================
class AuthenticationDialog : public Mediator {Button* loginButton_;Button* cancelButton_;TextBox* usernameTextBox_;TextBox* passwordTextBox_;CheckBox* rememberMeCheckBox_;public:AuthenticationDialog(Button* loginButton,Button* cancelButton,TextBox* usernameTextBox,TextBox* passwordTextBox,CheckBox* rememberMeCheckBox): loginButton_(loginButton),cancelButton_(cancelButton),usernameTextBox_(usernameTextBox),passwordTextBox_(passwordTextBox),rememberMeCheckBox_(rememberMeCheckBox) {loginButton_->setMediator(this);cancelButton_->setMediator(this);usernameTextBox_->setMediator(this);passwordTextBox_->setMediator(this);rememberMeCheckBox_->setMediator(this);}void notify(Component* sender, const std::string& event) const override {if (sender == loginButton_ && event == "click") {std::cout << "登录按钮点击 - 尝试登录..." << std::endl;if (usernameTextBox_->getText().empty() || passwordTextBox_->getText().empty()) {std::cout << "错误: 用户名和密码不能为空" << std::endl;} else {std::cout << "使用用户名 '" << usernameTextBox_->getText() << "' 和密码 '" << passwordTextBox_->getText() << "' 登录" << std::endl;if (rememberMeCheckBox_->isChecked()) {std::cout << "记住登录状态" << std::endl;}}} else if (sender == cancelButton_ && event == "click") {std::cout << "取消按钮点击 - 重置表单" << std::endl;usernameTextBox_->setText("");passwordTextBox_->setText("");rememberMeCheckBox_->check();} else if (sender == rememberMeCheckBox_ && (event == "checked" || event == "unchecked")) {std::cout << "记住我选项改变: " << event << std::endl;} else if ((sender == usernameTextBox_ || sender == passwordTextBox_) && event == "text_changed") {std::cout << "文本改变 - 验证输入..." << std::endl;}}
};// ==================== 客户端代码 ====================
int main() {std::cout << "=== 中介者模式演示: 登录对话框 ===" << std::endl;// 创建组件Button loginButton("登录");Button cancelButton("取消");TextBox usernameTextBox;TextBox passwordTextBox;CheckBox rememberMeCheckBox;// 创建中介者并关联组件AuthenticationDialog dialog(&loginButton, &cancelButton, &usernameTextBox, &passwordTextBox, &rememberMeCheckBox);// 模拟用户交互std::cout << "\n用户输入用户名和密码..." << std::endl;usernameTextBox.setText("user123");passwordTextBox.setText("password");std::cout << "\n用户点击记住我..." << std::endl;rememberMeCheckBox.check();std::cout << "\n用户点击登录按钮..." << std::endl;loginButton.click();std::cout << "\n用户点击取消按钮..." << std::endl;cancelButton.click();return 0;
}

模式变体

1. 观察者中介者

class ObserverMediator : public Mediator {std::vector<Component*> components_;public:void addComponent(Component* component) {components_.push_back(component);component->setMediator(this);}void notify(Component* sender, const std::string& event) override {for (auto component : components_) {if (component != sender) {// 通知其他组件}}}
};

2. 单例中介者

class SingletonMediator : public Mediator {static SingletonMediator* instance_;SingletonMediator() = default;public:static SingletonMediator* getInstance() {if (!instance_) {instance_ = new SingletonMediator();}return instance_;}void notify(Component* sender, const std::string& event) override {// 实现通知逻辑}
};