设计学习笔记10：使用状态模式和策略模式解决实际问题的例子

使用状态模式和策略模式解决实际问题的例子

状态模式示例：自动售货机

假设有一个自动售货机，其状态可以是“空闲”、“选择商品”、“等待支付”和“支付完成”。状态模式将允许售货机根据当前状态来改变其行为。

#include <iostream>
#include <memory>// 定义售货机的状态接口
class State {
public:virtual void insertMoney() = 0;virtual void selectProduct() = 0;virtual void dispenseProduct() = 0;virtual ~State() {}
};// 定义具体的状态
class NoProductSelectedState : public State {
public:void insertMoney() override {std::cout << "Cannot insert money, please select a product first." << std::endl;}void selectProduct() override {std::cout << "Product selected. Please insert money." << std::endl;}void dispenseProduct() override {std::cout << "No product selected." << std::endl;}
};class ProductSelectedState : public State {
public:void insertMoney() override {std::cout << "Money inserted. Please take your product." << std::endl;}void selectProduct() override {std::cout << "A product is already selected." << std::endl;}void dispenseProduct() override {std::cout << "Product dispensed. Enjoy!" << std::endl;}
};// 售货机上下文
class VendingMachine {std::unique_ptr<State> state;
public:VendingMachine() : state(std::make_unique<NoProductSelectedState>()) {}void setState(std::unique_ptr<State> newState) {state = std::move(newState);}void insertMoney() {state->insertMoney();}void selectProduct() {state->selectProduct();setState(std::make_unique<ProductSelectedState>());}void dispenseProduct() {state->dispenseProduct();}
};int main() {VendingMachine vm;vm.selectProduct(); // 选择商品vm.insertMoney();  // 投入货币vm.dispenseProduct(); // 领取商品return 0;
}

策略模式示例：排序算法

假设我们需要根据不同的条件对一组数据进行排序，比如按升序或降序排序。策略模式允许我们在运行时选择排序算法。

#include <iostream>
#include <vector>
#include <algorithm>// 定义排序策略接口
class SortStrategy {
public:virtual void sort(std::vector<int>& data) = 0;virtual ~SortStrategy() {}
};// 定义具体的排序策略
class AscendingSortStrategy : public SortStrategy {
public:void sort(std::vector<int>& data) override {std::sort(data.begin(), data.end());}
};class DescendingSortStrategy : public SortStrategy {
public:void sort(std::vector<int>& data) override {std::sort(data.begin(), data.end(), std::greater<int>());}
};// 排序上下文
class SortContext {SortStrategy* strategy;
public:SortContext(SortStrategy* strategy) : strategy(strategy) {}void setStrategy(SortStrategy* newStrategy) {strategy = newStrategy;}void executeSort(std::vector<int>& data) {strategy->sort(data);}
};int main() {std::vector<int> data = {5, 3, 8, 1, 4};SortContext context(new AscendingSortStrategy());context.executeSort(data); // 升序排序for (int num : data) {std::cout << num << " ";}std::cout << std::endl;context.setStrategy(new DescendingSortStrategy());context.executeSort(data); // 降序排序for (int num : data) {std::cout << num << " ";}std::cout << std::endl;return 0;
}