C++策略模式与函数指针结合使用

class Strategy {
public:
    virtual ~Strategy() = default;
    virtual void execute() = 0;
};
<p>class ConcreteStrategyA : public Strategy {
public:
void execute() override {
// 算法A
}
};</p><p>class Context {
public:
explicit Context(Strategy<em> s) : strategy(s) {}
void setStrategy(Strategy</em> s) { strategy = s; }
void doWork() { strategy->execute(); }
private:
Strategy* strategy;
};</p>

using StrategyFunc = void(*)();

class Context {
public:
    explicit Context(StrategyFunc func) : strategyFunc(func) {}
<pre class='brush:php;toolbar:false;'>void setStrategy(StrategyFunc func) {
    strategyFunc = func;
}

void doWork() {
    if (strategyFunc) strategyFunc();
}

void strategyA() { /* ... */ }
void strategyB() { /* ... */ }
<p>Context ctx(strategyA);
ctx.doWork(); // 执行A
ctx.setStrategy(strategyB);
ctx.doWork(); // 执行B</p>

#include <functional>
<p>class Context {
public:
using Strategy = std::function<void()>;</p><pre class='brush:php;toolbar:false;'>explicit Context(Strategy s) : strategy(std::move(s)) {}

void setStrategy(Strategy s) {
    strategy = std::move(s);
}

void doWork() {
    if (strategy) strategy();
}

int factor = 2;
Context ctx([factor]() {
    std::cout << "Factor: " << factor << '\n';
});
ctx.doWork();