C++策略模式与函数对象结合使用

struct Strategy {
    virtual ~Strategy() = default;
    virtual void execute() = 0;
};
<p>struct ConcreteStrategyA : Strategy {
void execute() override { /<em> 算法A </em>/ }
};</p><p>struct Context {
explicit Context(std::unique_ptr<Strategy> s) : strategy(std::move(s)) {}
void run() { strategy->execute(); }
private:
std::unique_ptr<Strategy> strategy;
};</p>

class FlexibleContext {
public:
    using StrategyFunc = std::function<void()>;
<pre class='brush:php;toolbar:false;'>explicit FlexibleContext(StrategyFunc func) : strategy(std::move(func)) {}

void run() { strategy(); }

void set_strategy(StrategyFunc func) { strategy = std::move(func); }

void function_strategy() { /* 普通函数 */ }
<p>int main() {
FlexibleContext ctx([]{ std::cout << "Lambda strategy\n"; });
ctx.run();</p><pre class='brush:php;toolbar:false;'>ctx.set_strategy(function_strategy);
ctx.run();

ctx.set_strategy(std::bind(&MyClass::method, myObj));
ctx.run();

template<typename Strategy>
class TemplateContext {
public:
    explicit TemplateContext(Strategy s) : strategy(std::move(s)) {}
<pre class='brush:php;toolbar:false;'>void run() { strategy(); }

auto lambda = [] { std::cout << "Fast lambda\n"; };
TemplateContext ctx(lambda);
ctx.run(); // 内联调用，无开销