std function 调用成员函数的两种方式

by 
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#include <functional>
 
class Test124 {
public:
	int Sum(int x, int y) {
		return x + y;
	}
};
 
int main()
{
	Test124 testObj;
 
	// functional1 can be defined using 'auto' keyword instead
	std::function<int(int, int)> functional1 = std::bind(&Test124::Sum, testObj,
		std::placeholders::_1, std::placeholders::_2);
	int result1 = functional1(1, 2);
 
	// functional2 can not be defined using 'auto' keyword instead
	std::function<int(Test124, int, int)> functional2 = &Test124::Sum;
	int result2 = functional2(testObj, 1, 2);
 
	return 1;
}

ON_SCOPE_GUARD

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class ScopeExit {
public:
	ScopeExit() = default;
 
	ScopeExit(const ScopeExit&) = delete;
	void operator=(const ScopeExit&) = delete;
 
	ScopeExit(ScopeExit&&) = default;
	ScopeExit& operator=(ScopeExit&&) = default;
 
	template <typename F, typename... Args>
	ScopeExit(F&& f, Args&&... args) {
		func_ = std::bind(std::forward<F>(f), std::forward<Args>(args)...);
	}
 
	~ScopeExit() {
		if (func_) {
			func_();
		}
	};
 
private:
	std::function<void()> func_;
};
 
#define _SCOPE_CONCAT(a, b) a##b
#define _SCOPE_MAKE_SCOPE_(line) ScopeExit _SCOPE_CONCAT(defer, line) = [&]()
 
#undef ON_SCOPE_GUARD
#define ON_SCOPE_GUARD _SCOPE_MAKE_SCOPE_(__LINE__)
 
int main()
{
	FILE* fp = fopen("d:/aa.txt", "w+");
 
	ON_SCOPE_GUARD {
		fclose(fp);
	};
 
	fprintf(fp, "hello, file system.\n");
	return 1;
}