类Python的C ++装饰器 [英] Python-like C++ decorators
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问题描述
@decorator
def装饰有没有方法用C ++来装饰函数或方法? (self,* args,** kwargs):
pass
使用宏例如:
DECORATE(decorator_method)
int修饰(int a,float b = 0)
{
返回0;
}
或
DECORATOR_MACRO
void decorated(mytype& a,mytype2 * b)
{
}
是否有可能?
解决方案
std :: function
为我提出的解决方案提供了大部分构建模块。
这是我提出的解决方案。
#include<的iostream>
#include< functional>
// -------------------------------
// BEGIN装饰器实现
// -------------------------------
template< class> struct Decorator;
模板< class R,class ... Args>
struct Decorator< R(Args ...)>
{
Decorator(std :: function< R(Args ...)> f):f_(f){}
R operator()(Args .. 。args)
{
std :: cout<< 调用装饰的功能。
返回f_(args ...);
}
std :: function< R(Args ...)> F_;
};
模板< class R,class ... Args>
Decorator< R(Args ...)> makeDecorator(R(* f)(Args ...))
{
返回装饰器< R(Args ...)>(std :: function< R(Args ...)> (F));
}
// -------------------------------
// END装饰器实现
// -------------------------------
// -------------------------------
//示例函数来装饰。
// -------------------------------
//建议的解决方案doesn没有使用默认值。
// int decorated1(int a,float b = 0)
int decorated1(int a,float b)
{
std :: cout<< a =<< a<< ,b =<< b<的std :: ENDL;
返回0;
}
void decorated2(int a)
{
std :: cout<< a =<< a<<的std :: ENDL;
}
int main()
{
auto method1 = makeDecorator(decorated1);
method1(10,30.3);
auto method2 = makeDecorator(decorated2);
method2(10);
}
输出:
调用装饰函数。
a = 10,b = 30.3
调用装饰函数。
a = 10
PS $ b
Decorator
提供了一个可以添加除函数调用之外的功能的地方。如果你想简单地传递 std :: function
,你可以使用:
template< class R,class ... Args>
std :: function< R(Args ...)> makeDecorator(R(* f)(Args ...))
{
return std :: function< R(Args ...)>(f);
}
Are there ways to decorate functions or methods in C++ like in python style?
@decorator
def decorated(self, *args, **kwargs):
pass
Using macros for example:
DECORATE(decorator_method)
int decorated(int a, float b = 0)
{
return 0;
}
or
DECORATOR_MACRO
void decorated(mytype& a, mytype2* b)
{
}
Is it possible?
解决方案
std::function
provides most of the building blocks for my proposed solution.
Here is my proposed solution.
#include <iostream>
#include <functional>
//-------------------------------
// BEGIN decorator implementation
//-------------------------------
template <class> struct Decorator;
template <class R, class... Args>
struct Decorator<R(Args ...)>
{
Decorator(std::function<R(Args ...)> f) : f_(f) {}
R operator()(Args ... args)
{
std::cout << "Calling the decorated function.\n";
return f_(args...);
}
std::function<R(Args ...)> f_;
};
template<class R, class... Args>
Decorator<R(Args...)> makeDecorator(R (*f)(Args ...))
{
return Decorator<R(Args...)>(std::function<R(Args...)>(f));
}
//-------------------------------
// END decorator implementation
//-------------------------------
//-------------------------------
// Sample functions to decorate.
//-------------------------------
// Proposed solution doesn't work with default values.
// int decorated1(int a, float b = 0)
int decorated1(int a, float b)
{
std::cout << "a = " << a << ", b = " << b << std::endl;
return 0;
}
void decorated2(int a)
{
std::cout << "a = " << a << std::endl;
}
int main()
{
auto method1 = makeDecorator(decorated1);
method1(10, 30.3);
auto method2 = makeDecorator(decorated2);
method2(10);
}
Output:
Calling the decorated function.
a = 10, b = 30.3
Calling the decorated function.
a = 10
PS
Decorator
provides a place where you can add functionality beyond making the function call. If you want a simple pass through to std::function
, you can use:
template<class R, class... Args >
std::function<R(Args...)> makeDecorator(R (*f)(Args ...))
{
return std::function<R(Args...)>(f);
}
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