[英]How to implement a generalized callback mechanism in C++03 without boost?
I have an http server that has a request handler like that : 我有一个http服务器,有一个像这样的请求处理程序:
bool handleRequest(const RequestObject& request, ResponseRequest& response);
I'm trying to write a wrapper that would provide an API like that : 我正在尝试编写一个提供类似API的包装器:
addRouteHandler(GET, "/foo/bar", handler);
With handler
able to be either : handler
可以是:
bool handleFooBarRequest(const RequestObject& request, ResponseRequest& response);
一个函数: bool handleFooBarRequest(const RequestObject& request, ResponseRequest& response);
FooResourceInstance
+ bool FooResource::handleFooBarRequest(const RequestObject& request, ResponseRequest& response);
现有对象上的方法: FooResourceInstance
+ bool FooResource::handleFooBarRequest(const RequestObject& request, ResponseRequest& response);
static bool FooResource::handleFooBarRequest(const RequestObject& request, ResponseRequest& response);
对象的静态方法: static bool FooResource::handleFooBarRequest(const RequestObject& request, ResponseRequest& response);
I insist : C++03 (gcc 4.1.2) and no Boost (the reason is NOT the point) 我坚持:C ++ 03(gcc 4.1.2)并没有Boost(原因不是重点)
So far the techniques I have found either use Boost, C++11 or third-party code ( http://www.codeproject.com/Articles/136799/Lightweight-Generic-C-Callbacks-or-Yet-Another-Del ) 到目前为止,我发现的技术要么使用Boost,C ++ 11或第三方代码( http://www.codeproject.com/Articles/136799/Lightweight-Generic-C-Callbacks-or-Yet-Another-Del )
Use an interface and a derived template class. 使用接口和派生模板类。 This technique is called "type erasure". 这种技术称为“类型擦除”。
class CallbackBase
{
public:
virtual ~CallbackBase() = 0;
virtual bool exec(const RequestObject& request, ResponseRequest& response) = 0;
};
template <typename F>
class CallbackImpl : public CallbackBase
{
public:
CallbackImpl(F f) : f_(f) {}
virtual bool exec(const RequestObject& request, ResponseRequest& response) {
return f_(request, response);
}
private:
F f_;
};
template <typename F>
void CreateCallback(F f, std::auto_ptr<CallbackBase>& r) {
r.reset(new CallbackImpl<F>(f));
}
// examples
std::auto_ptr<CallbackBase> my_callback;
CreateCallback(GlobalFooBarRequest, my_callback);
CreateCallback(&FooResource::staticFooBarRequest, my_callback);
// for member function, use std::mem_fun and std::bind1st
...
my_callback->exec(request, response);
You might want to use a shared_ptr or similar instead of auto_ptr, all depends on how you want to store these objects. 您可能希望使用shared_ptr或类似的而不是auto_ptr,所有这些都取决于您希望如何存储这些对象。
Edit: you can write your own member function wrapper/closure/function object. 编辑:您可以编写自己的成员函数包装器/闭包/函数对象。 Code would looks something like the following (I haven't tried compiling it so there could be some errors): 代码看起来像下面这样(我没有尝试编译它,所以可能会有一些错误):
template <typename T>
class RequestWrapper
{
typedef bool (T::*F)(const RequestObject&, ResponseRequest&);
T* obj_;
F f_;
public:
RequestWrapper(T* obj, F f)
: obj_(obj)
, f_(f)
{}
bool operator()(const RequestObject& request, ResponseRequest& response) const {
return (obj_->*f_)(request, response);
}
};
template <typename T, typename F>
RequestWrapper<T> BindRequestMfn(T* obj, F mfn)
{
return RequestWrapper<T>(obj, mfn);
}
CreateCallback(BindRequestMfn(foo, &FooResource::fooBarRequest), my_callback);
This solution described here fully works : http://www.codeproject.com/Articles/11015/The-Impossibly-Fast-C-Delegates 这里描述的解决方案完全有效: http : //www.codeproject.com/Articles/11015/The-Impossibly-Fast-C-Delegates
Only 3 headers. 只有3个标题。
C++03, gcc 4.1.2 OK and no Boost ; C ++ 03,gcc 4.1.2 OK,没有Boost; MIT license MIT许可证
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