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This article mainly explains "how to solve the problem that the C++ visitor mode template function cannot be overloaded". Interested friends may wish to take a look. The method introduced in this paper is simple, fast and practical. Let's let Xiaobian take you to learn "how to solve the problem that C++ visitor mode template function cannot be overloaded"!

background

Recently we encountered a tricky scenario where we had a bunch of modules with a common base class, which we assumed to be BaseClass, with some common structure and overloaded methods. These modules have a heap with the same name but different types.

Parameters, such as:

int DerivedClass1::DoNlpTask(const DerivedReq1& req, DerivedResp* resp);

Something like that. DoNlpTask of each DerivedClass has the same name and different parameters, and these should be implemented for the business. Normally, it's easy to think of ways to overload functions, but unfortunately template functions cannot be overloaded.

However, we want to decouple the framework layer from the business layer, and do not want to contaminate the structure of the framework scheduling module with specific types of services.

solutions

Here, we use the idea of visitor pattern, combined with C++ template to unify the process. First define a Visitor, which defines the general operation steps of specific business modules; during implementation, use template specialization to instantiate different business modules and their DoNlpTask functions. In this way, you only need to call Visitor's unified template interface at the framework level. See the code for details.

final code

#include #include //following simulated request protocols ============================//virtual int get_field_id() = 0; virtual void WormUp () {}};#define REGISTER_PROTOTYPE(req_type, resp_type) \ public: \ using ReqType = req_type; \ using RespType = resp_type;class DerivedClass : public BaseClass { //REGISTER REQUEST TYPE REGISTER_PROTOTYPE(DerivedReq, DerivedResp) public: int DoNlpTask(const DerivedReq&, DerivedResp* resp) { std::cout get_field_id(); std::cout

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