[英]How can I use different struct as template argument in a template function?
I am writing a template function like that:我正在编写这样的模板 function:
template<typename T>
std::string EncodeData(int DataType, T Data, std::string ReadCommandID, std::string& ThisID);
The type T
that I want to use is some different structs, for example:我想使用的类型T
是一些不同的结构,例如:
struct A
{
int A_data;
bool A_data_2;
// etc.......
};
struct B
{
double B_data;
char B_data_2;
// etc.......
};
I want the function can access different member variables depends on different struct
passing to T
,so I wrote such code:我希望 function 可以访问不同的成员变量取决于传递给T
的不同struct
,所以我写了这样的代码:
template<typename T>
std::string EncodeData(int DataType, T Data, std::string ReadCommandID, std::string& ThisID)
{
if(std::is_same<T, A>{})
{
// Do something with Data.A_data and Data.A_data_2
}
else if(std::is_same<T, B>{})
{
// Do something with Data.B_data and Data.B_data_2
}
// other code.
}
And use it:并使用它:
A data={100,false};
std::string id;
std::string result = EncodeData<A>(0,data,"read_id_xxxxxxxx",id);
But when I compile it, the following error happened:但是当我编译它时,发生了以下错误:
error C2039: "B_data": is not a member of "A".
error C2039: "B_data_2": is not a member of "A".
How can I fix this?我怎样才能解决这个问题? Or what else I can do to solve this problem in one single function?或者我还能做些什么来在一个 function 中解决这个问题?
PS I'm using MSVC Compiler(Visual Studio 2019) PS我正在使用 MSVC 编译器(Visual Studio 2019)
What else I can do to slove this problom in one single function ?我还能做些什么来解决一个 function中的这个问题?
This is not possible under c++11 compiler.这在c++11编译器下是不可能的。 However, in C++17 you have if constexpr
to do such:但是,在 C++17 中,您可以使用if constexpr
来执行此操作:
template<typename T>
std::string EncodeData(int DataType, T const& Data, std::string const& ReadCommandID, std::string& ThisID)
{
if constexpr (std::is_same_v<T, A>)
{
// Do something with Data.A_data and Data.A_data_2
}
else if constexpr (std::is_same_v<T, B>)
{
// Do something with Data.B_data and Data.B_data_2
}
}
For C++11 you still need two functions.对于 C++11,您仍然需要两个函数。 Therefore, I would suggest having a function overload for each, which might be more readable than having templates.因此,我建议为每个重载一个 function,这可能比使用模板更具可读性。
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