CODEWITHSUNDEEP
c++templatestypes
NOhs
NOhs

Reputation: 2830

Finding out type

So I have a wrapper for the default C++ vector. My class is a template class like vector so it basically works with all types I want to support. Now I have one issue. I would like to add a function to my wrapper that let's me save my internally stored vector to file. However, the library that I am using to do this has a poor C++ interface to C functions and requires me to pass over a void* and an entry of a predefined list of types.

Let's say I have the class:

template<class T>
class MyClass
{
    dataType type;
    std::vector<T> data;

    MyClass()
    {
        //
    }
};

And I have three types I want to support (e.g.):

Questions:

Upvotes: 0

Views: 68

Answers (2)

Thomas B Preusser
Thomas B Preusser

Reputation: 1189

If you only need support these three types, you can use a template function with specialized implementations exactly for them:

template<class T> class MyClass {
  ...
  f();
};

template<> MyClass<float>::f();
template<> MyClass<int>::f();
template<> MyClass<char>::f();

And provide the implementations exactly for these parameters in an associated C++ file. When calling f() on an instance with another template parameter, the linker will complain about a missing symbol because there is no specialized implementation available.

Upvotes: 2

Lks
Lks

Reputation: 146

If you only want to support some kinds of types T you could hide the template and provide the types you want:

typedef MyClass<int> MyClass_32s;
typedef MyClass<float> MyClass_32f;
...

After that you could write a wrapper for your c Interface:

void passToCInterface(MyClass_32s& dat) 
{
   callCInterfaceFunction(static_cast<void*>(&(dat.data)), INT_FLAG);
}

void passToCInterface(MyClass_32f& dat) 
{
   callCInterfaceFunction(static_cast<void*>(&(dat.data)), FLOAT_FLAG);
}

...

Upvotes: 0

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