C++ templated function with various amount of argument

Question

I have a templated function which generates a list of a certain type. For each type the list is formed by an overloaded function. Roughly it looks something like this

void Process(std::vector<Type1> &vector){
}

void Process(std::vector<Type2> &vector){
}

void Process(std::vector<Type3> &vector){
}

template <class T>
std::vector<T> DoFoo() {
    std::vector<T> my_vector;
    ...
    Process(my_vector);
    ...
    return my_vector;
}

However now the Process function for Type3 requires a second argument, the rest stays the same. For now I have just added this argument into all 3 of the Process functions but it's ugly and inelegant. Is there a way to implement it better?

mattlangford · Accepted Answer · 2021-07-09 14:56:50Z

2

An option would be something like this:

void Process(std::vector<Type2> &vector);
void Process(std::vector<Type3> &vector, const Config& config);

template <class T, typename...ProcessParams>
std::vector<T> DoFoo(ProcessParams&&... process_params) {
    std::vector<T> my_vector;
    ...
    Process(my_vector, std::forward<ProcessParams>(process_params)...);
    ...
    return my_vector;
}

You'd still be able to call DoFoo with Type2:

std::vector<Type2> result = DoFoo<Type2>();

but then would need to call it with an extra argument for Type3:

std::vector<Type3> result = DoFoo<Type3>(Config{});

edited Jul 9, 2021 at 14:56

answered Jul 8, 2021 at 16:10

mattlangford

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