C Instantiate Template Variadic Class-CodePudding

I have this code:

#include <iostream>

template<class P>
void processAll() {
    P p = P();
    p.process();
}

class P1 {
public:
    void process() { std::cout << "process1" << std::endl; }
};

int main() {
    processAll<P1>();
    return 0;
}

Is there a way to inject a second class 'P2' into my function 'processAll', using template variadic ? Something like this :

...

template<class... Ps>
void processAll() {
    // for each class, instantiate the class and execute the process method
}

...

class P2 {
public:
    void process() { std::cout << "process2" << std::endl; }
};

...

int main() {
    processAll<P1, P2>();
    return 0;
}

Can we iterate over each class ?

CodePudding user response：

Using C 17's fold expressions you may forward execution of several processes to the common "process single P" implementation:

template<typename P>
void processSingle() {
    P p = P();
    p.process();
}

template<typename... Ps>
void processAll() {
    (processSingle<Ps>(), ...);
}

If the logic of processSingle() is simple you could skip implementing it in a separate function and instead place all of it within the fold expression, as shown in @Jarod42's answer.

CodePudding user response：

With fold expression (c 17), you might do:

template<class... Ps>
void processAll()
{
    (Ps{}.process(), ...);
}