Re: [Boost-users] Scoped Pairs of functions?

Subject: Re: [Boost-users] Scoped Pairs of functions?
From: Nat Linden (nat_at_[hidden])
Date: 2011-08-19 13:58:41

On Fri, Aug 19, 2011 at 7:00 AM, Brian Allison
<brian.w.allison_at_[hidden]> wrote:

> Is there a way to generalize the return type so that ScopedResource could be in a library and the user could use it for pairing two functions that have int and void return types respectively?

? I don't think that's necessary. The following still works for me (g++):

#include <iostream>
#include <boost/function.hpp>
#include <boost/bind.hpp>

void acquire_fixed()
{
    std::cout << "Acquiring fixed resource\n";
}

int iacquire_fixed()
{
    int ret(34);
    std::cout << "Acquiring fixed resource, returning " << ret << '\n';
    return ret;
}

void release_fixed()
{
    std::cout << "Releasing fixed resource\n";
}

void acquire(const std::string& resource)
{
    std::cout << "Acquiring " << resource << '\n';
}

int iacquire(const std::string& resource)
{
    int ret(17);
    std::cout << "Acquiring " << resource << ", returning " << ret << '\n';
    return ret;
}

void release(const std::string& resource)
{
    std::cout << "Releasing " << resource << '\n';
}

class ScopedResource
{
public:
    typedef boost::function<void()> ResourceFunc;
    ScopedResource(const ResourceFunc& acq, const ResourceFunc& rel):
        mRelease(rel)
    {
        acq();
    }

    virtual ~ScopedResource()
    {
        mRelease();
    }

private:
    ResourceFunc mRelease;
};

int main(int argc, char *argv[])
{
    {
        ScopedResource fixed(acquire_fixed, release_fixed);
        std::cout << "during acquire_fixed()\n";
    }

    {
        ScopedResource fixed(iacquire_fixed, release_fixed);
        std::cout << "during iacquire_fixed()\n";
    }

    {
        ScopedResource something(boost::bind(acquire, "something"),
                                 boost::bind(release, "something"));
        std::cout << "during acquire('something')\n";
    }

    {
        ScopedResource something(boost::bind(iacquire, "something"),
                                 boost::bind(release, "something"));
        std::cout << "during iacquire('something')\n";
    }
    return 0;
}