Boost C++ Application Development Cookbook - Second Edition

How to do it...

Ladies and gentlemen, let me introduce you to the Boost.Optional library using the following example:

The try_lock_device() function tries to acquire a lock for a device and may succeed or not, depending on different conditions (in our example it depends on some try_lock_device_impl() function call):

#include <boost/optional.hpp>#include <iostream>class locked_device {    explicit locked_device(const char* /*param*/) {        // We have unique access to device.        std::cout << "Device is locked\n";    }    static bool try_lock_device_impl();public:    void use() {        std::cout << "Success!\n";    }    static boost::optional<locked_device> try_lock_device() {        if (!try_lock_device_impl()) {            // Failed to lock device.            return boost::none;        }        // Success! return ...