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// Copyright (C) 2008-2018 Lorenzo Caminiti
// Distributed under the Boost Software License, Version 1.0 (see accompanying
// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
//[mitchell02_counter
#ifndef COUNTER_HPP_
#define COUNTER_HPP_
#include "../observer/subject.hpp"
#include <boost/contract.hpp>
class counter
#define BASES public subject
: BASES
{
friend class boost::contract::access;
typedef BOOST_CONTRACT_BASE_TYPES(BASES) base_types;
#undef BASES
public:
/* Creation */
// Construct counter with specified value.
explicit counter(int a_value = 10) : value_(a_value) {
boost::contract::check c = boost::contract::constructor(this)
.postcondition([&] {
BOOST_CONTRACT_ASSERT(value() == a_value); // Value set.
})
;
}
// Destroy counter.
virtual ~counter() {
// Could have omitted contracts here (nothing to check).
boost::contract::check c = boost::contract::destructor(this);
}
/* Queries */
// Current counter value.
int value() const {
// Could have omitted contracts here (nothing to check).
boost::contract::check c = boost::contract::public_function(this);
return value_;
}
/* Commands */
// Decrement counter value.
void decrement() {
boost::contract::old_ptr<int> old_value = BOOST_CONTRACT_OLDOF(value());
boost::contract::check c = boost::contract::public_function(this)
.postcondition([&] {
BOOST_CONTRACT_ASSERT(value() == *old_value - 1); // Decrement.
})
;
--value_;
notify(); // Notify all attached observers.
}
private:
int value_;
};
#endif // #include guard
//]
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