ceph/src/boost/libs/contract/example/mitchell02/observer_main.cpp

   1
   2 // Copyright (C) 2008-2018 Lorenzo Caminiti
   3 // Distributed under the Boost Software License, Version 1.0 (see accompanying
   4 // file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
   5 // See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
   6
   7 //[mitchell02_observer_main
   8 #include "observer/observer.hpp"
   9 #include "observer/subject.hpp"
  10 #include <boost/contract.hpp>
  11 #include <cassert>
  12
  13 int test_state; // For testing only.
  14
  15 // Implement an actual subject.
  16 class concrete_subject
  17     #define BASES public subject
  18     : BASES
  19 {
  20     friend class boost::contract::access;
  21
  22     typedef BOOST_CONTRACT_BASE_TYPES(BASES) base_types; // Subcontracting.
  23     #undef BASES
  24
  25 public:
  26     typedef int state; // Some state being observed.
  27
  28     concrete_subject() : state_() {
  29         // Could have omitted contracts here (nothing to check).
  30         boost::contract::check c = boost::contract::constructor(this);
  31     }
  32
  33     virtual ~concrete_subject() {
  34         // Could have omitted contracts here (nothing to check).
  35         boost::contract::check c = boost::contract::destructor(this);
  36     }
  37
  38     void set_state(state const& new_state) {
  39         // Could have omitted contracts here (nothing to check).
  40         boost::contract::check c = boost::contract::public_function(this);
  41
  42         state_ = new_state;
  43         assert(state_ == test_state);
  44         notify(); // Notify all observers.
  45     }
  46
  47     state get_state() const {
  48         // Could have omitted contracts here (nothing to check).
  49         boost::contract::check c = boost::contract::public_function(this);
  50         return state_;
  51     }
  52
  53 private:
  54     state state_;
  55 };
  56
  57 // Implement an actual observer.
  58 class concrete_observer
  59     #define BASES public observer
  60     : BASES
  61 {
  62     friend class boost::contract::access;
  63
  64     typedef BOOST_CONTRACT_BASE_TYPES(BASES) base_types; // Subcontracting.
  65     #undef BASES
  66
  67     BOOST_CONTRACT_OVERRIDES(up_to_date_with_subject, update)
  68
  69 public:
  70     // Create concrete observer.
  71     explicit concrete_observer(concrete_subject const& subj) :
  72             subject_(subj), observed_state_() {
  73         // Could have omitted contracts here (nothing to check).
  74         boost::contract::check c = boost::contract::constructor(this);
  75     }
  76
  77     virtual ~concrete_observer() {
  78         // Could have omitted contracts here (nothing to check).
  79         boost::contract::check c = boost::contract::destructor(this);
  80     }
  81
  82     // Implement base virtual functions.
  83
  84     bool up_to_date_with_subject(boost::contract::virtual_* v = 0)
  85             const /* override */ {
  86         bool result;
  87         boost::contract::check c = boost::contract::public_function<
  88             override_up_to_date_with_subject
  89         >(v, result, &concrete_observer::up_to_date_with_subject, this);
  90
  91         return result = true; // For simplicity, assume always up-to-date.
  92     }
  93
  94     void update(boost::contract::virtual_* v = 0) /* override */ {
  95         boost::contract::check c = boost::contract::public_function<
  96                 override_update>(v, &concrete_observer::update, this);
  97
  98         observed_state_ = subject_.get_state();
  99         assert(observed_state_ == test_state);
 100     }
 101
 102 private:
 103     concrete_subject const& subject_;
 104     concrete_subject::state observed_state_;
 105 };
 106
 107 int main() {
 108     concrete_subject subj;
 109     concrete_observer ob(subj);
 110     subj.attach(&ob);
 111
 112     subj.set_state(test_state = 123);
 113     subj.set_state(test_state = 456);
 114
 115     return 0;
 116 }
 117 //]
 118