1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
|
// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef BASE_OBSERVER_LIST_H__
#define BASE_OBSERVER_LIST_H__
#include <algorithm>
#include <limits>
#include <vector>
#include "base/basictypes.h"
#include "base/logging.h"
///////////////////////////////////////////////////////////////////////////////
//
// OVERVIEW:
//
// A container for a list of observers. Unlike a normal STL vector or list,
// this container can be modified during iteration without invalidating the
// iterator. So, it safely handles the case of an observer removing itself
// or other observers from the list while observers are being notified.
//
// TYPICAL USAGE:
//
// class MyWidget {
// public:
// ...
//
// class Observer {
// public:
// virtual void OnFoo(MyWidget* w) = 0;
// virtual void OnBar(MyWidget* w, int x, int y) = 0;
// };
//
// void AddObserver(Observer* obs) {
// observer_list_.AddObserver(obs);
// }
//
// void RemoveObserver(Observer* obs) {
// observer_list_.RemoveObserver(obs);
// }
//
// void NotifyFoo() {
// FOR_EACH_OBSERVER(Observer, observer_list_, OnFoo(this));
// }
//
// void NotifyBar(int x, int y) {
// FOR_EACH_OBSERVER(Observer, observer_list_, OnBar(this, x, y));
// }
//
// private:
// ObserverList<Observer> observer_list_;
// };
//
//
///////////////////////////////////////////////////////////////////////////////
template <class ObserverType, bool check_empty = false>
class ObserverList {
public:
// Enumeration of which observers are notified.
enum NotificationType {
// Specifies that any observers added during notification are notified.
// This is the default type if non type is provided to the constructor.
NOTIFY_ALL,
// Specifies that observers added while sending out notification are not
// notified.
NOTIFY_EXISTING_ONLY
};
ObserverList() : notify_depth_(0), type_(NOTIFY_ALL) {}
ObserverList(NotificationType type) : notify_depth_(0), type_(type) {}
~ObserverList() {
// When check_empty is true, assert that the list is empty on destruction.
if (check_empty) {
Compact();
DCHECK_EQ(observers_.size(), 0U);
}
}
// Add an observer to the list.
void AddObserver(ObserverType* obs) {
DCHECK(find(observers_.begin(), observers_.end(), obs) == observers_.end())
<< "Observers can only be added once!";
observers_.push_back(obs);
}
// Remove an observer from the list.
void RemoveObserver(ObserverType* obs) {
typename ListType::iterator it =
std::find(observers_.begin(), observers_.end(), obs);
if (it != observers_.end()) {
if (notify_depth_) {
*it = 0;
} else {
observers_.erase(it);
}
}
}
size_t size() const {
return observers_.size();
}
ObserverType* GetElementAt(int index) const {
return observers_[index];
}
// An iterator class that can be used to access the list of observers. See
// also the FOREACH_OBSERVER macro defined below.
class Iterator {
public:
Iterator(const ObserverList<ObserverType>& list)
: list_(list),
index_(0),
max_index_(list.type_ == NOTIFY_ALL ?
std::numeric_limits<size_t>::max() :
list.observers_.size()) {
++list_.notify_depth_;
}
~Iterator() {
if (--list_.notify_depth_ == 0)
list_.Compact();
}
ObserverType* GetNext() {
ListType& observers = list_.observers_;
// Advance if the current element is null
size_t max_index = std::min(max_index_, observers.size());
while (index_ < max_index && !observers[index_])
++index_;
return index_ < max_index ? observers[index_++] : NULL;
}
private:
const ObserverList<ObserverType>& list_;
size_t index_;
size_t max_index_;
};
private:
typedef std::vector<ObserverType*> ListType;
void Compact() const {
typename ListType::iterator it = observers_.begin();
while (it != observers_.end()) {
if (*it) {
++it;
} else {
it = observers_.erase(it);
}
}
}
// These are marked mutable to facilitate having NotifyAll be const.
mutable ListType observers_;
mutable int notify_depth_;
NotificationType type_;
friend class ObserverList::Iterator;
DISALLOW_EVIL_CONSTRUCTORS(ObserverList);
};
#define FOR_EACH_OBSERVER(ObserverType, observer_list, func) \
do { \
ObserverList<ObserverType>::Iterator it(observer_list); \
ObserverType* obs; \
while ((obs = it.GetNext()) != NULL) \
obs->func; \
} while (0)
#endif // BASE_OBSERVER_LIST_H__
|
