forked from ReactiveX/RxJava
-
Notifications
You must be signed in to change notification settings - Fork 0
Expand file tree
/
Copy pathBehaviorSubject.java
More file actions
274 lines (255 loc) · 9.29 KB
/
Copy pathBehaviorSubject.java
File metadata and controls
274 lines (255 loc) · 9.29 KB
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
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
/**
* Copyright 2014 Netflix, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package rx.subjects;
import java.lang.reflect.Array;
import java.util.*;
import rx.Observer;
import rx.exceptions.Exceptions;
import rx.functions.Action1;
import rx.internal.operators.NotificationLite;
import rx.subjects.SubjectSubscriptionManager.SubjectObserver;
/**
* Subject that emits the most recent item it has observed and all subsequent observed items to each subscribed
* {@link Observer}.
* <p>
* <img width="640" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/S.BehaviorSubject.png" alt="">
* <p>
* Example usage:
* <p>
* <pre> {@code
// observer will receive all 4 events (including "default").
BehaviorSubject<Object> subject = BehaviorSubject.create("default");
subject.subscribe(observer);
subject.onNext("one");
subject.onNext("two");
subject.onNext("three");
// observer will receive the "one", "two" and "three" events, but not "default" and "zero"
BehaviorSubject<Object> subject = BehaviorSubject.create("default");
subject.onNext("zero");
subject.onNext("one");
subject.subscribe(observer);
subject.onNext("two");
subject.onNext("three");
// observer will receive only onCompleted
BehaviorSubject<Object> subject = BehaviorSubject.create("default");
subject.onNext("zero");
subject.onNext("one");
subject.onCompleted();
subject.subscribe(observer);
// observer will receive only onError
BehaviorSubject<Object> subject = BehaviorSubject.create("default");
subject.onNext("zero");
subject.onNext("one");
subject.onError(new RuntimeException("error"));
subject.subscribe(observer);
} </pre>
*
* @param <T>
* the type of item expected to be observed by the Subject
*/
public final class BehaviorSubject<T> extends Subject<T, T> {
/** An empty array to trigger getValues() to return a new array. */
private static final Object[] EMPTY_ARRAY = new Object[0];
private final SubjectSubscriptionManager<T> state;
/**
* Creates a {@link BehaviorSubject} without a default item.
*
* @param <T>
* the type of item the Subject will emit
* @return the constructed {@link BehaviorSubject}
*/
public static <T> BehaviorSubject<T> create() {
return create(null, false);
}
/**
* Creates a {@link BehaviorSubject} that emits the last item it observed and all subsequent items to each
* {@link Observer} that subscribes to it.
*
* @param <T>
* the type of item the Subject will emit
* @param defaultValue
* the item that will be emitted first to any {@link Observer} as long as the
* {@link BehaviorSubject} has not yet observed any items from its source {@code Observable}
* @return the constructed {@link BehaviorSubject}
*/
public static <T> BehaviorSubject<T> create(T defaultValue) {
return create(defaultValue, true);
}
private static <T> BehaviorSubject<T> create(T defaultValue, boolean hasDefault) {
final SubjectSubscriptionManager<T> state = new SubjectSubscriptionManager<T>();
if (hasDefault) {
state.setLatest(NotificationLite.next(defaultValue));
}
state.onAdded = new Action1<SubjectObserver<T>>() {
@Override
public void call(SubjectObserver<T> o) {
o.emitFirst(state.getLatest());
}
};
state.onTerminated = state.onAdded;
return new BehaviorSubject<T>(state, state);
}
protected BehaviorSubject(OnSubscribe<T> onSubscribe, SubjectSubscriptionManager<T> state) {
super(onSubscribe);
this.state = state;
}
@Override
public void onCompleted() {
Object last = state.getLatest();
if (last == null || state.active) {
Object n = NotificationLite.completed();
for (SubjectObserver<T> bo : state.terminate(n)) {
bo.emitNext(n);
}
}
}
@Override
public void onError(Throwable e) {
Object last = state.getLatest();
if (last == null || state.active) {
Object n = NotificationLite.error(e);
List<Throwable> errors = null;
for (SubjectObserver<T> bo : state.terminate(n)) {
try {
bo.emitNext(n);
} catch (Throwable e2) {
if (errors == null) {
errors = new ArrayList<Throwable>();
}
errors.add(e2);
}
}
Exceptions.throwIfAny(errors);
}
}
@Override
public void onNext(T v) {
Object last = state.getLatest();
if (last == null || state.active) {
Object n = NotificationLite.next(v);
for (SubjectObserver<T> bo : state.next(n)) {
bo.emitNext(n);
}
}
}
/* test support */ int subscriberCount() {
return state.observers().length;
}
@Override
public boolean hasObservers() {
return state.observers().length > 0;
}
/**
* Check if the Subject has a value.
* <p>Use the {@link #getValue()} method to retrieve such a value.
* <p>Note that unless {@link #hasCompleted()} or {@link #hasThrowable()} returns true, the value
* retrieved by {@code getValue()} may get outdated.
* @return true if and only if the subject has some value and hasn't terminated yet.
* @since 1.2
*/
public boolean hasValue() {
Object o = state.getLatest();
return NotificationLite.isNext(o);
}
/**
* Check if the Subject has terminated with an exception.
* @return true if the subject has received a throwable through {@code onError}.
* @since 1.2
*/
public boolean hasThrowable() {
Object o = state.getLatest();
return NotificationLite.isError(o);
}
/**
* Check if the Subject has terminated normally.
* @return true if the subject completed normally via {@code onCompleted()}
* @since 1.2
*/
public boolean hasCompleted() {
Object o = state.getLatest();
return NotificationLite.isCompleted(o);
}
/**
* Returns the current value of the Subject if there is such a value and
* the subject hasn't terminated yet.
* <p>The method can return {@code null} for various reasons. Use {@link #hasValue()}, {@link #hasThrowable()}
* and {@link #hasCompleted()} to determine if such {@code null} is a valid value, there was an
* exception or the Subject terminated (with or without receiving any value).
* @return the current value or {@code null} if the Subject doesn't have a value,
* has terminated or has an actual {@code null} as a valid value.
* @since 1.2
*/
public T getValue() {
Object o = state.getLatest();
if (NotificationLite.isNext(o)) {
return NotificationLite.getValue(o);
}
return null;
}
/**
* Returns the Throwable that terminated the Subject.
* @return the Throwable that terminated the Subject or {@code null} if the
* subject hasn't terminated yet or it terminated normally.
* @since 1.2
*/
public Throwable getThrowable() {
Object o = state.getLatest();
if (NotificationLite.isError(o)) {
return NotificationLite.getError(o);
}
return null;
}
/**
* Returns a snapshot of the currently buffered non-terminal events into
* the provided {@code a} array or creates a new array if it has not enough capacity.
* @param a the array to fill in
* @return the array {@code a} if it had enough capacity or a new array containing the available values
* @since 1.2
*/
@SuppressWarnings("unchecked")
public T[] getValues(T[] a) {
Object o = state.getLatest();
if (NotificationLite.isNext(o)) {
if (a.length == 0) {
a = (T[])Array.newInstance(a.getClass().getComponentType(), 1);
}
a[0] = NotificationLite.getValue(o);
if (a.length > 1) {
a[1] = null;
}
} else
if (a.length > 0) {
a[0] = null;
}
return a;
}
/**
* Returns a snapshot of the currently buffered non-terminal events.
* <p>The operation is thread-safe.
*
* @return a snapshot of the currently buffered non-terminal events.
* @since (If this graduates from being an Experimental class method, replace this parenthetical with the release number)
* @since 1.2
*/
@SuppressWarnings("unchecked")
public Object[] getValues() {
T[] r = getValues((T[])EMPTY_ARRAY);
if (r == EMPTY_ARRAY) {
return new Object[0]; // don't leak the default empty array.
}
return r;
}
}