/**
* 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;
/**
* An object representing a notification sent to an {@link Observable}.
* @param <T> the actual value type held by the Notification
*/
public final class
Notification<T> {
private final
Kind kind;
private final
Throwable throwable;
private final T
value;
private static final
Notification<
Void>
ON_COMPLETED = new
Notification<
Void>(
Kind.
OnCompleted, null, null);
/**
* Creates and returns a {@code Notification} of variety {@code Kind.OnNext}, and assigns it a value.
*
* @param <T> the actual value type held by the Notification
* @param t
* the item to assign to the notification as its value
* @return an {@code OnNext} variety of {@code Notification}
*/
public static <T>
Notification<T>
createOnNext(T
t) {
return new
Notification<T>(
Kind.
OnNext,
t, null);
}
/**
* Creates and returns a {@code Notification} of variety {@code Kind.OnError}, and assigns it an exception.
*
* @param <T> the actual value type held by the Notification
* @param e
* the exception to assign to the notification
* @return an {@code OnError} variety of {@code Notification}
*/
public static <T>
Notification<T>
createOnError(
Throwable e) {
return new
Notification<T>(
Kind.
OnError, null,
e);
}
/**
* Creates and returns a {@code Notification} of variety {@code Kind.OnCompleted}.
*
* @param <T> the actual value type held by the Notification
* @return an {@code OnCompleted} variety of {@code Notification}
*/
@
SuppressWarnings("unchecked")
public static <T>
Notification<T>
createOnCompleted() {
return (
Notification<T>)
ON_COMPLETED;
}
/**
* Creates and returns a {@code Notification} of variety {@code Kind.OnCompleted}.
*
* @param <T> the actual value type held by the Notification
* @param type the type token to help with type inference of {@code <T>}
* @deprecated this method does the same as {@link #createOnCompleted()} and does not use the passed in type hence it's useless.
* @return an {@code OnCompleted} variety of {@code Notification}
*/
@
Deprecated
@
SuppressWarnings("unchecked")
public static <T>
Notification<T>
createOnCompleted(
Class<T>
type) {
return (
Notification<T>)
ON_COMPLETED;
}
private
Notification(
Kind kind, T
value,
Throwable e) {
this.
value =
value;
this.
throwable =
e;
this.
kind =
kind;
}
/**
* Retrieves the exception associated with this (onError) notification.
*
* @return the Throwable associated with this (onError) notification
*/
public
Throwable getThrowable() {
return
throwable;
}
/**
* Retrieves the item associated with this (onNext) notification.
*
* @return the item associated with this (onNext) notification
*/
public T
getValue() {
return
value;
}
/**
* Indicates whether this notification has an item associated with it.
*
* @return a boolean indicating whether or not this notification has an item associated with it
*/
public boolean
hasValue() {
return
isOnNext() &&
value != null;
// isn't "null" a valid item?
}
/**
* Indicates whether this notification has an exception associated with it.
*
* @return a boolean indicating whether this notification has an exception associated with it
*/
public boolean
hasThrowable() {
return
isOnError() &&
throwable != null;
}
/**
* Retrieves the kind of this notification: {@code OnNext}, {@code OnError}, or {@code OnCompleted}
*
* @return the kind of the notification: {@code OnNext}, {@code OnError}, or {@code OnCompleted}
*/
public
Kind getKind() {
return
kind;
}
/**
* Indicates whether this notification represents an {@code onError} event.
*
* @return a boolean indicating whether this notification represents an {@code onError} event
*/
public boolean
isOnError() {
return
getKind() ==
Kind.
OnError;
}
/**
* Indicates whether this notification represents an {@code onCompleted} event.
*
* @return a boolean indicating whether this notification represents an {@code onCompleted} event
*/
public boolean
isOnCompleted() {
return
getKind() ==
Kind.
OnCompleted;
}
/**
* Indicates whether this notification represents an {@code onNext} event.
*
* @return a boolean indicating whether this notification represents an {@code onNext} event
*/
public boolean
isOnNext() {
return
getKind() ==
Kind.
OnNext;
}
/**
* Forwards this notification on to a specified {@link Observer}.
* @param observer the target observer to call onXXX methods on based on the kind of this Notification instance
*/
public void
accept(
Observer<? super T>
observer) {
if (
kind ==
Kind.
OnNext) {
observer.
onNext(
getValue());
} else if (
kind ==
Kind.
OnCompleted) {
observer.
onCompleted();
} else {
observer.
onError(
getThrowable());
}
}
/**
* Specifies the kind of the notification: an element, an error or a completion notification.
*/
public enum
Kind {
OnNext, OnError, OnCompleted
}
@
Override
public
String toString() {
StringBuilder str = new
StringBuilder(64).
append('[').
append(super.toString())
.
append(' ').
append(
getKind());
if (
hasValue()) {
str.
append(' ').
append(
getValue());
}
if (
hasThrowable()) {
str.
append(' ').
append(
getThrowable().
getMessage());
}
str.
append(']');
return
str.
toString();
}
@
Override
public int
hashCode() {
int
hash =
getKind().
hashCode();
if (
hasValue()) {
hash =
hash * 31 +
getValue().
hashCode();
}
if (
hasThrowable()) {
hash =
hash * 31 +
getThrowable().
hashCode();
}
return
hash;
}
@
Override
public boolean
equals(
Object obj) {
if (
obj == null) {
return false;
}
if (this ==
obj) {
return true;
}
if (
obj.
getClass() !=
getClass()) {
return false;
}
Notification<?>
notification = (
Notification<?>)
obj;
return
notification.
getKind() ==
getKind() && (
value ==
notification.
value || (
value != null &&
value.
equals(
notification.
value))) && (
throwable ==
notification.
throwable || (
throwable != null &&
throwable.
equals(
notification.
throwable)));
}
}