Package rx.subjects

Class BehaviorSubject<T>

java.lang.Object
rx.Observable<T>
rx.subjects.Subject<T,T>
rx.subjects.BehaviorSubject<T>
Type Parameters:
T - the type of item expected to be observed by the Subject
All Implemented Interfaces:
Observer<T>
public final class BehaviorSubject<T> extends Subject<T,T>
Subject that emits the most recent item it has observed and all subsequent observed items to each subscribed Observer.

Example usage: 

 

  // observer will receive all events.
  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 "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);

  • Field Details

  • Constructor Details

  • Method Details

    • create

      public static <T> BehaviorSubject<T> create()
      Creates a BehaviorSubject without a default item.
      Type Parameters:
      T - the type of item the Subject will emit
      Returns:
      the constructed BehaviorSubject

    • create

      public static <T> BehaviorSubject<T> create(T defaultValue)
      Creates a BehaviorSubject that emits the last item it observed and all subsequent items to each Observer that subscribes to it.
      Type Parameters:
      T - the type of item the Subject will emit
      Parameters:
      defaultValue - the item that will be emitted first to any Observer as long as the BehaviorSubject has not yet observed any items from its source Observable
      Returns:
      the constructed BehaviorSubject

    • create

      private static <T> BehaviorSubject<T> create(T defaultValue, boolean hasDefault)

    • onCompleted

      public void onCompleted()
      Description copied from interface: Observer
      Notifies the Observer that the Observable has finished sending push-based notifications.

      The Observable will not call this method if it calls Observer.onError(java.lang.Throwable).

    • onError

      public void onError(Throwable e)
      Description copied from interface: Observer
      Notifies the Observer that the Observable has experienced an error condition.

      If the Observable calls this method, it will not thereafter call Observer.onNext(T) or Observer.onCompleted().

      Parameters:
      e - the exception encountered by the Observable

    • onNext

      public void onNext(T v)
      Description copied from interface: Observer
      Provides the Observer with a new item to observe.

      The Observable may call this method 0 or more times.

      The Observable will not call this method again after it calls either Observer.onCompleted() or Observer.onError(java.lang.Throwable).

      Parameters:
      v - the item emitted by the Observable

    • subscriberCount

      int subscriberCount()

    • hasObservers

      public boolean hasObservers()
      Description copied from class: Subject
      Indicates whether the Subject has Observers subscribed to it.
      Specified by:
      hasObservers in class Subject<T,T>
      Returns:
      true if there is at least one Observer subscribed to this Subject, false otherwise

    • hasValue

      @Beta public boolean hasValue()
      Check if the Subject has a value.

      Use the getValue() method to retrieve such a value.

      Note that unless hasCompleted() or hasThrowable() returns true, the value retrieved by getValue() may get outdated.

      Returns:
      true if and only if the subject has some value and hasn't terminated yet.

    • hasThrowable

      @Beta public boolean hasThrowable()
      Check if the Subject has terminated with an exception.
      Returns:
      true if the subject has received a throwable through onError.

    • hasCompleted

      @Beta public boolean hasCompleted()
      Check if the Subject has terminated normally.
      Returns:
      true if the subject completed normally via onCompleted()

    • getValue

      @Beta public T getValue()
      Returns the current value of the Subject if there is such a value and the subject hasn't terminated yet.

      The method can return null for various reasons. Use hasValue(), hasThrowable() and hasCompleted() to determine if such null is a valid value, there was an exception or the Subject terminated (with or without receiving any value).

      Returns:
      the current value or null if the Subject doesn't have a value, has terminated or has an actual null as a valid value.

    • getThrowable

      @Beta public Throwable getThrowable()
      Returns the Throwable that terminated the Subject.
      Returns:
      the Throwable that terminated the Subject or null if the subject hasn't terminated yet or it terminated normally.

    • getValues

      @Beta public T[] getValues(T[] a)
      Returns a snapshot of the currently buffered non-terminal events into the provided a array or creates a new array if it has not enough capacity.
      Parameters:
      a - the array to fill in
      Returns:
      the array a if it had enough capacity or a new array containing the available values

    • getValues

      @Beta public Object[] getValues()
      Returns a snapshot of the currently buffered non-terminal events.

      The operation is threadsafe.

      Returns:
      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)