Package rx.subjects

Class AsyncSubject<T>

  • Type Parameters:
    T - the type of item expected to be observed by the Subject
    All Implemented Interfaces:
    Observer<T>

    public final class AsyncSubject<T>
    extends Subject<T,​T>
    Subject that publishes only the last item observed to each Observer once the source Observable has completed. The item is cached and published to any Observers which subscribe after the source has completed. If the source emitted no items, AsyncSubject completes without emitting anything. If the source terminated in an error, current and future subscribers will receive only the error.

    Example usage:

     
    
      // observer will receive no onNext events because the subject.onCompleted() isn't called.
      AsyncSubject<Object> subject = AsyncSubject.create();
      subject.subscribe(observer);
      subject.onNext("one");
      subject.onNext("two");
      subject.onNext("three");
    
      // observer will receive "three" as the only onNext event.
      AsyncSubject<Object> subject = AsyncSubject.create();
      subject.subscribe(observer);
      subject.onNext("one");
      subject.onNext("two");
      subject.onNext("three");
      subject.onCompleted();
    
       
    • Method Detail

      • create

        public static <T> AsyncSubject<T> create()
        Creates and returns a new AsyncSubject.
        Type Parameters:
        T - the result value type
        Returns:
        the new AsyncSubject
      • onError

        public void onError​(java.lang.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
      • 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 but not an error
      • 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 with an exception.

        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 without receiving any value.

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

        @Beta
        public java.lang.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.