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--- at:tutorial:appendix [2009/01/29 21:24] – adding elisag
+++ at:tutorial:appendix [2009/01/30 16:21] – *minor tvcutsem
@@ Line 83: / Line 83: @@
 It is also possible to use ''makeFuture()'' to create a fresh future explicitly within the unit test method, and to use the returned resolver to resolve the future at the appropriate time.
-<note hint>
+<note tip>
-See [[distribution#take_offline_remote_objects|distributed programming]] chapter for details about how to simulate network disconnections in distributed unit tests.
+See the [[distribution#take_offline_remote_objects|distributed programming]] chapter for details about how to simulate network disconnections in distributed unit tests.
 </note>
@@ Line 466: / Line 466: @@
 When the message sent to a multireference is annotated with @Due(t), the timeout is applied to the implicit multifuture, causing whenAll observers to trigger automatically. Note that the implicit multifuture of a multireference is bounded, so whenAll observers trigger automatically when all replies have been received.
+==== Leased Object References ====
+The module ''/.at.lang.leasedrefs'' provides support for leased object references. Leased object references have already been described as part of the [[:at:tutorial:distribution#dealing_with_permanent_failures|distributed programing]] section in the tutorial.
+<note>
+The implementation of leased object references actually consists of two files: ''/.at.lang.leasedrefs'' and ''/at.lang.leasedrefstrait''. ''leasedrefstrait'' module implements the behaviour common to the different types of leased references. This module is imported in the ''leasedrefs'' module which provides the public API for creating and managing leased object references.
+</note>
+The ''leasedrefs'' module exports language constructs to create three different types of leased object references:
+  * ''lease:for:''returns a leased reference that remains valid for the indicated time interval.
+  * ''renewOnCallLease:for:'' returns a leased reference that is automatically renewed (with the specified time interval) each time the remote object receives a message.
+  * ''singleCallLease:for:'' returns a leased reference that remains valid for only a single method call on the remote object.
+Variations of these constructs are also provided to allow developers to specify the renewal time interval in renew-on-call leased references and the name(s) of the method(s) which trigger expiration of a single-call leased reference.
+The ''leasedrefs'' module also provides the following constructs to explicitly manage the lifetime of leased references:
+<code>
+renew: leasedRef for: interval; // renews a lease
+revoke: leasedRef; // revokes a lease
+leaseTimeLeft: leasedRef; // return time left until lease expires
+when: lease expired: {...}; // trigger a closure when the lease expires
+</code>
+The ''when:expired:'' construct is provided to schedule clean-up actions with a leased reference upon its expiration.
+Finally, the ''leasedrefs'' module exports support primitives to manipulate time intervals (i.e. ''minutes'', ''seconds'', ''millisecs'') so that developers do not need to explicitly import the timer module to use leased references.
 ==== Dynamic Variables ====