Ambient-Oriented Programming

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at:tutorial:distribution [2007/12/18 13:57] – * tvcutsemat:tutorial:distribution [2008/06/25 17:31] – added tvcutsem
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 When a remote far reference receives a messages, it flushes the message to the remote object providing that it is connected. If the remote far reference is disconnected, messages are accumulate in its inbox in order to be transmitted once the reference becomes reconnected at a later point in time once the network connection is restored.  When a remote far reference receives a messages, it flushes the message to the remote object providing that it is connected. If the remote far reference is disconnected, messages are accumulate in its inbox in order to be transmitted once the reference becomes reconnected at a later point in time once the network connection is restored. 
  
-Therefore, a remote far reference abstracts a client object from the actual network connection state. However, it is often useful for an application to be informed when a connection to a remote object is lost or reconnected. To this end, AmbientTalk offers language constructs to install observers on a far reference which are triggered when the reference becomes disconnected or reconnected. For example, the instant messenger application can notify the user whenever a buddy moves in and out of the communication range as follows:+Therefore, a remote far reference abstracts a client object from the actual network connection state. However, it is often useful for an application to be informed when a connection to a remote object is lost or reconnected. To this end, AmbientTalk offers language constructs to install observers on a far reference which are triggered whenever the reference becomes disconnected or reconnected. For example, the instant messenger application can notify the user whenever a buddy moves in and out of the communication range as follows:
  
 <code> <code>
 when: InstantMessenger discovered: { |messenger| when: InstantMessenger discovered: { |messenger|
   ...   ...
-  when: messenger disconnected: {+  whenever: messenger disconnected: {
     system.println("Buddy offline: " + name);     system.println("Buddy offline: " + name);
   };   };
-  when: messenger reconnected: {+  whenever: messenger reconnected: {
     system.println("Buddy online: " + name);     system.println("Buddy online: " + name);
   };   };
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 The construct returns a table containing copies of all messenges that were sent to this far reference, but not yet transmitted by the far reference to the remote object pointed to. Note that this has the side effect that the returned messages will not be sent automatically anymore; the programmer is thus responsible to explicitly resend all messages that were retracted but still need to be sent.  The construct returns a table containing copies of all messenges that were sent to this far reference, but not yet transmitted by the far reference to the remote object pointed to. Note that this has the side effect that the returned messages will not be sent automatically anymore; the programmer is thus responsible to explicitly resend all messages that were retracted but still need to be sent. 
 +
 +The function ''when:disconnected:'' behaves like the previously discussed function ''whenever:disconnected:'', except it triggers the associated closure at most once, not upon //every// disconnect.
  
 ===== Garbage collecting remote references ===== ===== Garbage collecting remote references =====
at/tutorial/distribution.txt · Last modified: 2009/01/30 16:13 by tvcutsem