Delegation! Since it's clear that extracting services into delegation

classes is only going to become more common, I've gone and created a
comprehensive facility for creating and using delegates in the place
controller and manager as well as the game controller and manager. With
the pattern nicely set, it is also easy to extend to controller/managers
further up the hierarchy that might need to delegate special methods of
their own. Whee!


git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@994 542714f4-19e9-0310-aa3c-eee0fc999fb1

src/java/com/threerings/crowd/server/PlaceManager.java

@@ -1,8 +1,9 @@
 //
-// $Id: PlaceManager.java,v 1.25 2001/12/14 00:11:17 mdb Exp $
+// $Id: PlaceManager.java,v 1.26 2002/02/13 03:21:28 mdb Exp $
 
 package com.threerings.crowd.server;
 
+import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.Properties;
 
@@ -16,7 +17,10 @@ import com.threerings.presents.dobj.ObjectRemovedEvent;
 import com.threerings.presents.dobj.OidListListener;
 
 import com.threerings.crowd.Log;
-import com.threerings.crowd.data.*;
+import com.threerings.crowd.data.BodyObject;
+import com.threerings.crowd.data.OccupantInfo;
+import com.threerings.crowd.data.PlaceConfig;
+import com.threerings.crowd.data.PlaceObject;
 
 /**
  * The place manager is the server-side entity that handles all
@@ -101,6 +105,13 @@ public class PlaceManager
         _config = config;
         _omgr = omgr;
 
+        // initialize our delegates
+        applyToDelegates(new DelegateOp() {
+            public void apply (PlaceManagerDelegate delegate) {
+                delegate.didInit(_config);
+            }
+        });
+
         // let derived classes do initialization stuff
         didInit();
     }
@@ -131,6 +142,13 @@ public class PlaceManager
         // we'll need to hear about place object events
         plobj.addListener(this);
 
+        // let our delegates know that we've started up
+        applyToDelegates(new DelegateOp() {
+            public void apply (PlaceManagerDelegate delegate) {
+                delegate.didStartup(_plobj);
+            }
+        });
+
         // let our derived classes do their thang
         didStartup();
     }
@@ -153,6 +171,16 @@ public class PlaceManager
     {
         // destroy the object and everything will follow from that
         CrowdServer.omgr.destroyObject(_plobj.getOid());
+
+        // let our delegates know that we've shut down
+        applyToDelegates(new DelegateOp() {
+            public void apply (PlaceManagerDelegate delegate) {
+                delegate.didShutdown();
+            }
+        });
+
+        // let our derived classes do their thang
+        didShutdown();
     }
 
     /**
@@ -217,16 +245,23 @@ public class PlaceManager
     /**
      * Called when a body object enters this place.
      */
-    protected void bodyEntered (int bodyOid)
+    protected void bodyEntered (final int bodyOid)
     {
         Log.info("Body entered [ploid=" + _plobj.getOid() +
                  ", oid=" + bodyOid + "].");
+
+        // let our delegates know what's up
+        applyToDelegates(new DelegateOp() {
+            public void apply (PlaceManagerDelegate delegate) {
+                delegate.bodyEntered(bodyOid);
+            }
+        });
     }
 
     /**
      * Called when a body object leaves this place.
      */
-    protected void bodyLeft (int bodyOid)
+    protected void bodyLeft (final int bodyOid)
     {
         Log.info("Body left [ploid=" + _plobj.getOid() +
                  ", oid=" + bodyOid + "].");
@@ -239,6 +274,13 @@ public class PlaceManager
             _plobj.removeFromOccupantInfo(key);
         }
 
+        // let our delegates know what's up
+        applyToDelegates(new DelegateOp() {
+            public void apply (PlaceManagerDelegate delegate) {
+                delegate.bodyLeft(bodyOid);
+            }
+        });
+
         // if that leaves us with zero occupants, maybe do something
         if (_plobj.occupants.size() == 0) {
             placeBecameEmpty();
@@ -253,6 +295,12 @@ public class PlaceManager
      */
     protected void placeBecameEmpty ()
     {
+        // let our delegates know what's up
+        applyToDelegates(new DelegateOp() {
+            public void apply (PlaceManagerDelegate delegate) {
+                delegate.placeBecameEmpty();
+            }
+        });
     }
 
     /**
@@ -356,6 +404,38 @@ public class PlaceManager
         buf.append(", config=").append(_config);
     }
 
+    /**
+     * Adds the supplied delegate to the list for this manager.
+     */
+    protected void addDelegate (PlaceManagerDelegate delegate)
+    {
+        if (_delegates == null) {
+            _delegates = new ArrayList();
+        }
+        _delegates.add(delegate);
+    }
+
+    /**
+     * Used to call methods in delegates.
+     */
+    protected static interface DelegateOp
+    {
+        public void apply (PlaceManagerDelegate delegate);
+    }
+
+    /**
+     * Applies the supplied operation to the registered delegates.
+     */
+    protected void applyToDelegates (DelegateOp op)
+    {
+        if (_delegates != null) {
+            int dcount = _delegates.size();
+            for (int i = 0; i < dcount; i++) {
+                op.apply((PlaceManagerDelegate)_delegates.get(i));
+            }
+        }
+    }
+
     /** A distributed object manager for doing dobj stuff. */
     protected DObjectManager _omgr;
 
@@ -370,4 +450,7 @@ public class PlaceManager
 
     /** Message handlers are used to process message events. */
     protected HashMap _msghandlers;
+
+    /** A list of the delegates in use by this manager. */
+    protected ArrayList _delegates;
 }

src/java/com/threerings/crowd/server/PlaceManagerDelegate.java

@@ -0,0 +1,76 @@
+//
+// $Id: PlaceManagerDelegate.java,v 1.1 2002/02/13 03:21:28 mdb Exp $
+
+package com.threerings.crowd.server;
+
+import com.threerings.crowd.data.PlaceConfig;
+import com.threerings.crowd.data.PlaceObject;
+
+/**
+ * Provides an extensible mechanism for encapsulating delegated
+ * functionality that works with the place services.
+ *
+ * <p> Thanks to Java's lack of multiple inheritance, it will likely
+ * become necessary to factor certain services that might be used by a
+ * variety of {@link PlaceManager} derived classes into delegate classes
+ * because they do not fit into the single inheritance hierarchy that
+ * makes sense for a particular application. To facilitate this process,
+ * this delegate class is provided which the standard place manager can be
+ * made to call out to for all of the standard methods.
+ */
+public class PlaceManagerDelegate
+{
+    /**
+     * Provides the delegate with a reference to the manager for which it
+     * is delegating.
+     */
+    public PlaceManagerDelegate (PlaceManager plmgr)
+    {
+        _plmgr = plmgr;
+    }
+
+    /**
+     * Called when the place manager is initialized.
+     */
+    public void didInit (PlaceConfig config)
+    {
+    }
+
+    /**
+     * Called when the place manager is started up.
+     */
+    public void didStartup (PlaceObject plobj)
+    {
+    }
+
+    /**
+     * Called when the place manager is shut down.
+     */
+    public void didShutdown ()
+    {
+    }
+
+    /**
+     * Called when a body enters the place.
+     */
+    public void bodyEntered (int bodyOid)
+    {
+    }
+
+    /**
+     * Called when a body leaves the place.
+     */
+    public void bodyLeft (int bodyOid)
+    {
+    }
+
+    /**
+     * Called when the last body leaves the place.
+     */
+    public void placeBecameEmpty ()
+    {
+    }
+
+    /** A reference to the manager for which we are delegating. */
+    protected PlaceManager _plmgr;
+}