r13579 - /branches/gui_testing/observer.py -- July 13, 2011 - 12:04

Author: bugman
Date: Wed Jul 13 12:04:36 2011
New Revision: 13579

URL: http://svn.gna.org/viewcvs/relax?rev=13579&view=rev
Log:
Added a module and base class method Observer which implements the observer 
design pattern.


Added:
    branches/gui_testing/observer.py

Added: branches/gui_testing/observer.py
URL: 
http://svn.gna.org/viewcvs/relax/branches/gui_testing/observer.py?rev=13579&view=auto
==============================================================================
--- branches/gui_testing/observer.py (added)
+++ branches/gui_testing/observer.py Wed Jul 13 12:04:36 2011
@@ -1,0 +1,77 @@
+###############################################################################
+#                                                                            
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+# Copyright (C) 2011 Edward d'Auvergne                                       
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+#                                                                            
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+# This file is part of the program relax.                                    
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+#                                                                            
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+# relax is free software; you can redistribute it and/or modify              
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+# it under the terms of the GNU General Public License as published by       
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+# the Free Software Foundation; either version 2 of the License, or          
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+# (at your option) any later version.                                        
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+#                                                                            
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+# relax is distributed in the hope that it will be useful,                   
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+# but WITHOUT ANY WARRANTY; without even the implied warranty of             
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+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the              
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+# GNU General Public License for more details.                               
 #
+#                                                                            
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+# You should have received a copy of the GNU General Public License          
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+# along with relax; if not, write to the Free Software                       
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+# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA  
 #
+#                                                                            
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+###############################################################################
+
+# Module docstring.
+"""Module implementing the observer design pattern base class."""
+
+# relax module imports.
+from relax_errors import RelaxError
+
+
+class Observer:
+    """The observer design pattern base class."""
+
+    def __init__(self):
+        """Set up the object."""
+
+        # The dictionary of callback methods.
+        self._callback = {}
+
+
+    def notify_observers(self):
+        """Notify all observers of the state change."""
+
+        # Loop over the callback methods and execute them.
+        for key in self._callback.keys():
+            self._callback[key]()
+
+
+    def register_observer(self, key, method):
+        """Register a method to be called when the state changes.
+
+        @param key:     The key to identify the observer's method.
+        @type key:      str
+        @param method:  The observer's method to be called after a state 
change.
+        @type method:   method
+        """
+
+        # Already exists.
+        if key in self._callback.keys():
+            raise RelaxError("The observer '%s' already exists." % key)
+
+        # Add the method to the dictionary of callbacks.
+        self._callback[key] = method
+
+
+    def unregister_observer(self, key):
+        """Unregister the method corresponding to the key.
+
+        @param key:     The key to identify the observer's method.
+        @type key:      str
+        """
+
+        # Does not exist.
+        if key not in self._callback.keys():
+            raise RelaxError("The key '%s' does not exist." % key)
+
+        # Remove the method from the dictionary of callbacks.
+        self._callback.pop(key)