renamed package to pypattyrn

pypattyrn/behavioral/chain.py

@@ -0,0 +1,75 @@
+from abc import ABCMeta, abstractmethod
+
+
+class ChainLink(object, metaclass=ABCMeta):
+    """
+    Abstract ChainLink object as part of the Chain of Responsibility pattern.
+
+    - External Usage documentation: U{https://github.com/tylerlaberge/PyPatterns/wiki/Behavioral-Pattern-Usage}
+    - External Chain of Responsibility Pattern documentation: U{https://en.wikipedia.org/wiki/Chain-of-responsibility_pattern}
+    """
+    def __init__(self):
+        """
+        Initialize a new ChainLink instance.
+        """
+        self.successor = None
+
+    def set_successor(self, successor):
+        """
+        Set a chain link to call if this chain link fails.
+
+        @param successor: The chain link to call if this chain link fails.
+        @type successor: ChainLink
+        """
+        self.successor = successor
+
+    def successor_handle(self, request):
+        """
+        Have this chain links successor handle a request.
+
+        @param request: The request to handle.
+        """
+        return self.successor.handle(request)
+
+    @abstractmethod
+    def handle(self, request):
+        """
+        Handle a request.
+
+        @param request: The request to handle.
+        """
+        pass
+
+
+class Chain(object, metaclass=ABCMeta):
+    """
+    Abstract Chain class as part of the Chain of Responsibility pattern.
+
+    - External Usage documentation: U{https://github.com/tylerlaberge/PyPatterns/wiki/Behavioral-Pattern-Usage}
+    - External Chain of Responsibility Pattern documentation: U{https://en.wikipedia.org/wiki/Chain-of-responsibility_pattern}
+    """
+    def __init__(self, chainlink):
+        """
+        Initialize a new Chain instance.
+
+        @param chainlink: The starting chain link.
+        """
+        self.chainlink = chainlink
+
+    def handle(self, request):
+        """
+        Handle a request.
+
+        @param request: The request to handle.
+        """
+        try:
+            return self.chainlink.handle(request)
+        except AttributeError:
+            return self.fail()
+
+    @abstractmethod
+    def fail(self):
+        """
+        The method to call when the chain could not handle a request.
+        """
+        pass