def test_replace_non_leaf_node_types(self):
# keep the previous type as we want to restore it
OldDependNode = nt.DependNode
nold = nt.Network()
assert str(nold).startswith("network")
# overwriting the foundation of all nodes will not change anything
# for existing node types, as they have bound the previous type already.
class DependNode(nt.Node):
"""This type cannot do anything, we have removed functionality"""
def __str__(self):
return 'me_as_string'
# END custom DependNode
assert str(nold).startswith('network')
# new instances still use the default implementation
nnew = nt.Network()
assert str(nnew).startswith('network')
# also we cannot instatiate it explicitly as we are not inheriting
# from the type that MRV wants to create, Network
self.failUnlessRaises(TypeError, DependNode, nnew.object())
# we could get away with this, but we clean it up anyway
nt.removeCustomType(DependNode)
nt.addCustomType(OldDependNode)
# MONKEY PATCHING
#################
# The only way to get custom method implementation directly into the non-leaf
# node types is monkey patching, hence existing methods will be overwritten
# with your implementation
# Using the dict for retrieval as one would get class methods otherwise, these
# check for the actual type passed in which would fail in our case.
old_str = nt.DependNode.__dict__['__str__']
nt.DependNode.__str__ = DependNode.__dict__['__str__']
assert str(nold) == 'me_as_string'
# undo our changes
nt.DependNode.__str__ = old_str
def test_replace_non_leaf_node_types(self):
# keep the previous type as we want to restore it
OldDependNode = nt.DependNode
nold = nt.Network()
assert str(nold).startswith("network")
# overwriting the foundation of all nodes will not change anything
# for existing node types, as they have bound the previous type already.
class DependNode(nt.Node):
"""This type cannot do anything, we have removed functionality"""
def __str__(self):
return 'me_as_string'
# END custom DependNode
assert str(nold).startswith('network')
# new instances still use the default implementation
nnew = nt.Network()
assert str(nnew).startswith('network')
# also we cannot instatiate it explicitly as we are not inheriting
# from the type that MRV wants to create, Network
self.failUnlessRaises(TypeError, DependNode, nnew.object())
# we could get away with this, but we clean it up anyway
nt.removeCustomType(DependNode)
nt.addCustomType(OldDependNode)
# MONKEY PATCHING
#################
# The only way to get custom method implementation directly into the non-leaf
# node types is monkey patching, hence existing methods will be overwritten
# with your implementation
# Using the dict for retrieval as one would get class methods otherwise, these
# check for the actual type passed in which would fail in our case.
old_str = nt.DependNode.__dict__['__str__']
nt.DependNode.__str__ = DependNode.__dict__['__str__']
assert str(nold) == 'me_as_string'
# undo our changes
nt.DependNode.__str__ = old_str
def test_replacing_default_node_types(self):
n = nt.Network()
sn = StorageNetworkNode.create()
# REPLACING BUILTIN NODE TYPES
##############################
# if we want to play crazy, we can make all network nodes our special
# storage node, be replacing the existing Network node type.
# Any instantiation will fail as if its not one of our specialized nodes,
# but this is implementation defined of course.
# Defining a new derived Type automatically puts it into the nt module
OldNetwork = nt.Network
class Network(StorageNetworkNode):
def sayhello(self):
print "hello"
# yes, the official Network node is now our own one, automatically
assert nt.Network is Network
sn2 = nt.Node(str(sn))
assert isinstance(sn2, StorageNetworkNode)
assert isinstance(sn2.dataIDs(), list)
# and it can say something
sn2.sayhello()
# we cannot wrap normal nodes as our initializer on StorageNetworkNode barks
# if the vital data plug cannot be found.
self.failUnlessRaises(TypeError, nt.Node, str(n))
# reset the old one, we affect everything within MRV now
nt.removeCustomType(Network)
nt.addCustomType(OldNetwork)
# everything back to normal - we get plain old network nodes
sn_network = nt.Node(sn.object())
assert type(sn_network) is OldNetwork
assert type(sn_network) is nt.Network
# REPLACING BUILTIN NODES PROPERLY
##################################
class Network(OldNetwork, nt.StorageBase):
def __init__(self, node):
"""Implement the initializer such that we only initialize our base
if we have the 'data' attribute. Otherwise we keep it uninitialized, so it
will not be functional"""
try:
super(Network, self).__init__(node)
except TypeError:
pass
# END handle input type
def sayaloha(self):
print "aloha"
# END better Super-Network implementation
assert nt.Network is Network
# now plain network nodes will be new Network nodes, but we are allowed
# to create them
# NodeFromObj works as well, just to be sure
n2 = nt.NodeFromObj(n.object())
assert type(n2) is Network
# as the storage base has not been initialized, we cannot do anything
# with it. The actual point here though is that users who don't know the
# interface will get a fully functional network node at least.
# As we do not 'tighten' the interface, code that doesn't expect our type
# will not get into trouble.
self.failUnlessRaises(AttributeError, n2.dataIDs)
assert isinstance(n2, OldNetwork)
n2.sayaloha()
# and storage network nodes will be 'Network' nodes whose additional
# functions we can use
sn2 = nt.Node(sn.object())
assert type(sn2) is Network
sn2.sayaloha()
sn2.dataIDs()
# once again, get rid of our custom type, reset the old one
nt.removeCustomType(Network)
nt.addCustomType(OldNetwork)
assert nt.Network is OldNetwork
def test_replacing_default_node_types(self): n = nt.Network() sn = StorageNetworkNode.create() # REPLACING BUILTIN NODE TYPES ############################## # if we want to play crazy, we can make all network nodes our special # storage node, be replacing the existing Network node type. # Any instantiation will fail as if its not one of our specialized nodes, # but this is implementation defined of course. # Defining a new derived Type automatically puts it into the nt module OldNetwork = nt.Network class Network(StorageNetworkNode): def sayhello(self): print "hello" # yes, the official Network node is now our own one, automatically assert nt.Network is Network sn2 = nt.Node(str(sn)) assert isinstance(sn2, StorageNetworkNode) assert isinstance(sn2.dataIDs(), list) # and it can say something sn2.sayhello() # we cannot wrap normal nodes as our initializer on StorageNetworkNode barks # if the vital data plug cannot be found. self.failUnlessRaises(TypeError, nt.Node, str(n)) # reset the old one, we affect everything within MRV now nt.removeCustomType(Network) nt.addCustomType(OldNetwork) # everything back to normal - we get plain old network nodes sn_network = nt.Node(sn.object()) assert type(sn_network) is OldNetwork assert type(sn_network) is nt.Network # REPLACING BUILTIN NODES PROPERLY ################################## class Network(OldNetwork, nt.StorageBase): def __init__(self, node): """Implement the initializer such that we only initialize our base if we have the 'data' attribute. Otherwise we keep it uninitialized, so it will not be functional""" try: super(Network, self).__init__(node) except TypeError: pass # END handle input type def sayaloha(self): print "aloha" # END better Super-Network implementation assert nt.Network is Network # now plain network nodes will be new Network nodes, but we are allowed # to create them # NodeFromObj works as well, just to be sure n2 = nt.NodeFromObj(n.object()) assert type(n2) is Network # as the storage base has not been initialized, we cannot do anything # with it. The actual point here though is that users who don't know the # interface will get a fully functional network node at least. # As we do not 'tighten' the interface, code that doesn't expect our type # will not get into trouble. self.failUnlessRaises(AttributeError, n2.dataIDs) assert isinstance(n2, OldNetwork) n2.sayaloha() # and storage network nodes will be 'Network' nodes whose additional # functions we can use sn2 = nt.Node(sn.object()) assert type(sn2) is Network sn2.sayaloha() sn2.dataIDs() # once again, get rid of our custom type, reset the old one nt.removeCustomType(Network) nt.addCustomType(OldNetwork) assert nt.Network is OldNetwork
