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Composer - Building Complex Structures with Templates or Schemas
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($Id$)
>>> from cybertools.composer.base import Element, Compound, Template
>>> from cybertools.composer.instance import Instance
We set up a very simple demonstration system using a PC configurator.
We start with two classes denoting a configuration and a simple
component within this configuration.
>>> class Configuration(Template):
... def __init__(self, name):
... self.name = name
... super(Configuration, self).__init__()
>>> class BasicComponent(Element):
... def __init__(self, name):
... self.name = name
... def __repr__(self):
... return self.name
>>> desktop = Configuration('Desktop')
>>> desktop.components.append(BasicComponent('case'))
>>> desktop.components.append(BasicComponent('mainboard'))
>>> desktop.components.append(BasicComponent('cpu'))
>>> desktop.components.append(BasicComponent('harddisk'))
Now somebody wants to configure a desktop PC using this configuration.
We need another class denoting the product that will be created.
>>> class Product(object):
... def __init__(self, productId):
... self.productId = productId
... self.parts = {}
... def __repr__(self):
... return self.productId
>>> c001 = Product('c001')
The real stuff will be done by an instance adpater that connects the product
with the template.
>>> class ConfigurationAdapter(Instance):
... def applyTemplate(self):
... for c in self.template.components:
... print c, self.context.parts.get(c.name, '-')
>>> inst = ConfigurationAdapter(c001)
>>> inst.template = desktop
>>> inst.applyTemplate()
case -
mainboard -
cpu -
harddisk -
If we have configured a CPU for our configuration this will be listed.
>>> c001.parts['cpu'] = Product('z80')
>>> inst.applyTemplate()
case -
mainboard -
cpu z80
harddisk -
Note that the ConfigurationInstance's applyTemplate() method is fairly
primitive. In a real-world application there usually are a lot more methods
that do more stuff. In our PC configurator application there might be
methods that just list components (e.g. to provide a user interface),
retrieve candidate products (e.g. CPUs) to use in the
configuration and store the user's selection in the context object.
