[Subversion] / PEAK / src / peak / util / Meta.py  

Diff of /PEAK/src/peak/util/Meta.py

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version 339, Thu Feb 28 22:27:39 2002 UTC version 340, Fri Mar 1 19:57:23 2002 UTC
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 ### Metaclass Derivation Code  ### Metaclass Derivation Code
   
 metaReg = WeakValueDictionary()  metaReg = WeakValueDictionary()     # Weak, so unused metaclasses can die off
   
 def derivedMeta(metaclasses):  def derivedMeta(metaclasses):
     derived = metaReg.get(metaclasses)      derived = metaReg.get(metaclasses)
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     types.  Effectively, 'makeClass()' fully supports the three most popular      types.  Effectively, 'makeClass()' fully supports the three most popular
     Python metatypes: "classic classes", "new-style types", and      Python metatypes: "classic classes", "new-style types", and
     'ExtensionClass'.  You cannot, however, combine ExtensionClasses with      'ExtensionClass'.  You cannot, however, combine ExtensionClasses with
     new-style types, because their root metatype is different.  That is,      new-style types, because their root metatypes are different.  That is,
     'type(type) is type', and 'type(ExtensionClass) is ExtensionClass'.  There      'type(type) is type', and 'type(ExtensionClass) is ExtensionClass'.  There
     may be other ways to create illegal metatype combinations, but they should      may be other ways to create illegal metatype combinations, but they should
     be detected and result in a TypeError.      be detected and result in a TypeError.
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     names.  So if you set '__metaclasses__' to 'ThreadSafe, Persistent'      names.  So if you set '__metaclasses__' to 'ThreadSafe, Persistent'
     (or if your bases are instances of 'ThreadSafe' and 'Persistent'), the      (or if your bases are instances of 'ThreadSafe' and 'Persistent'), the
     derived metaclass will be called 'ThreadSafe_Persistent'.  That is,      derived metaclass will be called 'ThreadSafe_Persistent'.  That is,
     the return from 'makeClass()' will be of type (have a '__class__ of)      the return from 'makeClass()' will be of type (have a '__class__' of)
     'ThreadSafe_Persistent'.      'ThreadSafe_Persistent'.
   
     Metaclasses are derived according to the algorithm in the book "Putting      Metaclasses are derived according to the algorithm in the book "Putting
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           tomorrow, if one of your subclasses so desires!            tomorrow, if one of your subclasses so desires!
     """      """
   
     # Create either a plain Python class or an ExtensionClass,      # Create either a "classic" Python class, an ExtensionClass, or a new-style
     # based on the nature of the base classes involved      # class with autogenerated metaclass, based on the nature of the base
       # classes involved
   
     name = str(name)  # De-unicode      name = str(name)  # De-unicode
   
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     metaclasses = normalizeBases(metaclasses)      metaclasses = normalizeBases(metaclasses)
   
     if metaclasses:      if metaclasses:
         metaclass = derivedMeta(metaclasses)  
         return metaclass(name,bases,dict)  
   
     from new import classobj; return classobj(name,bases,dict)  
   
   
   
   
   
   
   
   
           # If we have metaclasses, it's not a classic class, so derive a
           # single metaclass, and ask it to create the class.
   
           metaclass = derivedMeta(metaclasses)
           return metaclass(name,bases,dict)
   
       # No metaclasses, it's a classic class, so use 'new.classobj'
   
       from new import classobj; return classobj(name,bases,dict)
   
   
 if __name__=='__main__':  if __name__=='__main__':

Generate output suitable for use with a patch program
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