[SQLObject] DTO : a simple implementation by proxy

[G. <fra...@cl...>]

Hi all,

I've made this very little piece of code to implement DTO pattern. I know using __getattr__ is not so speed as using properties, but I'm not yet a great meta-programmer ;-)

Usage :
# loading SQLObject
pers = Person(1)
# creating DTO
persDTO = SQLObjectProxy(pers)
# no UPDATE request is done while setting attributes
persDTO.firstname = 'Dark'
persDTO.lastname = 'Vador'
# UPDATE request is done here
persDTO.save()

Maybe I'll add a getDTO method on SQLObject, or pass an argument to constructor

Here's my code snippet :

##############################################################################
class SQLObjectProxy:
    """

    SQLObjectProxy implements a simple proxy for SQLObject to save network
    traffic by explicit saving, because SQLObject does a request each time an
    attribute is set.
    By calling the save() method, all changes made to the object are saved in
    the database
    """
    
    ##########################################################################
    def __init__( self, subject ):
        """
        SQLObjectProxy contructor.
        @param subject: the SQLObject to wrap
        """
        self.__subject = subject
    
    ##########################################################################
    def __getattr__( self, name ):
        """

        Here is the heart of proxy : delegating attribute reading to the subject
        """
        return getattr( self.__subject, name)

    ##########################################################################
    def save(self):
        """
        
        The save method flushes all changes made to the object.
        """
        kw = {}
        for colname in self._SO_columnDict.keys():
            kw[colname] = getattr(self, colname)
        self.set(**kw)