Update of /cvsroot/modeling/ProjectModeling/Modeling/doc/UserGuide
In directory sc8-pr-cvs1:/tmp/cvs-serv18199/Modeling/doc/UserGuide
Modified Files:
DefiningaModel.tex
Log Message:
Modeling many-to-many relationships
Index: DefiningaModel.tex
===================================================================
RCS file: /cvsroot/modeling/ProjectModeling/Modeling/doc/UserGuide/DefiningaModel.tex,v
retrieving revision 1.36
retrieving revision 1.37
diff -C2 -d -r1.36 -r1.37
*** DefiningaModel.tex 31 Aug 2003 17:22:50 -0000 1.36
--- DefiningaModel.tex 31 Aug 2003 17:32:25 -0000 1.37
***************
*** 1999,2009 ****
--- 1999,2079 ----
\end{verbatim}
+ We just defined a new entity, \class{PersonAddress}, and two associations
+ modeling the relationships between the correlation table and the correlated
+ ones.
+ Last, we'll need to add some code in classes \class{Person} and \code{Address}
+ to directly manipulate the many-to-many relationships. Since relating an
+ object to an other one is just a matter of adding a object/a row to the
+ correlation table, the code is pretty straightforward.
+
+ In \class{Person}, you'll add the following methods:
+ \begin{verbatim}
+ # Relationship: addresses
+ def getAddresses(self):
+ return self.valueForKeyPath('personAddresses.address')
+
+ def addToAddresses(self, address):
+ if address in self.getAddresses():
+ return
+ from PersonAddress import PersonAddress
+ _pa=PersonAddress() # Create an object in the correlation table
+ self.editingContext().insert(_pa)
+ self.addToPersonAddresses(_pa)
+ _pa.setPerson(self)
+ _pa.setAddress(address)
+ address.addToPersonAddresses(_pa)
+
+ def removeFromAddresses(self, address):
+ _pa=[pa for pa in self.getPersonAddresses() if address == pa.getAddress()]
+ if not _pa:
+ raise ValueError, 'Cannot find address'
+ # Here we simply need to remove the corresponding object in the
+ # correlation table
+ _pa=_pa[0]
+ self.removeFromPersonAddresses(_pa)
+ _pa.getAddress().removeFromPersonAddresses(_pa)
+ _pa.setAddress(None)
+ _pa.setPerson(None)
+ self.editingContext().delete(_pa)
+ \end{verbatim}
+ And you'll add the equivalent methods in \class{Address}:
+ \begin{verbatim}
+ # Relationship: persons
+ def getPersons(self):
+ return self.valueForKeyPath('personAddresses.person')
+
+ def addToPersons(self, person):
+ if person in self.getPersons():
+ return
+ from PersonAddress import PersonAddress
+ _pa=PersonAddress() # Create an object in the correlation table
+ self.editingContext().insert(_pa)
+ self.addToPersonAddresses(_pa)
+ _pa.setPerson(person)
+ _pa.setAddress(self)
+ person.addToPersonAddresses(_pa)
+ def removeFromPersons(self, person):
+ _pa=[pa for pa in self.getPersonAddresses() if person == pa.getPerson()]
+ if not _pa:
+ raise ValueError, 'Cannot find person'
+ # Here we simply need to remove the corresponding object in the
+ # correlation table
+ _pa=_pa[0]
+ self.removeFromPersonAddresses(_pa)
+ _pa.getPerson().removeFromPersonAddresses(_pa)
+ _pa.setAddress(None)
+ _pa.setPerson(None)
+ self.editingContext().delete(_pa)
+ \end{verbatim}
\makeatletter
\def\verbatim@font{\normalsize\ttfamily}
\makeatother
+ Now we can normally call e.g. \method{getAddresses} or \method{addToAddresses}
+ on a \class{Person} object, passing a \class{Address} object, without caring
+ about the details anymore.
\subsection{How to model inheritance \label{design-inheritance}}
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