[Modeling-cvs] ProjectModeling/Modeling/doc/UserGuide FAQ.tex,1.1,1.2

[<sbi...@us...>]

Update of /cvsroot/modeling/ProjectModeling/Modeling/doc/UserGuide
In directory sc8-pr-cvs1:/tmp/cvs-serv26741/Modeling/doc/UserGuide

Modified Files:
	FAQ.tex 
Log Message:
Added a technique to access the PK's value without making it class property

Index: FAQ.tex
===================================================================
RCS file: /cvsroot/modeling/ProjectModeling/Modeling/doc/UserGuide/FAQ.tex,v
retrieving revision 1.1
retrieving revision 1.2
diff -C2 -d -r1.1 -r1.2
*** FAQ.tex	19 May 2003 16:05:16 -0000	1.1
--- FAQ.tex	4 Jul 2003 17:02:45 -0000	1.2
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*** 27,30 ****
--- 27,32 ----
  \item[What if I want to see the primary key/foreign key values in my objects?]
  
+ \begin{description}
+ \item[Making it a class property]
  Really, you should not --simply because we do not support anything but {\em
  automatic} generation of {\em simple} primary key (one attribute only, no
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*** 41,44 ****
--- 43,72 ----
    for sure. You've been warned!
  \end{itemize}
+ 
+ \item[Accessing it at run-time]
+ However, there's a cleaner alternative to this: the primary key value can
+ always be retrieved from your objects, without requiring it to be a class
+ property. You can access it with \method{globalID}; every single object
+ managed by the framework is uniquely identified by its global id. Among other
+ things, this one has a dictionary holding the PK values:
+ 
+ \begin{verbatim}
+ >>> object=ec.fetch('Writer', qualifier='age<50')[0]
+ >>> object.globalID().keyValues()
+ {'id': 1}
+ \end{verbatim}
+ 
+   So if you need to access the PK for objects of a given class, you can add a
+   method like this one:
+ \begin{verbatim}
+   def pk(self):
+     "Returns the pk's value"
+     return self.globalID() and object.globalID()['id'] or None
+ \end{verbatim}
+ 
+   Note: \method{CustomObject.globalID()} can return \code{None} when an object
+   has just been inserted into an \class{EditingContext} but has not been saved
+   yet.
+ \end{description}
  
  \end{description}