[reportlab-users] doctemplate.py: use of isinstance on NullActionFlowable instance

[Hans Brand]

Hello, this is my first use of this list. Please have a look at the
following problem.

I received the following error message:


> Traceback (most recent call last):

>   File "/usr/local/www/Zope210/first/Extensions/StudentPDF_double.py", line 310, in StudentPDF_double

>     content = str(MakeStudent(self, date, termname, term, klas, format, report_type))

>   File "/usr/local/www/Zope210/first/Extensions/StudentPDF_double.py", line 223, in __init__

>     pdf_student.build(lst, onFirstPage=self.myAllPages, onLaterPages=self.myAllPages)

>   File "/usr/local/lib/python2.4/site-packages/reportlab/platypus/doctemplate.py", line 911, in build

>     BaseDocTemplate.build(self,flowables, canvasmaker=canvasmaker)

>   File "/usr/local/lib/python2.4/site-packages/reportlab/platypus/doctemplate.py", line 740, in build

>     self.handle_flowable(flowables)

>   File "/usr/local/lib/python2.4/site-packages/reportlab/platypus/doctemplate.py", line 633, in handle_flowable

>     f.apply(self)

> TypeError: apply() takes exactly 1 argument (2 given)

>   


Looking up the location in doctemplate.py gives the following code:


> 628                     self.handle_pageBreak(slow=1)

> 629                 else:

> 630                     self.handle_pageBreak()

> 631                 self.afterFlowable(f)

> 632             elif isinstance(f,ActionFlowable):

> 633  ->             f.apply(self)

> 634                 self.afterFlowable(f)

> 635             else:

> 636                 frame = self.frame

> 637                 #try to fit it then draw it

> 638                 if frame.add(f, self.canv, trySplit=self.allowSplitting):


Using the pdb debugger I get the following results:


> (Pdb) f

> <reportlab.platypus.doctemplate.NullActionFlowable instance at 0xeaac06c>

> (Pdb) isinstance(f,ActionFlowable)

> True

> (Pdb) isinstance(f,NullActionFlowable)

> True

> (Pdb)


This reveals that f is a NullActionFlowable but that it is (also)
recognised as being an ActionFlowable instance.

So when f is a NullActionFlowable then the code at line

> 632             elif isinstance(f,ActionFlowable):

will be true.

However, the NullActionFlowable.apply function:


> class NullActionFlowable(ActionFlowable):

>     def apply(self):

>         pass


differs from the ActionFlowable.apply function:


> class ActionFlowable(Flowable):

>     '''This Flowable is never drawn, it can be used for data driven 

> controls

>        For example to change a page template (from one column to two, 

> for example)

>        use NextPageTemplate which creates an ActionFlowable.

>     '''

>     def __init__(self,action=()):

>         #must call super init to ensure it has a width and height (of 

> zero),

>         #as in some cases the packer might get called on it...

>         Flowable.__init__(self)

>         if type(action) not in (ListType, TupleType):

>             action = (action,)

>         self.action = tuple(action)

>

>     def apply(self,doc):


The python documentation states:

> *isinstance*( 	object, classinfo)

>

> Return true if the object argument is an instance of the classinfo 

> argument, or of a (direct or indirect) subclass thereof.


My question is now whether the code


> 632             elif isinstance(f,ActionFlowable):


was not meant to include the NullActionFlowable
      OR
that the apply function of the NullActionFlowable
needs to include the doc parameter.

Thanks in advance for your replies,
Hans Brand