Steve Alexander wrote:

Chris Withers wrote:

...

I have an external method called navTree (dtml-tree was too broken to fix in the time frame :( ) with a spec as follows:

def navTree(self,start):

It's called in some DTML as:

<dtml-var "nav_tree(PARENTS[-2])">

which is fine, unless I call it with the following:

<dtml-var "nav_tree(start=PARENTS[-2])">

in which case I get: TypeError: not enough arguments; expected 2, got 0

So, in the first case, you're not getting the current context passed in, but you are getting it in the second case.

... Looks like it is assumed that the first non-keyword argument should be passed as the client (ie "self").

So, you can fix your exception by giving "start" a default value:

def navTree(self,start=''):

However, you'll have to always use the keyword form of calling it:

<dtml-var "nav_tree(start=PARENTS[-2])">

Or otherwise, provide a client for it:

<dtml-var "nav_tree(this(), PARENTS[-2])">

As for why this is the case... I have other things to do this morning, so I won't go rooting around in the DTML source just now. [ Although, it sure is tempting :-) ]

The problem is near the bottom of ExternalMethod.py. The PythonMethod product is based partly on ExternalMethod, so I'm now familiar with the invocation mechanism. Here's the logic: ExternalMethod sets up func_* attributes so it can masquerade as a function. The trick works well enough to convince ZPublisher's mapply() to pass in a "self" argument as the first argument when needed. However, if you invoke the method directly (as you're doing here), mapply is not part of the mechanism. So you're supposed to provide the "self" argument manually. This is nonintuitive IMHO. BUT if you don't provide the "self" argument, and ExternalMethod can see that the method signature includes "self" as the first argument, ExternalMethod will try to call the method again with the self argument prepended. So if you have arguments with defaults or use variable argument lists, that last algorithm falls to pieces. The solution is to always provide the "self" argument. Shane

Chris Withers wrote:

Shane Hathaway wrote:

...

that last algorithm falls to pieces. The solution is to always provide the "self" argument.

When calling or in the signature of your external method?

If the former, then would that have to be:

<dtml-var "external_method(this(),...other args..."> ?

Yes, sorry I didn't make that clear. The solution is to always call the external method with an explicit "self" argument. Shane

Steve Alexander wrote:

Both. def external_method(self, ...other args...):

...

<dtml-var "external_method(this(),...other args..."> ?

I'll go with this advice since I still can't make heads or tails which of the two Shane thinks I need to do ;-) Of course, it's not documented like this. I think the docs say just make sure the def has self as the first argument... Can someone from DC pick up the Issue I dropped in the collector relating to this and solve the problem in some sensible way ;-) cheers, Chris PS: Doing both proved to be an extremely bad idea :( Suddenly I'm getting lots of key errors and the like. I'm going back to what I was doing: -self argument first in def -call with <dtml-var "nav_tree(PARENTS[-2])">

Chris Withers wrote:

Shane Hathaway wrote:

...

Here's the logic: ExternalMethod sets up func_* attributes so it can masquerade as a function. The trick works well enough to convince ZPublisher's mapply() to pass in a "self" argument as the first argument when needed.

What 'self' does mapply pass? I always though it would be the object being rendered (the one that would appear before PARENTS[0] in PARENTS if such a thing were possible ;-) but it appears to in fact be PARENTS[0].

...which seems silly

Ah... but are you calling the external method from a DTML method? These are all methods, and therefore you'd expect the "self" object to be the object the methods are subobjects of. -- Steve Alexander Software Engineer Cat-Box limited http://www.cat-box.net

Chris Withers wrote:

...which doesn't give quite what I want objects[-1] should be the object getting rendered, however, for folders getting rendered where index_html is a DTML document, it is the index_html document.

Well, I think I solved it for now, but this is horrible! ;( def navTree(self,startlevel,this): # strip off acquisition wrappers, reverse the list... yum yum ;-) objects = map(lambda o : getattr(o, 'aq_base', o),self.REQUEST.PARENTS[:-startlevel]) objects.reverse() # unless we're rendering a folder, add this() to objects if not self.REQUEST['URL'][-10:]=='index_html': objects.append(getattr(this, 'aq_base', this)) Someone please give me something mroe elegeant ;-) cheers, Chris