Storing additional Information with the view config

[Gerhard Schmidt]

Hi

is it possible to store additional information in the view config.

Background is that i would like to add more information the the view
processed later by the layout tho generate the navigation of a page
automatically.

I would like to store the title of a page (for the navigation link) and
the navigation type.

The simplest solution would be to copy any unknown keyword arguments
given to view_config to the Introspectable or be able to add custom
keywords to be copied via config statement like adding custom predicates
to the view config.

Regards
Estartu

[Mike Orr]

I don't know whether you can store additional args this way, but it
sounds like the wrong structure for this kind of information. A page
title is page specific, not view specific, and parent titles (for
navigation links or previous/next links) sound like resource
information. Is this a pure URL Dispatch application with no resource
tree that could hold this information? I generally put my page title
in a Mako template function or I set it during the view's action. If
you have class-based views, you could store the navigation tree in a
view class attribute, and then use the runtime view's name to figure
out the current position in the tree. You may not need a multilevel
tree to navigate just one level up and one level across, with a
well-known "Home" link above that.

[Gerhard Schmidt]

Hi Mike,

first, why didn't i get you mail via mailinglist?

It's a traversal application. so views are bound to context rather than urls.

Right now i have a action_config decorator that adds a view with the given information and store the additional information in a second Introspectable in the registry.

Would be much more convenient to store this information directly at the view.

The pagetitle in my application is quite view specific and the navigation I am implementing is not only the site navigation (the site navigation is quite trivial) but the navigation within the object which can be quite complex.

Storing this information in the registry works quite well for me. And being able to do that directly in the view Introspectable would cut some complexity.

But my use case must not be the only one. So I think the question is not if the view Introspectable is the right place to store a pagetitle. The question is, should there be a way to store more information in the View Introspectable and how difficult is this to be implemented.

Regards
   Estartu
 

[Mike Orr]

I had an idea about this. When you want to associate data with a
callable you can use a partial function. For instance:

# views.py
def my_view(title, request):
....

# __init__.py
import functools
title = "My Title"
view1 = functools.partial(my_view, title)
config.add_view(view1, ...)

Or you could write a wrapper for view_config that does this.

I've never needed additional view data like this because my titles are
in my templates or in my view code. (I have a Mako site template with
a 'page_title' function which I override in the individual templates.)
But if you can't specify the title in either of those places or in the
context, then I'd use a partial function like this.

Outside Pyramid I'd use a callable class:

class MyClass:
def __init__(self, title):
self.title = title
def __call__(self, request):
# Use self.title.

But that wouldn't work as a view class because Pyramid makes certain
assumptions about view classes that are incompatible with this. You
might be able to configure an instance of it:

config.add_view(MyClass("My Title"), ...)

But I haven't tried it and I don't know whether Pyramid would treat it
like a function.

[Arndt Droullier]

I had the same 'problem' with an older pyramid version. To pass additional configuration values to view code I came to a similar solution like the one described by Mike.

For class based views I used dynamic type generation to store specific values as class attributes which is then used as view code. Its easy to serialize and load the values

e.g from a json file.

def view_class(values, cls):
    newcls = type("_extended_"+cls.__name__, (cls,), {})
    newcls.__values__ = values
    return newcls

def MyView:

    # view code

    # ....

ViewCls = view_class(dict(title="Title"), MyView)

config.add_view(view=ViewCls, ...)

Arndt.

[Mike Orr]

You could also use a metaclass to generate the class with class
variables baked into it, but that is complicated to do and it may take
a few tries to get it right.

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--
Mike Orr <slugg...@gmail.com>

[Gerhard Schmidt]

Am 02.01.19 um 09:09 schrieb Mike Orr:

Hi,

I'm not trying to hack this (I'm already done the hack). I proposing to
add a clean documented way to do something like that. Hacking around the
system always introduce the possibility of future incompatibility. I'm
developing systems that are long living and under my maintenance for the
whole time. So I try to stay rather close to the system to minimize
update issues.

The Introspectable is already a dict like object. So adding any
additional information would not be a technical problem. There is right
now code in place that checks if there are arguments that are unknown
before adding everything to the Introspectable. There is a way to
register arguments to store information for tween to work with, but my
code is no tween but just rendering. Just removing the checking code
would add this feature. But I really like the checking. So a way to just
add to the list of known arguments would do.

I try to get some code done in the near future.

Regards
Estartu

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