djay commented 8 years ago

User problem

Currently a block works like this.

If there is a action.blah in the request - execute that. If its a redirect then redirect
else render the template
execute each element as its reached in the template

There are a range of issues with this

if you want to execute code before rendering a template (such as redirect) then you have create a fake action in your request
if you want to do some heavy calculations shared between many elements its not clear where to put that code. It's also not clear where to store the results.
if you want to have those shared values easily accessible in the template, how do you do that? Would you have to create a new element for each value?
if you don't want to return html but return json or a pdf, how do you do that? You can currently call a element directly but this doesn't seem to be the right level and it results in long urls. Elements normally are used to render html into a template but suddenly now they are api endpoints?
if you want set which record is being used in the context, how do you do that?
History

pyramid

Handles this by making making the python callable always the first thing called. It then produces a dict and that gets passed to the a template. but alternatively you can return whatever you want.

plone browserviews

These are classes that have an init method that always gets called with context and request. There is also the call method you can override.

Options

controller function

Make it such that you can have controller function that can direct or return custom content without the need of templates or elements.

def on_init(context):
   # tuple or list lets you create a simple response
   return ("text/xml","<mycustom>response</mycustom")

or

def on_init(context):
   context.mime_type = 'text/xml'
   return "<mycustom>response</mycustom"

or it will accept a zope response

def on_init(context):
   return context.request.response

or a file

def on_init(context):
   return StringIO("stream my response")

If you want to redirect then do

def on_init(context):
   return context.redirect = "./myotherblock"

but if its a dict (or None) it will look the template and use that.

def on_init(context):
    return dict(element1="blah", element2="something else")

and these can be used directly in a zpt (no more using ${elements/element1})

<html><body>${element1}</body></html>

ebrehault commented 8 years ago

Sorry I haven't told, but I have implemented it last week (I named it on_display instead of on_open), see https://github.com/plomino/rapido.core/commit/2f88bf52ee97583050eec01801b243c37aecfbed (If it matches your needs, just close the issue).

djay commented 8 years ago

Cool!. I think it would be good to consider some of the other ideas as well. Like controling the record and being able to insert things into the context and template.

ebrehault commented 8 years ago

It does it already:

in on_display, you can put things in the context e.g.: context.thing = "something" and elemnst can access it
everything which is in the context is accessible in the template e.g. tal:content="context/something"
you can use it to store a record e.g. context.my_current_record=context.app.get_record('person1')
you can use it to change the response content-type or to redirect

Test it a little bit, if you think there is something missing, tell me.

djay commented 8 years ago

@ebrehault working on a patch now to show my ideas. The idea is instead of just on display it gets called on request and first. In the simplest case you can have no elements or template, just a single function called on_init or on_open or similar.

def on_init(context):
   # tuple or list lets you create a simple response
   return ("text/xml","<mycustom>response</mycustom")

or it will accept a zope response

def on_init(context):
   return context.request.response

or a file

def on_init(context):
   return StringIO("stream my response")

to it consistent with actions I think returning a string should redirect.

def on_init(context):
   return "./myotherblock"

but if its a dict (or None) it will look the template and use that.

def on_init(context):
    return dict(element1="blah", element2="something else")

and these can be used directly in a zpt (no more elements dict)

<html><body>${element1}</body></html>

These would be combined with any defined elements. The dict items returned from on_init would take precedence.

Anything else returned from on_init would give an error.

collective / rapido.core

not obvious to control block execution (on_display/on_init) #21

User problem

History

pyramid

plone browserviews

Options

controller function