Default parameter is not working?

[Raj]

Hi,

I have a TG app with following controllers:

• RootController
  
• MediaController
• News Controller

In the RootController i have added subcontroller as media=MediaController()

In MediaController i have added news=NewsController()

NewsController is having an index() method with a parameter named 'url'

The NewsController()->index() page is displaying when the following URLs are invoked

• http://localhost:8080/media/news/
  
• http://localhost:8080/media/news/index/<value-of-url-param>
  
• http://localhost:8080/media/news/index?url=<value-of-url-param>
• http://localhost:8080/media/news?url=<value-of-url-param>

But the following URL shows a 404 error

• http://localhost:8080/media/news/<value-of-url-param>

I am expecting this should display the same result as of the URL http://localhost:8080/media/news/index/<value-of-url-param>

What is happening while removing index from URL?

What is the solution?

Regards,

Raj

[Michael Pedersen]

This comes down to a misunderstanding of what happens with the / character in URLs and how to use _lookup. I don't know that I have good examples for how to use _lookup, so I can't help there, but the other part I can explain:

TG separates the URL based on the / character. It goes to the top most controller (RootController), and says "Do you know how to handle /media". The RootController has a MediaController named "media", so it goes to that controller and asks about the next item: news. Since that controller has a NewsController named "news", it goes to the NewsController and asks it how to handle the next part.

You have a method named index, so whenever the next part is named "index", it passes everything to that method. That covers "/index/<value-of-param>" and "index?url=<value-of-param>". If there is nothing after the final / TG assumes you want to get the index method called, so uses that method. That covers "news/" and even "news?url=<value-of-param>" since there's a hidden / between "news" and "?url=" (that's how TG interprets it).

The final one, though, doesn't cover any of these cases. "news/<value-of-param>" doesn't actually match anything. NewsController is asked "do you have any attribute named <value-of-param>" and it doesn't, so it can't process it. It returns a 404. What you would need to do is add a method named _lookup() that would then tell TG that the index method knows how to handle <value-of-param>.

As I said, I don't have examples to share for this right now, so I can't do much to give code. I'm sorry. But at least this provides an explanation for what to do next.

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[Moritz Schlarb]

The _default and _lookup methods are explained here:
http://turbogears.readthedocs.org/en/latest/turbogears/objectdispatch.html
The difference is basically that _default returns a "page" like normal @expose'd
methods, whereas _lookup returns a new controller object where the dispatching
process continues.

> Michael Pedersen <m.ped...@icelus.org> hat am 9. Juli 2015 um 13:09
> geschrieben:

> > I have a TG app with following *controllers*:
> >
> > - RootController
> > - MediaController
> > - News Controller
> >
> > In the RootController i have added subcontroller as *media*
> > =MediaController()
> > In MediaController i have added *news*=NewsController()

> >
> > NewsController is having an index() method with a parameter named 'url'
> >
> > The NewsController()->index() page is displaying when the following URLs
> > are invoked
> >

> > - http://localhost:8080/media/news/
> > - http://localhost:8080/media/news/index*/<value-of-url-param>*
> > - http://localhost:8080/media/news/index*?url=<value-of-url-param>*
> > - http://localhost:8080/media/news*?url=<value-of-url-param>*
> >
> > But the following URL shows a* 404 error*
> >
> > - http://localhost:8080/media/news*/<value-of-url-param>*
> >
> > I am expecting *this should display the same result* as of the URL
> > http://localhost:8080/media/news*/index/<value-of-url-param>*
> > What is happening while removing *index *from URL?

[Raj]

Dear Michale Pedersen and Moritz Schlarb,

Thanks for your replies. It helps me to understand TG better.

Regards,

Raj

(^!^)
Raj

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