break/continue for templates
George Sakkis
there have been at least three threads in this list alone from people
asking how to "break" from a for loop in templates, so the following
snippet [1] might be useful to some. Leaving aside the "thou shalt not
use logic in templates" religious debate, it's interesting in that it
is syntactically more powerful than the respective Python statements:
you can continue/break not just from the innermost loop but from outer
ones too. Here's a small example:
{% for key,values in mapping.iteritems %}<br/>
{% for value in values %}
{{ key }}: {{ value }}<br/>
{% if value|divisibleby:3 %}
{{ value }} is divisible by 3<br/>
{{ forloop.parentloop|continue }}
{% endif %}
{% endfor %}
{{ key }}: No value divisible by 3<br/>
{% endfor %}
Given context = {'mapping': dict(a=[1,2,3], c=[2,4,5], b=[3,5,7])},
the output is:
a: 1
a: 2
a: 3
3 is divisible by 3
c: 2
c: 4
c: 5
c: No value divisible by 3
b: 3
3 is divisible by 3
Tested (lightly) on Django 1.2 / Python 2.6; please let me know if you
hit any bugs or unexpected behavior.
Cheers,
George
[1] http://djangosnippets.org/snippets/2092/
euan.g...@gmail.com
It sounds like a neat idea. However, I've never come across a
situation where I've needed to do that in 2.5 years of developing
Django templates, and, whilst I agree that we don't want to get into a
holy war about whether stuff should be done in templates or views, I
reckon the reason I've avoided this sort of thing is because I must
have done that sort of work in the view :)
Euan
George Sakkis
Sorry, it was accidentally double posted and the original was deleted.
Here it is now: http://djangosnippets.org/snippets/2093/.
> It sounds like a neat idea. However, I've never come across a
> situation where I've needed to do that in 2.5 years of developing
> Django templates, and, whilst I agree that we don't want to get into a
> holy war about whether stuff should be done in templates or views, I
> reckon the reason I've avoided this sort of thing is because I must
> have done that sort of work in the view :)
apparently others did ([1-4]). As for the "just put it in the view"
argument, remember that until last month this was the response for
people wanting "if" to be a bit smarter :)
George
[1] http://bit.ly/9ordv7
[2] http://bit.ly/9B0b89
[3] http://bit.ly/aldiqA
[4] http://bit.ly/bXMmap
Torsten Bronger
George Sakkis writes:
> [...]
>
> To be honest, I never *had to* do it (in the strict sense) either
> but apparently others did ([1-4]). As for the "just put it in the
> view" argument, remember that until last month this was the
> response for people wanting "if" to be a bit smarter :)
People will want to do *everything* in the template. The lowest
rated snippet on djangosnippets currently is an {% exec %} tag. :-)
Therefore, it's important to enforce some discipline, so that the
templates don't become sort of PHP. I use "break" and "continue" a
lot, but I've never thought about it in templates. You can easily
prepare the list in the Python land.
Tsch�,
Torsten.
--
Torsten Bronger, aquisgrana, europa vetus
Jabber ID: torsten...@jabber.rwth-aachen.de
or http://bronger-jmp.appspot.com
George Sakkis
wrote:
>
> George Sakkis writes:
> > [...]
>
> > To be honest, I never *had to* do it (in the strict sense) either
> > but apparently others did ([1-4]). As for the "just put it in the
> > view" argument, remember that until last month this was the
> > response for people wanting "if" to be a bit smarter :)
>
> People will want to do *everything* in the template. The lowest
> rated snippet on djangosnippets currently is an {% exec %} tag. :-)
votes, let alone the "smart" {% if %} tag that is at last part of
Django now. I'm curious if break/continue or the just posted {% while
%} tag [2] will end up closer to switch or to exec :-)
George
[1] http://djangosnippets.org/snippets/967/
[2] http://djangosnippets.org/snippets/2096/
Torsten Bronger
George Sakkis writes:
> On Jul 5, 2:25�pm, Torsten Bronger <bron...@physik.rwth-aachen.de>
> wrote:
>
>> [...]
>>
>> People will want to do *everything* in the template. �The lowest
>> rated snippet on djangosnippets currently is an {% exec %}
>> tag. �:-)
>
> But then again there is a {% switch %} tag [1] that has 8/8
> positive votes, let alone the "smart" {% if %} tag that is at last
> part of Django now.
The question is whether non-programmers can handle it. In this
context, a smart if was a good thing to do because it just made a
necessary control structure more intuitive. But the other things
are simply bringing full-blown programming into templates. Besides,
it is *very* easy to migrate them into the Python code.