Add 'loop.parity' for zebra row coloring

[tuomassalo]

Hello,

it's very common that one wants to color even and odd rows of a list/table/etc. with alternative colors. That's why I'm suggesting a shortcut variable 'loop.parity' that yields 'even' or 'odd'. It could be used like this:

  <tr class="{{ loop.parity }}">...</tr>

Very readable, and it also makes the css code more readable.

Here's a patch:

*** Twig.orig/Node/For.php  Wed Mar 17 21:39:34 2010
--- Twig/Node/For.php   Thu Mar 18 02:17:57 2010
***************
*** 90,95 ****
--- 90,96 ----
          ->write("  'revindex'  => \$length,\n")
          ->write("  'first'     => true,\n")
          ->write("  'last'      => 1 === \$length,\n")
+         ->write("  'parity'    => 'odd',\n")
          ->write(");\n")
        ;
      }
***************
*** 120,125 ****
--- 121,127 ----
          ->write("--\$context['loop']['revindex'];\n")
          ->write("\$context['loop']['first'] = false;\n")
          ->write("\$context['loop']['last'] = 0 === \$context['loop']['revindex0'];\n")
+         ->write("\$context['loop']['parity'] = (\$context['loop']['parity']==='even'?'odd':'even');\n")
        ;
      }

[tuomassalo]

Oops, found |even and |odd only now. :)

So, without the patch one could write something like:

  <tr class="{{ loop.index|even ? 'even' : 'odd' }}">

Not as nice as the suggestion, but quite ok still.

[lmammino]

cycle node support would be nice too.
With Django, whose twig is widely inspired on, you can do something like this:
{% for o in some_list %}

...

{% endfor %}

[lmammino]

http://docs.djangoproject.com/en/dev/ref/templates/builtins/ :P

[fabpot]

added the cycle filter (closed by 075f541)

[tuomassalo]

Great work! The cycle seems far better than the patch I suggested.

[Koc]

Fabien, can you make cycle as tag, not filter?

{% for item in items %}
  {{ item }} - {% cycle ['apple', 'orange', 'citrus'] %}
{% endfor %}

[fabpot]

If I do that, on which variable should I cycle? A global variable? If so, then depending on what you have on the page before, it won't always start at the same element.

[Koc]

Static variable inside Twig_Node_Cycle?

$var = rand(1, 999999);
$compiler
  ->write("\$seq$var = twig_iterator_to_array(")
  ->subcompile($this->seq)
  ->raw(");\n");

Does cycle tag can get access to name of variable name "\$seq$var"?

[fabpot]

That's not possible. But even if it was, it means that the cycle is not predictable.

[lmammino]

This new feature is really great and makes many common and troubleful tasks a piece of cake ;) Thanks a lot for adding it!

However with django you can do:
{% for o in some_list %}

...

{% endfor %}

it seems that django cycles on the current iteration index variable (I have no idea about how django cycle beahves with nested iterations)...

I don't know how django implemented it (and how twig architecture is similiar to django template system) but its approch sometimes could be more readable and easier to use.

[fabpot]

In Django, there is no state for the cycle tag, which means that you cannot tell which will be the first value used in a loop. To me, this is not a good thing.

[fabpot]

That said, that's quite easy to implement a cycle tag like the one in Django.

[lmammino]

In Django, there is no state for the cycle tag, which means that you cannot tell which will be the first value used in a loop. To me, this is not a good thing.

So, with django, if you do something like this:
{% for o in some_list %}

...

{% endfor %}
...
{% for p in some_list2 %}

...

{% endfor %}
are you saying that the first cycle value used in the second loop is not predictable?
If so, it's NOT really a good thing!

On the other way, using the current twig cycle implementation, i'd like to know what could be the best way to use cycle inside a "foreach" loop.

Maybe:
{% for row in rows %}
...
{% endfor %}

... a little bit tricky for designers