Re: Code and html separation - always or mostly doable?

[saberworks]

I've always wondered how you separate things like alternating table row background colors. Currently, I assign it in code, but that sucks. HTML::Template doesn't appear to have enough logic features to allow you to do modulus division on each iteration and pick a bgcolor from an array. So I have color definitions in my code - which sucks if the designer wants to change the colors. Of course, then I could use something like a config file or store the colors in a db, but that way, it's separated into 3 different areas instead of just two.

my @colors = ('#FFFFFF', '#F0F0F0');
my $cnt = 1;

foreach my $row (@$list) {
    $row->{bgcolor} = $colors[$cnt % 2];
    # Assign $row to your template engine or AoH or whatever...
    $cnt++;
}

[amw1]

for Template Toolkit this macro will do it This does it using CSS classes for coloring but setting it in a different way works as well.

create a block macro
[% MACRO alt_color(loop_count) BLOCK %]
  [% IF loop_count % 2 == 0 %]
    color1
  [% ELSE %]
    color2
  [% END %]
[% END %]

in your template you do
loop.count is a special property of the iterator
[% FOREACH thing = things %]
  <td class=[% alt_color(loop.count) %]>[% thing %]</td>
[% END %]

for H::T you can do

<tmpl_loop name='things'>
  <td class=<TMPL_IF __ODD__>color<TMPL_ELSE>color2</TMPL_IF>> thing</
+td>
</tmpl_loop>

you need to make sure you have loop_context_vars set to 1 in H::T to h
+ave access to __ODD__/__EVEN__

[Michalis]

Hi,

If you only speak of two colors, it's quite easy in the template system I use (and I guess, even easier on standard Template systems).
I create an array (call it @array) on my perl program, containing hashes. One of the hash elements is named "bgcolor" and is actually a boolean value. Let's say for example that it also has a "content" value which is string and a "cnt" value which is integer (a counter).

The code notation provided works for HTMLTP, but it should work anywhere as the logical part.

<table>
<!--: ascending array :-->
<tr class="<!--: if bgcolor :-->colored<!--: else :-->noncolored<!--: 
+end :-->"><td>[:cnt:]</td><td>The content of the [:cnt:]th element is
+ : [:content:]</td></tr>
<!--: end :-->
</table>


The only remaining part is to define the "colored" and "noncolored" classes on your CSS.

[saberworks]

Both of the above are fine for two colors, but in my code, you can easily add an arbitrary number of colors and it will still work. I think template systems should provide functionality to handle very common cases such as this. Maybe something like (haven't used html::template in forever so I don't remember the syntax for loops, but I'll guess):

<TMPL_LOOP NAME=rows ALTERNATE=FFFFFF,F0F0F0,CCCCCC>
    <td bgcolor=rows.alternate>
    ....
    </td>
</TMPL_LOOP>

I guess I could add it ;)

[Michalis]

I thought I'ld let it as an exercise, but...
If I use bgcolor as integer, not boolean, I can easily do that:

<td class="color[:bgcolor:]">....</td>


So I can not only define classes color1,color2 etc, but if in the future we decide we want a 57th special case we haven't thought of before, we don't need to change any code, we just create a class57 and "feed" the bgcolor with the number 57.
As I said before, there is always a matter of good analysis in order to trully and forever seperate perl code (business logic) from presentation (I consider the loops and if/then/else cases in the final HTML pages to be presentation-specific and not business specific)