The MotivationMy first real job assignment out of college was todeliver a suped up front-end for an Access databasefile implemented in Cold Fusion. That was when a veryimportant lesson that I had been taught reared itsugly head at me: "seperate your interface from yourimplementation". This mantra has more than one meaning- in this particular scenario it meant don't mix thebusiness rules with the presentation documents.What did I do wrong? I used ColdFusion to generate keyHTML elements - I painted myself in a corner. When theperson who wrote the HTML needed to change something,I was the one who did the changing. I had just assignedmyself a new job on top of the one I had with no extra pay!That's what HTML::Template is all about - the abilityto keep your Perl code decoupled from your HTML pages.Instead of serving up HTML files or generating HTMLinside your Perl code, you create templates - textfiles that contain HTML and special tags that willbe substituted with dynamic data by a Perl script.If you find yourself lacking as a web designer or generallycouldn't care less, you can give your templates to a webdesigner who can spice them up. As long as they do notmangle the special tags or change form variable names,your code will still work, providing your code worked in the first place. :PThe TagsHTML::Template provides 3 kinds of tags:variables: loops: conditionals: Variables and conditionals are very simple - a variabletag such as will be replacedby whatever value is assigned to the HTML::Templateobject's paramater FOO. Example Perl code follows, butplease note that this is not a CGI script - let's stickto the command line for now:Example 1# secret.pluse HTML::Template;my $bar = 'World';my $template = HTML::Template->new(filename => 'secret.tmpl');$template->param(SECRET_MESSAGE => $bar);print $template->output;[download]and it's corresponding template file:Hello [download](p.s. this tutorial discusses CGI below - if youreally want to try this out as a CGI script then don'tforget to print out a content header. I recommend the ubiquitousheadermethod avaible from using CGI.pm)
Also, something very important - that last bit of perl codewas not very smart. In his documentation, the author mentionsthat a maintenance problem can be created by thinking likethis. Don't write matching conditionals inside your Perlcode. My example is very simple, so it is hard to see howthis could get out of hand. Example 2 would be better as:Example 2 (revised) Move along, nothing to see . . .# secret.plmy $message = 'Yes there is' if is_member($id);my $template = HTML::Template->new(filename => 'secret2.tmpl');$template->param(SECRET => $message);print $template->output;[download]Now only one parameter is needed instead of two. $messagewill be undefined if is_member() returns false, and since anundefined value is false, the TMPL_IF for 'SECRET' will befalse and the message will not be displayed.By using the same attribute name in the TMPL_IF tag and theTMPL_VAR tag, decoupling has been achieved. The conditionalin the code is for the message, not the conditional in thetemplate. The presence of the secret message triggers theTMPL_IF. This becomes more apparent when using data froma database - I find the best practice is to place templateconditionals on table column names, not a boolean value that will be calculated in the Perl script. I will discuss using a database shortly.Now, you may be tempted to simply use one TMPL_VAR tag anduse a variable in your Perl script to hold the HTML code.Now you don't need a TMPL_IF tag, right? Yes, but that iswrong. The whole point of HTML::Template is to keep theHTML out of your Perl code, and to have fun doing it!Loops are more tricky than variables or conditionals,even more so if you do not grok Perl's anonymous data structures.HTML::Template's param method will only accept a referenceto an array that contains references to hashes. Here is an example:Example 3 Name:
GPA: # students.plmy $template = HTML::Template->new(filename => 'students.tmpl');$template->param( STUDENT => [ { NAME => 'Bluto Blutarsky', GPA => '0.0' }, { NAME => 'Tracey Flick' , GPA => '4.0' }, ]);print $template->output;[download]This might seem a bit cludgy at first, but it is actuallyquite handy. As you will soon see, the complexity of thedata structure can actually make your code simpler.A Concrete Example part 1So far, my examples have not been very pratical - the realpower of HTML::Template does not kick in until you bringDBI and CGI along for the ride.To demonstrate, suppose you have information about yourmp3 files stored in a database table - no need for worryingabout normalization, keep it simple. All you need to dois display the information to a web browser. The table(named songs) has these 4 fields:titleartistalbumyearOk, confesion - I wrote a script that dumped my mp3 files'ID3 tags into a database table for this tutorial. This program has no usefulness other than to demonstrate thefeatures of HTML::Tempate in a relatively simple manner. Onward!We will need to display similar information repeatly, sounds like a loop will be needed - one that displays 4 variables. And this time, just because it is possible,the HTML::Template tags are in the form of HTML comments,which is good for HTML syntax validation and editor syntax highlighting.Example 4Song ListingMy Songs # songs.cgiuse DBI;use CGI;use HTML::Template;use strict;my $DBH = DBI->connect( qw(DBI:vendor:database:host user pass), { RaiseError => 1});my $CGI = CGI->new();# grab the stuff from the databasemy $sth = $DBH->prepare(' select title, artist, album, year from songs');$sth->execute();# prepare a data structure for HTML::Templatemy $rows;push @{$rows}, $_ while $_ = $sth->fetchrow_hashref(); # instantiate the template and substitute the valuesmy $template = HTML::Template->new(filename => 'songs.tmpl');$template->param(ROWS => $rows);print $CGI->header();print $template->output();$DBH->disconnect();[download]And that's it. Notice what I passed to the HTML::Template object's param method: one variable that took care of that entire loop. Now, how does it work? Everything should be obvious except this little oddity:push @{$rows}, $_ while $_ = $sth->fetchrow_hashref();[download]fetchrow_hashref returns a hash reference like so:{ 'artist' => 'Van Halen', 'title' => 'Spanish Fly', 'album' => 'Van Halen II', 'year' => '1979',};[download] This hash reference describes one row. The line of codetakes each row-as-a-hash_ref and pushes it to an arrayreference - which is exactly what param() wants fora Template Loop: "a list (an array ref) of parameter assignments (hash refs)". (ref: HTML::Template docs)Some of the older versions of DBI allowed you to utitizean undocumented feature. dkubb presented ithere. The result was being able to callthe DBI selectall_arrayref() method and be returned adata structure that was somehow magically suited forHTML::Template loops, but this feature did not survivesubsequent revisions.
Best Html Template Free Download
tag_hash_107 🔥 https://urlca.com/2yjYlw 🔥
Another extremely useful attribute is associate. When I wrotemy first project with HTML::Template, I ran into a problem:if the users of my application submitted bad form data, I neededto show them the errors and allow them to correct them, withouthaving to fill in the ENTIRE form again.In my templates I used variables like so:
That way I could populate form elements with database information if the item already existing, or leave them blank when the user was creating a new item. I only needed one template for creating and updating items. (Notice that I named my text box the same as the template variable - also the same as the database field.)But when the user had invalid data, they would loose what they just typed in - either to the old data or to blank form fields. Annoying!That's where associate saves the day. It allows you to inheritparamter values from other objects that have a param() methodthat work like HTML::Template's param() - objects like CGI.pm!my $CGI = CGI->new();my $template = HTML::Template->new( filename => 'foo.tmpl', associate => $CGI,);[download]Problem solved! The parameters are magically set, and you can override them with your own values if need be. No need for those nasty and cumbersome hidden tags. :)loop_context_vars allows you to access 4 variables that control loop output: first, last, inner, and odd. They can be used in conditionals to vary your table output: the first is usually a header odd rows are red even rows are blue you have no chance to survive so choose # pill.cgimy $template = HTML::Template->new( filename => 'pill.tmpl', loop_context_vars => 1,);# etc.[download]No need to keep track of a counter in your Perl code, the conditions take care of it for you. Remember, if youuse a conditional in a template, you should not have totest for that condition in your code. Code smart.A Concrete Example part 2Let's supe up our previous song displayer to allow sortingby the column names. And while we are at it, why botherhard coding the names of the database fields in the template. Let's set a goal to store the database field names in one list and one list only.Of course, this means that we will have to design a new data structure, because the only way to accomplish our lofty goal cleanly is to use two template loops: one for each row of data, and one for the indidividual fields themselves.As for sorting - let's just use plain old anchor tags instead of a full blown form. We can make the headers links back to the script with a parameter set to sort by the name of the header: Title.Also, let's get rid of the hard coded script name, in case we decide to change the extension from .cgi to .asp, because we can. CGI.pm provides a method, script_name which returns the name of the script, relative to the web server's root.Here is the final example. If you think the Perl code is abit convoluted, well you are right, it is. But it is alsoflexible enough to allow you add or remove database fieldssimply by changing the @COLS list. This makes it trivial toallow the user to choose which fields she or he sees, anexercise I leave to the reader, as well as adding the ability to sort fields in descending or ascending order.Last note, notice the use of the built-in filehandle to store the template in this script. Thisallows you to contain your code and template in onetext document, but still fully seperated. You can specify a scalar reference in the constructor like so:my $template = HTML::Template->new(scalarref => \$scalar);[download]And now...The Last Example#!/usr/bin/perl -Twuse DBI;use CGI;use HTML::Template;use strict;my $DBH = DBI->connect( qw(DBI:mysql:mp3:host user pass), { RaiseError => 1 },);my $CGI = CGI->new();my @COLS = (qw(title artist album));# verify the sort param - never trust user inputmy %sort_lookup = map {$_ => $_} @COLS;my $sort = $sort_lookup{$CGI->param('sort')||''} || 'title';my $data = $DBH->selectall_arrayref(" select @{[join(',', @COLS)]} from songs order by ?", undef, ($sort));# prepare the DS for the headersmy $headers = [ map {{ URL => $CGI->script_name . "?sort=$_", LINK => ucfirst($_), }} @COLS ];# prepare the DS for the rowsmy $i;my $rows = [ map { my $row = $_; (++$i % 2) ? { ODD => [ map { {VALUE => $_} } @{$row} ] } : { EVEN => [ map { {VALUE => $_} } @{$row} ] } } @{$data}];# remove excess blood from ears after that last expression# read the template as a scalar from DATAmy $html = do { local $/; };# prepare the template and substitute the valuesmy $template = HTML::Template->new( scalarref => \$html, loop_context_vars => 1,);$template->param( HEADERS => $headers, ROWS => $rows, SORT => $sort,);# print the goodsprint $CGI->header();print $template->output();$DBH->disconnect();__DATA__Songs sorted by Songs sorted by [download]Thanks to dkubb and deprecated for corrections; SamTregar for writing the module; aijin, orkysoft,and bladx for pointing out typos; and dws for bringing you the letter 'D'.See also: HTML::Template and 'perldoc HTML::Template'after you install it.Comment on HTML::Template TutorialSelect or Download Code 0852c4b9a8
windows 8 go sms theme free download
nokia sms tones mp3 free download