NAME Template::Plex - Templates in (P)erl using (Lex)ical Aliasing SYNOPSIS Import "plex" and "plx" into you package: use Template::Plex; Setup variables/data you want to alias: my $vars={ size=>"large", slices=>8, people=>[qw<Kim Sam Harry Sally> ] }; local $"=", "; Write a template: #Contents of my_template.plex Ordered a $size pizza with $slices slices to share between @$people and myself. That averages @{[$slices/(@$people+1)]} slices each. Load the template with "plex": my $template= plex "my_template.plex", \%vars; Render it: my $output=$template->render; #OUTPUT Ordered a large pizza with 8 slices to share between Kim, Sam, Harry, Sally and myself. That averages 1.6 slices each. Change values and render it again: $vars->{size}="extra large"; $vars->{slices}=12; $output=$template->render; #OUTPUT Ordered a extra large pizza with 12 slices to share between Kim, Sam, Harry, Sally and myself. That averages 2.4 slices each. DESCRIPTION This module facilitates the use of perl (not embedded perl) as a text processing template language and system capable of loading, caching and rendering powerful templates. It does this by implementing a handful of subroutines to perform template loading/management (i.e. "plex" and "plx") and also includes a couple of convenience routines to make processing simpler (i.e. "block" and "jmap"). String::Util string filtering routines are also made available in templates for the most common of filtering tasks. Of course you can "use" any modules you like within the template, or define your own subroutines within the template. The template is just perl! Conceptually, a "Template::Plex" template is just a string in perl's double quoted context, with the outer operators removed: #PERL "This is a perl string interpolating @{[ map uc, qw<a b c d>]}" # or qq{This is a perl string interpolating @{[ map uc, qw<a b c d>]}} #PLEX template. Same as PERL syntax, without the outer double quotes This is a perl string interpolating @{[ map uc, qw<a b c d>]}; #OUTPUT is the same for all of the above: This is a perl string interpolating A B C D The 'lexical' part of this modules refers to ability of variables to be aliased into the template (more on this later). It improves the style and usage of variables in a template while also allowing sub templates to access/override variables using lexical scoping. The synopsis example only scratches the surface in terms of what is possible. For more examples, checkout the examples directory in this distribution. I hope to add more in the future FEATURES The following are snippets of templates demonstrating some of the feature: * Templates are written in perl syntax: This template is a valid $perl code @{[ uc "minus" ]} the outer quotes * Templates are compiled into a perl subroutine, with automatic caching (plx) Sub/template is loaded only the first time in this map/loop @{[map {plx "path_to_template",{}} qw< a b c d e >]} * Lexical and package variables accessed/created within templates @{[ block { $input_var//=1; #set default } }] Value is $input_var; * Call and create subroutines within templates: @{[ block { sub my_great_calc { my $input=shift; $input*2/5; } } }] Result of calculation: @{[my_great_calc(12)]} * 'Include' Templates within templates easily: @{[include("path_to_file")]} * Recursive sub template loading @{[ plx "path_to_sub_template" ]} * Conditional rendering @{[ $flag and $var]} @{[ $flag?$var:""]} @{[ pl { if($flag){ #do stuff } } ]} * Lists/Loops/maps template interpolates @$lists directly Items that are ok: @{[ do { #Standard for loop my $output; for(@$items){ $output.=$_."\n" if /ok/; } $output; } }] More ok items: @{[map {/ok/?"$_\n":()} @$items]} * "use" other modules directly in templates: @{[ block { use Time::HiRes qw<time> } ]} Time of day right now: @{[time]} MOTIATION * So many templating systems available, yet none use perl as the template language? * Lexical aliasing allows the input variables to be accessed directly by name (i.e. $name) instead of as a member of a hash ref (i.e. "$fields->{name}") or by delimiting with custom syntax (i.e. "<%= name %>") * The perl syntax "@{[...]}" will execute arbitrary perl statements in a double quoted string. * Other templating system are very powerful, but have huge a huge APIs and options. Template::Plex could have a very minimal API with perl doing the hard work API "plex" plex $path, $variables_hash, %options Creates a new instance of a template, loaded from a scalar, file path or an existing file handle. $path This is a required argument. If $path is a string, it is treated as a file path to a template file. The file is opened and slurped with the content being used as the template. If $path is a filehandle, or GLOB ref, it is slurped with the content being used as the template. Can be used to read template stored in "__DATA__" for example If $path is an array ref, the items of the array are joined into a string, which is used directly as the template. $variables_hash This is an optional argument but if present must be an empty hash ref "{}" or "undef". The top level items of the $variables_hash hash are aliased into the template using the key name (key names must be valid for a variable name for this to operate). This allows an element such as "$fields{name"}> to be directly accessible as $name in the template and sub templates. External modification of the items in $variable_hash will be visible in the template. This is thee primary mechanism change inputs for subsequent renders of the template. In addition, the $variables_hash itself is aliased to %fields variable (note the %) and directly usable in the template like a normal hash e.g. $fields{name} If the $variables_hash is an empty hash ref "{}" or "undef" then no variables will be lexically aliased. The only variables accessible to the template will be via the "render" method call. %options These are non required arguments, but must be key value pairs when used. Options are stored lexically for access in the template in the variable %options. This variable is automatically used as the options argument in recursive calls to "plex" or "plx", if no options are provided Currently supported options are: root "root" is a directory path, which if present, is prepended to to the $path parameter if $path is a string (file path). no_include Disables the uses of the preprocessor include feature. The template text will not be scanned and will prevent the "include" feature from operating. See "include" for more details This doesn't impact recursive calls to "plex" or "plx" when dynamically/conditionally loading templates. no_block_fix Disables removing of EOL after a "@{[]}" when the closing "}]" starts on a new line. Does not effect "@{[]}" on a single line or embedded with other text eg Line 1 @{[ "" ]} <-- this NL removed by default Line 3 In the above example, the default behaviour is to remove the newline after the closing "]}" when it is on a separate line. The rendered output would be: Line1 Line3 If block fix was disabled (i.e. "no_block_fix" was true) the output would be: Line1 Line3 package Specifies a package to run the template in. Any "our" variables defined in the template will be in this package. If a package is not specified, a unique package name is created to prevent name collisions Return value The return value is "Template::Plex" object which can be rendered using the "render" method Example Usage my $hash={ name=>"bob", age=>98 }; my $template_dir="/path/to/dir"; my $obj=plex "template.plex", $hash, root=>$template_dir; "plx" plex $path, $variables_hash, %options Arguments are the same as "plex". Similar to the "plex" subroutine, however it loads, caches and immediately executes the template. Somewhat equivalent to: state $template=plex ...; $template->render; The template is cached so that next time "plx" is called from the same file/line, it reuses the code. Makes using recursive templates very easy: eg @{[ plx "path to sub template"]} Does have the slight overhead of generating cache keys and actually performing the cache lookup compared to manually caching using "plex" "render" $obj->render($fields); This object method renders a template object created by "plex" into a string. It takes an optional argument $fields which is a reference to a hash containing field variables. "fields" is aliased into the template as %fields which is directly accessible in the template eg my $more_data={ name=>"John", }; my $string=$template->render($more_data); #Template: My name is $fields{John} Note that the lexically aliased variables setup in "plex" or "plx" are independent to the %fields variable and can both be used simultaneously in a template "include" @{[include("path")}] where $path is path to template file to inject Used in templates only. This is a special directive that substitutes the text similar to @{[include("path")]} with the contents of the file pointed to by path. This is a preprocessing step which happens before the template is prepared for execution This API is only available in templates. If "root" was included in the options to "plex", then it is prepended to "path" if defined. When a template is loaded by "plex" the processing of this is subject to the "no_include" option. If "no_include" is specified, any template text that contains the "@{[include("path")}]" text will result in a syntax error pl block block { ... } pl { ... } By default this is only exported into a templates namespace. A subroutine which executes a block just like the built in "do". However it always returns an empty string. When used in a template in the "@{[]}" construct, arbitrary statements can be executed. However, as an empty string is returned, perl's interpolation won't inject anything at that point in the template. If you DO want the last statement returned into the template, use the built in "do". eg @{[ # This will assign a variable for use later in the template # but WILL NOT inject the value 1 into template when rendered pl { $i=1; } ]} @{[ # This will assign a variable for use later in the tamplate # AND immediately inject '1' into the template when rendered do { $i=1 } ]} plex_clear plex_clear; Subject to change. Clears all compiled templates from the current level. jmap jmap {block} $delimiter, $array_ref; Performs a join using $delimiter between each item in the $array_ref after they are processed through "block" $delimiter is optional with the default being an empty string Very handy for rendering lists: eg <ul> @{[jmap {"<li>$_</li>"} "\n", $items]} </ul> skip Template with potential output @{[ block { skip if $flag; } ]} Any more potential output This subroutine prevents the current template from generating rendered output. Instead it will return an empty string. Variables can still be manipulated by template before the "skip" call. Useful to conditionally skip the body of a template, but configure the variable hash for preprocessing in a "@{[block{...}]}" structure FILTERS There is no special syntax for filters as in other template languages. Filters are simply subroutines and you chain them the usual way in perl: @{[ third_filer second_filter first_filter @data]} To get you started, the string filters from String::Util are imported into the template namespace. This includes: collapse crunch htmlesc trim ltrim rtrim define repeat unquote no_space nospace fullchomp randcrypt jsquote cellfill crunchlines file_get_contents Please consult the String::Util documentation for details TIPS ON USAGE Potential Pitfalls * Remeber to set $" locally to your requied seperator The default is a space, however when generating HTML lists for example, a would make it easier to read: #Before executing template local $"="\n"; plex ... Or alternatively use "jmap" to explicitly set the interpolation separator each time * Aliasing is a two way steet Changes made to aliased variables external to the template are available inside the template (one of the main tenets of this module) Changes make to aliased variables internal to the template are available outside the template. * Unbalanced Delimiter Pairs Perl double quote operators are smart and work on balanced pairs of delimiters. This allows for the delimiters to appear in the text body without error. However if your template doesn't have balanced pairs (i.e. a missing "}" in javascript/c/perl/etc), the template will fail to compile and give a strange error. If you know you don't have balanced delimiters, then you can escape them with a backslash Currently Template::Plex delimiter pair used is { }. It isn't changeable in this version. * Are you sure it's one statement? If you are having trouble with "@{[...]}", remember the result of the last statement is returned into the template. Example of single statements @{[time]} #Calling a sub and injecting result @{[$a,$b,$c,time,my_sub]} #injecting list @{[our $temp=1]} #create a variable and inject @{[our ($a,$b,$c)=(7,8,9)]} #declaring a If you are declaring a package variable, you might not want its value injected into the template at that point. So instead you could use "block{..}" or "pl{..}" to execute multiple statements and not inject the last statement: @{[ pl {our $temp=1;} }]; * Last newline of templates are chomped Most text editors insert a newline as the last character in a file. A chomp is performed before the template is prepared to avoid extra newlines in the output when using sub templates. If you really need that newline, place an empty line at the end of your template More on Input Variables If the variables to apply to the template completely change (note: variables not values), then the aliasing setup during a "plex" call will not reflect what you want. However the "render" method call allows a hash ref containing values to be used. The hash is aliased to the %fields variable in the template. my $new_variables={name=>data}; $template->render($new_variables); However to use this data the template must be constructed to access the fields directly: my $template='my name is $fields{name} and I am $fields{age}'; Note that the %field is aliased so any changes to it is reflected outside the template Interestingly the template can refer to the lexical aliases and the direct fields at the same time. The lexical aliases only refer to the data provided at preparation time, while the %fields refer to the latest data provided during a "render" call: my $template='my name is $fields{name} and I am $age my $base_data={name=>"jimbo", age=>10}; my $override_data={name=>"Eva"}; my $template=plex $template, $base_data; my $string=$template->render($override_data); #string will be "my name is Eva and I am 10 As an example, this could be used to 'template a template' with global, slow changing variables stored as the aliased variables, and the fast changing, per render data being supplied as needed. Security This module uses "eval" to generate the code ref for rendering. This means that your template, being perl code, is being executed. If you do not know what is in your templates, then maybe this module isn't for you. Aliasing means that the template has access to variables outside of it. That's the whole point. So again if you don't know what your templates are doing, then maybe this module isn't for you ISSUES Currently caching of templates when using "plx" is primitive. It works, but management will likely change. Manual caching with "state $template=plex ..." gives you better control and performance Debugging templates could be much better Unless specifically constructed to write to file, templates are completely processed in memory. "plx" caching will not be effective with literal templates unless they are stored in an anonymous array. SEE ALSO Yet another template module right? Do a search on CPAN for 'template' and make a cup of coffee. REPOSITORY and BUG REPORTING Please report any bugs and feature requests on the repo page: GitHub <http://github.com/drclaw1394/perl-template-plex> AUTHOR Ruben Westerberg, <drclaw@mac.com> COPYRIGHT AND LICENSE Copyright (C) 2022 by Ruben Westerberg This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, or under the MIT license