Provided by: libtext-xslate-perl_3.5.6-1build1_amd64 bug

NAME

       Text::Xslate::Manual::FAQ - Frequently asked questions and answers

DESCRIPTION

       This manual page lists FAQs, which we've heard for now.

QUESTIONS

   General
       How do you pronounce 'Xslate'?

       We read it "/eks-leit/".

       What 'Xslate' stands for?

       It stands for XS template, a template engine written in XS, although pure Perl
       implementations are also provided.

       What are 'Kolon', 'Metakolon', and 'TTerse' ?

       Xslate supports multiple template syntaxes. Kolon is the default syntax, Metakolon is
       suitable to output Kolon templates, and TTerse is compatible with Template-Toolkit 2. You
       can specify the template syntax by passing "syntax" option to the Text::Xslate
       constructor.

           my $tx = Text::Xslate->new(
               syntax => 'TTerse', # by moniker
           );

           my $tx = Text::Xslate->new(
               syntax => 'Text::Xslate::Syntax::TTerse', # by fully qualified name
           );

       What version of perl does Xslate require?

       Xslate is tested on perl v5.8.1. No special settings should be required.

       How can I install the pure-Perl version of Xslate?

       Pass "PUREPERL_ONLY=1" to Makefile.PL, which requests the Xslate build system not to make
       XS parts.

       Note that "cpanm 1.7" supports "--pp" option to install pure-Perl alternatives, so you can
       type "cpanm --pp Text::Xslate".

       What optimizations does Xslate employs?

       Here are some optimizations worth noting that makes Text::Xslate run so fast, in no
       particular order:

       Pre-compiled templates
           Text::Xslate is among the template engines that pre-compile the templates.  This is
           similar to, say, Template::Toolkit, but Text::Xslate compiles the templates to C
           structures and stores them as binary data.

       Built on top of a virtual machine
           Text::Xslate is built on top of virtual machine that executes bytecode, and this
           virtual machine is fine-tuned specifically for template processing.

           The virtual machine also employs optimizations such as direct-threading style coding
           to shave off any extra milliseconds that the engine might take otherwise

       Custom byte codes for oft-used operations
           Some operations which are used very often are optimized into its own byte code. For
           example (as described elsewhere) Text::Xslate automatically escapes HTML unless you
           tell it not to. Text::Xslate implements this process which involves escaping the
           string while appending the result to the output buffer in C, as a custom byte code.
           This lets you avoid the penalties usually involved in such operations.

       Pre-allocation of output buffers
           One of the main things to consider to reduce performance degradation while processing
           a template is to avoid the number of calls to "malloc()".  One of the tricks that
           Text::Xslate employs to reduce the number of calls to "malloc()" is to pre-allocate
           the output buffer in an intelligent manner: For example, Text::Xslate assumes that
           most templates will be rendered to be about the same as the previous run, so when a
           template is rendered it uses the size allocated for the previous rendering as an
           approximation of how much space the current rendering will require. This allows you to
           greatly reduce the number of "malloc()" calls required to render a template.

       How can I throw errors in functions and/or methods?

       Handle warnings by "warn_handler" and raises exceptions if needed.

       That's because Xslate catches exceptions in templates and emits them as warnings.

   Configuration
       When I create the Xslate instance?

       Xslate instances are reusable and creating the instance costs somewhat so you're
       recommended to reuse them as much as possible.  That is, you should make the instance
       global.

       Consider a PSGI application:

           # create Xslate here, not in psgi_app();
           my $xslate = Text::Xslate->new(...);

           sub psgi_app {
               my($env) = @_;
               # use $xslate and create $response
               return $response;
           }
           return \&psgi_app; # as a PSGI app

       Don't create the instance in each request. It's less efficient.

       How can I change instance attributes dynamically?

       Instance attributes, e.g. "include_path", "function", or "syntax", are immutable, so you
       cannot change them dynamically.

       Instead, you can create multiple instances by different options.  instance in order to
       avoid conflicts with cache directories.

       For example:

           my %common_config = ( cache_dir => $dir, module => \@module );
           my %xslate = (
               ja => Text::Xslate->new( path => [ $template_ja ], %common_config ),
               en => Text::Xslate->new( path => [ $template_en ], %common_config ),
               ro => Text::Xslate->new( path => [ $template_ro ], %common_config ),
           );
           $xslate{$lang}->render(...);

   Templates
       How can I changes template tags?

       Use "start_tag", "end_tag", and "line_start" options to "new" method, which can be joined
       together with "syntax" option:

           my $tx = Text::Xslate->new(
               syntax     => 'TTerse',
               tag_start  => '{{',
               tag_end    => '}}',
               line_start => undef,
           );
           print $tx->render_string('Hello, {{lang}} world!', { lang => 'Xslate' });

       Note that you'd better to avoid symbols which can be used for operators.

       How can I iterate over HASH references?

       Convert HASH references into ARRAY references because "for" methods can deal with just
       ARRAY references.

           : # in Kolon
           : # iterate $hash by keys
           : for $hash.keys() -> $key {
               <: $key :>
           : }
           : # by values
           : for $hash.values() -> $value {
               <: $value :>
           : }
           : # by key-value pairs
           : for $hash.kv() -> $pair {
               <: $pair.key :>=<: $pair.value :>
           : }

       Note that the above methods return ARRAY references sorted by the keys.

       How can I use Template-Toolkit virtual methods and filters?

       Xslate itself does not support these methods and filters, but there are modules on CPAN
       that implement them.

       Text::Xslate::Bridge::TT2 provides almost all the TT methods and filters, but it requires
       Template-Toolkit installed.

       Text::Xslate::Bridge::TT2Like provides the same features as "T::X::Bridge::TT2", and it
       does not require the Template-Toolkit runtime.

       These bridge modules are useful not only for TTerse users, but also for Kolon users.

       How can I (write|get) plugins?

       It is unlikely to need to write plugins for Xslate, because Xslate allows you to export
       any functions to templates. Any function-based modules are available by the "module"
       option.

       Xslate also allows you to call methods for object instances, so you can use any object-
       oriented modules, except for classes which only provide class methods (they need
       wrappers).

       If you want to add methods to builtin data types (nil, scalars, arrays and hashes), you
       can write bridge modules. See Text::Xslate::Bridge for details.

       How to limit while-loop like Template-Toolkit?

       While Template-Toolkit has a loop counter to prevent runaway "WHILE" loop, Xslate has no
       arbitrary limitation.

       Instead, you can use "alarm()" to limit any runaway code:

           eval {
               local $SIG{ALRM} = sub { die @_ };
               alarm(1); # set timeout
               $tx->render('<: while true { } :>', \%vars);
           };
           if($@ =~ /\b ALRM \b/xms) {
               # timeout!
           }

       Does Xslate process text strings, or binary strings?

       (The meaning of text string and binary string is that of Perl, see perlunifaq.)

       Xslate assumes template files to be encoded in "UTF-8" by default, so the output is a text
       string and template parameters, including values which registered functions return, must
       be text strings.

       However, if you want to process binary strings, you can do so by passing ":bytes" to
       "input_layer", although it's not recommended.

       Why doesn't I cannot access $object.attr like TT2?

       Template-Toolkit allows objects (i.e. blessed references) to access its element if the
       object has no accessor methods, i.e. "[% object.attr %]" might mean "$object->{attr}".
       This behavior breaks encapsulation and hides typos, so Xslate doesn't allow such
       fallbacks.

       If you want to access object attributes, define the accessors of them, or prepare values
       as a non-object before calling "render()".

       Can I load macros in other template files?

       Not yet. Currently Xslate doesn't support external macros.

   Functions, filters and macros
       Where are the list of builtin functions?

       See Text::Xslate::Manual::Builtin.

       How can I use macros as a callback to high-level functions?

       Macros are objects that overload "&{}", the CODE dereference operator, so all you have to
       do is to call them simply, but don't check their types because they are not a real CODE
       reference.

           my $tx = Text::Xslate->new(
               function => {
                   count => sub {
                       my($a, $cb) = @_;
                       # Don't check the type of $cb!
                       return scalar grep { $cb->($_) } @{$a};
                   },
               },
           );

           print $tx->render_string('<: count($a, -> $x { $x >= 50 }) :>',
               { a => [ 0 .. 100 ] },
           ); # => 50

   Web Application Frameworks
       How can I use Xslate in $my_favorite_WAF?

       There are bridges that integrate Xslate into WAFs:

       ·   Catalyst::View::Xslate for Catalyst

       ·   MojoX::Renderer::Xslate for Mojolicious

       ·   Tiffany for general usage

       There are WAFs which adopt Xslate as the default template engine:

       ·   Amon2

       ·   Pickles

       Where are examples which use Xslate in Catalyst?

       There is a real-world project that uses Xslate with Catalyst.

       <https://github.com/duckduckgo/community-platform>

       Initializing Xslate:
       <https://github.com/duckduckgo/community-platform/blob/master/lib/DDGC.pm#L268>

       Working on: <https://dukgo.com/>

       Enjoy!

   Development and support
       How can I colorize Xslate templates?

       For "vim" user, there is xslate.vim for Kolon:

       <https://github.com/motemen/xslate-vim>

       For "emacs" user, there are plugins:

       <https://github.com/samvtran/kolon-mode>

       <https://github.com/yoshiki/tx-mode>

       Where can I ask questions?

       The mailing list is recommended to ask questions.

       <http://groups.google.com/group/xslate>

       If you find a bug or have a request, creating github issues is better because those
       tickets are less likely to disappear than the ports in the mailing list.

       <https://github.com/xslate/p5-Text-Xslate/issues>

       I found a bug! What can I do for you?

       Please make a minimal test case to show the problem clearly.  The code is the common
       language both I and you speak fluently ;)

SEE ALSO

       Text::Xslate

       Text::Xslate::Manual

       Text::Xslate::Manual::Cookbook