/ 
Text-Xslate-0.1044
River stage two • 72 direct dependents • 86 total dependents
/ Text::Xslate::Syntax::Kolon

NAME

Text::Xslate::Syntax::Kolon - The default template syntax

SYNOPSIS

use Text::Xslate;
my $tx = Text::Xslate->new(
    syntax => 'Kolon', # optional
);

print $tx->render_string(
    'Hello, <: $dialect :> world!',
    { dialect => 'Kolon' }
);

DESCRIPTION

Kolon is the default syntax, using <: ... :> tags and : ... line code.

SYNTAX

Variable access

Variable access:

<: $var :>

Field access:

<: $var.0 :>
<: $var.field :>
<: $var.accessor :>

<: $var["field"] :>
<: $var[0] :>

Variables may be HASH references, ARRAY references, or objects. Because $var.field and $var["field"] are the same semantics, $obj["accessor"] syntax may be call object methods.

Literals

Special:

: nil   # indicates "nothing"
: true  # as the integer 1
: false # as the integer 0

String:

: "foo\n" # the same as perl
: 'foo\n' # the same as perl

Number:

: 42
: 3.14
: 0xFF
: 0b1010

Array:

: for [1, 2, 3] -> $i { ... }

Hash:

: foo({ foo => "bar" })

{ ... } is always parsed as hash literals, so you need not to use prefix + as Perl sometimes requires:

:  {}.kv(); # ok
: +{}.kv(); # also ok

Expressions

Conditional operator (?:):

: $var.value == nil ? "nil" : $var.value

Relational operators (== != < <= > >=):

: $var == 10 ? "10"     : "not 10"
: $var != 10 ? "not 10" : "10"

Note that == and != are similar to Perl's eq and ne except that $var == nil is true iff $var is uninitialized, while other relational operators are numerical.

Arithmetic operators (+ - * / % min max):

: $var * 10_000
: ($var % 10) == 0
: 10 min 20 min 30 # 10
: 10 max 20 max 30 # 30

Logical operators (! && || // not and or)

: $var >= 0 && $var <= 10 ? "ok" : "too smaller or too larger"
: $var // "foo" # as a default value

String operators (~)

: "[" ~ $var ~ "]" # concatination

Operator precedence is the same as Perl's:

. () []
! prefix<+> prefix<->
* / %
+ - ~
prefix<defined>
< <= > >=
== !=
|
&&
|| // min max
?:
not
and
or

Constants (or binding)

You can define lexical constants with constant, which requires a bare name, and my, which requires a variable name.

: constant FOO = 42;
: my      $foo = 42;

These two statements has the same semantics, so you cannot modify $foo.

: my $foo = 42; $foo = 3.14; # compile error!

Loops

There is for loops that are like Perl's foreach.

: # $data must be an ARRAY reference
: for $data -> $item {
    [<: $item.field :>]
: }

You can get the iterator index in for statements as $~ITERATOR_VAR:

: for $data -> $item {
    : if ($~item % 2) == 0 {
        Even (0, 2, 4, ...)
    : }
    : else {
        Odd (1, 3, 5, ...)
    : }
: }

$~item is a pseudo object, so you can access its elements via the dot-name syntax.

: for $data -> $i {
    : $~i       # iterator index (0, 1, 2, ...)
    : $~i.index # the same as $~i
    : $~i.count # the same as $~i + 1

    : if ($~i.index % 2) == 0 {
        even
    : }
    : else {
        odd
    : }
    : $i~.cycle("even", "odd") # => "even" -> "odd" -> "even" -> "odd" ...
: }

Supported iterator elements are index :Int, count :Int, body : ArrayRef, size : Int, max_index :Int, is_first :Bool, is_last :Bool, peek_next :Any, peek_prev :Any, cycle(...) :Any.

while loops are also supported in the same semantics as Perl's:

: # $obj might be an iteratable object
: while $dbh.fetch() -> $item {
    [<: $item.field :>]
: }

while defined expr -> $item is interpreted as while defined(my $item = expr) for convenience.

: while defined $obj.fetch() -> $item {
    [<: $item # $item can be false-but-defined:>]
: }

Conditional statements

There are if-else and given-when conditional statements.

if-else:

: if $var == nil {
    $var is nil.
: }
: else if $var != "foo" { # elsif is okay
    $var is not nil nor "foo".
: }
: else {
    $var is "foo".
: }

: if( $var >= 1 && $var <= 10 ) {
    $var is 1 .. 10
: }

Note that if doesn't require parens, so the following code is okay:

: if ($var + 10) == 20 { } # OK

given-when(also known as switch statement):

: given $var {
:   when "foo" {
        it is foo.
:   }
:   when ["bar", "baz" ] {
        it is either bar or baz.
:   }
:   default {
        it is not foo nor bar.
    }
: }

You can specify the topic variable.

: given $var -> $it {
:   when "foo" {
        it is foo.
:   }
:   when $it == "bar" or $it == "baz" {
        it is either bar or baz.
:   }
: }

Functions and filters

You can register functions via function or module options for Text::Xslate->new().

Once you have registered functions, you can call them with the () operator. infix:<|> is also supported as a syntactic sugar to ().

: f()        # without args
: f(1, 2, 3) # with args
: 42 | f     # the same as f(42)

Functions are Perl's subroutines, so you can define dynamic functions:

# code
sub mk_indent {
    my($prefix) = @_;
    return sub {
        my($str) = @_;
        $str =~ s/^/$prefix/xmsg;
        return $str;
    }
}
my $tx = Text::Xslate->new(
    function => {
        indent => \&mk_indent,
    },
);

:# template
: $value | indent("> ")
: indent("> ")($value)

There are several builtin functions, which you cannot redefine:

: $var | mark_raw   # marks it as a raw string
: $var | raw        # synonym to mark_raw
: $var | unmark_raw # removes "raw" marker from it
: $var | html       # does html-escape to it and marks it as raw
: $var | dump       # dumps it with Data::Dumper

Note that you should not use mark_raw in templates because it can make security hole easily just like as type casts in C. If you want to generate HTML components dynamically, e.g. by HTML form builders, application code should be responsible to make strings as marked raw.

Methods

When $var is an object instance, you can call its methods with the dot operator.

<: $var.method() :>
<: $var.method(1, 2, 3) :>
<: $var.method( foo => [ 1, 2, 3 ] ) :>

There is an autoboxing mechanism that provides primitive types with builtin methods.

For any primitive types:

# note that if $any is an object, defined() will return nil
# unless the object has defined() method.
<: $any.defined() :>

For arrays:

<: $array.size() :>
<: $array.join(",") :>
<: $array.reverse() :>
<: $array.map(-> $x { $x + 1 }) :>
<: $array.sort(-> $x, $y { $x <=> $y }) :>
<: $array.reduce(-> $x, $y { $x min $y }) :>

For hashes:

<: $hash.size() :>
<: $hash.keys()   # sorted by keys :>
<: $hash.values() # sorted by keys :>
<: for $hash.kv() -> $pair { # sorted by keys :>
    <: # $pair is a pair type with 'key' and 'value' fields -:>
    <: $pair.key :> = <: $pair.value :>
<: } :>

You can define more methods with the function option. See Text::Xslate.

Template inclusion

Template inclusion is a traditional way to extend templates.

: include "foo.tx";
: include "foo.tx" { var1 => value1, var2 => value2, ... };

Xslate templates may be recursively included, but the including depth is limited to 100.

Template cascading

Template cascading is another way to extend templates other than include.

First, make base templates myapp/base.tx:

: block title -> { # with default
    [My Template!]
: }

: block body -> { } # without default

Then extend from base templates with the cascade keyword:

: cascade myapp::base
: cascade myapp::base { var1 => value1, var2 => value2, ...}
: cascade myapp::base with myapp::role1, myapp::role2
: cascade with myapp::role1, myapp::role2

In derived templates, you may extend templates (e.g. myapp/foo.tx) with block modifiers before, around (or override) and after.

: # cascade "myapp/base.tx" is also okay
: cascade myapp::base
: # use default title
: around body -> {
    My template body!
: }

And, make yet another derived template myapp/bar.tx:

: cascade myapp::foo
: around title -> {
    --------------
    : super
    --------------
: }
: before body -> {
    Before body!
: }
: after body -> {
    After body!
: }

Then render it as usual.

my $tx = Text::Xslate->new( file => 'myapp/bar.tx' );
$tx->render({});

The result is something like this:

--------------
[My Template!]
--------------

Before body!
My template tody!
After body!

You can also cascade templates just like Moose's roles:

: cascade myapp::base with myapp::role1, myapp::role2

You can omit the base template.

Given a file myapp/hello.tx:

: around hello -> {
    --------------
    : super
    --------------
: }

Then the main template:

: cascade with myapp::hello

: block hello -> {
    Hello, world!
: }

Output:

--------------
Hello, world!
--------------

In fact, you can omit the base template, and components can include any macros.

Given a file common.tx

: macro hello -> $lang {
    Hello, <: $lang :> world!
: }

: around title -> {
    --------------
    : super
    --------------
: }

The main template:

: cascade with common

: block title -> {
    Hello, world!
: }
: hello("Xslate")

Output:

    --------------
    Hello, world!
    --------------
Hello, Xslate world!

There is a limitation that you cannot pass variables to the cascade keyword, because template cascading is statically processed.

Macro blocks

Macros are supported, which are called in the same way as functions and return a raw string. Macros returns what their bodies render, so macros cannot returns references nor objects including other macros.

: macro add ->($x, $y) {
:   $x + $y;
: }
: add(10, 20)

: macro signeture -> {
    This is foo version <: $VERSION :>
: }
: signeture()

: macro factorial -> $x {
:   $x == 0 ? 1 : $x * factorial($x-1)
: }
: factorial(1)  # as a function
: 1 | factorial # as a filter

If you want to html-escape the return values of macros, you can use unmark_raw to remove raw-ness from the values.

: macro em -> $s {
<em><: $s :></em>
: }
: em("foo")               # renders "<em>foo</em>"
: em("foo") | unmark_raw  # renders "&lt;em&gt;foo&lt;em&gt;"

Macros are first-class objects, so you can bind them to symbols.

<: macro foo -> { "foo" }
   macro bar -> { "bar" }
   my $dispatcher = {
       foo => foo,
       bar => bar,
   }; -:>
: $dispatcher{$key}()

Anonymous macros are also supported, although they can return only strings.

<: -> $x, $y { $x + $y }(1, 2) # => 3 :>

The block keyword is used to make a group of template code, and you can apply filters to that block with infix:<|>. Here is an example to embed HTML source code into templates.

Template: : block source | unmark_raw -> { <em>Hello, world!</em> : }

Output: &lt;em&gt;Hello, world!&lt;/em&gt;

See also "Using FillInForm" in Text::Xslate::Cookbook for another example to use this block filter syntax.

Comments

Comments start from # to a new line or semicolon.

:# this is a comment
<:
  # this is also a comment
  $foo # $foo is rendered
:>

<: $bar # this is ok :>
<: # this is comment; $baz # $baz is rendered :>

SEE ALSO

Text::Xslate

Text::Xslate::Cookbook