Template::Stash - Magical storage for template variables
use Template::Stash;
my $stash = Template::Stash->new(\%vars);
# get variable values
$value = $stash->get($variable);
$value = $stash->get(\@compound);
# set variable value
$stash->set($variable, $value);
$stash->set(\@compound, $value);
# default variable value
$stash->set($variable, $value, 1);
$stash->set(\@compound, $value, 1);
# set variable values en masse
$stash->update(\%new_vars)
# methods for (de-)localising variables
$stash = $stash->clone(\%new_vars);
$stash = $stash->declone();
The Template::Stash module defines an object class which is used to store
variable values for the runtime use of the template processor. Variable
values are stored internally in a hash reference (which itself is blessed
to create the object) and are accessible via the get() and set() methods.
Variables may reference hash arrays, lists, subroutines and objects
as well as simple values. The stash automatically performs the right
magic when dealing with variables, calling code or object methods,
indexing into lists, hashes, etc.
The stash has clone() and the declone() manpage methods which are used by the
template processor to make temporary copies of the stash for
localising changes made to variables.
The new() constructor method creates and returns a reference to a new
Template::Stash object.
my $stash = Template::Stash->new();
A hash reference may be passed to provide variables and values which
should be used to initialise the stash.
my $stash = Template::Stash->new({ var1 => 'value1',
var2 => 'value2' });
The get() method retrieves the variable named by the first parameter.
$value = $stash->get('var1');
Dotted compound variables can be retrieved by specifying the variable
elements by reference to a list. Each node in the variable occupies
two entries in the list. The first gives the name of the variable
element, the second is a reference to a list of arguments for that
element, or 0 if none.
[% foo.bar(10).baz(20) %]
$stash->get([ 'foo', 0, 'bar', [ 10 ], 'baz', [ 20 ] ]);
The set() method sets the variable name in the first parameter to the
value specified in the second.
$stash->set('var1', 'value1');
If the third parameter evaluates to a true value, the variable is
set only if it did not have a true value before.
$stash->set('var2', 'default_value', 1);
Dotted compound variables may be specified as per get() above.
[% foo.bar = 30 %]
$stash->set([ 'foo', 0, 'bar', 0 ], 30);
The magical variable 'IMPORT ' can be specified whose corresponding
value should be a hash reference. The contents of the hash array are
copied (i.e. imported) into the current namespace.
# foo.bar = baz, foo.wiz = waz
$stash->set('foo', { 'bar' => 'baz', 'wiz' => 'waz' });
# import 'foo' into main namespace: bar = baz, wiz = waz
$stash->set('IMPORT', $stash->get('foo'));
This method can be used to set or update several variables in one go.
$stash->update({
foo => 10,
bar => 20,
});
This undocumented feature returns a closure which can be called to get the
value of a variable. It is used to implement variable references which are
evaluated lazily.
[% x = \foo.bar.baz %] # x is a reference to foo.bar.baz
[% x %] # evalautes foo.bar.baz
The clone() method creates and returns a new Template::Stash object
which represents a localised copy of the parent stash. Variables can be freely
updated in the cloned stash and when the declone() manpage is called, the original stash
is returned with all its members intact and in the same state as they were
before clone() was called.
For convenience, a hash of parameters may be passed into clone() which
is used to update any simple variable (i.e. those that don't contain any
namespace elements like foo and bar but not foo.bar ) variables while
cloning the stash. For adding and updating complex variables, the set()
method should be used after calling clone(). This will correctly resolve
and/or create any necessary namespace hashes.
A cloned stash maintains a reference to the stash that it was copied
from in its _PARENT member.
The declone() method returns the _PARENT reference and can be used to
restore the state of a stash as described above.
This method can be used to define new virtual methods. The first argument
should be either scalar or item to define scalar virtual method, hash
to define hash virtual methods, or either array or list for list virtual
methods. The second argument should be the name of the new method. The third
argument should be a reference to a subroutine implementing the method. The
data item on which the virtual method is called is passed to the subroutine as
the first argument.
$stash->define_vmethod(
item => ucfirst => sub {
my $text = shift;
return ucfirst $text
}
);
This is the core dot operation method which evaluates elements of
variables against their root.
This method is called when get() encounters an undefined value. If the
STRICT option is in effect then it will
throw an exception indicating the use of an undefined value. Otherwise it
will silently return an empty string.
The method can be redefined in a subclass to implement alternate handling
of undefined values.
Andy Wardley <abw@wardley.org> http://wardley.org/
Copyright (C) 1996-2013 Andy Wardley. All Rights Reserved.
This module is free software; you can redistribute it and/or
modify it under the same terms as Perl itself.
Template, the Template::Context manpage
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