NAME¶
Text::MicroMason::Base - Abstract Template Compiler
SYNOPSIS¶
Create a MicroMason object to interpret the templates:
use Text::MicroMason;
my $mason = Text::MicroMason->new();
Use the execute method to parse and evalute a template:
print $mason->execute( text=>$template, 'name'=>'Dave' );
Or compile it into a subroutine, and evaluate repeatedly:
$coderef = $mason->compile( text=>$template );
print $coderef->('name'=>'Dave');
print $coderef->('name'=>'Bob');
Templates stored in files can be run directly or included in others:
print $mason->execute( file=>"./greeting.msn", 'name'=>'Charles');
DESCRIPTION¶
Text::MicroMason::Base is an abstract superclass that provides a parser and
execution environment for an extensible templating system.
Public Methods¶
- new()
-
$mason = Text::MicroMason::Base->new( -Mixin1, -Mixin2, %attribs );
Creates a new Text::MicroMason object with mixins and attributes.
Arguments beginning with a dash will be added as mixin classes. Other
arguments are added to the hash of attributes.
- compile()
-
$code_ref = $mason->compile( text => $template, %options );
$code_ref = $mason->compile( file => $filename, %options );
Parses the provided template and converts it into a new Perl
subroutine.
- execute()
-
$result = $mason->execute( text => $template, @arguments );
$result = $mason->execute( file => $filename, @arguments );
$result = $mason->execute( code => $code_ref, @arguments );
$result = $mason->execute( $type => $source, \%options, @arguments );
Returns the results produced by the template, given the provided
arguments.
Attributes¶
Attributes can be set in a call to
new() and locally overridden in a call
to
compile().
- output_sub
- Optional reference to a subroutine to call with each piece of template
output. If this is enabled, template subroutines will return an empty
string.
Private Methods¶
The following internal methods are used to implement the public interface
described above, and may be overridden by subclasses and mixins.
- class()
-
$class = Text::MicroMason::Base->class( @Mixins );
Creates a subclass of this package that also inherits from the other classes
named. Provided by Class::MixinFactory::HasAFactory.
- create()
-
$mason = $class->create( %options );
$clone = $mason->create( %options );
Creates a new instance with the provided key value pairs.
To obtain the functionality of one of the supported mixin classes, use the
class method to generate the mixed class before calling create(),
as is done by new().
- defaults()
- This class method is called by new() to provide key-value pairs to
be included in the new instance.
- prepare()
-
($self, $src_type, $src_data) = $self->prepare($src_type, $src_data, %options)
Called by compile(), the prepare method allows for single-use
attributes and provides a hook for mixin functionality.
The prepare method provides a hook for mixins to normalize or resolve the
template source type and value arguments in various ways before the
template is read using one of the read_type() methods.
It returns an object reference that may be a clone of the original mason
object with various compile-time attributes applied. The cloning is a
shallow copy performed by the create() method. This means that the
$m object visible to a template may not be the same as the MicroMason
object on which compile() was originally called.
Please note that this clone-on-prepare behavior is subject to change in
future releases.
- interpret
-
$perl_code = $mason->interpret( $src_type, $src_data );
Called by compile(), the interpret method then calls the
read(), lex(), and assemble() methods.
- read
-
$template = $mason->read( $src_type, $src_data );
Called by interpret(). Calls one of the below read_* methods.
- read_text
-
$template = $mason->read_text( $template );
Called by read() when the template source type is "text",
this method simply returns the value of the text string passed to it.
- read_file
-
( $contents, %path_info ) = $mason->read_file( $filename );
Called by read() when the template source type is "file",
this method reads and returns the contents of the named file.
- read_handle
-
$template = $mason->read_handle( $filehandle );
Called by read() when the template source type is "handle",
this method reads and returns the contents of the filehandle passed to
it.
- lex
-
@token_pairs = $mason->lex( $template );
Called by interpret(). Parses the source text and returns a list of
pairs of token types and values. Loops through repeated calls to
lex_token().
- lex_token
-
( $type, $value ) = $mason->lex_token();
Attempts to parse a token from the template text stored in the global $_ and
returns a token type and value. Returns an empty list if unable to parse
further due to an error.
Abstract method; must be implemented by subclasses.
- assemble
-
$perl_code = $mason->assemble( @tokens );
Called by interpret(). Assembles the parsed token series into the
source code for the equivalent Perl subroutine.
- assembler_rules()
- Returns a hash of text elements used for Perl subroutine assembly. Used by
assemble().
The assembly template defines the types of blocks supported and the order
they appear in, as well as where other standard elements should go. Those
other elements also appear in the assembler hash.
- eval_sub
-
$code_ref = $mason->eval_sub( $perl_code );
Called by compile(). Compiles the Perl source code for a template
using eval(), and returns a code reference.
- croak_msg
- Called when a fatal exception has occurred.
- NEXT
- Enhanced superclass method dispatch for use inside mixin class methods.
Allows mixin classes to redispatch to other classes in the inheritance
tree without themselves inheriting from anything. Provided by
Class::MixinFactory::NEXT.
Private Functions¶
- _printable
-
$special_characters_escaped = _printable( $source_string );
Converts non-printable characters to readable form using the standard
backslash notation, such as "\n" for newline.
EXTENDING¶
You can add functionality to this module by creating subclasses or mixin
classes.
To create a subclass, just inherit from the base class or some
dynamically-assembled class. To create your own mixin classes which can be
combined with other mixin features, examine the operation of the
class() and
NEXT() methods.
Key areas for subclass writers are:
- prepare
- You can intercept and re-write template source arguments by overriding
this method.
- read_*
- You can support a new template source type by creating a method with a
corresponding name prefixed by "read_". It is passed the
template source value and should return the raw text to be lexed.
For example, if a subclass defined a method named read_from_db, callers
could compile templates by calling "->compile( from_db =>
'welcome-page' )".
- lex_token
- Replace this to parse a new template syntax. Is receives the text to be
parsed in $_ and should match from the current position to return the next
token type and its contents.
- assembler_rules
- The assembler data structure is used to construct the Perl subroutine for
a parsed template.
- assemble_*
- You can support a new token type be creating a method with a corresponding
name prefixed by "assemble_". It is passed the token value or
contents, and should return a new token pair that is supported by the
assembler template.
For example, if a subclass defined a method named assemble_sqlquery, callers
could compile templates that contained a "<%sqlquery> ...
</%sqlquery>" block. The assemble_sqlquery method could return
a "perl => $statements" pair with Perl code that performed
some appropriate action.
- compile
- You can wrap or cache the results of this method, which is the primary
public interface.
- execute
- You typically should not depend on overriding this method because callers
can invoke the compiled subroutines directly without calling execute.
SEE ALSO¶
For an overview of this templating framework, see Text::MicroMason.
For distribution, installation, support, copyright and license information, see
Text::MicroMason::Docs::ReadMe.