component(3)

NAME

HTML::Mason::Component - Mason Component Class

SYNOPSIS

my $comp1 = $m->current_comp;
my $comp2 = $m->callers(1);
my $comp3 = $m->fetch_comp('foo/bar');
foreach ($comp1,$comp2,$comp3) {
   print "My name is ".$_->title.".0;
}

DESCRIPTION

Mason uses the Component class to store components loaded
into memory. Components come from three distinct sources:

1 File-based: loaded from a source or object file.

2 Subcomponents: embedded components defined with the: "<%def>" tag.
3 Anonymous: created on-the-fly with the "make_compo: nent" Parser method.
Some of the methods below return different values (or nothing at all) depending on the component type.
The component API is primarily useful for introspection, e.g. "what component called me" or "does the next compo nent take a certain argument". You can build complex Mason sites without ever dealing directly with a component object.
CREATING AND ACCESSING COMPONENTS
Common ways to get handles on existing component objects include the the current_comp entry in the Request manpage, the callers entry in the Request manpage, and the fetch_comp entry in the Request manpage Request methods.
There is no published "new" method, because creating a component requires a parser. Use the the make_component entry in the Parser manpage Parser method to create a new component dynamically.
Similarly, there is no "execute" or "call" method, because calling a component requires a request. All of the inter faces for calling a component (<& &>, "$m-"comp>, "$interp->exec" which normally take a component path, will also take a component object.

METHODS

attr (name): Looks for the specified attribute in this component
and its parents, returning the first value found. Dies
with an error if not found. Attributes are declared in
the "<%attr>" section.
attr_exists (name): Returns true if the specified attribute exists in this
component or one of its parents, undef otherwise.
cache_file: Returns the data cache filename for this component.
create_time: Returns the time (in Perl time() format) when this
component object was created.
declared_args: Returns a reference to a hash of hashes representing
the arguments declared in the "<%args>" section. The
keys of the main hash are the variable names including
prefix (e.g. "$foo", "@lst"). Each secondary hash
contains:; � 'default': the string specified for default value
(e.g. 'fido') or undef if none specified. Note
that in general this is not the default value
itself but rather an expression that gets evalu
ated every time the component runs.; For example:

# does $comp have an argument called $fido?
if (exists($comp->declared_args->{'$fido'})) { ... }

# does $fido have a default value?
if (defined($comp->declared_args->{'$fido'}->{de

fault})) { ... }; dir_path
Returns the component's notion of a current directory,
relative to the component root; this is used to
resolve relative component paths. For file-based com
ponents this is the full component path minus the
final piece. For subcomponents this is the same as
its parent component. Undefined for anonymous compo
nents.; first_time
Returns true if this is the first time the component
has executed, false otherwise. Useful for initializ
ing persistent component lexicals:

if ($m->current_comp->first_time) {
$dbh = DBI->connect(...);

Note that in a web-based environment, this "first
time" will come once for each child and every time the
component is reloaded.

flag (name)

Returns the value for the specified system flag.
Flags are declared in the "<%flags>" section and
affect the behavior of the component.

is_subcomp

Returns true if this is a subcomponent of another com
ponent.

is_file_based

Returns true if this component was loaded from a
source or object file.

call_method (name, args...)

Looks for the specified user-defined method in this
component and its parents, calling the first one
found. Dies with an error if not found. Methods are
declared in the "<%method>" section.

method_exists (name)

Returns true if the specified user-defined method
exists in this component or one of its parents, undef
otherwise.

name

Returns a short name of the component. For file-based
components this is the filename without the path. For
subcomponents this is the name specified in "<%def>".
Undefined for anonymous components.

object_file

Returns the object filename for this component.

owner

Defined only for subcomponents; returns the component
that this subcomponent was defined in.

parent

Returns the parent of this component for inheritance
purposes, by default the nearest "autohandler" in or
above the component's directory. Can be changed via
the "inherit" flag.

path

Returns the absolute path of this component.

run_count

Returns the number of times this component has been
invoked. In a web-based environment, this value is
separate for each child and resets every time the com
ponent is reloaded.

scall_method (name, args...)

Like the call_method entry in the Component manpage,
but returns the method output as a string instead of
printing it. (Think sprintf versus printf.) The
method's return value is discarded.

subcomps

With no arguments, returns a hashref containing the
subcomponents defined in this component, with names as
keys and component objects as values. With one argu
ment, returns the subcomponent of that name or undef
if no such subcomponent exists. e.g.

if (my $subcomp = $comp->subcomps('.link')) {
...

}

Subcomponents are declared in the "<%def>" section.

title

Returns a printable string denoting this component.
It is intended to uniquely identify a component within
a given interpreter although this is not 100% guaran
teed. Mason uses this string in error messages, the
previewer component trace, and "$m-"comp_stack>.

For file-based components this is the component path.
For subcomponents this is "parent_component_path:sub
component_name". For anonymous components this is a
unique label like "[anon 17]".

FILE-BASED METHODS

The following methods apply only to file-based components
(those loaded from source or object files). They return
undef for other component types.

source_file: Returns the source filename for this component.
source_dir: Returns the directory of the source filename for this
component.

AUTHOR

Jonathan Swartz, swartz@pobox.com

docs.sk

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