HTML::Mason::Component - Mason Component Class

- NAME
- SYNOPSIS
- DESCRIPTION

- CREATING AND ACCESSING COMPONENTS

- METHODS
- FILE-BASED METHODS
- SEE ALSO

# 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.".\n";
        }

# DESCRIPTION

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

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

Subcomponents: embedded components defined with the `<%def>` or `<%method>` tags.

Anonymous: created on-the-fly with the `make_component` Interp 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 component 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 Request->current_comp, Request->callers, and Request->fetch_comp methods.

There is no published `new` method, because creating a component requires an Interpreter. Use the Interp's make_component 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 interfaces 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_if_exists (name)
  This method works exactly like the one above but returns undef if the attribute does not exist.

attr_exists (name)
  Returns true if the specified attribute exists in this component or one of its parents, undef otherwise.

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.

create_time
  A synonym for load_time (deprecated).

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`, `@list`). 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 a Perl expression that gets evaluated 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'}->{default})) { ... }

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 components this is the full component path minus the filename. For subcomponents this is the same as the component that defines it. Undefined for anonymous components.

flag (name)
  Returns the value for the specified system flag. Flags are declared in the `<%flags>` section and affect the behavior of the component. Unlike attributes, flags values do not get inherited from parent components.

is_subcomp
  Returns true if this is a subcomponent of another component. For historical reasons, this returns true for both methods and subcomponents.

is_method
  Returns true if this is a method.

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

load_time
  Returns the time (in Perl `time()` format) when this component object was created.

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

methods
  This method works exactly like the subcomps method, but it returns methods, not subcomponents.

  Methods are declared in `<%method>` sections.

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 entire path of this component, relative to the component root.

scall_method (name, args...)
  Like Component->call_method (name, args...), but returns the method output as a string instead of printing it. (Think sprintf versus printf.) The method's return value, if any, 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 argument, 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 `<%def>` sections.

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% guaranteed. Mason uses this string in error messages, among other places.

  For file-based components this is the component path. For subcomponents this is ``parent_component_path:subcomponent_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.

# SEE ALSO

HTML::Mason, HTML::Mason::Devel, HTML::Mason::Request