DESCRIPTION

This is a base class for packages, classes, and objects which need to manage basic functionality in the UR framework such as inheritance, AUTOLOAD/AUTOSUB methods, error/status/warning/etc messages.

UR::ModuleBase is in the @ISA list for UR::Object, but UR::ModuleBase is not a formal UR class.

METHODS

"class"

  $class = $obj->class;

This returns the class name of a class or an object as a string. It is exactly equivalent to:

    (ref($self) ? ref($self) : $self)

"super_can"

  $sub_ref = $obj->super_can('func');

This method determines if any of the super classes of the $obj object can perform the method "func". If any one of them can, reference to the subroutine that would be called (determined using a depth-first search of the @ISA array) is returned. If none of the super classes provide a method named "func", "undef" is returned.

"inheritance"

  @classes = $obj->inheritance;

This method returns a depth-first list of all the classes (packages) that the class that $obj was blessed into inherits from. This order is the same order as is searched when searching for inherited methods to execute. If the class has no super classes, an empty list is returned. The "UNIVERSAL" class is not returned unless explicitly put into the @ISA array by the class or one of its super classes.

"parent_classes"

  MyClass->parent_classes;

This returns the immediate parent class, or parent classes in the case of multiple inheritance. In no case does it follow the inheritance hierarchy as ->inheritance() does.

"base_dir"

  MyModule->base_dir;

This returns the base directory for a given module, in which the modules's supplemental data will be stored, such as config files and glade files, data caches, etc.

It uses %INC.

methods

Undocumented.

"context_return"

  return MyClass->context_return(@return_values);

Attempts to return either an array or scalar based on the calling context. Will die if called in scalar context and @return_values has more than 1 element.

AUTOLOAD

This package impliments AUTOLOAD so that derived classes can use AUTOSUB instead of AUTOLOAD.

When a class or object has a method called which is not found in the final class or any derived classes, perl checks up the tree for AUTOLOAD. We impliment AUTOLOAD at the top of the tree, and then check each class in the tree in order for an AUTOSUB method. Where a class implements AUTOSUB, it will receive a function name as its first parameter, and it is expected to return either a subroutine reference, or undef. If undef is returned then the inheritance tree search will continue. If a subroutine reference is returned it will be executed immediately with the @_ passed into AUTOLOAD. Typically, AUTOSUB will be used to generate a subroutine reference, and will then associate the subref with the function name to avoid repeated calls to AUTOLOAD and AUTOSUB.

Why not use AUTOLOAD directly in place of AUTOSUB?

On an object with a complex inheritance tree, AUTOLOAD is only found once, after which, there is no way to indicate that the given AUTOLOAD has failed and that the inheritance tree trek should continue for other AUTOLOADS which might impliment the given method.

Example:

    package MyClass;
    our @ISA = ('UR');
    ##- use UR;    
    
    sub AUTOSUB
    {
        my $sub_name = shift;        
        if ($sub_name eq 'foo')
        {
            *MyClass::foo = sub { print "Calling MyClass::foo()\n" };
            return \&MyClass::foo;
        }
        elsif ($sub_name eq 'bar')
        {
            *MyClass::bar = sub { print "Calling MyClass::bar()\n" };
            return \&MyClass::bar;
        }
        else
        { 
            return;
        }
    }
    package MySubClass;
    our @ISA = ('MyClass');
    
    sub AUTOSUB
    {
        my $sub_name = shift;
        if ($sub_name eq 'baz')
        {
            *MyClass::baz = sub { print "Calling MyClass::baz()\n" };
            return \&MyClass::baz;
        }
        else
        { 
            return;
        }
    }
    package main;
    
    my $obj = bless({},'MySubClass');    
    $obj->foo;
    $obj->bar;
    $obj->baz;

MESSAGING

UR::ModuleBase implements several methods for sending and storing error, warning and status messages to the user.

  # common usage
  sub foo {
      my $self = shift;
      ...
      if ($problem) {
          $self->error_message("Something went wrong...");
          return;
      }
      return 1;
  }
  unless ($obj->foo) {
      print LOG $obj->error_message();
  }

Messaging Methods

message_types

  @types = UR::ModuleBase->message_types;
  UR::ModuleBase->message_types(@more_types);

With no arguments, this method returns all the types of messages that this class handles. With arguments, it adds a new type to the list.

Standard message types are error, status, warning, debug and usage.

Note that the addition of new types is not fully supported/implemented yet.

For each message type, several methods are created for sending and retrieving messages, registering a callback to run when messages are sent, controlling whether the messages are printed on the terminal, and whether the messages are queued up.

For example, for the ``error'' message type, these methods are created:

error_message

    $obj->error_message("Something went wrong...");
    $obj->error_message($format, @list);
    $msg = $obj->error_message();

When called with one or more arguments, it sends an error message to the object. The error_message_callback will be run, if one is registered, and the message will be printed to the terminal. When given a single argument, it will be passed through unmodified. When given multiple arguments, error_message will assume the first is a format string and the remainder are parameters to sprintf. When called with no arguments, the last message sent will be returned. If the message is "undef" then no message is printed or queued, and the next time error_message is run as an accessor, it will return undef.

dump_error_messages

    $obj->dump_error_messages(0);
    $flag = $obj->dump_error_messages();

Get or set the flag which controls whether messages sent via "error_message()" is printed to the terminal. This flag defaults to true for warning and error messages, and false for others.

queue_error_messages

    $obj->queue_error_messages(0);
    $flag = $obj->queue_error_messages();

Get or set the flag which control whether messages send via "error_message()" are saved into a list. If true, every message sent is saved and can be retrieved with error_messages() or error_messages_arrayref(). This flag defaults to false for all message types.

error_messages_callback

    $obj->error_messages_callback($subref);
    $subref = $obj->error_messages_callback();

Get or set the callback run whenever an error_message is sent. This callback is run with two arguments: The object or class error_message() was called on, and a string containing the message. This callback is run before the message is printed to the terminal or queued into its list. The callback can modify the message (by writing to $_[1]) and affect the message that is printed or queued. If $_[1] is set to "undef", then no message is printed or queued, and the last recorded message is set to undef as when calling error_message with undef as the argument.

error_messages

    @list = $obj->error_messages();

If the queue_error_messages flag is on, then this method returns the entire list of queued messages.

error_messages_arrayref

    $listref = $obj->error_messages_arrayref();

If the queue_error_messages flag is on, then this method returns a reference to the actual list where messages get queued. This list can be manipulated to add or remove items.

error_message_source

    %source_info = $obj->error_message_source

Returns a hash of information about the most recent call to error_message. The key ``error_message'' contains the message. The keys error_package, error_file, error_line and error_subroutine contain info about the location in the code where error_message() was called.

error_package

error_file

error_line

error_subroutine

These methods return the same data as $obj->error_message_source().