============ Horde_Argv ============ ---------------------- Extending Horde_Argv ---------------------- Since the two major controlling factors in how *Horde_Argv* interprets command-line options are the action and type of each option, the most likely direction of extension is to add new actions and new types. Adding new types ================ To add new types, you need to define your own subclass of the ``Horde_Argv_Option class``. This class has a couple of properties that define *Horde_Argv*'s types: ``$TYPES`` and ``$TYPE_CHECKER``. ``$TYPES`` is a tuple of type names; in your subclass, simply define a new tuple ``$TYPES`` that builds on the standard one. ``$TYPE_CHECKER`` is a dictionary mapping type names to type-checking functions. A type-checking function has the following signature: :: foo check_foo(Horde_Argv_Option $option, string $opt, string $value) You can name it whatever you like, and make it return any type you like (e.g. the hypothetical type foo). The value returned by a type-checking function will wind up in the ``Horde_Argv_Values`` instance returned by ``Horde_Argv_Parser->parseArgs()``, or be passed to callbacks as the ``$value`` parameter. Your type-checking function should throw ``Horde_Argv_OptionValueException`` if it encounters any problems. ``Horde_Argv_OptionValueException`` takes a single string argument, which is passed as-is to ``Horde_Argv_Parser``'s ``parserError()`` method, which in turn prepends the program name and the string ``"error:"`` and prints everything to stderr before terminating the process. Here's a silly example that demonstrates adding an imaginary ``MyComplex`` option type to parse complex numbers on the command line. You need to define your type-checker, since it's referred to in the ``$TYPE_CHECKER`` class attribute of your ``Horde_Argv_Option`` subclass: :: class MyOption extends Horde_Argv_Option { public function __construct() { $this->TYPES[] = 'complex'; $this->TYPE_CHECKER['complex'] = 'checkComplex'; } public function checkComplex($option, $opt, $value) { try { return new MyComplex(value); } catch (Exception $e) { throw new Horde_Argv_OptionValueException( sprintf('option %s: invalid complex value: %s', (opt, value)) ); } } } That's it! Now you can write a script that uses the new option type just like any other *Horde_Argv*-based script, except you have to instruct your ``Horde_Argv_Parser`` to use ``MyOption`` instead of ``Horde_Argv_Option``: :: $parser = new Horde_Argv_Parser(array('optionClass' => 'MyOption')); $parser->addOption('-c', array('type' => 'complex')); Alternately, you can build your own option list and pass it to ``Horde_Argv_Parser``; if you don't use ``addOption()`` in the above way, you don't need to tell ``Horde_Argv_Parser`` which option class to use: :: $option_list = array( new MyOption( '-c', array('action' => 'store', 'type' => 'complex', 'dest' => 'c') ) ); parser = new Horde_Argv_Parser(array('optionList' => $option_list)); Adding new actions ================== Adding new actions is a bit trickier, because you have to understand that *Horde_Argv* has a couple of classifications for actions: :"store" actions: actions that result in *Horde_Argv* storing a value to a property of the current ``Horde_Argv_Values`` instance; these options require a ``dest`` attribute to be supplied to the ``Horde_Argv_Option`` constructor :"typed" actions: actions that take a value from the command line and expect it to be of a certain type; or rather, a string that can be converted to a certain type. These options require a type attribute to the ``Horde_Argv_Option`` constructor. These are overlapping sets: some default "store" actions are ``store``, ``store_const``, ``append``, and ``count``, while the default "typed" actions are ``store``, ``append``, and ``callback``. When you add an action, you need to decide if it's a "store" action, a "typed" action, neither, or both. Three class properties of ``Horde_Argv_Option`` (or your ``Horde_Argv_Option`` subclass) control this: :``$ACTIONS``: all actions must be listed in ``$ACTIONS`` :``$STORE_ACTIONS``: "store" actions are additionally listed here :``$TYPED_ACTIONS``: "typed" actions are additionally listed here In order to actually implement your new action, you must override ``Horde_Argv_Option``'s ``takeAction()`` method and add a case that recognizes your action. For example, let's add an ``extend`` action. This is similar to the standard ``append`` action, but instead of taking a single value from the command-line and appending it to an existing list, extend will take multiple values in a single comma-delimited string, and extend an existing list with them. That is, if ``"--names"`` is an ``extend`` option of type ``string``, the command line :: --names=foo,bar --names blah --names ding,dong would result in a list :: array('foo', 'bar', 'blah', 'ding', 'dong') Again we define a subclass of ``Horde_Argv_Option``: :: class MyOption extends Horde_Argv_Option { public function __construct() { $this->ACTIONS[] = 'extend'; $this->STORE_ACTIONS[] = 'extend'; $this->TYPED_ACTIONS[] = 'extend'; } public function takeAction($action, $dest, $opt, $value, $values, $parser) { if ($action == 'extend') { $lvalue = explode(',', $value); $values->dest = array_merge($values->ensureValue('dest', array()), $lvalue); } else { parent::takeAction($action, $dest, $opt, $value, $values, $parser); } } } Features of note: * ``extend`` both expects a value on the command-line and stores that value somewhere, so it goes in both ``$STORE_ACTIONS`` and ``$TYPED_ACTIONS`` * ``MyOption::takeAction()`` implements just this one new action, and passes control back to ``Horde_Argv_Option::takeAction()`` for the standard *Horde_Argv* actions * ``$values`` is an instance of the ``Horde_Argv_Values`` class, which provides the very useful ``ensureValue()`` method. ``ensureValue()`` is essentially a getter with a safety valve; it is called as ``$values->ensureValue($attr, $value)`` If the ``$attr`` property of ``$values`` doesn't exist or is ``null``, then ``ensureValue()`` first sets it to ``$value``, and then returns ``$value``. This is very handy for actions like ``extend``, ``append``, and ``count``, all of which accumulate data in a variable and expect that variable to be of a certain type (an array for the first two, an integer for the latter). Using ``ensureValue()`` means that scripts using your action don't have to worry about setting a default value for the option destinations in question; they can just leave the default as ``null`` and ``ensureValue()`` will take care of getting it right when it's needed. Other reasons to extend Horde_Argv ================================== Adding new types and new actions are the big, obvious reasons why you might want to extend *Horde_Argv*. I can think of at least two other areas to play with. First, the simple one: ``Horde_Argv_Parser`` tries to be helpful by calling ``exit()`` when appropriate, i.e. when there's an error on the command line or when the user requests help. In the former case, the traditional course of letting the script crash with a traceback is unacceptable; it will make users think there's a bug in your script when they make a command-line error. In the latter case, there's generally not much point in carrying on after printing a help message. If this behaviour bothers you, it shouldn't be too hard to "fix" it. You'll have to 1. subclass ``Horde_Argv_Parser`` and override ``parserError()`` 2. subclass ``Horde_Argv_Option`` and override ``takeAction()`` -- you'll need to provide your own handling of the ``help`` action that doesn't call ``exit()`` The second, much more complex, possibility is to override the command-line syntax implemented by *Horde_Argv*. In this case, you'd leave the whole machinery of option actions and types alone, but rewrite the code that processes ``argv``. You'll need to subclass ``Horde_Argv_Parser`` in any case; depending on how radical a rewrite you want, you'll probably need to override one or all of ``parseArgs()``, ``_processLongOpt()``, and ``_processShortOpts()``. Both of these are left as an exercise for the reader. I have not tried to implement either myself, since I'm quite happy with *Horde_Argv*'s default behaviour (naturally). Happy hacking, and don't forget: Use the Source, Luke.