Inject Configuration Object Into Functor

[jimdelois]

Currently, when mapping, the mapping functor cannot read other values from the container. It may be desirable to do so, however. Consider the following example:

EMAIL_FROM_ADDR=admin@example.com
EMAIL_FROM_NAME="Organization Administrator"

We may want our call to $config->get('EMAIL_FROM_ADD'); to return something like 'Organization Administrator <admin@example.com>'. This behavior is not currently possible.

By injecting the configuration object, itself, in to the MapperFactory, the factory can install it as a property in the Mapper, which can then be passed to the functor (defined as optional):

$config->map('EMAIL_FROM_ADD')
	->using(function($val, Configuration $config) {
		return sprintf('%s <%s>', $config->get('EMAIL_FROM_NAME'), $val);
	});

This behavior could further be improved by creating a new method create on the Configuration object which would behave nearly identically to the map method, but skipping the existence check (rather, inverting it). This would avoid the confusing "re-assignment" of the environment variable, above.

E.g.,

// Install a new config value in the Configuration object, generated from other values
$config->create('EMAIL_ADDRESS_RFC2822')->using( /* ... etc ... */ );

$config->get('EMAIL_ADDRESS_RFC2822'); // "Organization Administrator <admin@example.com>"