Charms, once instantiated and loaded with data from their respective sources, are immutable and read-only. This reflects the reality of how we interact with them.

Charm instances can represent both environment charms and charm store charms. A charm id is reliably and uniquely associated with a given charm only within a given context: the environment or the charm store.

Charms begin their lives with full charm ids, as provided by services in the environment and the charm store:

[SCHEME]:(~[OWNER]/)?[SERIES]/[PACKAGE NAME]-[REVISION]

With an id, we can instantiate a charm: typically we use db.charms.add({id: [ID]}). Finally, we load the charm's data over the network using the standard YUI Model method load, providing an object with a get_charm callable, and an optional callback (see YUI docs). Both the env and the charm store have a get_charm method, so, by design, it works easily: charm.load(env, optionalCallback) or charm.load(charm_store, optionalCallback). The get_charm method must either callback using the default YUI approach for this code, a boolean indicating failure, and a result; or it must return what the env version does: an object with a result object containing the charm data, or an object with an err attribute.

In both cases, environment charms and charm store charms, a charm's loaded attribute is set to true once it has all the data from its environment.