Add helper methods to DBusValue to reduce casting.

[robert-ancell]

The intention was to make helper methods to reduce the amount of typing and brackets required when using casting. However, I wanted to make it clear that it still is casting internally, which is why the methods are all prefixed with 'as'.

Not sure if the documentation on the methods is the best, but found it difficult to come up with better words than 'Converts' and 'Extracts'. Some types are just a cast because this can't be natively represented, while others are just simple types.

[jpnurmi]

Awesome! This makes a big difference in how convenient it is to read the values. 👍

Given that the new API is for convenient reading of the contained values, I'd propose following the (this as DBusType).value/children pattern for DBusMaybe, DBusArray, and DBusDict too. The old syntax would be ok for the (rare?) cases when there's a need to access the containing DBus type.

[robert-ancell]

Awesome! This makes a big difference in how convenient it is to read the values. +1

Given that the new API is for convenient reading of the contained values, I'd propose following the (this as DBusType).value/children pattern for DBusMaybe, DBusArray, and DBusDict too. The old syntax would be ok for the (rare?) cases when there's a need to access the containing DBus type.

I did it because I thought we would be losing useful information, but as you point out you can manually cast if necessary. Also the normal usage is to test the signature of the top-level object, which means all the sub-objects should have the signatures you expect.