How do I whitelist an activity for a UIActivityViewController and not a blacklist?

Most use cases UIActivityViewController

show how to exclude activity types, but they do not show how to specify only the types you want.

For example,

I want the displayed actions to show only emails and messages . The init method UIActivityViewController

has a parameter applicationActivities

, which is an array from UIActivity .

This means that passing an array UIActivity

and not nil will set up a whitelist. It seems that populating this array will achieve what I want. Is my guess correct? If so, what are the classes for email and messages .

Question:

How do I instantiate instances? Or, generally, how can I define a class for any of the standard operation types and instantiate them?