Feature: Anchor repeaters

[quickthyme]

Basically a cheap way to provide some basic broadcast-like capabilities.

NOTE: Depends on PR #7

Repeaters

Repeaters offer a way to fork multiple streams off of the main path.

When an Anchor has repeaters applied, then it will echo any value and error changes
to each of them.

By default, it forwards all changes to all repeaters. In order to make it conditional, we can
set an EchoFilter, which gets called prior to forwarding to each repeater. Return false
from the EchoFilter to block that repeater from receiving the change.

EchoFilter

• (Input?, QLAnchor) -> (Bool)

Default filter returns true. You can evaluate the input value and decide whether or not the
particular anchor (repeater) should receive the new value.

To identify the anchor, you will need to do so using the object reference.

example:

let progressRepeater = viewController.progressAnchor
let finalRepeater = viewController.downloadCompleteAnchor

let baseAnchor = QLAnchor<DownloadStatus>(
    echoFilter: ({ obj, repeater in
        return (obj.isProgress && repeater === progressRepeater)
            || (obj.isFinal && repeater === finalRepeater)
    }),
    repeaters: progressRepeater, finalRepeater
)

[diedrix]

🏅