observer.coffee
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# Rivets.Observer
# ----------------------
# Parses and observes a full keypath with the appropriate adapters. Also
# intelligently re-realizes the keypath when intermediary keys change.
class Rivets.Observer
# Performs the initial parse, variable instantiation and keypath realization.
constructor: (@view, @model, @keypath, @callback) ->
@parse()
@initialize()
# Parses the keypath using the interfaces defined on the view. Sets variables
# for the tokenized keypath, as well as the end key.
parse: =>
interfaces = (k for k, v of @view.adapters)
if @keypath[0] in interfaces
root = @keypath[0]
path = @keypath.substr 1
else
root = @view.config.rootInterface
path = @keypath
@tokens = Rivets.KeypathParser.parse path, interfaces, root
@key = @tokens.pop()
initialize: =>
@objectPath = []
@target = @realize()
@set true, @key, @target, @callback if @target?
# Updates the keypath. This is called when any intermediary key is changed.
update: =>
unless (next = @realize()) is @target
@set false, @key, @target, @callback if @target?
@set true, @key, next, @callback if next?
oldValue = @value()
@target = next
@callback() unless @value() is oldValue
adapter: (key) =>
@view.adapters[key.interface]
set: (active, key, obj, callback) =>
action = if active then 'subscribe' else 'unsubscribe'
@adapter(key)[action] obj, key.path, callback
read: (key, obj) =>
@adapter(key).read obj, key.path
publish: (value) =>
if @target?
@adapter(@key).publish @target, @key.path, value
value: =>
@read @key, @target if @target?
# Realizes the full keypath, attaching observers for every key and correcting
# old observers to any changed objects in the keypath.
realize: =>
current = @model
unreached = null
for token, index in @tokens
if current?
if @objectPath[index]?
if current isnt prev = @objectPath[index]
@set false, token, prev, @update
@set true, token, current, @update
@objectPath[index] = current
else
@set true, token, current, @update
@objectPath[index] = current
current = @read token, current
else
unreached ?= index
if prev = @objectPath[index]
@set false, token, prev, @update
@objectPath.splice unreached if unreached?
current
# Unobserves any current observers set up on the keys.
unobserve: =>
for token, index in @tokens
if obj = @objectPath[index]
@set false, token, obj, @update