Property Accessors
A mixin for defining fancy dynamic properties.
Basic Usage
To define a basic property accessor, use the accessor declaration. If you've
included the mixin into a class, you define a prototype property by calling
@::accessor on its prototype.
PropertyAccessors = require 'property-accessors'
class Vehicle
PropertyAccessors.includeInto(this)
@::accessor 'type', ->
get: ->
switch @doorCount
when 4 then 'sedan' # i know this isn't strictly accurate
when 2 then 'coupe'
set: (type) ->
switch type
when 'sedan' then @doorCount = 4
when 'coupe' then @doorCount = 2
car = new Vehicle
car.doorCount = 2
car.type # => 'coupe'
You can define a class-level property by extending with the mixin rather than including it (which extends the prototype).
class Vehicle
PropertyAccessors.extend(this)
@accessor 'vehicleCount', get: -> @allVehicles.length
You can just pass a single function if you only want to define a getter:
class Vehicle
PropertyAccessors.includeInto(this)
@::accessor 'type', -> # ...
Fancy Usage
Lazy Accessors
Lazy accessors call a function the first time a property is accessed. You are still free to overwrite this value by assigning the property explicitly.
class ScienceLab
PropertyAccessors.includeInto(this)
@::lazyAccessor 'crazyComputation', -> computeCrazyComputation()
Advised Accessors
Advised accessors allow you to call code before the reading or writing of a property value. If a property is being assigned, your advice function is called with the value being assigned and the old value.
class SpyStation
@advisedAccessor 'online',
get: -> @ensureAllSystemsNominal()
set: -> @ensureUserIsSpy()
station = new SpyStation
station.online = true # ensures user is a spy, then assigns true
station.online # ensures all systems are nominal, then returns true