Property Accessors Mixin
A mixin for defining dynamic properties.
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', -> # ...
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 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