arximboldi / heterarchy Goto Github PK

Hi,

apparently the tests I wrote for the class method inheritance (using super) are not sufficient.
Here is an example where the instance methods work correctly but the class methods do not:

class Widget
    @getDefaultProperties: () ->
        console.log "Widget"
        return {}
    getDefaultProperties: () ->
        console.log "Widget"
        return {}

class MoveableWidget extends Widget
class ResizeableWidget extends Widget
class MoveableResizableWidget extends heterarchy.multi MoveableWidget, ResizeableWidget

class ConfigurableWidget extends Widget
class HideableWidget extends ConfigurableWidget
    @getDefaultProperties: () ->
        console.log "HideableWidget"
        props = super()
        props.hidden = false
        return props
    getDefaultProperties: () ->
        console.log "HideableWidget"
        props = super()
        props.hidden = false
        return props

class TextWidget extends heterarchy.multi MoveableResizableWidget, HideableWidget
    @getDefaultProperties: () ->
        console.log "TextWidget"
        props = super()
        props.text = ""
        return props
    getDefaultProperties: () ->
        console.log "TextWidget"
        props = super()
        props.text = ""
        return props

console.log (new TextWidget).getDefaultProperties() # {"hidden":false,"text":""}
console.log TextWidget.getDefaultProperties() # {"text":""}

As of now, it is impossible to find the base class(es) of a subclass. The existing introspection functions mro, inherited and hierarchy cannot be used for task (if I am right).
In another project of mine I need this feature for generating a UML class diagram.

It would be nice to have a __bases__ attribute at least on those classes classes that extend multi(...).

The bases only get passed into the multi function so I guess the bases must be attached there are passed along.

The example given in your documentation is wrong.

{multi} = require 'heterarchy'

class A
    method: -> "A"

class B extends A
    method: -> "B > #{super}"

class C extends A
    method: -> "C > #{super}"

class D extends multi B, C
    method: -> "D > #{super}"

Calling method on a D instance does not return the string D > C > B > A.
Instead it returns D > B > C > A.

Hi,

when enumerable properties are defined on a class's prototype they are not correctly inherited.
The problem is the generate function.
In case of data descriptors no errors occur but the descriptor be dropped (since only the value will be copied).
In case of accessor descriptors errors can occurs (for example if the getter calls something on this) because

for own key, val of obj
  ...

is compiled to

for (key in obj) {
  if (!hasProp.call(obj, key)) continue;
  val = obj[key];
  ...
}

and val = obj[key] will trigger the getter to be evaluated with the prototype as context instead of the instance.

Object.getOwnPropertyDescriptor(obj, propName) can be used to determine if an attribute is a defined property or not.
This should be used in both loops - maybe like this:

for own key of next
  descriptor = Object.getOwnPropertyDescriptor(next, key)
  if not descriptor?
    value = next[key]
    @[key] = reparent next, @, value
  else
    # I don't know if this really does it
    Object.defineProperty @, key, descriptor

I am not quite sure if Object.defineProperty @, key, descriptor does the job.
However, if the descriptor contains get: () -> this.something or get: () -> this.doSomething() (or a setter) the function body is evaluated when property is accessed so I think everything is fine because at that time heterarchy should have taken care of everything, right?

I guess properties on the class itself behave similarly.

See https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertyDescriptor