I'm not a javascript guru either, but it was easy to create ES6 classes (left
pane) and see the output (right pane), so, for the setter, it creates:
For class A (simple):
get: function () {
return this._property;
},
set: function (value) {
this._property = value;
}
For class B:
set: function (value) {
_set(Object.getPrototypeOf(B.prototype), "property", value, this);
}
Which calls:
var _set = function set(object, property, value, receiver) {
var desc = Object.getOwnPropertyDescriptor(object, property); // Get the
property on B
if (desc === undefined) { // If not overrided, will set the parent
recursively if the parent doesn't override the property either.
var parent = Object.getPrototypeOf(object);
if (parent !== null) {
set(parent, property, value, receiver);
}
} else if ("value" in desc && desc.writable) { // didn't get this part
desc.value = value;
} else { // Else call the setterv of this Object
var setter = desc.set;
if (setter !== undefined) {
setter.call(receiver, value);
}
}
return value;
};
get: function () {
return _get(Object.getPrototypeOf(B.prototype), "property", this);
},
Which calls:
this for the getter, do recursive call to the prototype to check if the
property has been overriden, if Yes, get the value.
var _get = function get(_x, _x2, _x3) {
var _again = true;
_function: while (_again) {
var object = _x, property = _x2, receiver = _x3;
desc = parent = getter = undefined;
_again = false;
var desc = Object.getOwnPropertyDescriptor(object, property);
if (desc === undefined) {
var parent = Object.getPrototypeOf(object);
if (parent === null) {
return undefined;
} else {
_x = parent;
_x2 = property;
_x3 = receiver;
_again = true;
continue _function;
}
} else if ("value" in desc) {
return desc.value;
} else {
var getter = desc.get;
if (getter === undefined) {
return undefined;
}
return getter.call(receiver);
}
}
};
Does it do the trick ?
Frédéric THOMAS
> Date: Thu, 28 May 2015 07:47:45 -0400
> Subject: Re: [FalconJX] JXEmitter accessors
> From: teotigraphix...@gmail.com
> To: dev@flex.apache.org
>
> Interesting Fred, I am no javascript guru so I need people to "tell" me
> what I should have output.
>
> So let me get this straight, the left pane is ES6 and it converted it to
> ES5 in the right pane?
>
> Mike
>
> On Thu, May 28, 2015 at 7:19 AM, Frédéric THOMAS <webdoubl...@hotmail.com>
> wrote:
>
> > I just tried in babel, see what it generates:
> >
> >
> > http://babeljs.io/repl/#?experimental=true&evaluate=true&loose=false&spec=false&code=class%20A%20{%0A%09constructor%28%29%20{%0A%09%20%20this._property%20%3D%20%22init%22%3B%0A%09}%0A%09get%20property%28%29%3Astring%20{%0A%09%09return%20this._property%3B%0A%09}%0A%09%0A%09set%20property%28value%3Astring%29%20{%0A%09%09this._property%20%3D%20value%3B%0A%09}%20%0A%09%0A%09showMyValue%28%29%20{%0A%09%09alert%28this._property%29%3B%0A%09}%0A%0A}%0A%0Aclass%20B%20extends%20A%20{%0A%09get%20property%28%29%3Astring%20{%0A%09%09return%20super.property%3B%0A%09}%0A%09%0A%09set%20property%28value%3Astring%29%20{%0A%09%09super.property%20%3D%20value%3B%0A%09}%0A}
> >
> > Frédéric THOMAS
> >
> > > Date: Thu, 28 May 2015 06:54:31 -0400
> > > Subject: Re: [FalconJX] JXEmitter accessors
> > > From: teotigraphix...@gmail.com
> > > To: dev@flex.apache.org
> > >
> > > > I’m still surprised that in 2015, TS hasn’t been forced to handle
> > super.
> > > Are people not using inheritance much in TS?
> > >
> > > They tell them to use standard getValue(), setValue() in the property if
> > > they need inheritance overrides.
> > >
> > > I'm kind of bummed about this whole thing, I stuck my foot in mouth here,
> > > since I totally forgot about this stuff. Since I really wanted to do this
> > > for Josh's POC, I am interested in what he "needs" to get his project
> > > working, Josh?
> > >
> > > Mike
> > >
> > >
> > > On Wed, May 27, 2015 at 7:51 PM, Alex Harui <aha...@adobe.com> wrote:
> > >
> > > >
> > > >
> > > > On 5/27/15, 4:16 PM, "Michael Schmalle" <teotigraphix...@gmail.com>
> > wrote:
> > > >
> > > > >Ok, This needs to be clear to me before I go off to OZ.
> > > > >
> > > > >In Flex JS you have;
> > > > >
> > > > >Object.defineProperties(Base.prototype, /** @lends {Base.prototype}
> > */ {
> > > > >/** @expose */
> > > > >text: {
> > > > >get: /** @this {Base} */ function() {
> > > > > return "A" + org_apache_flex_utils_Language.superGetter(Base, this,
> > > > >'text');
> > > > >},
> > > > >set: /** @this {Base} */ function(value) {
> > > > > if (value != org_apache_flex_utils_Language.superGetter(Base, this,
> > > > >'text')) {
> > > > > org_apache_flex_utils_Language.superSetter(Base, this, 'text',
> > "B" +
> > > > >value);
> > > > > }
> > > > >}}}
> > > > >);
> > > > >
> > > > >I must use this obviously since hardly any actionscript could be cross
> > > > >compiled if you can't call super accessors.
> > > >
> > > > I’m still surprised that in 2015, TS hasn’t been forced to handle
> > super.
> > > > Are people not using inheritance much in TS?
> > > >
> > > > >
> > > > >Alex, when you have time, can you explain what this is doing so I can
> > > > >implement it.
> > > >
> > > > I have not read the spec, but Object.defineProperties appears to
> > associate
> > > > a data structure with a “class”. When asked to interpret/execute
> > > >
> > > > Someinstance.someprop
> > > >
> > > > the JS runtime appears to check this data structure first, and call the
> > > > get or set as needed. As I see it, there is no way to switch from
> > > >
> > > > SomeSubClass.someProp
> > > >
> > > > back to
> > > >
> > > > SomeBaseClass.someProp
> > > >
> > > > and retain the ‘this’ pointer and scope. If you had a variable called
> > > > super it would still point to the same instance so super.someProp would
> > > > just cause the runtime to find the subclass’s property map.
> > > >
> > > > In looking around the internet, the solutions seemed to:
> > > > 1) get the superclass
> > > > 2) get the property map of defined properties
> > > > 3) get the getter or setter from the data structure
> > > > 4) call it with the right ‘this’ pointer.
> > > >
> > > > So that’s what is in the current JSFlexJSEmitter, but it assumes
> > > > goog.inherit is going to leave references to the base class in a
> > > > particular way. TS probably leaves references to base classes some
> > how so
> > > > some abstraction around step 1 is probably required, but steps 2
> > through 4
> > > > can be the same.
> > > >
> > > > It is step 4 that re-introduces “re-writing” that you may be referring
> > to
> > > > as hell. The super setter again becomes a function call, so the AST
> > walk
> > > > needs to know that and walk the tree differently, saving a whole
> > branch to
> > > > be evaluated as the parameter to the function call. IOW, a binary
> > > > operator becomes a function call. I’ll bet there are still bugs in the
> > > > current JSFlexJSEmitter.
> > > >
> > > > And I think I still haven’t fixed the scenario where only a getter or
> > > > setter is overridden. The generated code must propagate a “pass
> > through”
> > > > for the missing getter or setter to the subclass’s data structure
> > > > otherwise the runtime will not find the setter or getter and think the
> > > > property is now read-only or write-only.
> > > >
> > > > >
> > > > >So correct me if I am wrong but, since there is really no solution
> > without
> > > > >an external utility to call a super accessor, we can't really say that
> > > > >this
> > > > >transpiler is producing vanilla javascript. Chicken egg thing.
> > > >
> > > > Technically, you could inline everything in the utility function and
> > still
> > > > called it vanilla. But it would be high-fat vanilla. ;-)
> > > >
> > > > A question for Josh is whether it would be ok to have a Google Closure
> > > > Library dependency. These libraries exist to encapsulate some of these
> > > > object oriented patterns like finding the base class and loading
> > > > dependency definitions in a particular order. It seems to be somewhat
> > > > pay-as-you-go. If no inheritance, then almost no “goog”.
> > > >
> > > > -Alex
> > > >
> > > >
> >
> >
