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Mike Rumble

2008-Apr-23 11:22 UTC

Extending instances from classes with inheritance

Hello,

I can''t make my mind up over some finer points of an API design and
would appreciate any feedback on my code. Hopefully this example is
clear...

var A = Class.create({
  initialize : function(obj){
    Object.extend(this, obj)
  }
});

var B = {
  method : function(){
    ....
  }
};

var C = {
  method: function(){
    ....
  }
};

var d = new A(B);
var e = new A(C);


On initialization each instance of class A is extended with methods
from a separate object via Object.extend. I''ve chosen not to use
Class#addMethods because each instance of can be extended with a
different object, and therefore the prototype chain of class A should
remain unaffected.

So for so good.

However I''m looking to use this taking advantage of
Prototype''s
inheritance features for the extension objects. I''ve currently got
something that looks like this...


var A = Class.create({
  initialize : function(obj){
    Object.extend(this, obj.prototype)
  }
});

var B = Class.create({
  method : function(){
    ....
  }
})

var C = (B, {
  method: function($super){
    $super();
  }
};

var d = new A(B);
var e = new A(C);


It works OK but feels a little clunky. To me it would make more sense
to do something like this...


var A = Class.create({
  initialize : function(obj){
    Object.extend(this, obj)
  }
});

var B = Class.create({
  method : function(){
    ....
  }
})

var C = (B, {
  method: function($super){
    $super();
  }
};

var d = new A(new (B));
var e = new A(new (C));


Anybody got any strong opinions on which approach is best?
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kangax

2008-Apr-23 21:53 UTC

head link

Re: Extending instances from classes with inheritance

I don''t see how "var d = new A(B); " is "chunkier"
than "var e = new
A(new (B));" : )
Am I correct that you want to extend instance with methods, and
preserve their (methods'') inheritance?

- kangax


On Apr 23, 7:22 am, Mike Rumble
<mike.rum...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:> Hello,
>
> I can''t make my mind up over some finer points of an API design
and
> would appreciate any feedback on my code. Hopefully this example is
> clear...
>
> var A = Class.create({
>   initialize : function(obj){
>     Object.extend(this, obj)
>   }
>
> });
>
> var B = {
>   method : function(){
>     ....
>   }
>
> };
>
> var C = {
>   method: function(){
>     ....
>   }
>
> };
>
> var d = new A(B);
> var e = new A(C);
>
> On initialization each instance of class A is extended with methods
> from a separate object via Object.extend. I''ve chosen not to use
> Class#addMethods because each instance of can be extended with a
> different object, and therefore the prototype chain of class A should
> remain unaffected.
>
> So for so good.
>
> However I''m looking to use this taking advantage of
Prototype''s
> inheritance features for the extension objects. I''ve currently got
> something that looks like this...
>
> var A = Class.create({
>   initialize : function(obj){
>     Object.extend(this, obj.prototype)
>   }
>
> });
>
> var B = Class.create({
>   method : function(){
>     ....
>   }
>
> })
>
> var C = (B, {
>   method: function($super){
>     $super();
>   }
>
> };
>
> var d = new A(B);
> var e = new A(C);
>
> It works OK but feels a little clunky. To me it would make more sense
> to do something like this...
>
> var A = Class.create({
>   initialize : function(obj){
>     Object.extend(this, obj)
>   }
>
> });
>
> var B = Class.create({
>   method : function(){
>     ....
>   }
>
> })
>
> var C = (B, {
>   method: function($super){
>     $super();
>   }
>
> };
>
> var d = new A(new (B));
> var e = new A(new (C));
>
> Anybody got any strong opinions on which approach is best?--~--~---------~--~----~------------~-------~--~----~
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-~----------~----~----~----~------~----~------~--~---

Mike Rumble

2008-Apr-25 11:06 UTC

head link

Re: Extending instances from classes with inheritance

> I don''t see how "var d = new A(B); " is
"chunkier" than "var e = new
> A(new (B));" : )
I guess it''s a matter of taste then. I prefer Object.extend(this, obj)
to Object.extend(this, obj.prototype), just wanted to know if there
was really any difference in the two different approaches, and for the
record both function identically.
> Am I correct that you want to extend instance with methods, and
> preserve their (methods'') inheritance?
Yeah that''s spot on.


On Apr 23, 10:53 pm, kangax
<kan...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> Am I correct that you want to extend instance with methods, and
> preserve their (methods'') inheritance?
>
> - kangax
>
> On Apr 23, 7:22 am, Mike Rumble
<mike.rum...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>
> > Hello,
>
> > I can''t make my mind up over some finer points of an API
design and
> > would appreciate any feedback on my code. Hopefully this example is
> > clear...
>
> > var A = Class.create({
> >   initialize : function(obj){
> >     Object.extend(this, obj)
> >   }
>
> > });
>
> > var B = {
> >   method : function(){
> >     ....
> >   }
>
> > };
>
> > var C = {
> >   method: function(){
> >     ....
> >   }
>
> > };
>
> > var d = new A(B);
> > var e = new A(C);
>
> > On initialization each instance of class A is extended with methods
> > from a separate object via Object.extend. I''ve chosen not to
use
> > Class#addMethods because each instance of can be extended with a
> > different object, and therefore the prototype chain of class A should
> > remain unaffected.
>
> > So for so good.
>
> > However I''m looking to use this taking advantage of
Prototype''s
> > inheritance features for the extension objects. I''ve
currently got
> > something that looks like this...
>
> > var A = Class.create({
> >   initialize : function(obj){
> >     Object.extend(this, obj.prototype)
> >   }
>
> > });
>
> > var B = Class.create({
> >   method : function(){
> >     ....
> >   }
>
> > })
>
> > var C = (B, {
> >   method: function($super){
> >     $super();
> >   }
>
> > };
>
> > var d = new A(B);
> > var e = new A(C);
>
> > It works OK but feels a little clunky. To me it would make more sense
> > to do something like this...
>
> > var A = Class.create({
> >   initialize : function(obj){
> >     Object.extend(this, obj)
> >   }
>
> > });
>
> > var B = Class.create({
> >   method : function(){
> >     ....
> >   }
>
> > })
>
> > var C = (B, {
> >   method: function($super){
> >     $super();
> >   }
>
> > };
>
> > var d = new A(new (B));
> > var e = new A(new (C));
>
> > Anybody got any strong opinions on which approach is best?--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Spinoffs" group.
To post to this group, send email to
rubyonrails-spinoffs-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
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kangax

2008-Apr-25 17:32 UTC

head link

Re: Extending instances from classes with inheritance

I''m not sure I understand how these 2 are identical. Former one is a
constructor function (with properties like "prototype",
"subclasses",
"superclass"), while latter one is a "prototype" object
(with all the
shared "instance" methods).

As far as mixins and inheritance, I would do something like this:

var Predator = Class.create({
  hunt: function() {
    return this.name + '' is hunting'';
  }
});

var WaterPredator = Class.create(Predator, {
  hunt: function($super) {
    return $super() + '' under water'';
  }
})

var Shark = Class.create({
  initialize : function(name) {
    this.name = name;
  },
  speak: function(msg) {
    return this.name + '': '' + msg;
  }
})

// Create a temporary class and blend both prototypes in:
var MixedIn = Class.create(WaterPredator, Shark.prototype);

new MixedIn(''Sharkie'').name; // "Sharkie"
new MixedIn(''Sharkie'').speak(''Hello underwater
world''); // "Sharkie:
Hello underwater world"
new MixedIn(''Sharkie'').hunt(); // "Sharkie is hunting
under water"

Best,
kangax

On Apr 25, 7:06 am, Mike Rumble
<mike.rum...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:> > I don''t see how "var d = new A(B); " is
"chunkier" than "var e = new
> > A(new (B));" : )
>
> I guess it''s a matter of taste then. I prefer Object.extend(this,
obj)
> to Object.extend(this, obj.prototype), just wanted to know if there
> was really any difference in the two different approaches, and for the
> record both function identically.
>
> > Am I correct that you want to extend instance with methods, and
> > preserve their (methods'') inheritance?
>
> Yeah that''s spot on.
>
> On Apr 23, 10:53 pm, kangax
<kan...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>
> > Am I correct that you want to extend instance with methods, and
> > preserve their (methods'') inheritance?
>
> > - kangax
>
> > On Apr 23, 7:22 am, Mike Rumble
<mike.rum...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>
> > > Hello,
>
> > > I can''t make my mind up over some finer points of an API
design and
> > > would appreciate any feedback on my code. Hopefully this example
is
> > > clear...
>
> > > var A = Class.create({
> > >   initialize : function(obj){
> > >     Object.extend(this, obj)
> > >   }
>
> > > });
>
> > > var B = {
> > >   method : function(){
> > >     ....
> > >   }
>
> > > };
>
> > > var C = {
> > >   method: function(){
> > >     ....
> > >   }
>
> > > };
>
> > > var d = new A(B);
> > > var e = new A(C);
>
> > > On initialization each instance of class A is extended with
methods
> > > from a separate object via Object.extend. I''ve chosen
not to use
> > > Class#addMethods because each instance of can be extended with a
> > > different object, and therefore the prototype chain of class A
should
> > > remain unaffected.
>
> > > So for so good.
>
> > > However I''m looking to use this taking advantage of
Prototype''s
> > > inheritance features for the extension objects. I''ve
currently got
> > > something that looks like this...
>
> > > var A = Class.create({
> > >   initialize : function(obj){
> > >     Object.extend(this, obj.prototype)
> > >   }
>
> > > });
>
> > > var B = Class.create({
> > >   method : function(){
> > >     ....
> > >   }
>
> > > })
>
> > > var C = (B, {
> > >   method: function($super){
> > >     $super();
> > >   }
>
> > > };
>
> > > var d = new A(B);
> > > var e = new A(C);
>
> > > It works OK but feels a little clunky. To me it would make more
sense
> > > to do something like this...
>
> > > var A = Class.create({
> > >   initialize : function(obj){
> > >     Object.extend(this, obj)
> > >   }
>
> > > });
>
> > > var B = Class.create({
> > >   method : function(){
> > >     ....
> > >   }
>
> > > })
>
> > > var C = (B, {
> > >   method: function($super){
> > >     $super();
> > >   }
>
> > > };
>
> > > var d = new A(new (B));
> > > var e = new A(new (C));
>
> > > Anybody got any strong opinions on which approach is best?--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Spinoffs" group.
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Mike Rumble

2008-Apr-26 13:07 UTC

head link

Re: Extending instances from classes with inheritance

> I''m not sure I understand how these 2 are identical. Former one is
a
> constructor function (with properties like "prototype",
"subclasses",
> "superclass"), while latter one is a "prototype" object
(with all the
> shared "instance" methods).
I guess my point is not that they are identical, but whether I copy
methods to my instance from an instance of another class, or directly
from it''s prototype I end up with the same result.

Thanks for your code example, it looks like a sensible way of doing
things and I''ll be sure to explore it further.


On Apr 25, 6:32 pm, kangax
<kan...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:> I''m not sure I understand how these 2 are identical. Former one is
a
> constructor function (with properties like "prototype",
"subclasses",
> "superclass"), while latter one is a "prototype" object
(with all the
> shared "instance" methods).
>
> As far as mixins and inheritance, I would do something like this:
>
> var Predator = Class.create({
>   hunt: function() {
>     return this.name + '' is hunting'';
>   }
>
> });
>
> var WaterPredator = Class.create(Predator, {
>   hunt: function($super) {
>     return $super() + '' under water'';
>   }
>
> })
>
> var Shark = Class.create({
>   initialize : function(name) {
>     this.name = name;
>   },
>   speak: function(msg) {
>     return this.name + '': '' + msg;
>   }
>
> })
>
> // Create a temporary class and blend both prototypes in:
> var MixedIn = Class.create(WaterPredator, Shark.prototype);
>
> new MixedIn(''Sharkie'').name; // "Sharkie"
> new MixedIn(''Sharkie'').speak(''Hello underwater
world''); // "Sharkie:
> Hello underwater world"
> new MixedIn(''Sharkie'').hunt(); // "Sharkie is
hunting under water"
>
> Best,
> kangax
>
> On Apr 25, 7:06 am, Mike Rumble
<mike.rum...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>
> > > I don''t see how "var d = new A(B); " is
"chunkier" than "var e = new
> > > A(new (B));" : )
>
> > I guess it''s a matter of taste then. I prefer
Object.extend(this, obj)
> > to Object.extend(this, obj.prototype), just wanted to know if there
> > was really any difference in the two different approaches, and for the
> > record both function identically.
>
> > > Am I correct that you want to extend instance with methods, and
> > > preserve their (methods'') inheritance?
>
> > Yeah that''s spot on.
>
> > On Apr 23, 10:53 pm, kangax
<kan...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>
> > > Am I correct that you want to extend instance with methods, and
> > > preserve their (methods'') inheritance?
>
> > > - kangax
>
> > > On Apr 23, 7:22 am, Mike Rumble
<mike.rum...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>
> > > > Hello,
>
> > > > I can''t make my mind up over some finer points of
an API design and
> > > > would appreciate any feedback on my code. Hopefully this
example is
> > > > clear...
>
> > > > var A = Class.create({
> > > >   initialize : function(obj){
> > > >     Object.extend(this, obj)
> > > >   }
>
> > > > });
>
> > > > var B = {
> > > >   method : function(){
> > > >     ....
> > > >   }
>
> > > > };
>
> > > > var C = {
> > > >   method: function(){
> > > >     ....
> > > >   }
>
> > > > };
>
> > > > var d = new A(B);
> > > > var e = new A(C);
>
> > > > On initialization each instance of class A is extended with
methods
> > > > from a separate object via Object.extend. I''ve
chosen not to use
> > > > Class#addMethods because each instance of can be extended
with a
> > > > different object, and therefore the prototype chain of class
A should
> > > > remain unaffected.
>
> > > > So for so good.
>
> > > > However I''m looking to use this taking advantage of
Prototype''s
> > > > inheritance features for the extension objects.
I''ve currently got
> > > > something that looks like this...
>
> > > > var A = Class.create({
> > > >   initialize : function(obj){
> > > >     Object.extend(this, obj.prototype)
> > > >   }
>
> > > > });
>
> > > > var B = Class.create({
> > > >   method : function(){
> > > >     ....
> > > >   }
>
> > > > })
>
> > > > var C = (B, {
> > > >   method: function($super){
> > > >     $super();
> > > >   }
>
> > > > };
>
> > > > var d = new A(B);
> > > > var e = new A(C);
>
> > > > It works OK but feels a little clunky. To me it would make
more sense
> > > > to do something like this...
>
> > > > var A = Class.create({
> > > >   initialize : function(obj){
> > > >     Object.extend(this, obj)
> > > >   }
>
> > > > });
>
> > > > var B = Class.create({
> > > >   method : function(){
> > > >     ....
> > > >   }
>
> > > > })
>
> > > > var C = (B, {
> > > >   method: function($super){
> > > >     $super();
> > > >   }
>
> > > > };
>
> > > > var d = new A(new (B));
> > > > var e = new A(new (C));
>
> > > > Anybody got any strong opinions on which approach is best?--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Spinoffs" group.
To post to this group, send email to
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Rails spinoffs - Apr 2008 - Extending instances from classes with inheritance

Extending instances from classes with inheritance

Re: Extending instances from classes with inheritance

Re: Extending instances from classes with inheritance

Re: Extending instances from classes with inheritance

Re: Extending instances from classes with inheritance