Rails spinoffs - May 2007 - Enumerable.each() and custom object functions?

Hi,

I have code for a custom object (this is just a mockup, but the
principal applies):

var Player = Class.create();
Player.prototype = {
  initialize: function(_id) {
    this.id = _id;
  }

  something: function() {
    alert(this.id);
  }
}

I also have some code that creates the objects in a for loop (that
reads some xml fyi) and stashes them away in a hash. All fine and
dandy. I can access these objects from this hash by calling

myhash[some_id].something();

and I get a lovely alert!!

However, what I would like to do is call the something function for
all members of the hash (ok so I don;t want them to display a message
box, but again, the principal applies)

I assumed i could use

myhash.each( function(item) { item.something(); } );

but i can''t, all i get

"item.something is not a function"

Any ideas? In the meantime i have solved this by doing  at keys() then
looping over the keys and calling myhash[keys[loop_var]].something()
which seems really obtuse!!!

Thanks for any help!!

esp05


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If you want to invoke the same method for all items in an Enumerable
you can use invoke: http://www.prototypejs.org/api/enumerable/invoke

e.g., myEnum.invoke(''something'')

On 5/20/07, emma.persky-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org
<emma.persky-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
>
> Hi,
>
> I have code for a custom object (this is just a mockup, but the
> principal applies):
>
> var Player = Class.create();
> Player.prototype = {
>   initialize: function(_id) {
>     this.id = _id;
>   }
>
>   something: function() {
>     alert(this.id);
>   }
> }
>
> I also have some code that creates the objects in a for loop (that
> reads some xml fyi) and stashes them away in a hash. All fine and
> dandy. I can access these objects from this hash by calling
>
> myhash[some_id].something();
>
> and I get a lovely alert!!
>
> However, what I would like to do is call the something function for
> all members of the hash (ok so I don;t want them to display a message
> box, but again, the principal applies)
>
> I assumed i could use
>
> myhash.each( function(item) { item.something(); } );
>
> but i can''t, all i get
>
> "item.something is not a function"
>
> Any ideas? In the meantime i have solved this by doing  at keys() then
> looping over the keys and calling myhash[keys[loop_var]].something()
> which seems really obtuse!!!
>
> Thanks for any help!!
>
> esp05
>
>
> >
>

-- 
Jesse E.I. Farmer
e: jesse-h8Qh2m8E5SHQT0dZR+AlfA@public.gmane.org
w: http://20bits.com

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Hey Emma,

What exactly do you call a hash?  A *Hash* instance?  Or just a good
ol''
JavaScript object?  Or even an Array, perhaps?

Now, if you''re indeed using a Hash, look at the docs to see that
enumerating a hash gets the *pairs*, not the values alone.  So you''d
need to access the pair''s 1-indexed property, or "value"
property
(they''re basically the same, in two notations), and call your method on
it.

  var h = new Hash();
  h[''john''] = new Player(''john'');
  h[''mary''] = new Player(''mary'');

  h.each(function(pair) { pair[1].something(); });
  // or:
  h.each(function(pair) { pair.value.something(); });

Because of this, invoke won''t work as expected, since it requires the
invoked method to be present in the passed object.  But you can trick it:

  h.pluck(''value'').invoke(''something'');

Check out the docs for these:

  http://prototypejs.org/api/hash/each
  http://prototypejs.org/api/enumerable/invoke
  http://prototypejs.org/api/enumerable/pluck

''HTH,

-- 
Christophe Porteneuve a.k.a. TDD
"[They] did not know it was impossible, so they did it." --Mark Twain
Email: tdd-x+CfDp/qHev2eFz/2MeuCQ@public.gmane.org

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Heya,

thanks. I think i was having a slow day. I didn''t even think to try
value.something()!!!! It seems a little odd that you get back the pair
when iterating, and not the value, given that the point of a hash is
retreiving the values by key or iteration overall).

Atleast its now here and documented a little more clearly for all to
read!!

Emma xx

On May 21, 7:41 am, Christophe Porteneuve
<t...-x+CfDp/qHev2eFz/2MeuCQ@public.gmane.org>
wrote:
> Hey Emma,
>
> What exactly do you call a hash?  A *Hash* instance?  Or just a good
ol''
> JavaScript object?  Or even an Array, perhaps?
>
> Now, if you''re indeed using a Hash, look at the docs to see that
> enumerating a hash gets the *pairs*, not the values alone.  So
you''d
> need to access the pair''s 1-indexed property, or "value"
property
> (they''re basically the same, in two notations), and call your
method on it.
>
>   var h = new Hash();
>   h[''john''] = new Player(''john'');
>   h[''mary''] = new Player(''mary'');
>
>   h.each(function(pair) { pair[1].something(); });
>   // or:
>   h.each(function(pair) { pair.value.something(); });
>
> Because of this, invoke won''t work as expected, since it requires
the
> invoked method to be present in the passed object.  But you can trick it:
>
>   h.pluck(''value'').invoke(''something'');
>
> Check out the docs for these:
>
>  http://prototypejs.org/api/hash/each
>  http://prototypejs.org/api/enumerable/invoke
>  http://prototypejs.org/api/enumerable/pluck
>
> ''HTH,
>
> --
> Christophe Porteneuve a.k.a. TDD
> "[They] did not know it was impossible, so they did it." --Mark
Twain
> Email: t...-x+CfDp/qHev2eFz/2MeuCQ@public.gmane.org

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