Rails spinoffs - Feb 2007 - How to try out Class Animal example (Example 4.1) using prototype 1.5? More options

Someone told to try to ask the question here:

I tried to copy the example into a html file. And when I run the
page,
I didn''t see anything. When I put an alert under

var Animal = Class.create();

I didn''t see my alert.


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Hey Steve,

findingsteve-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org a écrit
:
> I didn''t see anything. When I put an alert under
> var Animal = Class.create();
> I didn''t see my alert.
Check your browser for JS errors.  It appears the HTML page you copied 
this into does not load Prototype before running this script.  Do you 
have something like:

<script type="text/javascript"
src="your/path/to/prototype.js"></script>

...present before the script you''re playing with?  If not, then
"Class"
does not exist, so doing "Class.create" won''t work:
you''ll get a JS
error.  Depending on the browser you''re playing with, such errors are 
more or less visible.

-- 
Christophe Porteneuve aka TDD
tdd-x+CfDp/qHev2eFz/2MeuCQ@public.gmane.org

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Yes, I have my prototype.js. I didn''t see any error mesg using IE. I
will try to see check it out if there is there is any error using
Mozila''s Firebug. Thanks.

From,
Steve


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Yah, my fault. Indeed I didn''t have my prototype.js. And after I make
sure I have my prototype.js, and run it again, I still didn''t see
anything and got 1 error in Mozila, saying:

sound is not defined

How do I go about it now? Below are the whole code:

<script>
var Animal = Class.create();

Animal.prototype = {
	initialize: function(name, sound) {
		this.name = name;
		this.sound = sound;
	},
	speak: function() {
	alert(name + " says: " + sound + "!");
	}
};

var snake = new Animal("Ringneck", "hissssssssss");
snake.speak();
// -> alerts "Ringneck says: hissssssssss!"

var Dog = Class.create();
Dog.prototype = Object.extend(new Animal(), {
	initialize: function(name) {
		this.name = name;
		this.sound = "woof";
	}
});

var fido = new Dog("Fido");
fido.speak();
// -> alerts "Fido says: woof!"
</script>


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findingsteve-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org
wrote:
> ...
> initialize: function(name, sound) {
>   this.name = name;
>   this.sound = sound;
> },
> speak: function() {
>   alert(name + " says: " + sound + "!");
> }
just a typo.  "sound" should be "this.sound" :

speak: function() {
  alert(name + " says: " + this.sound + "!");
}


Regards,
Ken Snyder

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Thanks. I saw the result now after this changes. I realize that name
also need to change to this.name.


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There is one problem in this approach. In Animal, name and sound are
the named properties which is not part of Animal.prototype, but they
becomes prototype properties in Dog class, so if you create many
different dogs from Dog class, all dogs will share the one name and
sound properties, which means if you change the name in one dog, then
all the other dogs will get the same name. The prototype Object.extend
is mainly for extending property and not good for implementing
inheritance.

On Feb 23, 1:54 am,
"findingst...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org"
<findingst...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> Thanks. I saw the result now after this changes. I realize that name
> also need to change to this.name.

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Kerdosa, STOP spewing out fallacies about how prototype works.  Read my
reply to your previous post, then read again how prototype actually
works (e.g. on DevMo, or in the ECMA-262 spec), then we''ll welcome your
replies once they''re, er... correct.

-- 
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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