Let me suggest the module pattern - which not inconsequently also enables
true private fields and methods (just because it seems you're looking for
alternative patterns). Also, since the module pattern allows for true
private members, you can just create a helper function at the module level,
thus avoiding placing the "f" function at the instance level. This assumes
you probably don't want calling code to create and instance of Sub2 and then
just randomly make calls to myInstance.f()...
// (if you don't use a globally accessible namespace object to tack your
> classes onto, then declare the class variable outside of the module function
> so the reference is visible elsewhere, but I highly recommend just using a
> namespace object to hold all your classes instead)
var Sub2; //as in the note above, only required here if not using a
namespace object
(function() {
//put the handler here, as a helper function, and no need for it to be
public because you typically won't want outside code to do someInstance.f(),
right? (no more of this "it has an underscore so it's private" stuff, people
:)
function f() {
alert("Class:" + this.fu + this.baz);
}
Sub2 = Class.create(Super2, { // notice no "var" since in this example
we declared outside the module so it's available outside the module
baz: "bat",
initialize: function () {
document.observe("click", f.bind(this)); //just in-line the
binding to make it cleaner, unless you need to re-user the bound function,
then maybe cache it in a variable
}
});
})();
new Sub2();
On Mon, Aug 3, 2009 at 12:05 PM, T.J. Crowder <[email protected]>
wrote:
>
> Hi,
>
> > But it's really inelegant. How am I supposed to handle this?
>
> Pretty much like that, except I haven't reassigned the property like
> that. It *should* be fine, you'll create an own property 'f' on the
> instance (rather than an inherited one from the prototype) that's
> bound. But it bothers me and I can't give you a good reason for
> it. :-) I've done that sort of thing before (keep a bound copy around
> on the instance, if I'm going to reuse it), I've just for some reason
> always used a different prop name, I guess so I'm not in doubt whether
> I've bound it. But doing it in the initializer like you have, there
> wouldn't be any confusion...
>
> Also, the odds are pretty high you just want #bind, not
> #bindAsEventListener.[1]
>
> [1]
> http://proto-scripty.wikidot.com/prototype:tip-you-probably-don-t-need-bindaseventlistener
>
> HTH,
> --
> T.J. Crowder
> tj / crowder software / com
> Independent Software Engineer, consulting services available
>
>
> On Aug 3, 2:39 pm, Cédric <[email protected]> wrote:
> > Hello,
> >
> > I'm trying to use the Class methods to manage my object hierarchy on
> > my current project, but I have some trouble with the "this" keyword in
> > conjonction with Class.create.
> >
> > Here is a piece of plain-js code using prototypes to get inheritance:
> >
> > var Super1 = function () {
> > this.fu = "bar";
> >
> > }
> >
> > var Sub1 = function () {
> > this.baz = "bat";
> > this.f = function () {
> > alert("classic:"+this.fu+this.baz);
> > }.bind(this);
> > document.observe("click", this.f);};
> >
> > Sub1.prototype = new Super1();
> > new Sub1();
> >
> > Here is my attempt at mimic this with Class.create:
> >
> > var Super2 = Class.create({
> > fu: "bar"
> >
> > });
> >
> > var Sub2 = Class.create(Super2, {
> > baz: "bat",
> > f: function () {
> > alert("Class:"+this.fu+this.baz);
> > }.bindAsEventListener(this),
> > initialize: function () {
> > document.observe("click", this.f);
> > }});
> >
> > new Sub2();
> >
> > But of course it doesn't work, f in bound to window, not the object
> > create by new. The only way I found is:
> >
> > var Super2 = Class.create({
> > fu: "bar"
> >
> > });
> >
> > var Sub2 = Class.create(Super2, {
> > baz: "bat",
> > f: function () {
> > alert("Class:"+this.fu+this.baz);
> > },
> > initialize: function () {
> > this.f = this.f.bindAsEventListener(this);
> > document.observe("click", this.f);
> > }});
> >
> > new Sub2();
> >
> > But it's really inelegant. How am I supposed to handle this?
> >
>
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