[mochikit] callLater and this
Is it intentional that the callLater() function causes the 'this' reference
to get scrapped?
Say I run the following. It should call the __repr__ function for my object
that I created but it I suppose the function gets moved to another object
during the callLater call. See http://www.ianlewis.org/dump/test.html for a
running example.
test = new Object();
test.__repr__ = function() {
return This is my repr.;
}
test.myfunc = function() {
logDebug(repr(this));
}
test.init = function() {
createLoggingPane(true);
callLater(3.0, test.myfunc);
}
addLoadEvent(test.init);
--
Ian Lewis
[EMAIL PROTECTED]
http://www.ianlewis.org
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[mochikit] Re: callLater and this
On 12/20/07, Ian Lewis [EMAIL PROTECTED] wrote:
Is it intentional that the callLater() function causes the 'this' reference
to get scrapped?
Has nothing to do with MochiKit, JavaScript doesn't have bound methods
like Python does. The binding of this is done by the method call
syntax. It would be impossible to preserve it unless the function was
wrapped.
See MochiKit.Base.{bind,method,bindMethods} for the typical workarounds, also:
http://bob.pythonmac.org/archives/2005/07/06/this-sucks-in-javascript/
-bob
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[mochikit] Re: callLater and this
On 12/20/07, Ian Lewis [EMAIL PROTECTED] wrote:
Thanks bob, I guess it's been about 8 years. Good to talk to you again.
High school feels a lot longer ago than that :)
Tricky. I suppose you would run into this pretty much any time you pass
around foo.bar when bar bound (or not) to the object foo as you wouldn't be
able to do the call with this syntax. If your blog post is right then it
looks like the only way to do call with this explicitly calling the
function via the object in code.
Welcome to JavaScript.
That's pretty much what bind does, but Function.prototype.call and
Function.prototype.apply let you jigger this for a given call.
foo.bar(a, b) is the same as foo.bar.apply(foo, [a, b]) or
foo.bar.call(foo, a, b).
Anyway, changing the test code to
test.init = function() {
createLoggingPane(true);
callLater(3.0, bind(test.myfunc, test));
}
works. It's cute how bind returns a function that calls your function but
goes out and finds the this for you first. Pretty useful hack.
Well you give it 'this' as the second argument, it doesn't do all that
much magic.
bind(test.myfunc, test) is equivalent to function () { return
test.myfunc.apply(test, arguments); }
-bob
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[mochikit] Re: callLater and this
Thanks bob, I guess it's been about 8 years. Good to talk to you again.
Tricky. I suppose you would run into this pretty much any time you pass
around foo.bar when bar bound (or not) to the object foo as you wouldn't be
able to do the call with this syntax. If your blog post is right then it
looks like the only way to do call with this explicitly calling the
function via the object in code.
Anyway, changing the test code to
test.init = function() {
createLoggingPane(true);
callLater(3.0, bind(test.myfunc, test));
}
works. It's cute how bind returns a function that calls your function but
goes out and finds the this for you first. Pretty useful hack.
Ian
2007/12/21, Bob Ippolito [EMAIL PROTECTED]:
On 12/20/07, Ian Lewis [EMAIL PROTECTED] wrote:
Is it intentional that the callLater() function causes the 'this'
reference
to get scrapped?
Has nothing to do with MochiKit, JavaScript doesn't have bound methods
like Python does. The binding of this is done by the method call
syntax. It would be impossible to preserve it unless the function was
wrapped.
See MochiKit.Base.{bind,method,bindMethods} for the typical workarounds,
also:
http://bob.pythonmac.org/archives/2005/07/06/this-sucks-in-javascript/
-bob
--
Ian Lewis
[EMAIL PROTECTED]
http://www.ianlewis.org
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[mochikit] Re: callLater and this
2007/12/21, Bob Ippolito [EMAIL PROTECTED]: On 12/20/07, Ian Lewis [EMAIL PROTECTED] wrote: Thanks bob, I guess it's been about 8 years. Good to talk to you again. High school feels a lot longer ago than that :) Indeed. Welcome to JavaScript. I feel a my eyes twitching when I go to sleep. That's pretty much what bind does, but Function.prototype.call and Function.prototype.apply let you jigger this for a given call. foo.bar(a, b) is the same as foo.bar.apply(foo, [a, b]) or foo.bar.call(foo, a, b). Thank goodness it's there. works. It's cute how bind returns a function that calls your function but goes out and finds the this for you first. Pretty useful hack. Well you give it 'this' as the second argument, it doesn't do all that much magic. Only if you're kind enough to give it. I just happen to be a nice guy. Anywho, thanks for the insight. -- Ian Lewis [EMAIL PROTECTED] http://www.ianlewis.org --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups MochiKit group. To post to this group, send email to mochikit@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/mochikit?hl=en -~--~~~~--~~--~--~---
