Subj : JS_IsAssigning
To   : netscape.public.mozilla.jseng
From : jmtn@blueyonder.co.uk (James Turner)
Date : Thu Aug 28 2003 09:48 am

I have the following problem; I have an object 'foo', defined with a
custom class, and custom property getter / setters. I need, in my
implementation of the property getter callback, to distuinguish
between the following:

var foo = ..... ; // instance of my custom JS_Class with getters /
setters

var tmp = foo.bar.x;

FROM

foo.bar.x = 42;

I.e, get property needs to be able to tell if it's being used on the
LHS of an assignment. Note that I don't have control over what 'bar'
is; it might be another native-backed object, a vanilla Object, etc,
etc.

Then I found JS_IsAssigning(), and I was happy, until I tried using
it. The problem is, it never, ever returns 'true' for me, in either of
the cases above (naturally, I'd expect it to return false for the
first case, and true for the second). Have I misunderstood what is's
supposed to do? I also note that there's some JS_RESOLVE flags that
mention assignment; are these something I could be investigating?

Hoping this is possible,
James

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