Re: Shell-Extension: unwanted behavior

[俞颐超 <yyc1992 gmail com>]

On Thu, Aug 18, 2011 at 10:41 AM, Jasper St. Pierre
<jstpierre mecheye net> wrote:
> On Thu, Aug 18, 2011 at 8:06 AM, Ole Ernst <oleernst web de> wrote:
>> Hello everybody,
>>
>> I encountered a problem while writing a shell-extension. Based on a
>> config-array (which gets loaded at start up) I want to create a variable
>> number of PopupMenuItems, which should be connected to different functions.
>>
>> Here is the simplified code, which shows the unwanted behavior:
>> http://pastebin.com/GsjzHVyK
>>
>> The problem is: no matter on what menu I click, the log always says
>> Entry3 (last connected function). Actually I'd like it to show Entry1 to
>> Entry3 based on the menu I click.
>>
>> Am I missing something? Is there another way of doing it? (Note: That's
>> pretty much my first contact with javascript)
>
> JavaScript has funky scoping rules.
>
> First, make sure you use "const presets" or "let presets", otherwise
> you're defining a global there.
>
> Second, the problem is that you're declaring "item" *outside* of the
> for loop, which means that there's one variable which is updated per
> loop, and all the closures reference the same variable. Putting "let
> item;" inside the loop body should make it scoped to the block itself.
>
it is ok to "let item" outside the loop since "item = ..." will make
"item" point to different variables each time.

I think the problem is which "key" the function get each time and the
problem is the same with the following code:
let set = {"a": 1, "b": 2, "c": 3};
let func = {};
for (let key in set) {
    func[key] = function() {
        print(key);
    }
    func[key]();
}
for (let key in set) {
    func[key]();
}
for (let ke in set) {
    let key = ke;
    func[key] = function() {
        print(key);
    }
    func[key]();
}
for (let key in set) {
    func[key]();
}

run it with gjs will print
a
b
c
c
c
c
a
b
c
a
b
c

I think the problem is that you need to "let key" inside the loop.
Somehow, in "for (let a in b)" a point to a same variable each
time.~~~(afaik)


>> Thanks in advance!
>>
>> Ole Ernst
>> _______________________________________________
>> gnome-shell-list mailing list
>> gnome-shell-list gnome org
>> http://mail.gnome.org/mailman/listinfo/gnome-shell-list
>>
>
>
>
> --
>   Jasper
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