Silas Silva <silasdb@gmail.com> wrote:

Hello there!

I've written a very simple Tk application that is very serial.
Recently I added support for http requests like this:

set token [::http::geturl example.com]
set data [::http::data $token]
(configure .toplevel.mywidget with $data)

I soon discovered that ::http::geturl doesn't block the main loop,
which is great, but it happens that for my very serial application,
it can be problematic sometimes. For instance: sometimes I destroy
the toplevel in which mywidget lives before it got a chance to
receive $data, so when geturl resumes its execution, my code throws
an error because it tries to configure mywidget.
[...]
Alternatively, is there a more elegant solution that is not to add a
bunch of if's to check if widgets still exist?

If it is just a missing toplevel, you could wrap the 'configure' in a
try:

try {
configure .toplevel.mywidget with $data
} on error {a b} {
# do whatever you should do here when the configure fails
}

Or you can check for the toplevel before trying to configure it:

if {[winfo exists .toplevel]} {
configure .toplevel.mywidget with $data
} else {
# do what you need to do when the toplevel has been destroyed
}

Note that the "do whatever" should include freeing the return token
from geturl, otherwise you will have a memory leak.

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