Adding Delay/Condition on For Each

gilbertman77 · October 21, 2021, 5:18pm

I am writing code to perform a curl GET HTML request to get data from a key/value database.

I'm using a dictionary to store the key/values, and cycling through each key using a for each loop.

The issue is that even when I try to wait for a web response, only the last key in the dictionary get populated with data. Not sure how to insert a delay and recheck inside the loop, or if that even works based on how MIT multi-threading works. Wondering if anyone knows of a workaround are possible implementation that will wait to perform the next loop iteration until after the "web.GotText" response has been completed.

http://ai2.appinventor.mit.edu/#4851997483597824

Thanks,
Josh

ABG · October 21, 2021, 5:35pm

You need a work queue, not a loop.

Load the work queue (list) with URLs, then launch your first (item 1) URL's Web Get.

When Web1 GotText fires,

process the incoming text based on the URL
if the work queue is not empty,
- remove item 1
if the work queue is not empty,
- launch your first (item 1) URL's Web Get.

AI2 does not like looping for waiting. It goes into a coma.

gilbertman77 · October 21, 2021, 5:39pm

Thanks ABG.. New to the MIT construct (loops, threads, delays are more my world). Can you point me in the right direction for how to implement a "work queue"? How to start, process, complete, reiterate.. within the MIT App construct?

Much appreciated.

Josh

ABG · October 21, 2021, 5:40pm

@Taifun has a code sample to download multiple files at his puravidaapps.com site.

P.S. Found it:
http://puravidaapps.com/filebyfile.php

P.P.S. Also see

gilbertman77 · October 21, 2021, 6:33pm

Ahh.. Ok.. I think I see the key idea here. You iterate using a global counter, and call the subsequent "GET" requests in the GOTTEXT event. Makes sense. I'll give it a go.

Thanks again.

gilbertman77 · October 22, 2021, 12:50am

FYI, thought I'd post my working code here for future readers.

Thanks again.