StackOverflow2013

Note that there are some explanatory texts on larger screens.

plurals

POswitching views with grand central dispatch
text
Body
copied!<p>I've looked at a lot of topics but I still can't figure it out. </p> <p>I have a UITableview which downloads its content online. Each cell has an image, and I use GCD to let the image download. The downloaded image will be saved to disk, and before each time a cell is loaded there is checked if the file already exist, if not -> gcd, nsdata etc.</p> <p>All goes well if someone has a good internet connection (wifi), but if I'm going to hop from View to View (back and forth), with my crappy 3G connection, what happens is that it wants to finish its queue (about 4 cells), but already gets assigned a new one, and a new one, and a new one and eventually the user has to wait a looong time before the others are executed (which he doesnt see) before the actual UITableview gets populated. With NSLog I can see that even I'm in a different view, it's still downloading and making uiimages that were visible on the screen. Each task is approximately 100 kb, and with a slow (or even no internet connection?!) it can take a while if you have a lot.</p> <p>I know it's not possible to cancel it, but I read in other topics about using a BOOL variable but I don't really get it. Even if the BOOL variable change when the user leaves the screen, the cells are already in queue right?</p> <p>Is it possible that when a user taps the back button in my Navigationcontroller, so he leaves the view, I change the data the blocks in queue use (empty it), so there is nothing to download and the blocks will be executed right away (there is nothing to do). So something like, making every value in array newsitems nil? Is it possible to change the datasource, or will the blocks that are waiting already have their datasource with them while waiting?</p> <p>Then there is another problem, this doesn't have effect on the the currently executed block. </p> <p>Can someone point me in a good direction? </p> <p>Thank you.</p> <p>Prastow</p>

Querying!

Guidance

An individual column

Larger individual text columns get their own page to allow for proper reading.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload