Dealing with table updates

[bobspryn]

I'm trying to think if there's a more RAC way to deal with table updates.

Basically I have a table that has 4 or 5 distinct states. As a user goes through building a question, they trigger a state update by doing something like clicking a button to advance, or clicking a pseudo back button to move back.

Now all the cells can observe the state on the viewModel and update themselves accordingly. Where it gets hair is all the rows/sections that are inserted/removed/reloaded (to update height).

If I didn't need to run beginUpdates and endUpdates with all the respective table changes in between, it would be pretty easy to filter and map the changes into some nice clean code, but those begin and end calls really throw a wrench in the the works.

So I end up with code like this:

[self.tableView beginUpdates];

if(viewState.integerValue == TCAskQuestionStateAPIBroad) {
    if(self.viewModel.previousAskQuestionViewState == TCAskQuestionStateTypeQuestion) {
        // reload the question row
        [self.tableView reloadRowsAtIndexPaths:@[[NSIndexPath indexPathForRow:0 inSection:0]] withRowAnimation:UITableViewRowAnimationAutomatic];
        // insert the broad category rows
        [self.tableView reloadSections:[NSIndexSet indexSetWithIndex:TableSectionAPICategories] withRowAnimation:UITableViewRowAnimationRight];
    } else {
        // coming the other way
    }
} else if (viewState.integerValue == TCAskQuestionStateAPIGranular) {

} else if (viewState.integerValue == TCAskQuestionStateAPISomething) {

}
//etc

[self.tableView endUpdates];

I thought about having a beginUpdatesSubject that mapReplaces into the view state signal and splitting lots of signals off of that, but then I have to also somehow observe for all those other signals to complete to call endUpdates. In the end it didn't end up looking much better than a nested if.

Thoughts?

[nikolaykasyanov]

Why not wrap several table updates into some kind of batch? And when some view model signal sends next (a batch), call beginUpdate/endUpdate and perform all updates from batch.

I'd love to hear some best practices in managing table/collection views too.

[notxcain]

I'm in the process of crafting TableViewModel right now. Here is the implementation of change object. This objects are sent by change signal of view model.
https://gist.github.com/denis-mikhaylov/7889166

You need to create category on UITableView and implement QWSectionedList protocol. Then simply send applyToList:tableView.

[notxcain]

Here is a protocol (WIP) for table view model
https://gist.github.com/denis-mikhaylov/7889347

[bobspryn]

@denis-mikhaylov Interesting strategy. I like the concept. Thanks! Curious if others have thoughts on this too.

[bobspryn]

@denis-mikhaylov When you wrap that up, it would be awesome if you put together a quick sample app showing it off. Good learning tool.

[notxcain]

@sprynmr sure I will!

[kastiglione]

@sprynmr Have a look at #1032.

[bobspryn]

@denis-mikhaylov Back to this again. Looking at your list which is pretty cool. Curious if you made updates?

[notxcain]

@sprynmr Well. After the introduction of #1032 it became as trivial as observing collection of collections and animating corresponding changes. So I decided not to waste time on sectioned list.

[bobspryn]

Makes sense. I'm just not using 3.0 yet.

[notxcain]

Me neither. Just implemented this using rac_valuesAndChanges:forKeypath:options:observer: