Allow drop on empty part of table

[cvconover]

I thought it was not as intuitive to force the user to drop the first item at the very top on an empty table, so I made some mods that I think could improve the UX but I am not certain if there are any negative repercussions as I have not done extensive testing, yet, but so far it looks good. Here's what I did.

In I3DragBetweenHelper, I commented out lines 792 - 797 (if nil check on drop index)
https://github.com/ice3-software/i3-dragndrop/blob/master/Classes/I3DragBetweenHelper.m#L792

Then in the delegate method, droppedOnDstAtIndexPath:to fromSrcIndexPath:from, I check for index==nil and just create a new NSIndexPath with row set to the size of the datasource of the target table. I have to do the same in the srcTable as I did in the dstTable, obviously.

if (to == nil)
{
    to = [NSIndexPath indexPathForRow:(self.dstDataSource.count) inSection:0];
}

Hope this can make it into your sources as feature if you see it as useful.

[SteveFortune]

Looks good. Please create a PR to the dev branch and I'll review and merge when I get a chance.

Before you PR, could you run through the Test App scenarios just to double check that it doesn't cause any issues?

Thanks!

[cvconover]

Will do. I'll have to follow up on this over the next several days but I will run the tests.

[cvconover]

Made significant progress on this tonight. More to do than I thought but should have it solid for all Test app scenarios soon.

[SteveFortune]

See issues with #18

[pboushy]

Hi Steve and Craig, I'm currently using this library in one of my apps and looking forward to having this functionality. Is there anything I could assist with to help implement this?

[SteveFortune]

Hi @prbsparx, check out Craig's PR. If you want to move this issue along, it would be very helpful if you could review and try to resolve the issues that I've highlighted in the comments. I'd me happy to merge it into the next release if we can make it more stable. :)

[SteveFortune]

Proposing the following algorithm for coordination on drag stop, which should resolve this and #34:

• If data source says delete at this drop origin
  • Delete
• Else if stop drag on collection && if drag stopped on same collection as origin && valid item at drop origin && data source says rearrangeable
  • Rearrange
• Else if drag stopped on different collection
  • If the data source says we can exchange the items at the given points in these collections && there is a valid item in the target collection
    • Exchange
    • Note that the coordinator assumes that if the data source says ‘yes’ but there is no valid item in the target collection, that the data source is wrong. Advantage here is that we’re safeguarding the user against violating integrity constraints
  • Else if the data source says that we can append the item onto the target collection
    • Append
    • Note that here we don't check whether there isn't a valid item at the drop origin. This is because a user may want to configure drops across the whole of a collection to be appendations not exchanges. Appending items only if the drop origin allows and there is no item at that point in the collection is too opinionated.
  • Else
    • Reset
• Else
  • Reset

[SteveFortune]

We need to change the render delegate protocol as well to offer methods for rendering both appendation and exchanging.