Help: Empty and Single Unit Dropzone

[Genei180]

Hey, thanks for your Work.

Unfortunately, I am having a lot of Issues, getting it to fit into my Use case.
(But i got to admit, still in a Learning Curve).
Unfortunately, the Documentation Provided is not really helping.

My Use Case is a need for Empty Individual Drag and Drop Zone that accept just one Item.
(Those Correspond to Vehicle Seats, with a Corresponding Training Qualification needed for the Position.)
On Start, they need to be Empty, and Ready to Accept a Drop.

If I understand this Correctly, this is not Possible with your Module, as a List needs to Always be passed to the DND Zone?
When passing an Empty List to dndzone Items, it causes me a lot of Trouble.
Either not rendering at all, or not accepting something.

It feels like I am missing something very Obvious.

Additionally, i don't fully understand if it would be Possible to Block the Drop Event, and Resetting the Element, when the Condition of the Qualification is not met at the Drop Zone.

Who would have known, that adding Drag and Drop with Touch, would be such a Rabbit hole. :/

Thanks a lot for your Help.

[isaacHagoel]

Can you create a repl illustrating your issue? You can pass in an empty list to a drop zone or a list with a single item. You can you dragDisabled and dropFromOthersDisabled to control the number of items allowed

…

On Sun, Apr 6, 2025, 08:26 Genei180 ***@***.***> wrote: Hey, thanks for your Work. Unfortunately, I am having a lot of Issues, getting it to fit into my Use case. (But i got to admit, still in a Learning Curve). Unfortunately, the Documentation Provided is not really helping. My Use Case is a need for Empty Individual Drag and Drop Zone that accept just one Item. (Those Correspond to Vehicle Seats, with a Corresponding Training Qualification needed for the Position.) On Start, they need to be Empty, and Ready to Accept a Drop. If I understand this Correctly, this is not Possible with your Module, as a List needs to Always be passed to the DND Zone? When passing an Empty List to dndzone Items, it causes me a lot of Trouble. Either not rendering at all, or not accepting something. It feels like I am missing something very Obvious. Additionally, i don't fully understand if it would be Possible to Block the Drop Event, and Resetting the Element, when the Condition of the Qualification is not met at the Drop Zone. Thanks a lot for your Help. — Reply to this email directly, view it on GitHub <#643>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AE4OZC7RY5KB6DRRVIHU4SL2YBKAPAVCNFSM6AAAAAB2Q62JJCVHI2DSMVQWIX3LMV43ASLTON2WKOZSHE3TINJTHAZTKOI> . You are receiving this because you are subscribed to this thread.Message ID: ***@***.***> [image: Genei180]*Genei180* created an issue (isaacHagoel/svelte-dnd-action#643) <#643> Hey, thanks for your Work. Unfortunately, I am having a lot of Issues, getting it to fit into my Use case. (But i got to admit, still in a Learning Curve). Unfortunately, the Documentation Provided is not really helping. My Use Case is a need for Empty Individual Drag and Drop Zone that accept just one Item. (Those Correspond to Vehicle Seats, with a Corresponding Training Qualification needed for the Position.) On Start, they need to be Empty, and Ready to Accept a Drop. If I understand this Correctly, this is not Possible with your Module, as a List needs to Always be passed to the DND Zone? When passing an Empty List to dndzone Items, it causes me a lot of Trouble. Either not rendering at all, or not accepting something. It feels like I am missing something very Obvious. Additionally, i don't fully understand if it would be Possible to Block the Drop Event, and Resetting the Element, when the Condition of the Qualification is not met at the Drop Zone. Thanks a lot for your Help. — Reply to this email directly, view it on GitHub <#643>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AE4OZC7RY5KB6DRRVIHU4SL2YBKAPAVCNFSM6AAAAAB2Q62JJCVHI2DSMVQWIX3LMV43ASLTON2WKOZSHE3TINJTHAZTKOI> . You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

[Genei180]

First of, thanks for taking your Time Helping me out. It's greatly appreciated.

You can you dragDisabled and dropFromOthersDisabled to control the number of items allowed

That was the Part of what I figured out somewhat, but it was part of my Problem.

Basically, it boiled down to a Misunderstanding of Typescript in my Understanding.

This Works:

let items = [];

     [...]

<section use:dndzone={{items: items}} on:consider="{handleConsiderDrop}" on:finalize={handleFinaliceDrop}>

This doesn't: (It doesn't let you Drop to it, i tried many Different Versions of it)

let item;

     [...]

<section use:dndzone={{items: [item]}} on:consider="{handleConsiderDrop}" on:finalize={handleFinaliceDrop}>

In Core, in my understanding, it boils down to the "Undefined" State, which I am not Really Familiar of. (Coming from other Languages)

Code	Value of items	Meaning
let item; { items: [item] }	[undefined]	One item, not initialized
let item = null; { items: [item] }	[null]	One item, intentionally "nothing"
let items = []; { items: items }	[]	No items at all yet

And I Expected another behavior off, which was driving me nuts, because I couldn't Crasp, what the Problem was.
Maybe it would have been Helpful if it had thrown a warning/different Behavior.

Now Working Minimal Example:

Be Aware, my Use Case Involved a List, Of Objects.
Those Objects (Vehicle_Position), contained Childs (Crew Members), that when Undefined, should display the
Vehicle_Position. Qualification that should get Replaced, when Vehicle_Position.Crew Member becomes assigned via the Drag and Drop.
In other Words, i expected a Different Behavior or atleast a Warning from DND.
This Behavior can be made Possible via

let item;
let items = item? [item] : []

     [...]

<section use:dndzone={{items: [item]}} on:consider="{handleConsiderDrop}" on:finalize={handleFinaliceDrop}>

Thanks for this Awesome Lib.

If you don't want to take Action about this, feel free too close this issue.
If you do want to take Action, I would Rename the Issue, to "Missing Undefined Warning/Behavior in dndzone"

If the Expected Behavior is of Type , please help me learn something.
Thanks a lot!

[Genei180]

Side Note, to the Minimal Example,

There is a Div Inside, that should be replaced, by Another.
The Placeholder Div, becomes Draggable, even tho it's not meant to be and Errors out with:
Uncaught TypeError: draggedElData is undefined

-> Can be Disabled, with "dragDisable"