Prevent multiple users from editing same records

[joshieboy]

I'm seeing several solutions around this and hoping that mine is simple to implement.  

I have a marketplace app that allows users to upload items for sale, and by default the status will set to "Available."   There are two statuses - Available and Reserved.  If someone goes to the marketplace, the gallery filters all items where Availability = "Available.",and  once someone selects a Reserve this item button and submits it, the status Availability updates to "Reserved" and removes the item from the catalogue, while also sending the seller an email that someone wants to purchase their item.  Therefore the catalog only shows available items for sale.  If the transaction does not go through because of loss of interest or anything, the seller can update the Availability of the item to "Available", making it show up again in the Catalogue.

My issue is if two users have the same item open, one probably all day and the other clicking the Reserve button, and it removes the catalog, but the other user still has the open item up on their screen, so they may also get to reserve it.  The SharePoint field in the list is "Availability" and its status once reserved changes to "Reserved."  Is there a way for the system on submit of the second user or any user after the who may also have it open- to check if Availability is set to Reserved and block them from submitting, whist also showing a message of some sort.  Any help to execute this appreciated.  

[joshieboy]

Hi again @WarrenBelz - is there a specific period of time that has to pass for the system to generate the message?  While it worked well and blocked some users from being able to reserve items already reserved, a user got this error message yesterday.

[WarrenBelz]

Hi @joshieboy ,

That would be the message a user would receive if another user has saved the same record since they loaded it. They simply need to reload the record (which will then contain the changes from the other user). The code I supplied in theory should stop that as it checks if the record has been saved since they loaded it, however there could be a couple of seconds "gap" in there if the records were saved very close together.

[joshieboy]

Thanks @WarrenBelz  - its only after I sent you this I realized that.  And it does work.  The second person was not able to reserve the item even though it appeared that it went through.  Thanks.