Memory crash using EmplaceAt

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1

Hey!

I may misunderstanding the usage of EmplaceAt but if I do something like this:

UTestObject* NewSlot = DuplicateObject<UTestObject>(DefaultSlot, this); InventorySlots.EmplaceAt(Index, NewSlot);The engine crashes.

UTestObject in an UObject instantiated inline (but I got this crash using a nullptr as well) and EmplaceAt Index is equals to 3 (any value different than zero should do the job).

Code is pretty simple so I may be doing something wrong, I thought that EmplaceAt would have reserved the amount of memory I need it but It’s crashing. I also tried call Reserve first with Index+1 and It changed the ArrayMax value but the crash is still present.

Would you mind to point me how I can inject an object in an array at the specified index?

2

Steps to Reproduce

  1. Create an TArray of an UObject child class.
  2. Use EmplaceAt with an index different than zero.
  3. Crash
3

Hi,

You cannot ‘EmplaceAt’ or ‘Insert’ at an index greater than TArray<>::Count(). Since you have an array of pointers, you can add a couple of null elements first like below. Reserving the memory would possibly avoid reallocation, but this doesn’t construct the array ‘type’ item in the container.

if (Index > InventorySlots.Count()) { InventorySlots.AddDefaulted(Index - InventorySlots.Count()); } InventorySlots.EmplaceAt(Index, DuplicateObject<UTestObject>(DefaultSlot, this));Regards,

Patrick