TArray::InsertUninitialized
#include "Containers/Array.h"
Access: public
Specifiers: inline
Description
Opens a gap of Count uninitialized element slots at Index, shifting later elements right. The caller must construct each new slot before any further array operation.
Caveats & Gotchas
- • The opened slots contain garbage memory. Unlike Insert(), no constructor is called — all Count slots must be placement-new'd or memcpy'd into before they can be read safely.
- • Inserting into the middle of the array requires shifting all elements after Index, which is an O(N) operation. Prefer appending + sorting, or use a different data structure if mid-array insertions are frequent.
- • Do not use with element types that have non-trivial constructors; use InsertDefaulted() or Insert() instead.
Signature
UE_NODEBUG UE_FORCEINLINE_HINT void InsertUninitialized(SizeType Index, SizeType Count = 1)Parameters
| Name | Type | Description | Default |
|---|---|---|---|
| Index | SizeType | Position at which to open the gap. Existing elements at and after this index are shifted right. | — |
| Count | SizeType | Number of uninitialized slots to insert. | 1 |
Return Type
void Example
Reserve a slot in the middle for a placement-new C++
TArray<FMyPOD> Data;
Data.SetNum(5);
// Open a slot at index 2
Data.InsertUninitialized(2);
// Placement-new into the raw slot
::new(&Data[2]) FMyPOD(42);Tags
Version History
Introduced in: 4.0
| Version | Status | Notes |
|---|---|---|
| 5.6 | stable | — |
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