TArray::Reserve

function Core Since unknown

#include "Containers/Array.h"

Access: public

Description

Pre-allocates memory for at least Number elements without changing the logical size. Prevents repeated reallocations when the final element count is known in advance.

Signature

void Reserve(SizeType Number)

Parameters

Name	Type	Description	Default
Number	int32	The minimum number of elements to reserve capacity for.	—

Return Type

void

Caveats & Gotchas

• Reserve() only grows capacity — it never shrinks it. To release excess memory, use Shrink() after removing elements.
• Calling Reserve() does not change Num() — the array's logical size stays the same. Only Add/Emplace/etc. increase Num().
• If Number is less than the current capacity, the call is a no-op.

Example

Reserve before a known-size population loop C++

TArray<FHitResult> Hits;
Hits.Reserve(32); // Expect up to 32 hits

GetWorld()->LineTraceMultiByChannel(Hits, Start, End, ECC_Visibility, Params);

// No reallocation occurred during the trace population

Version History

Introduced in: unknown

Version	Status	Notes
5.6	stable	—

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