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.

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.

Signature

void Reserve(SizeType Number)

Parameters

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

Return Type

void

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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