TArray::RangeCheck

function Core Since 4.0

#include "Containers/Array.h"

Access: protected Specifiers: inline

Description

Validates that an index is within the array bounds, triggering a checkf assertion on failure. Only active when the allocator's RequireRangeCheck policy is true; allocators like TInlineAllocator with NoRangeCheck disable this at compile time.

Caveats & Gotchas

• This is a protected internal method called by operator[], Last(), Pop(), and other accessors — you almost never call it directly. Use IsValidIndex() for conditional checks that should not crash.
• The check is a compile-time no-op when AllocatorType::RequireRangeCheck is false (e.g. with stack allocators configured for maximum performance). Do not rely on it firing in all configurations.
• A two-parameter overload exists — RangeCheck(Index, Count) — that validates an entire subrange; use it when validating slice operations.

Signature

UE_FORCEINLINE_HINT void RangeCheck(SizeType Index) const

Parameters

Name	Type	Description	Default
Index	SizeType	Index to validate against the array bounds.	—

Return Type

void

Example

Using IsValidIndex instead of RangeCheck for safe conditional access C++

TArray<int32> MyArray = {10, 20, 30};
int32 QueryIndex = 5;
if (MyArray.IsValidIndex(QueryIndex))
{
    // Safe — use operator[] which calls RangeCheck internally
    int32 Val = MyArray[QueryIndex];
}

Version History

Introduced in: 4.0

Version	Status	Notes
5.6	stable	—

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