No Operator Found Which Takes a Left-Hand Operand in UE5 – What It Means & How to Fix It

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🧠 Why You’re Seeing This Error

The C2678 error means you tried to use a binary operator (like +, -, *, ==, etc.) with a type on the left-hand side that doesn’t support it.

In simpler terms, the compiler is saying:

“I don’t know how to apply this operator to the type on the left.”

In UE5, this often happens when:

• You try to compare or combine custom types like FVector, FString, or FName with incompatible types (like int or const char*)
• You use ==, +, or += between types that don’t define how to interact
• You accidentally reverse the order of operands (left-hand vs right-hand matters in C++)
• You forget to call a method like .ToString() before concatenating/logging UE5 types

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💥 Example Error Message

error C2678: binary '==' : no operator found which takes a left-hand operand of type 'FVector' (or there is no acceptable conversion)

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🛠️ Example Code

FVector Location = GetActorLocation();
if (Location == 100.f) // ❌ C2678: can't compare FVector with float
{
    // ...
}

The == operator is being used on a FVector and a float, which doesn’t make sense.

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✅ How to Fix C2678 in UE5 – Step-by-Step

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✔️ 1. Use Compatible Types on Both Sides of the Operator

Make sure you’re comparing the same or compatible types.

Fix:

if (Location.X == 100.f) // ✅ Now both sides are floats
{
    // ...
}

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✔️ 2. Use .ToString() for FString Conversion or Logging

Wrong:

FVector Loc = GetActorLocation();
FString Log = "Location: " + Loc; // ❌ C2678: can't add FString + FVector

Fix:

FString Log = "Location: " + Loc.ToString(); // ✅ Now it's FString + FString

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✔️ 3. If You’re Using Custom Structs, Overload the Operator

If you’re using your own struct/class and want it to work with operators, you’ll need to define them yourself.

Fix inside your struct:

bool operator==(const FMyStruct& Other) const
{
    return Value == Other.Value;
}

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✅ Summary: How to Fix C2678 in UE5

Cause	Fix Example
Left-hand type doesn’t support op	Use .X, .ToString(), or convert the type
Wrong type comparison	Compare compatible types (e.g., float to float)
Mixing FString and literals	Use TEXT() or convert with .ToString()
Custom struct has no operator	Overload the binary operator manually