What It Means & How to Fix It

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🧠 Why You’re Seeing This Error

C2662 means you’re calling a non-const method on a const object, and the compiler won’t allow it. C++ protects const objects from being modified, and UE5 (being C++) follows this rule strictly.

In UE5, this often happens when:

• You call a non-const method inside a const function
• You try to use Blueprint-accessible getters/setters on const references
• You mark a function const in the header but not in the source

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💥 Example Error Message

error C2662: 'FString AMyActor::GetName()': cannot convert 'this' pointer from 'const AMyActor' to 'AMyActor &'

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🛠️ Example Code

FString AMyActor::GetDescription() const
{
    return GetName(); // ❌ C2662: GetName is not marked const
}

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✅ How to Fix C2662 in UE5 – Step-by-Step

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✔️ 1. Mark the Called Method as const

If GetName() doesn’t change the object’s state, mark it const.

Fix:

FString GetName() const; // In header
FString AMyActor::GetName() const { return Name; } // In cpp

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✔️ 2. Don’t Call Non-Const Methods from Const Functions

If the method modifies the object, either:

• Don’t call it from a const context, or
• Remove const from the calling function (if appropriate)

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✔️ 3. Const-Correctness Is Mandatory in UE5

UE5 requires clean and consistent const usage across declarations and definitions — mismatches will lead to errors like C2662 or C2556.

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✅ Summary: How to Fix C2662 in UE5

Cause	Fix Example
Calling non-const method from const	Mark method const or remove const from caller
Header/cpp method mismatch	Add const in both header and source
Blueprint method missing const	Add const to BlueprintCallable getters where needed