How to know when to forward declare - ToonTanks

[Luca_Cientanni]

Why do we need to forward declare UCapsuleComponent but not UStaticMesh or the USceneComponent when creating our APawnBase?

Relevant code:

class UCapsuleComponent;
class AProjectileBase;
class UHealthComponent;

UCLASS()
class TOONTANKS_API APawnBase : public APawn
{
	GENERATED_BODY()

public:
	// Sets default values for this pawn's properties
	APawnBase();
	virtual void HandleDestruction();

private:
	// COMPONENTS
	UPROPERTY(VisibleAnywhere, BlueprintReadOnly, Category="Components", meta=(AllowPrivateAccess="true"))
	UCapsuleComponent* CapsuleComponent;

	UPROPERTY(VisibleAnywhere, BlueprintReadOnly, Category="Components", meta=(AllowPrivateAccess="true"))
	UStaticMeshComponent* BaseMesh;

	UPROPERTY(VisibleAnywhere, BlueprintReadOnly, Category="Components", meta=(AllowPrivateAccess="true"))
	UStaticMeshComponent* TurretMesh;

	UPROPERTY(VisibleAnywhere, BlueprintReadOnly, Category="Components", meta=(AllowPrivateAccess="true"))
	USceneComponent* ProjectileSpawnPoint;

[Luca_Cientanni]

Just revisited the lecture, the Actor class already knows what a UStaticMeshComponent is so no need to forward declare it.