c++ - 错误 : invalid initialization of non-const reference of type 'Vector2D&' from an rvalue of type 'Vector2D'

Question

这是代码，CodeBlocks 指出错误在 shwon 行:

bool SoccerTeam::isPassSafeFromOpponent(Vector2D    from,
                                        Vector2D    target,
                                        const PlayerBase* const receiver,
                                        const PlayerBase* const opp,
                                        double       PassingForce)const
{
    Vector2D ToTarget = target - from;
    Vector2D ToTargetNormalized = Vec2DNormalize(ToTarget);

    Vector2D LocalPosOpp = PointToLocalSpace(opp->Pos(),
                                             ToTargetNormalized,
                                             ToTargetNormalized.Perp(),
                                             from); // *** ERROR ***

错误信息:

error: invalid initialization of non-const reference of type 'Vector2D&'
from an rvalue of type 'Vector2D'`

Answer 1

问题出在第三个参数上，您在其中尝试传递 Vector2D::Perp() 函数的返回值作为引用。 (这同样适用于第一个参数，但我猜这是一个 const Vector2D&，所以它可能不会哭。)尝试以下操作:

bool SoccerTeam::isPassSafeFromOpponent(Vector2D    from,
                                        Vector2D    target,
                                        const PlayerBase* const receiver,
                                        const PlayerBase* const opp,
                                        double       PassingForce)const
{
    Vector2D ToTarget = target - from;
    Vector2D ToTargetNormalized = Vec2DNormalize(ToTarget);
    Vector2D ToTargetNormalizedPerp = ToTargetNormalized.Perp();

    Vector2D LocalPosOpp = PointToLocalSpace(opp->Pos(),
                                             ToTargetNormalized,
                                             ToTargetNormalizedPerp,
                                             from);