c++ - 将标题分类为 8 个方向时如何避免 if/else if 链？

Question

我有以下代码:

if (this->_car.getAbsoluteAngle() <= 30 || this->_car.getAbsoluteAngle() >= 330)
  this->_car.edir = Car::EDirection::RIGHT;
else if (this->_car.getAbsoluteAngle() > 30 && this->_car.getAbsoluteAngle() <= 60)
  this->_car.edir = Car::EDirection::UP_RIGHT;
else if (this->_car.getAbsoluteAngle() > 60 && this->_car.getAbsoluteAngle() <= 120)
  this->_car.edir = Car::EDirection::UP;
else if (this->_car.getAbsoluteAngle() > 120 && this->_car.getAbsoluteAngle() <= 150)
  this->_car.edir = Car::EDirection::UP_LEFT;
else if (this->_car.getAbsoluteAngle() > 150 && this->_car.getAbsoluteAngle() <= 210)
  this->_car.edir = Car::EDirection::LEFT;
else if (this->_car.getAbsoluteAngle() > 210 && this->_car.getAbsoluteAngle() <= 240)
  this->_car.edir = Car::EDirection::DOWN_LEFT;
else if (this->_car.getAbsoluteAngle() > 240 && this->_car.getAbsoluteAngle() <= 300)
  this->_car.edir = Car::EDirection::DOWN;
else if (this->_car.getAbsoluteAngle() > 300 && this->_car.getAbsoluteAngle() <= 330)
  this->_car.edir = Car::EDirection::DOWN_RIGHT;

我想避免 ifs 链；真的很丑。有没有另一种可能更简洁的写法？

Answer 1

#include <iostream>

enum Direction { UP, UP_RIGHT, RIGHT, DOWN_RIGHT, DOWN, DOWN_LEFT, LEFT, UP_LEFT };

Direction GetDirectionForAngle(int angle)
{
    const Direction slices[] = { RIGHT, UP_RIGHT, UP, UP, UP_LEFT, LEFT, LEFT, DOWN_LEFT, DOWN, DOWN, DOWN_RIGHT, RIGHT };
    return slices[(((angle % 360) + 360) % 360) / 30];
}

int main()
{
    // This is just a test case that covers all the possible directions
    for (int i = 15; i < 360; i += 30)
        std::cout << GetDirectionForAngle(i) << ' ';

    return 0;
}

我会这样做。 (根据我之前的评论)。