C++ 函數參數傳遞：引用與指針的實戰差異對比

編輯：關於C語言

遊戲開發中直線軌跡運算用 DDA 演算法。C 版本用指針參數，C++ 改用引用，對比鮮明。

函數原型對比

// C 風格指針
static bool autoMove(int* x1, int* y1, int x2, int y2, int speed);

// C++ 引用
static bool autoMove(int& x1, int& y1, int x2, int y2, int speed);

實現代碼對比

指針版（C）

bool Tool::autoMove(int* x1, int* y1, int x2, int y2, int speed) {
  int x_old = *x1, y_old = *y1, x_new, y_new, step_time = 0;
  double x = *x1, y = *y1, deltx, delty, length;
  if (*x1 == x2 && *y1 == y2) return TRUE;
  length = (abs(x2 - *x1) >= abs(y2 - *y1)) ? abs(x2 - *x1) : abs(y2 - *y1);
  if (length < 1) return TRUE;
  deltx = (x2 - *x1) / length; delty = (y2 - *y1) / length;
  int k = 1;
  while (k <= length) {
    x += deltx; y += delty;
    x_new = (int)x; y_new = (int)y;
    if (x_old != x_new || y_old != y_new) {
      x_old = x_new; y_old = y_new; step_time++;
    }
    if (step_time >= speed) { *x1 = (int)x; *y1 = (int)y; return FALSE; }
    k++;
  }
  *x1 = (int)x; *y1 = (int)y; return FALSE;
}

引用版（C++）

bool Tool::autoMove(int& x1, int& y1, int x2, int y2, int speed) {
  int x_old = x1, y_old = y1, x_new, y_new, step_time = 0;
  double x = x1, y = y1, deltx, delty, length;
  if (x1 == x2 && y1 == y2) return TRUE;
  length = (abs(x2 - x1) >= abs(y2 - y1)) ? abs(x2 - x1) : abs(y2 - y1);
  if (length < 1) return TRUE;
  deltx = (x2 - x1) / length; delty = (y2 - y1) / length;
  int k = 1;
  while (k <= length) {
    x += deltx; y += delty;
    x_new = (int)x; y_new = (int)y;
    if (x_old != x_new || y_old != y_new) {
      x_old = x_new; y_old = y_new; step_time++;
    }
    if (step_time >= speed) { x1 = (int)x; y1 = (int)y; return FALSE; }
    k++;
  }
  x1 = (int)x; y1 = (int)y; return FALSE;
}

調用處對比

// 指針調用
bool isAutoMoveOk = Tool::autoMove(&x, &y, map_destination_x, map_destination_y, speed);

// 引用調用
bool isAutoMoveOk = Tool::autoMove(x, y, map_destination_x, map_destination_y, speed);