错误的'if'语句导致错误的结果

Question

在调试器中，我已经验证了moveAmount在应该是时等于1，但是当我到达类中的if语句时，它会执行第二个if语句movementAmount为10.

我的点对象，位置，最后加上一个额外的，所以Y坐标结果是11而不是10，我认为这可能是问题的一部分。

类：

public partial class Robot 
{ 
    public string direction = "north"; 
    private Point position = new Point(0, 0); 
    private int movementAmount = 1; 

    public Robot() {} 

    public void moveRobot() 
    { 
     if (direction == "north" || direction == "North" & movementAmount == 1) 
     { 
      position.Y += movementAmount; 
     } 
     if (direction == "north" || direction == "North" & movementAmount == 10) 
     { 
      position.Y += movementAmount; 
     } 
     if (direction == "east" || direction == "East" & movementAmount == 1) 
     { 
      position.X += movementAmount; 
     } 
     if (direction == "east" || direction == "East" & movementAmount == 10) 
     { 
      position.X += movementAmount; 
     } 
     if (direction == "south" || direction == "South" & movementAmount == 1) 
     { 
      position.Y -= movementAmount; 
     } 
     if (direction == "south" || direction == "South" & movementAmount == 10) 
     { 
      position.Y -= movementAmount; 
     } 
     if (direction == "west" || direction == "West" & movementAmount == 1) 
     { 
      position.X -= movementAmount; 
     } 
     if (direction == "west" || direction == "West" & movementAmount == 10) 
     { 
      position.X -= movementAmount; 
     } 
    } 

    public Point Position 
    { 
     get 
     { 
      return position; 
     } 
    } 

    public int MovementAmount 
    { 
     get 
     { 
      return movementAmount; 
     } 
     set 
     { 
      movementAmount = value; 
      if (movementAmount != 1 & movementAmount != 10) 
      { 
       throw new ArgumentOutOfRangeException("Must be 1 or 10"); 
      } 
     } 
    } 
} 

} 

主程序：

public partial class frmSimpleRobot : Form 
{ 
    public frmSimpleRobot() 
    { 
     InitializeComponent(); 
    } 

    Robot arrow = new Robot(); 

    private void btnGoOne_Click(object sender, EventArgs e) 
    { 
     arrow.MovementAmount = 1; 
    } 

    private void btnGoTen_Click(object sender, EventArgs e) 
    { 
     arrow.MovementAmount = 10; 
    } 

    private void btnNorth_Click(object sender, EventArgs e) 
    { 
     arrow.direction = "north"; 
     arrow.moveRobot(); 
     lblRobotPos.Text = "(X=" + arrow.Position.X.ToString() + ", " + "Y=" + arrow.Position.Y.ToString() + ")"; 
    } 

    private void btnEast_Click(object sender, EventArgs e) 
    { 
     arrow.direction = "east"; 
     arrow.moveRobot(); 
     lblRobotPos.Text = "(X=" + arrow.Position.X.ToString() + ", " + "Y=" + arrow.Position.Y.ToString() + ")"; 
    } 

    private void btnSouth_Click(object sender, EventArgs e) 
    { 
     arrow.direction = "south"; 
     arrow.moveRobot(); 
     lblRobotPos.Text = "(X=" + arrow.Position.X.ToString() + ", " + "Y=" + arrow.Position.Y.ToString() + ")"; 
    } 

    private void btnWest_Click(object sender, EventArgs e) 
    { 
     arrow.direction = "west"; 
     arrow.moveRobot(); 
     lblRobotPos.Text = "(X=" + arrow.Position.X.ToString() + ", " + "Y=" + arrow.Position.Y.ToString() + ")"; 
    } 


} 

}

援助吗？

Answer 1

您应该将||表达式放在括号内。运算符&（和&&运算符，这是你实际应该使用的）具有更高的优先级，只要方向字符串匹配，整个表达式就是真实的。

这就是说，这段代码太疯狂了（没有任何意图:)）。这很难阅读，效率低下，容易出错（您的问题案例）。尝试这样的事情，而不是：

public void moveRobot() 
{ 
    switch (direction) 
    { 
    case "north": 
    case "North": 
     position.Y += movementAmount; 
     break; 
    case "east": 
    case "East": 
     position.X += movementAmount; 
     break; 
    case "south": 
    case "South": 
     position.Y -= movementAmount; 
     break; 
    case "west": 
    case "West": 
     position.X -= movementAmount; 
     break; 
    } 
} 

更妙的是使direction的enum代替string，以确保您始终获得一个有效的值。