针对switch语句枚举编程，这是你的方式做？ [英] Programming against an enum in a switch statement, is this your way to do?

问题描述

看代码片段：

这是对一个枚举编码时，我通常做的。我有一个InvalidOperationException一个缺省的逃逸（因为编码是对一个私有实例字段没有传入的参数我不使用的ArgumentException或其derivals之一）。

我在想，如果你的开发伙伴与此逃生记....

 公共枚举DrivingState {中性，驱动器还编码，停车，逆向}; 
 
公共类MyHelper 
 {
私人DrivingState drivingState = DrivingState.Neutral; 
 
公共无效的run（）
 {
开关（this.drivingState）
 {
情况下DrivingState.Neutral：
 DoNeutral（）; 
中断; 
情况下DrivingState.Drive：
 DoDrive（）; 
中断; 
情况下DrivingState.Parking：
 DoPark（）; 
中断; 
情况下DrivingState.Reverse：
 DoReverse（）; 
中断; 
默认：
抛出新的InvalidOperationException异常（
的String.Format（CultureInfo.CurrentCulture，
Drivestate {0}未知状态，this.drivingState））; 
} 
} 
} 
  

在代码审查，我遇到很多实现只有在默认逃生break语句。这可能是随着时间的推移一个问题....

解决方案

由于默认情况下是无法验证的，我不喜欢这种方式。这导致减少覆盖单元测试，这虽然不一定是世界末日，惹恼强迫我。<​​/ p>

我更喜欢简单的单元测试每一种情况下，并有一个额外的断言仅存在四种可能的情况。一旦有人添加了新的枚举值，单元测试将打破。

类似

  [测试] 
公共无效ShouldOnlyHaveFourStates（）
 {
 Assert.That（Enum.GetValues​​（typeof运算（DrivingState））。长度== 4，更新单元测试新DrivingState !!!）; 
} 
  

Look at the code snippet:

This is what I normally do when coding against an enum. I have a default escape with an InvalidOperationException (I do not use ArgumentException or one of its derivals because the coding is against a private instance field an not an incoming parameter).

I was wondering if you fellow developers are coding also with this escape in mind....

public enum DrivingState {Neutral, Drive, Parking, Reverse};

public class MyHelper
{
    private DrivingState drivingState = DrivingState.Neutral;

    public void Run()
    {
        switch (this.drivingState)
        {
            case DrivingState.Neutral:
                DoNeutral();
                break;
            case DrivingState.Drive:
                DoDrive();
                break;
            case DrivingState.Parking:
                DoPark();
                break;
            case DrivingState.Reverse:
                DoReverse();
                break;
            default:
                throw new InvalidOperationException(
                    string.Format(CultureInfo.CurrentCulture, 
                    "Drivestate {0} is an unknown state", this.drivingState));
        }
    }
}

In code reviews I encounter many implementations with only a break statement in the default escape. It could be an issue over time....

解决方案

I don't like this approach because the default case is untestable. This leads to reduced coverage in your unit tests, which while isn't necessarily the end of the world, annoys obsessive-compulsive me.

I would prefer to simply unit test each case and have an additional assertion that there are only four possible cases. If anyone ever added new enum values, a unit test would break.

Something like

[Test]
public void ShouldOnlyHaveFourStates()
{
    Assert.That(Enum.GetValues( typeof( DrivingState) ).Length == 4, "Update unit tests for your new DrivingState!!!");
}

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