我执行这个简单的合同不正确吗？ [英] Am I implementing this simple contract incorrectly?

问题描述

这是我的代码：

public class RegularPolygon
{
    public int VertexCount;
    public double SideLength;

    public RegularPolygon(int vertexCount, double sideLength)
    {
        Contract.Requires(vertexCount >= 3);
        VertexCount = vertexCount;
        SideLength = sideLength;
    }

    [ContractInvariantMethod]
    private void RegularPolygonInvariants()
    {
        Contract.Invariant(VertexCount>=3);
    }

}

我都尝试过 Contract.Requires 和 Contract.Invariant 方法，可防止vertexCount变量小于或等于2；但是，我仍然可以初始化2面或更少面的RegularPolygon。我的（简化的）NUnit测试如下所示：

I have tried with both the Contract.Requires and Contract.Invariant methods to prevent the vertexCount variable from becoming less than or equal to 2; however I am still able to initialise a RegularPolygon with 2 or fewer sides. My (simplified) NUnit test looks like this:

[TestFixture]
class TestRegularPolygon
{
    private RegularPolygon _polygon;

    [SetUp]
    public void Init()
    {
        _polygon = new RegularPolygon(1, 50);
    }

    [Test]
    public void Constructor()
    {
        Assert.That(_polygon.VertexCount,Is.GreaterThanOrEqualTo(3));
    }

}

上述测试也通过了无法弄清楚原因！

The above test also passes and I cannot figure out why!

起初，我认为ReSharper可能已经搞砸了，因为它使行变灰并在我尝试在其中使用方法时显示此消息。 合同命名空间：

At first I thought ReSharper might have been messing something up because it greys out the line and displays this message whenever I try to use a method in the Contract namespace:

将跳过方法调用。

Method invocation is skipped. Compiler will not generate method invocation because the method is conditional, or it is partial method without implementation.

但是，挂起R＃并运行该程序时，编译器不会生成方法调用，因为该方法是有条件的，或者它是不执行的部分方法。 NUnit中的测试具有相同的结果，而VS中没有错误或警告。因此，我认为这仅仅是因为ReSharper尚未突出强调代码合同的兼容性。

But suspending R# and running the tests in NUnit has the same result with no errors or warnings in VS either. So I assume that is just because ReSharper does not have highlighting compatibility for code contracts yet.

我看了看文档，据我所知我不应该这样做

I have looked at the documentation and as far as I can tell I shouldn't be having this problem.

我是错误地使用了代码合同，还是我的环境阻止了它以某种方式工作？

谢谢。

推荐答案

要检查的第一件事-您是否已打开合同检查功能？如果没有，您的任何合同都不会做任何事情。那也将解释R＃警告。在构建属性的代码合同下查看，并在运行时检查下查看其内容。

First thing to check - have you actually got contract checking turned on? If not, none of your contracts will do anything. That would explain the R# warning, too. Look under "Code Contracts" in the build properties, and see what it says under "Runtime Checking".

根据注释，确保您有 CONTRACTS_FULL 定义为编译符号-似乎是R＃所需要的。

As per comments, ensure you have CONTRACTS_FULL defined as a compilation symbol - that appears to be what R# requires.

第二点：您有公共可变字段，该字段是表示有人在任何时候都会侵犯您的不变式

Second point: you've got public mutable fields, which means your invariant can be violated at any moment by someone writing

polygon.VertexCount = 0;

请不要使用公共字段，尤其是不可写的字段。 ：）

Please don't use public fields, particularly not writable ones. :)

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