舉例說明如何使用FieldInfo.IsInitOnly
以遞歸方式測試不可變性。
可能還有更多的特殊情況需要考慮,比如我如何處理string
,但它只會給出我認爲是錯誤的否定結果,即會告訴你一些事情是可變的,而不是相反。
邏輯是,每個字段必須是readonly
並且本身是不可變的類型。請注意,它不會處理自引用類型或循環引用。
using System;
using System.Linq;
using System.Reflection;
using Microsoft.VisualStudio.TestTools.UnitTesting;
namespace ImmutableTests
{
[TestClass]
public class AssertImmutableTests
{
[TestMethod]
public void Is_int_immutable()
{
Assert.IsTrue(Immutable<int>());
}
[TestMethod]
public void Is_string_immutable()
{
Assert.IsTrue(Immutable<string>());
}
[TestMethod]
public void Is_custom_immutable()
{
Assert.IsTrue(Immutable<MyImmutableClass>());
}
[TestMethod]
public void Is_custom_mutable()
{
Assert.IsFalse(Immutable<MyMutableClass>());
}
[TestMethod]
public void Is_custom_deep_mutable()
{
Assert.IsFalse(Immutable<MyDeepMutableClass>());
}
[TestMethod]
public void Is_custom_deep_immutable()
{
Assert.IsTrue(Immutable<MyDeepImmutableClass>());
}
[TestMethod]
public void Is_propertied_class_mutable()
{
Assert.IsFalse(Immutable<MyMutableClassWithProperty>());
}
private static bool Immutable<T>()
{
return Immutable(typeof(T));
}
private static bool Immutable(Type type)
{
if (type.IsPrimitive) return true;
if (type == typeof(string)) return true;
var fieldInfos = type.GetFields(BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance);
var isShallowImmutable = fieldInfos.All(f => f.IsInitOnly);
if (!isShallowImmutable) return false;
var isDeepImmutable = fieldInfos.All(f => Immutable(f.FieldType));
return isDeepImmutable;
}
}
public class MyMutableClass
{
private string _field;
}
public class MyImmutableClass
{
private readonly string _field;
}
public class MyDeepMutableClass
{
private readonly MyMutableClass _field;
}
public class MyDeepImmutableClass
{
private readonly MyImmutableClass _field;
}
public class MyMutableClassWithProperty
{
public string Prop { get; set; }
}
}
對匿名downvoter:當你認爲這個問題有什麼問題,請通知我。 – 2014-09-13 22:02:55