C# - 在结构中强制执行子对象不变性

Question

我正在尝试创建一个不可变结构。问题是，它内部包含可变对象。是否可以使它们不可变（不修改它们的 class）？例如 (https://dotnetfiddle.net/KTiTzB):

public class IntHolder
{
    public int X
    {
        get;
        set;
    }
}

public struct ImmutableStruct
{
    public int ImmutableInt
    {
        get;
        private set;
    }

    public IntHolder MyIntHolder
    {
        get;
        private set;
    }

    public ImmutableStruct(int immutableInt, IntHolder myIntHolder): this ()
    {
        ImmutableInt = immutableInt;
        MyIntHolder = myIntHolder;
    }
}

public class Program
{
    public static void Main()
    {
        Console.WriteLine("Immutability");
        IntHolder intHolder = new IntHolder();
        intHolder.X = 40;
        Console.WriteLine(intHolder.X == 40); // TRUE
        ImmutableStruct immStruct = new ImmutableStruct(10, intHolder);
        Console.WriteLine(immStruct.ImmutableInt == 10); // TRUE
        // immStruct.ImmutableInt = 4; // THIS DOESN'T WORK, AS EXPECTED. Hurray!
        // immStruct.MyIntHolder = new IntHolder(3); // ALSO DOESN'T WORK, GOOD!
        immStruct.MyIntHolder.X = 4; // how can I prevent this from working?
    }
}

有没有办法在不修改 IntHolder class 的情况下使 IntHolder 成员不可变？

Answer 1

其实是个大问题：如何处理不可变数据中的嵌套对象？

在我看来，值得创建不可变子模型以确保整个对象不可变。

查看下面代码中的注释：

public class IntHolder
{
    public int X
    {
        get;
        set;
    }

    public ImmutableIntHolder ToImmutable()//convert itself to ImmutableIntHolder 
    {
        return new ImmutableIntHolder(X);
    }
}
public class ImmutableIntHolder
{
    public ImmutableIntHolder(int x)
    {
        X = x;
    }
    public int X
    {
        get;
        private set;
    }

    public IntHolder ToIntHolder() //convert it back to mutable IntHolder 
    {
        return new IntHolder()
        {
            X = this.X
        };
    }
}
public struct ImmutableStruct
{
    public int ImmutableInt
    {
        get;
        private set;
    }

    public ImmutableIntHolder IntHolder //use ImmutableIntHolder instead
    {
        get;
        private set;
    }

    public ImmutableStruct(int immutableInt, IntHolder myIntHolder) : this()
    {
        ImmutableInt = immutableInt;
        IntHolder = myIntHolder.ToImmutable(); // convert to immutable
    }
}

另一种选择是：

public class IntHolder
{
    public int X
    {
        get;
        set;
    }
}


public class ImmutableStruct //changed to class
{
    public int ImmutableInt
    {
        get;
        private set;
    }

    public ImmutableIntHolder IntHolder
    {
        get;
        private set;
    }

    public ImmutableStruct(int immutableInt, IntHolder myIntHolder) //: this()
    {
        ImmutableInt = immutableInt;
        IntHolder = new ImmutableIntHolder(myIntHolder); // convert here.
    }

    public class ImmutableIntHolder
    {
        public ImmutableIntHolder(IntHolder intHolder)
        {
            //map all properties
            X = intHolder.X;
        }
        public int X
        {
            get;
            private set;
        }
    }
}

C# - 在结构中强制执行子对象不变性

C# - Enforce Child Object Immutability in Struct

c#

struct

immutability