[英]C# - Enforce Child Object Immutability in Struct
我正在嘗試創建一個不可變的結構。 問題是,它里面包含可變對象。 是否可以使那些不可變(不修改它們的類)? 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?
}
}
有沒有辦法在不修改 IntHolder 類的同時使 IntHolder 成員不可變?
這實際上是一個大問題:如何處理不可變數據中的嵌套對象?
https://softwareengineering.stackexchange.com/questions/279580/how-to-make-complex-objects-immutable
https://redux.js.org/recipes/structuringreducers/immutableupdatepatterns
在我看來,創建不可變的子模型以確保整個對象不可變是值得的。
請參閱以下代碼中的注釋:
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
}
}
另一種選擇是:
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;
}
}
}
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