CODEWITHSUNDEEP
c#genericsvalue-typereference-type
Oztaco
Oztaco

Reputation: 3459

Best way to use Value types as Reference types?

I've been using something similar to this whenever I needed to reference a Value type:

    public class RefHost<T> {
        public RefHost(T val)
        {
            Value = val;
        }
        private T _value;
        public T Value {
            get {
                return _value;
            }
            set {
                _value = value;
            }
        }
    }

What I'm wondering is there a built in way or an easier way to use an existing Value type as a Reference type?

Example:

public class Editor {
    public RefHost<int> Blah = new RefHost<int>(5);

    // Some kind of timer to increase the value of Blah every few ticks
}

Kind of like that where the user of Editor specifies a value type that needs to be changed, and there can be multiple instances of Editor each with it's own value. I used the timer as an example but most of the time it's a user control like a slider.

Upvotes: 0

Views: 145

Answers (5)

supercat
supercat

Reputation: 81143

Replace the property and backing field with a public field. While it is generally good for classes to use properties rather than fields, the whole purpose of your type is to be a simple mutable container for a single value-type instance; the state encapsulated by any reference to an instance of the type should be precisely defined by two things:

  1. The value of the `Value` member
  2. The whereabouts of all other references to the instance that exist anywhere in the universe

If two instances have the same Value, and if within the entire universe only one reference exists to each one, the two references should be semantically indistinguishable [since in both cases the set of "other references" that exist to the instances would be empty]

While there are various helper methods that a type of that style might implement, it would be impossible for a future version of the type to add additional state without violating the expected semantics. Since the whole purpose of the type is to behave like a class object containing a single field of type T, code will be clearest if one writes the object to in fact be a class object containing a single field of type T.

BTW, if you don't want to define a custom type, another option is to use a single-element T[1]. That will use a little bit of extra storage to hold the dimension, and adding [0] to all references will be a little uglier than .Value, but such an approach will nonetheless work pretty simply.

Upvotes: 0

Steve
Steve

Reputation: 6424

Boxing and unboxing is what this is called. Your solution might be more type safe though.

See http://msdn.microsoft.com/en-us/library/yz2be5wk.aspx

Upvotes: 0

Tim S.
Tim S.

Reputation: 56536

What's wrong with this?

public class Editor {
    public int Blah = 5;

    // Some kind of timer, with a handler like:
    void MyTimerTicker(object sender, EventArgs e)
    {
        this.Blah += 1;
    }
}

Upvotes: 1

Andrew Savinykh
Andrew Savinykh

Reputation: 26280

I think you are looking for Tuple.

Upvotes: 2

It&#39;sNotALie.
It&#39;sNotALie.

Reputation: 22794

Sure there is. If you want to pass it as a reference type to a method just use the ref modifier:

public static void Main()
{
    int n = 1;
    Test(ref n);
    Console.WriteLine(n); //will print out 2 and not 1.
    Console.ReadKey(true);
}
public static void Test(ref int x)
{
    x = 2;
}

Upvotes: 1

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