I have tears because I don't know how to field initialize a Dictionary with Action?

Question

In Unity projects featuring explosions you often do this

private Dictionary<string, System.Action> explosions;

void .. initialize in your class constructor .. ()
    {
    explosions = new Dictionary<string, System.Action>();
    explosions.Add("huge", SomeCall);
    explosions.Add("huger", SomeCall);
    etc
    }

No problem, but it would make me happy if you could do this...

private Dictionary<string, System.Action> explosions =
    new Dictionary<string, System.Action>()
    {
    {"huge", SomeCall},
    {"huge", SomeCall},
    etc
    };

That would make me much happier ... you know that feeling when you sleep better, enjoy meals with more of a smile?

Of course, that doesn't work because:

Assets/scripts/objects/flite groups/ReallyTremendousExplosions.cs(134,26): error CS0236: A field initializer cannot reference the nonstatic field, method, or property `ReallyTremendousExplosions.SomeCall()'

Can anyone bring me peace on this?

Is there a way to get around the fact that you have to do it at initialization time?

Less drama would be appropriate ;-) – Claudio P Feb 11 '16 at 15:14 — Claudio P, Feb 11 '16 at 15:14

Tewr · Answer 1 · 2016-02-12T22:01:47.770

3

I love dictionary initializers and I use them all the time. I feel your tears.

The answer is in your question, use a delegate!

public class ReallyTremendousExplosions
    {
        private delegate void ExplosionFactory(ReallyTremendousExplosions source);

        private Dictionary<string, ExplosionFactory> Explosions = new Dictionary<string, ExplosionFactory>()
        {
            { "huge", x => x.SomeMethod() },
            { "huger", x => x.SomeMethod() }
        };

        private void SomeMethod()
        {
              //Render massive explosions...
        }

        public void RenderNamedExplosion(string explosionName) {
            ExplosionsFactory explosionFactory;
            if (!Explosions.TryGet(explosionName, out explosionFactory) {
                    throw new NoSuchExplosionException(explosionName);
            }

            explosionFactory(this);
        }
    }

Code fully tested in Unity5/Mono.

edited Feb 12 '16 at 22:01

answered Feb 11 '16 at 15:29

Tewr

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Holy Explosions. Just you wait until I try this out! "OMGC#" – Fattie Feb 11 '16 at 15:39
1

That actually works. You dont' really need the delegate declaration tho, you could pass Action. Note that it requires to pass the calling object dict[str](this); – Everts Feb 11 '16 at 15:39
@fafase what syntax do you mean there buddy? – Fattie Feb 11 '16 at 23:12
public Dictionary> Explosions; , that is the only difference. The rest remains the same. – Everts Feb 12 '16 at 05:09

score 1 · Accepted Answer · answered Feb 11 '16 at 15:14

1

It seems that SomeCall is a non static method and that's why you can't use it in the field initializer. However you can put the initialization into constructor:

  public class MyClass {
    ...
    // non static method
    private void SomeCall() { ... }

    private Dictionary<string, System.Action> explosions;

    public MyClass() {
      explosions = new Dictionary<string, System.Action>() {
        {"huge", SomeCall},
        {"huger", SomeCall},
      };
    }
    ...
  }

answered Feb 11 '16 at 15:14

Dmitry Bychenko

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Hi Dimitry - yes, **that's exactly what I did**. (In the code example `prep` (preparation) is obviously a initializer.) I want to know if there's a way to **get around that and do a field initialization!** Perhaps using a .. delegate, or something? It makes me very said I have to initialize in the constructor :/ – Fattie Feb 11 '16 at 15:16
@Joe Blow: No there's no such a way; in *.Net* (unlike *Java*) you can't reference non-static fields/methods/properties... in a field initializer. – Dmitry Bychenko Feb 11 '16 at 15:19

I have tears because I don't know how to field initialize a Dictionary with Action?

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