CODEWITHSUNDEEP
c#with-statement
Gurman8r
Gurman8r

Reputation: 311

With Statement in C# like that of AS3/GML

I'm making a game using Monogame, and I've been trying to figure out how to implement a function that acts similarly to AS3's and GML's with statement.

So far I have a system that works, but not entirely the way I want it to. I store my GameObjects in a Dictionary of Lists. This is so I can get to the specific type of object I want to access without having to loop through a list of ALL objects. The key used is the name of the type.

public static Dictionary<string, List<GameObject>> All = 
    new Dictionary<string, List<GameObject>>();

I access all of a specific type of object using AllOf. If a List containing that type exists in the Dictionary, it returns that List, else it returns an empty list.

public static List<GameObject> AllOf(Type type)
{
    string key = type.Name;

    if(All.ContainsKey(key))
    {
        return All[key];
    }

    return new List<GameObject>();
}

An example of how these are implemented

public override void Update(GameTime gameTime)
{
    List<GameObject> list = Instance.AllOf(typeof(Dummy));

    for(int i = 0; i < list.Count; i++)
    {
        list[i].Update(gameTime);
        list[i].foo += bar;
    }
}

But I'd rather use something similar to the AS3/GML with statement, which would also allow for other, non-member codes to be executed.

with(typeof(Dummy))
{
    Update(gameTime);
    foo += bar;

    int fooBar = 2;
    someObject.someMemberFunction(fooBar);
}

Is there a way to accomplish this? My end goal is just to make my code look a little cleaner, and make it easier to make a lot of changes without having to type out a for loop each time.

Upvotes: 0

Views: 90

Answers (3)

omgomgomgd
omgomgomgd

Reputation: 11

I have a small solution for this use case. This may be a bit of a necropost, but it is a pretty neat solution. Additionally, I think all of the C# features that are required existed back when this question was asked.

You can do something very similar to the GML with(x){} by using some form of delegate as a parameter to a static method, and passing a lambda as that parameter. The function can even be genericised, and you can call it without the class name by the using static statement. You will need to explicitly provide the typed/named parameter, but it is possible. You would need to hook it up to your own types, but the general idea is:

namespace NiftyStuff {
    public static class With {
        public static void with<T>(Action<T> proc) where T : GameObj {
            var typeName = typeof(T).Name;
            foreach (var item in GameObj.AllOf(typeName)) { proc((T)item); }
        }
    }

    public class GameObj {
        private static Dictionary<string, List<GameObj>> All = new Dictionary<string, List<GameObj>>();
        public static List<GameObj> AllOf(string name) {
            return All.ContainsKey(name) ? All[name] : null;
        }
        public static void Add(GameObj foo) {
            string typeName = foo.GetType().Name;
            List<GameObj> foos = All.ContainsKey(typeName) ? All[typeName] : (All[typeName] = new List<GameObj>());
            foos.Add(foo);
        }
        public float x, y, angle;
        public GameObj() { x = y = angle = 0; }
        public void Destroy() { AllOf(GetType().Name)?.Remove(this); }
    }

    public class Enemy : GameObj {
        public float maxHealth, curHealth;
        public Enemy() : base() { maxHealth = curHealth = 300; }
        public Enemy(float health) : base() { maxHealth = curHealth = health; }
        public bool Damage(float amt) {
            if (curHealth > 0) {
                curHealth -= amt;
                return curHealth <= 0;
            }
            return false;
        }
    }

    public class Pumpkin : GameObj {
        public bool exists = false;
        public Pumpkin() : base() { exists = true; }
        public bool LookAt() { return (exists = !exists); }
    }
}

Actually using the above code would work as follows:

using NiftyStuff;
using static NiftyStuff.With;

//...

    with ((Enemy e) => {
        if (e.Damage(50)) {
            Log("Made a kill!"); // Whatever log function you have...
        }
    });

    with ((Pumpkin p) => {
        if (p.LookAt()) {
            Log("You see the pumpkin");
        } else {
            Log("You no longer see the pumpkin");
        }
    });

While not exactly like GML's with statement, it would at least let you run code against all of the registered objects of some type.

One important note is that you can't destroy objects inside of a with this way (due to concurrent modification of a collection while iterating it). You would need to collect all objects to be destroyed, and then remove them from the list in All, typically in a game loop this is done at the end of a frame.

Hope this helps, despite being 2 years out of date.

Upvotes: 0

D Stanley
D Stanley

Reputation: 152556

No such syntax exists in C#, but you can access methods within the for that have nothing to do with the collection:

public override void Update(GameTime gameTime)
{
    List<GameObject> list = Instance.AllOf(typeof(Dummy));

    for(int i = 0; i < list.Count; i++)
    {
        list[i].Update(gameTime);
        list[i].foo += bar;

        int fooBar = 2;
        someObject.someMemberFunction(fooBar);
    }
}

Note that you can also use foreach, which is a little cleaner if you don't need the indexer:

foreach(var item in list)
{
    item.Update(gameTime);
    item.foo += bar;

    int fooBar = 2;
    someObject.someMemberFunction(fooBar);
}

Upvotes: 1

Nikerym
Nikerym

Reputation: 515

try

using(Object myObject = new Object()){

}

i think this might be what your looking to use?

Upvotes: 0

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