sorting arraylist

Unity Engine
1

I created a targetsList class which has a sorting method using the .net Sort() function
Everything is goo except for
“TargetsList.Asc' does not implement interface member System.Collections.IComparer.Compare(object, object)'”

and tl*.distance returns a "object doesn’t contain a definition for distance…*
```
*using System;
using System.Collections;
using UnityEngine;

class TargetsList
{
public bool sorted = false;
public ArrayList list = new ArrayList();
public struct target
{
public int health;
public int power;
public float distance;
public Transform transform;
}
public TargetsList FindClosest(float maxDistance)
{
ArrayList tl = new ArrayList();
if (sorted)
{
tl = list;
for (int i =0; i< tl.Count; i++)
{
if (tl[i].distance >maxDistance) return;
}
tl.TrimToSize(i);
}
return tl;
}

public void Sort()
{
    list.Sort(0, list.Count, new Asc());
}

public class Asc : IComparer 
{
    public int Compare(target x, target y) 
    {
        return (x.distance).CompareTo(y.distance);
    }
}

}*
```

2

I haven’t looked at your code fully and I am heading to bed finally, but like I mentioned quickly on IRC (I should have spent more time explaining it, sry) you need to box the arraylist to access members of stored objects…

Like this:

((TargetList)tl[i]).distance = 5.0F;

//so:
((MyObjectType)myArrayList[index]).myMember

Took me a while to find that out the first time too.

HTH,
-Jeremy

3

Thanks, object types are brutal…

Here is what came up with and it’s giving me a hard time on the (Target)o, it wants a TargetsList but I need the .distance … what’s the secret sauce?

using System;
using System.Collections;
using UnityEngine;

class TargetsList
{
    public bool sorted = false;
    public ArrayList list = new ArrayList();
    public struct Target
    {
        public int health;
        public int power;
        public float distance;
        public Transform transform;
    }
    public TargetsList FindClosest(float maxDistance)
    {
        TargetsList tl = new TargetsList();
        if (sorted)
        {
            tl.list = list;
            int i = 0;
            foreach (object o in tl.list)
            {
                if (((Target)o).distance > maxDistance) return;
                i++;
            }
            tl.list.RemoveRange(i,tl.list.Count-i);
        }
        return tl;
    }
    public void SortDistance()
    {
        list.Sort(0, list.Count, new Asc());
    }

    public class Asc : IComparer
    {
        public int Compare(Target x, Target y)
        {
            return (x.distance).CompareTo(y.distance);
        }
    } 

}
4

You switched from a for loop to a foreach loop, and o is an object, so you don’t need that boxing anymore.

foreach (object o in tl.list)  //object
{
    if (((Target)o).distance > maxDistance) return;
    i++;
}

See, in that loop you use the contents of tl.list as object.

To handle that properly, cast o as your type normally without the boxing.

You really want to go through some tutorials on types and loops, etc, as hack-and-slash refactoring will just drive you crazy and mess up your code. It’s a pain to do, but the time spent will really help in the long-run :slight_smile:

-Jeremy