Serializeable dictionary: exceptions after code change

Unity Engine
1

I’m using Unity 5.0.1 64bit on windows 7 64bit.

I have this class:

using UnityEngine;
using System.Collections;
using System.Collections.Generic;

namespace CharacterCustomizer{
    [System.Serializable]
    public class SerialDictionary<Key, Value>: Dictionary<Key, Value>, ISerializationCallbackReceiver{
        [SerializeField]
        List<Key> serialKeys = new List<Key>();
        [SerializeField]
        List<Value> serialValues = new List<Value>();

        public void OnAfterDeserialize(){
            base.Clear();
            if(serialKeys.Count != serialValues.Count){
                throw new System.Exception(
                    string.Format("there are {0} keys and {1} values after deserialization. Lengths do not match.")
                    );
            }
            for (int i = 0; i < serialKeys.Count; i++){
                Add(serialKeys[i], serialValues[i]);
            }
        }

        public void OnBeforeSerialize(){
            serialKeys.Clear();
            serialValues.Clear();
            var tmpKeys = base.Keys;
            //
            foreach(var curKey in tmpKeys){
            //foreach(var keyVal in this){
                serialKeys.Add(curKey);
                serialValues.Add(base[curKey]);
                //serialKeys.Add(keyVal.Key);
                //serialValues.Add(keyVal.Value);
            }
        }
    }
}

Problem: when I change source code a bit in monodevelop AND unity editor reloads script, the class starts crashing furiously at this line:

        public void OnBeforeSerialize(){
.....
            foreach(var curKey in tmpKeys){//<== here
....

With this exception:

And values start disappearing from dictionary. I’ve noticed similar problems with dictionaries in few other places.

The behavior continues till I reload the scene.

How do I fix this?

2

Problem solved. Apparently I had a dictionary with non-serializable data type somewhere, and it caused big mess during deserialization (which happens when unity reloads scene after source file change)

3

I’m having a similar issue. Can’t seem to make sense of it. Could you explain a bit more how you fixed it? Got a feeling it’s a threading issue…

2 Likes
4

I have exact same issue. It also goes berserk on that line. Restarting the IDE stops the issue until it gets triggered again.

Can you elaborate on your solution?

5

Ok after really digging in I have come to a strange conclusion.

So to be clear, I have created a seralizable dictionary like so:

[System.Serializable]
public class SerializableDictionary<TKey,TValue> : Dictionary<TKey,TValue>, ISerializationCallbackReceiver
{
  [SerializeField]
  protected List<TKey> keys = new List<TKey>();

  [SerializeField]
  protected List<TValue> values = new List<TValue>();

  //Save the dictionary to lists
  public void OnBeforeSerialize()
  {
    keys.Clear();
    values.Clear();
    foreach(KeyValuePair<TKey,TValue> pair in this)
    {
        keys.Add(pair.Key);
        values.Add(pair.Value);
    }
  }

  //Load the dictionary from lists
  public void OnAfterDeserialize()
  {
    this.Clear();

    if(keys.Count != values.Count)
    {
      throw new System.Exception(string.Format("there are {0} keys and {1} values after deserialization. Make sure that both key and value types are serializable."));
    }

    for(int i = 0; i<keys.Count; i++)
    {
      this.Add(keys[i], values[i]);
    }
  }
}

[System.Serializable]
public class DictionaryOfStringAndInt : SerializableDictionary<string, int> { }

[System.Serializable]
public class DictionaryOfIntAndSerializableObject : SerializableDictionary<int, ScriptableObject>
{
    /// <summary>
    /// Returns a random key in the dictionary
    /// </summary>
    /// <returns></returns>
    public int RandomID
    {
      get
      {
        int value = keys[Random.Range(0, keys.Count)];
        return value;
      }
    }
}

What was happening it seems is that any time my dictionary exceeded 12 items, it would throw this error. I suspect that by the 13th item, the serialization can’t handle the memory of it and crashes. I don’t know exactly why this is occuring but my research has found that after my serialized dictionary exceeds 12 items it crashes.

6

it’s a fascinating problem, but did you simply toss in some Debug.Log to determine how often it is running, if it is in some sort of recursive loop, etc ?

Surely the objects you use for the ScriptableObject matter? (I just filled it with nulls and it was fine …)

7

@Fattie I have all my details outlined here. The rabbit hole is deep indeed.

http://stackoverflow.com/questions/36194178/unity-serialized-dictionary-index-out-of-range-after-12-items

Filling with nulls is fine, but ScriptableObjects is not it seems?

8

Don’t know if you guys seen this, but this worked best for me. Finally, a serializable dictionary for Unity! (extracted from System.Collections.Generic) - Unity Engine - Unity Discussions

9

Hey @vexe ,

I’ve been following the Finally, a serializable dictionary for Unity! (extracted from System.Collections.Generic) - Unity Engine - Unity Discussions thread and using your solution for a while now… the only thing i dislike, is that when it serializes, the string is pretty bloated big for ex:

{"_Buckets":[-1,0,-1],"_HashCodes":[110182,0,0],"_Next":[-1,0,0],"_Count":1,"_Version":1,"_FreeList":-1,"_FreeCount":0,"_Keys":["one","",""]}

Now that’s fine, but i had to look for another solution (like serializing key/value pairs only). But here you (and others) mentioned the issue/bug with extending the Dictionary<Key, Value> and using ISerializationCallbackReceiver and i was wondering, if the problematic use-case has been fixed, because lookie here, found this on AssetStore today:

https://assetstore.unity.com/packages/tools/integration/serializabledictionary-90477

And it seems to use the same approach as outlined here to cause issues.

Wonder if you noticed the asset and perhaps can give me your 2 cents on what you think about it. I’m gonna do some tests with it now, but as i was about to do just that, i noticed the code seems vaguely familiar (to this thread’s code approach), so i thought to ask you also.

Cheers!

EDIT
2018/05/26 - The package (for now) seems to work well enough for me. I only did simple tests required for my use-case, so i cant say its crash-free. The serialized output however is desirable.

EDIT2
Suddenly the error appeared with the abovementioned package after simply adding definition for another SerializableDictionary type (eg StringFloatDictionary). When i tried to open the inspector for the object containing script that uses the dictionary, the dictionary did not show in inspector, instead there were a lot of errors output, similiar to what i see in your error logs. I had to reimport the source codes for the SerializableDictionary from asset store, and add the required definitions again, and suddenly it works again. Dumbfounded why this happens, and unable to prevent it, ill resign to use this implementation as much as i would otherwise.