Dictionary TryGetValue not finding key, even though it exists

Questions & Answers
1

Hello,
I have the following monobehaviour attached to my weapon to detect the other collider’s physicmaterial; run it in “clips.TryGetValue(x, x)”; outputting to a variable and then calling a method to play the audio while passing in the value found. I have a debug line before the TryGetValue call. This is running. It finds the material successfully. It seems I’m getting an exception error for the key not existing in the dictionary. However, it has been added on awake. I’ve tried multiple solutions. I’m going to try to print out a list of the keys and their values after I initialize everything right now.

Any help would be great. Thanks!
using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Snd_ImpactListener : MonoBehaviour {

    public Dictionary<PhysicMaterial, AudioClip> clips = new Dictionary<PhysicMaterial, AudioClip>();

    public AudioClip metalImpact;
    public AudioClip woodImpact;
    public AudioClip fleshImpact;

    public PhysicMaterial metalMaterial;
    public PhysicMaterial woodMaterial;
    public PhysicMaterial fleshMaterial;

    private AudioSource source;

    private void Start()
    {
        if (!clips.ContainsKey(metalMaterial))
            clips.Add(metalMaterial, metalImpact);

        if (!clips.ContainsKey(woodMaterial))
            clips.Add(woodMaterial, woodImpact);

        if (!clips.ContainsKey(fleshMaterial))
            clips.Add(fleshMaterial, fleshImpact);
    }

    private void OnEnable()
    {

        if (!GetComponent<AudioSource>())
        {
            source = gameObject.AddComponent<AudioSource>();
        }
        else
        {
            source = GetComponent<AudioSource>();
        }
    }

    private void OnTriggerEnter(Collider collision)
    {
        PhysicMaterial materialFound = collision.material;
        AudioClip clip;
        Debug.Log("Hit detected. attempting to play sound ==> " + materialFound.name.ToString());

        if (clips.TryGetValue(materialFound, out clip))
        {
            PlayRequestedAudio(clip);
            Debug.Log("Played sound: " + clips[materialFound].name);
        }
    }

    public void PlayRequestedAudio(AudioClip audio)
    {
        Debug.Log("Playrequestedaudio");
        source.PlayOneShot(audio);
    }
}
2

What I can imagine as the cause is that the key of the dictionary is a reference to an object. So even if the objects are equal, they’re not the same and since the key stores the reference the dictionary of course can’t find the reference to the material from the collider since it’s different. Also comparing the references is faster than doing a deep inspection of the object (which isn’t generic, so it would require a separate implementation for every existing class and possible combinations of them).

Instead using the material object as the key I’d use the material name. you should be able to access it by the public name variable.

3

For anyone wondering about the answer to this question.
Instead of using materialFound.material. I had to use materialFound.sharedMaterial.
It was trying to find a key that wasn’t available in the dictionary. sharedMaterial works perfectly for what I need. Thank you @NoDumbQuestion

    private void OnTriggerEnter(Collider collision)
    {
        if (clips.Count == 0)
            return;

        AudioClip clip;
        PhysicMaterial materialFound;

        if (collision.sharedMaterial != null)
        {
            materialFound = collision.sharedMaterial;

            if (clips.TryGetValue(materialFound, out clip))
            {
                PlayRequestedAudio(clip);
            }
            else
            {
                PlayDefaultAudio();
            }

            Debug.Log("Hit detected. attempting to play sound ==> " + materialFound.name.ToString());
        }
    }

    private void PlayRequestedAudio(AudioClip audio)
    {
        source.PlayOneShot(audio);
    }

    private void PlayDefaultAudio()
    {
        if (defaultImpact == null)
            return;

        source.PlayOneShot(defaultImpact);
    }