A superclass for classes that manipulate particles in Update.

ParticleManipulator.cs

using UnityEngine;

/// <summary>
/// Create a subclass of this class to manipulate particles in Update any way you see fit.
/// </summary>
[RequireComponent(typeof(ParticleSystem))]
[ExecuteInEditMode]
public abstract class ParticleManipulator : MonoBehaviour
{
    new protected ParticleSystem particleSystem { get; private set; }
    protected ParticleSystem.Particle[] particles { get; private set; }

    private void Awake()
    {
        particleSystem = GetComponent<ParticleSystem>();
        UpdateMaxParticles();
    }

    private void Update()
    {
        if (!IsAvailable()) return;
#if UNITY_EDITOR
        if (!particleSystem)
        {
            Awake();
        }
#endif

        var size = particleSystem.GetParticles(particles);

        for (var i = 0; i < size; i++)
        {
            UpdateParticle(i);
        }

        particleSystem.SetParticles(particles);
    }

    /// <summary>
    /// Override this to define per-particle behaviour.
    /// Update particles[index] any way you see fit.
    /// Consider using particles.Length fpr some effects.
    /// </summary>
    protected abstract void UpdateParticle(int index);

    /// <summary>
    /// Override this to return false if for some reason, update should not happen.
    /// For example: If there are values missing in the subclass.
    /// </summary>
    protected virtual bool IsAvailable()
    {
        return true;
    }

    /// <summary>
    /// Call this after you happened to change "Max Particles" of the ParticleSystem.
    /// </summary>
    public void UpdateMaxParticles()
    {
        particles = new ParticleSystem.Particle[particleSystem.main.maxParticles];
    }
}