Event Bubbling

Event bubbling is the core mechanism of Apq.ChangeBubbling, allowing child node changes to propagate up to parent nodes.

Bubbling Mechanism

When a child node changes, the event automatically bubbles up to all ancestor nodes:

Root (receives all events)
├── Users (receives Users and its children's events)
│   ├── User1
│   └── User2
└── Settings (receives Settings and its children's events)
    ├── Theme
    └── Language

Change Types

NodeChangeKind enum defines all change types:

Type	Description
PropertyChanged	Property value changed
CollectionAdd	Element added to collection
CollectionRemove	Element removed from collection
CollectionReplace	Element replaced in collection
CollectionClear	Collection cleared
ChildAttached	Child node attached
ChildDetached	Child node detached

Subscribing to Events

Direct Subscription

root.NodeChanged += (sender, change) =>
{
    Console.WriteLine($"[{change.Kind}] {change.NodeName}");
    Console.WriteLine($"  Path: {change.Path}");
    Console.WriteLine($"  OldValue: {change.OldValue}");
    Console.WriteLine($"  NewValue: {change.NewValue}");
};

Using Rx Streams

using Apq.ChangeBubbling.Messaging;
using System.Reactive.Linq;

ChangeMessenger.AsObservable()
    .Where(c => c.Kind == NodeChangeKind.CollectionAdd)
    .Subscribe(c => Console.WriteLine($"Added: {c.NewValue}"));

BubblingChange Structure

public readonly struct BubblingChange
{
    public NodeChangeKind Kind { get; }
    public string NodeName { get; }
    public string? PropertyName { get; }
    public string Path { get; }
    public object? OldValue { get; }
    public object? NewValue { get; }
    public DateTime Timestamp { get; }
}

Path Tracking

Each change event includes full path information:

// List nodes use index paths
users.Add(new User()); // Path: Root/Users/[0]

// Dictionary nodes use key paths
settings.Put("Theme", "Dark"); // Path: Root/Settings/Theme