binding.swift

/// This code defines an init method for the Binding type. This method accepts three parameters:
/// 
///     An object of any type T
///     A key path to a property of type Value on that object
///     An optional UndoManager object
/// 
/// The init method sets the Binding value to the value of the property specified by the key path. It also sets the set value of the Binding to a closure that updates the value of the property at the key path and registers an undo operation with the provided UndoManager, if one is given.
/// 
/// This allows the Binding object to be used to access and update the value of the specified property on the provided object, and to register undo operations for those updates with the UndoManager.

extension Binding {
    
    init<T>(_ object: T, _ keyPath: ReferenceWritableKeyPath<T, Value>, undoManager: UndoManager? = nil) {
        self.init {
            object[keyPath: keyPath]
        } set: { newValue in
            let originalValue = object[keyPath: keyPath]
            object[keyPath: keyPath] = newValue
            
            if let undoManager = undoManager {
                undoManager.registerUndo(withTarget: undoManager, handler: { _ in
                    object[keyPath: keyPath] = originalValue
                })
            }
        }
    }
    
}