A RealityKit Entity extension that enumerates the entities in a hierarchy

Entity+EnumerateHierarchy.swift

//
//  Entity+EnumerateHierarchy.swift
//
//  Created by Drew Olbrich on 7/18/23.
//  Copyright © 2023 Lunar Skydiving LLC. All rights reserved.
//
//  MIT License
//
//  Permission is hereby granted, free of charge, to any person obtaining a copy
//  of this software and associated documentation files (the "Software"), to deal
//  in the Software without restriction, including without limitation the rights
//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
//  copies of the Software, and to permit persons to whom the Software is
//  furnished to do so, subject to the following conditions:
//
//  The above copyright notice and this permission notice shall be included in all
//  copies or substantial portions of the Software.
//
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
//  SOFTWARE.
//

import RealityKit

extension Entity {
    
    /// Executes a closure for each of the entity's child and descendant entities, as
    /// well as for the entity itself.
    func enumerateHierarchy(body: (Entity) -> Void) {
        enumerateHierarchy { entity, _ in
            body(entity)
        }
    }
    
    /// Asynchronously executes a closure for each of the entity's child and descendant
    /// entities, as well as for the entity itself.
    ///
    /// This method does not return until all asynchronous `body` closures have finished
    /// executing.
    ///
    /// If you see the compiler error "Ambiguous use of 'enumerateHierarchy(body:)'",
    /// call `enumerateHierarchy` like this:
    ///
    ///     await rootEntity.enumerateHierarchy { entity async in
    ///         ...
    ///     }
    func enumerateHierarchy(body: @escaping (Entity) async -> Void) async {
        await withTaskGroup(of: Void.self) { taskGroup in
            enumerateHierarchy { entity, _ in
                taskGroup.addTask {
                    await body(entity)
                }
            }
        }
    }
    
    /// Executes a closure for each of the entity's child and descendant entities, as
    /// well as for the entity itself.
    ///
    /// Set `stop` to true in the closure to abort further processing of the child entity subtree.
    func enumerateHierarchy(body: (Entity, UnsafeMutablePointer<Bool>) -> Void) {
        var stop = false
        func enumerate(body: (Entity, UnsafeMutablePointer<Bool>) -> Void) {
            guard !stop else {
                return
            }
            body(self, &stop)
            for child in children {
                guard !stop else {
                    break
                }
                child.enumerateHierarchy(body: body)
            }
        }
        enumerate(body: body)
    }
    
}