Undefined unknown-undefined

Core Data

-com.apple.CoreData.SQLDebug 1-3 - print all SQL queries called by Core Data
- -com.apple.CoreData.Logging.stderr 1-3 - needed alongside with the SQLDebug from iOS 10+ because of new logging system, more on that in changelog
-com.apple.CoreData.SyntaxtColoredLogging YES - probably syntax colored logging (not tried)
-com.apple.CoreData.SQLiteDebugSynchronous 1 - preference controls some aspects of the SQLite store. See the "Configuring a SQLite Store's Save Behavior" section of the Core Data Programming Guide for details
-com.apple.CoreData.SQLiteIntegrityCheck 1 - the SQLite store does extra integrity checking
-com.apple.CoreData.MigrationDebug 1 - Core Data will log information about exceptional cases as it migrates data
-com.apple.CoreData.ThreadingDebug - preference enables assertions to enforce Core Data's multi-threading policy. It is a number, where incre

Configure Git to use a proxy

##In Brief

You may need to configure a proxy server if you're having trouble cloning or fetching from a remote repository or getting an error like unable to access '...' Couldn't resolve host '...'.

Consider something like:

	import UIKit

	extension UIControl {
	/// add handler for specific `UIControl.Event`
	func addEvent(_ event: UIControl.Event, handler: @escaping (UIControl) -> Void) {
	let holder = EventHandlerHolder(action: handler)
	retainHolder(holder, for: event)
	addTarget(holder, action: #selector(holder.invokeHandler), for: event)
	}

	//
	// SectionBackgroundFlowLayout.swift
	//
	// Created by Samuel's on 2020/7/29.

	import UIKit

	@objc protocol SectionBackgroundFlowLayoutDelegate: NSObjectProtocol {
	func sectionsNeedBackgroundColor(in collectionView: UICollectionView, layout: UICollectionViewFlowLayout) -> [Int]
	func classForBackgroundViewAttributes() -> UICollectionViewLayoutAttributes.Type

	// do common initilizer
	class BaseNavigationController: UINavigationController {
	override func viewDidLayoutSubviews() {
	super.viewDidLayoutSubviews()
	fixNavigationItemsMargin()
	}

	override func viewDidAppear(_ animated: Bool) {
	super.viewDidAppear(animated)
	fixNavigationItemsMargin()