Jimmy Bui freeworld1995

Understanding `UIViewController` Rotation

Problem

To enable the rotation of a single view controller used to display the preview of Images/Videos. It is intuitive to allow user to rotate there device and screen changes accordingly, so it feels pleasant. But to achieve this, we need to enable the (almost) all Supported Device orientations.

Ex: `Portrait`, `LandscapeLeft`, `LandscapeRight`.

libdispatch efficiency tips

The libdispatch is one of the most misused API due to the way it was presented to us when it was introduced and for many years after that, and due to the confusing documentation and API. This page is a compilation of important things to know if you're going to use this library. Many references are available at the end of this document pointing to comments from Apple's very own libdispatch maintainer (Pierre Habouzit).

My take-aways are:

You should create very few, long-lived, well-defined queues. These queues should be seen as execution contexts in your program (gui, background work, ...) that benefit from executing in parallel. An important thing to note is that if these queues are all active at once, you will get as many threads running. In most apps, you probably do not need to create more than 3 or 4 queues.
Go serial first, and as you find performance bottle necks, measure why, and if concurrency helps, apply with care, always validating under system pressure. Reuse

// reference: https://stackoverflow.com/a/42705208/1477298

You can do a lot of fun stuff to collection views. I like to subclass UICollectionViewFlowLayout. Here is an example that fades the top and the bottom of the collection view based on distance from center. I could modify it to fade only the very edges but you should figure it after you look through the code.

import UIKit

class FadingLayout: UICollectionViewFlowLayout,UICollectionViewDelegateFlowLayout {

    //should be 0<fade<1

Threads

Foundation offers a Thread class, internally based on pthread, that can be used to create new threads and execute closures.

// Detaches a new thread and uses the specified selector as the thread entry point.
Thread.detachNewThreadSelector(selector: Selector>, toTarget: Any, with: Any)

// Subclass
class MyThread: Thread {

	// The MIT License (MIT)
	//
	// Copyright (c) 2017 Alexander Grebenyuk (github.com/kean).

	import Foundation
	import RxSwift
	import RxCocoa


	extension ObservableType {

	import UIKit

	extension UIView {

	var allSubviews: [UIView] {
	subviews + subviews.flatMap { $0.allSubviews }
	}

	func firstSubview<T: UIView>(of type: T.Type) -> T? {
	allSubviews.first { $0 is T } as? T


	func setupGoogleButton() {

	GIDSignIn.sharedInstance().delegate = self

	let button = GIDSignInButton()
	button.translatesAutoresizingMaskIntoConstraints = false

	let buttonBottom = NSLayoutConstraint(item: button, attribute: .bottom, relatedBy: .equal, toItem: self.view, attribute: .bottom, multiplier: 1.0, constant: -96)
	let buttonTrailing = NSLayoutConstraint(item: button, attribute: .trailing, relatedBy: .equal, toItem: self.view, attribute: .trailing, multiplier: 1.0, constant: -24)

	func setupFacebookButton() {
	let button = FBSDKLoginButton()
	let manager = FBSDKLoginManager()

	button.translatesAutoresizingMaskIntoConstraints = false

	let buttonBottom = NSLayoutConstraint(item: button, attribute: .bottom, relatedBy: .equal, toItem: self.view, attribute: .bottom, multiplier: 1.0, constant: -32)
	let buttonTrailing = NSLayoutConstraint(item: button, attribute: .trailing, relatedBy: .equal, toItem: self.view, attribute: .trailing, multiplier: 1.0, constant: -24)
	let buttonLeading = NSLayoutConstraint(item: button, attribute: .leading, relatedBy: .equal, toItem: self.view, attribute: .leading, multiplier: 1.0, constant: 24)
	let buttonHeight = NSLayoutConstraint(item: button, attribute: .height, relatedBy: .equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1.0, constant: 48)

Jimmy Bui freeworld1995

Understanding UIViewController Rotation

Problem

libdispatch efficiency tips

Threads

Understanding `UIViewController` Rotation