Lukasz Warchol lukewar

Swift Concurrency Manifesto

Hacking UIView animation blocks for fun and profit

In this article, I'm going to explore a way that we can create views that implement custom Core Animation property animations in a natural way.

As we know, layers in iOS come in two flavours: Backing layers and hosted layers. The only difference between them is that the view acts as the layer delegate for its backing layer, but not for any hosted sublayers.

In order to implement the UIView transactional animation blocks, UIView disables all animations by default and then re-enables them individually as required. It does this using the actionForLayer:forKey: method.

Somewhat strangely, UIView doesn't enable animations for every property that CALayer does by default. A notable example is the layer.contents property, which is animatable by default for a hosted layer, but cannot be animated using a UIView animation block.

Pry Cheat Sheet

Youtube Tutorial 2013

Command Line

pry -r ./config/app_init_file.rb - load your app into a pry session (look at the file loaded by config.ru)
pry -r ./config/environment.rb - load your rails into a pry session

Debugger

Storyboard Segues initially seem like a pretty cool way to construct interfaces using minimal glue code. But actually, ordinary nibs already support this, and in a much more flexible way.

Certainly, a Storyboard lets you bind a button action up to display a view controller with no code, but in practice you will usually want to pass some data to the new controller, depending on which button you used to get there, and this means implementing the -prepareForSegue:sender: method, which rapidly becomes a giant if/elseif statement of doom, negating most of the benefit of the codeless segue:

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    if ([segue.identifier isEqualToString:@"modalSegue"])
    {
        ModalViewController *controller = (ModalViewController *)segue.destination;

controller.someProperty = someValue;

Make it real

Ideas are cheap. Make a prototype, sketch a CLI session, draw a wireframe. Discuss around concrete examples, not hand-waving abstractions. Don't say you did something, provide a URL that proves it.

Ship it

Nothing is real until it's being used by a real user. This doesn't mean you make a prototype in the morning and blog about it in the evening. It means you find one person you believe your product will help and try to get them to use it.

Do it with style

OS X Screencast to animated GIF

This gist shows how to create a GIF screencast using only free OS X tools: QuickTime, ffmpeg, and gifsicle.

Instructions

To capture the video (filesize: 19MB), using the free "QuickTime Player" application:

	#!/bin/sh

	if [ "$#" -ne 1 ]; then
	echo "$0 <path>"
	exit 1
	fi

	APP_PATH=$1
	BUNDLE_ID=`/usr/libexec/PlistBuddy -c "Print :CFBundleIdentifier" "$APP_PATH/Info.plist"`
	for DEVICE in $(xcrun simctl list -j devices \| jq --raw-output ".devices[][] \| select(.state == \"Booted\") \| .udid"); do

	- (void)tableView:(UITableView )tableView willDisplayCell:(UITableViewCell )cell forRowAtIndexPath:(NSIndexPath *)indexPath
	{
	if ([tableView respondsToSelector:@selector(setSeparatorInset:)]) {
	[tableView setSeparatorInset:UIEdgeInsetsZero];
	}
	if ([tableView respondsToSelector:@selector(setLayoutMargins:)]) {
	[tableView setLayoutMargins:UIEdgeInsetsZero];
	}
	if ([cell respondsToSelector:@selector(setLayoutMargins:)]) {
	[cell setLayoutMargins:UIEdgeInsetsZero];

	import Foundation

	class Foo {
	let length = 255

	// !!! not like this because self.length can't be used here
	// var arrayConstantLength = [Byte](count:self.length, repeatedValue:0)

	// but like this (with lazy I can use self.length constant)
	lazy var arrayConstantLength:[Byte] = {

	//
	// NBResponderChainUtilities.h
	//
	// Created by Nicolas @ bou.io on 19/04/13.
	//

	#import <UIKit/UIKit.h>

	@interface UIView (NBResponderChainUtilities)
	- (UIView*) nb_firstResponder; // Recurse into subviews to find one that responds YES to -isFirstResponder