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https://github.com/zwaldowski/ParksAndRecreation

Various Swift playgrounds, for fun and for profit.
https://github.com/zwaldowski/ParksAndRecreation

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Various Swift playgrounds, for fun and for profit.

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# ParksAndRecreation



Various Swift and SwiftUI tidbits, for fun and for profit.



## Swift



### [Asynchronous Operations](https://github.com/zwaldowski/ParksAndRecreation/blob/master/Latest/Asynchronous%Operations.playground)



Base classes for tracking work inside `OperationQueue` that takes place outside of the queue, without causing a thread to hang by waiting. Includes an `Operation` for wrapping `URLSessionTask`.



Inspired by and lovingly nerd-sniped by [@jaredsinclair](https://github.com/jaredsinclair).



### [Badge Formatter](https://github.com/zwaldowski/ParksAndRecreation/blob/master/Latest/Badge%20Formatter.playground)



A simple class for using Unicode to encircle some characters or single-digit numbers in the iOS system font, inspired by [this tweet](https://twitter.com/Tricertops/status/952265724789129216). Includes a gallery live view for demonstration.



![Badge gallery](https://raw.githubusercontent.com/zwaldowski/ParksAndRecreation/master/Media/2018-01-17%20Badge%20Formatter.png)



### [Chunk Sequence](https://github.com/zwaldowski/ParksAndRecreation/blob/master/Latest/Chunk%20Sequence.playground)



Derived from @krzyzanowskim's [blog post](http://blog.krzyzanowskim.com/2015/10/24/chunksequence-have-cake-and-eat-it/): use a protocol extension to split any collection into a group of slices. Think `flatten()`, but in reverse.



### [Combinatorial Parsers](https://github.com/zwaldowski/ParksAndRecreation/blob/master/Latest/Combinatorial%20Parsers.playground)



A thought exercise strongly inspired by @khanlou (blog post [here](http://khanlou.com/2019/12/regex-vs-combinatorial-parsing/)) and @pointfreeco for a more protocol-oriented, composable parsing flavored like Swift Combine.



### [Custom Truncation](https://github.com/zwaldowski/ParksAndRecreation/blob/master/Swift-2/CustomTruncation.playground)



Use [TextKit](https://developer.apple.com/library/ios/documentation/StringsTextFonts/Conceptual/TextAndWebiPhoneOS/CustomTextProcessing/CustomTextProcessing.html) to perform custom truncation with high performance. Also an example of creating building a drop-in `UILabel` backed by TextKit.



### [Debounce](https://github.com/zwaldowski/ParksAndRecreation/blob/master/Latest/Debounce.playground)



Use [`DispatchSource`](https://developer.apple.com/reference/dispatch/dispatchsource) to coalesce calls that shouldn't be called more than once per runloop iteration, like UI reconfiguration.



### [Delimited](https://github.com/zwaldowski/ParksAndRecreation/blob/master/Swift-3/Delimited.playground)



A fast recursive-descent parser for CSVs and similarly structured data inspired by [Matt Gallagher](http://www.cocoawithlove.com/2009/11/writing-parser-using-nsscanner-csv.html).



### [Deriving Scroll Views](https://github.com/zwaldowski/ParksAndRecreation/blob/master/Latest/Deriving%20Scroll%20Views.playground)



Based on a technique used in the iOS 10 Music app, subclasses of `UICollectionView` and `UITableView` that derive their intrinsic content size and visible bounds from their content and context, respectively, when `isScrollEnabled = false`. This is similar to behavior on `UITextView`. It enables, for instance, putting three collection views in a stack view in a scroll view with low performance impact.



### [Geometry](https://github.com/zwaldowski/ParksAndRecreation/blob/master/Swift-2/Geometry.playground)



Mathematical operators and idiomatic bridging for Core Graphics types.



### [HTML Reader](https://github.com/zwaldowski/ParksAndRecreation/blob/master/Latest/HaitchTee.playground)



Extremely simple read-only HTML parser based on `libxml2` with 100% test coverage.



### [Keyboard Layout Guide](https://github.com/zwaldowski/ParksAndRecreation/blob/master/Latest/Keyboard%20Layout%20Guide)



An extension on `UIViewController` providing a `keyboardLayoutGuide` property. The layout guide normally mirrors the safe area, but automatically shrinks to avoid the keyboard. It also allows emulating the automatic content keyboard insets applied to `UICollectionViewController` and `UITableViewController`. It avoids the pitfalls of most keyboard avoidance implementations, like correctly syncing animations.



The Swift 3 version requires iOS 9.0.



### [Living Wallpapers](https://github.com/zwaldowski/ParksAndRecreation/tree/master/Latest/Living%20Wallpapers.playground)



Create your own sun-, time-, or light/dark-based wallpaper for macOS Mojave.



![Wallpaper changing from light to dark](https://raw.githubusercontent.com/zwaldowski/ParksAndRecreation/master/Media/2018-06-30%20Living%20Wallpapers.gif)



Playground requires Swift 4.2 beta and macOS Mojave.



### [String Localization](https://github.com/zwaldowski/ParksAndRecreation/blob/master/Swift-2/Localize.playground)



Formatted localization using Swift string formatting. Introduces `localize` with

a similar prototype to `NSLocalizedString`:



```swift

func localize(text: LocalizableText, tableName: String? = default, bundle: NSBundle = default, value: String = default, comment: String)

```



What's a `LocalizableText`? It's an intermediary type that deconstructs

interpolation segments for use with string formatting. But that's not important,

what's important is that it's literal convertible:



```swift

let filesLeft = 4

let filesTotal = 5

let labelText = localize("test-progress-\(filesLeft)-of-\(filesTotal)", comment: "Help text used for a positional description")

```



And in your `Localizable.strings`, just like in Cocoa:



```swift

/* Help text used for a positional description */

"test-progress-%@-of-%@" = "%1$@ of %2$@ remaining.";



```



All placeholders should be `%@` on the end of the key, and be represented

positionally, i.e., with `%1$@`, `%2$@`, and so on.



### [Target-Action Notifier](https://github.com/zwaldowski/ParksAndRecreation/blob/master/Latest/Notifier.playground)



A helper for performing type-safe multicast callbacks. The result is a lot like

using `UIControl`, but for weakly held objects and without unsafe selectors.



Heavily inspired by [this blog post](http://oleb.net/blog/2014/07/swift-instance-methods-curried-functions/) from @ole.



### [`NSView` Layout Margins](https://github.com/zwaldowski/ParksAndRecreation/blob/master/Latest/NSView%20Layout%20Margins.playground)



Extending `NSView` Auto Layout with conveniences from iOS, including

a view-level version of `NSWindow.contentLayoutGuide` (think of it like you

would safe areas), `directionalLayoutMargins`, `layoutMarginsGuide`, and

`readableContentGuide`.



![Layout margins](https://raw.githubusercontent.com/zwaldowski/ParksAndRecreation/master/Media/2018-12-09%20Layout%20Margins.png)



### [Ordered Dictionary](https://github.com/zwaldowski/ParksAndRecreation/blob/master/Latest/Ordered%20Dictionary.playground)



A simple glueing-together of `Dictionary` and `Array` into an ordered, hashed data structure. Useful if your keys are indeed already `Hashable`, but doesn't have great performance; insertion and removal tend towards the worst of both structures. If you have any alternative, prefer something [B-Tree based](https://github.com/lorentey/BTree) instead.



### [Custom Size Classes](https://github.com/zwaldowski/ParksAndRecreation/blob/master/Swift-2/Overrides)



"Size classes are fine, but I can't customize them!" Yeah, you can! By inspecting what Mobile Safari does, you can do the same, using override trait collections.



### [Custom Readable Width](https://github.com/zwaldowski/ParksAndRecreation/blob/master/Latest/Readable%20Width.playground)



Emulating the calculation of [`UIView.readableContentGuide`](https://developer.apple.com/reference/uikit/uiview/1622644-readablecontentguide).



### [Receding Navigation Title](https://github.com/zwaldowski/ParksAndRecreation/blob/master/Latest/Receding%20Navigation%20Title.playground)



Approximating multi-line large titles in navigation bars seen in News, Music, etc.



![Badge gallery](https://raw.githubusercontent.com/zwaldowski/ParksAndRecreation/master/Media/2019-05-20%20Receding%20Navigation%20Title.gif)



### [Regular Expressions](https://github.com/zwaldowski/ParksAndRecreation/blob/master/Swift-2/RegularExpression.playground)



Simple Swift bridging for [`NSRegularExpression`](https://developer.apple.com/library/mac/documentation/Foundation/Reference/NSRegularExpression_Class/), as well as general patterns to go from `String.UTF16View` and `Range` to `NSString` and `NSRange`.



### [Repeatable UUIDs](https://github.com/zwaldowski/ParksAndRecreation/blob/master/Latest/Repeatable%20UUID.playground)



A Swift 5 implementation of the [UUID version 5 algorithm](http://tools.ietf.org/html/4122), which is based on a SHA-1 hash of some input data. These can be useful as database primary keys identifying some model that has no identifier of its own. Like all UUIDs, version 5 hashed UUIDs still have an astronomically low chance of collision.



### [String Views](https://github.com/zwaldowski/ParksAndRecreation/blob/master/Latest/String%20Views.playground)



Line, paragraph, sentence, and word views for `Swift.String`, providing a more idiomatic take on `StringProtocol.getLineStart(_:end:contentsEnd:for:)` and `StringProtocol.getParagraphStart(_:end:contentsEnd:for:)` as Swift collections.



```swift

Array(string.lines) // -> [Substring]

```



### [Floating Now Playing Bar](https://github.com/zwaldowski/ParksAndRecreation/blob/master/Latest/Tab%20Bar%20Palette.playground)



Experiment adding an accessory to `UITabBarController`, like Now Playing in Music.​app.



![Tab bar palette gallery](https://raw.githubusercontent.com/zwaldowski/ParksAndRecreation/master/Media/2018-01-17%20Tab%20Bar%20Palette.png)



- Drop-in UITabBarController with a `paletteViewController` property

- Palette is forwarded appearance (i.e., `viewWillAppear`) and trait collection events

- Palette supports sizing through Auto Layout and `preferredContentSize` and animating changes to those

- Can animate in, out, and between palette changes

- Detects and supports highlighting of palette background on tap

- Supports Interface Builder, 3D Touch, and modal view controllers



### [Thread with Function](https://github.com/zwaldowski/ParksAndRecreation/blob/master/Latest/Thread%20with%20Function.playground)



Spawn and join with a `pthread_t` returning a result from a Swift function, inspired by [the Swift stdlib](https://github.com/apple/swift/blob/master/stdlib/private/SwiftPrivatePthreadExtras/SwiftPrivatePthreadExtras.swift). See also [`Thread.init(block:)`](https://developer.apple.com/documentation/foundation/thread/2088561-init) from iOS 10 and up.



### [UI Geometry](https://github.com/zwaldowski/ParksAndRecreation/blob/master/Swift-2/UI%20Geometry.playground)



Conveniences for using Core Graphics types in UI programming, such as retina-friendly

rounding and equation operators that account for floating point inaccuracy.



### [View Recursion](https://github.com/zwaldowski/ParksAndRecreation/blob/master/Swift-2/ViewRecursion.playground)



Showing off the simple power of Swift iterators by performing breadth-first travel through the trees created by `UIView`, `UIViewController`, and `CALayer`.



## SwiftUI



### [Stickiness](https://github.com/zwaldowski/ParksAndRecreation/blob/master/SwiftUI/Stickiness)



Hiding and unhiding the top and bottoms bars of on scroll to match the various onboarding UIs in iOS (Settings, Apple Pay, Health, etc.)



Similar to [Receding Navigation Title](https://github.com/zwaldowski/ParksAndRecreation#receding-navigation-title) in UIKit.



## Archive



### Obsoleted in Swift 4



#### [ConcretePlusProtocol](https://github.com/zwaldowski/ParksAndRecreation/blob/master/Swift-2/ConcretePlusProtocol.playground)



If you're hurting for Objective-C's `MyClassType *`, try this on for size.



Obsoleted in Swift 4 by `MyClass & SomeProtocol` syntax.



#### [Value Coding](https://github.com/zwaldowski/ParksAndRecreation/blob/master/Latest/ValueCodable.playground)



A simple bridge to bridges concrete value types into `NSCoding`.



Obsoleted in Swift 4 by `Codable`.



### Obsoleted in Swift 3



#### [BetterCoreDataInit](https://github.com/zwaldowski/ParksAndRecreation/blob/master/Swift-2/BetterCoreDataInit.playground)



Use protocol extension to achieve simpler Core Data, like `MyManagedObject(context:)`.



#### [Data](https://github.com/zwaldowski/ParksAndRecreation/blob/master/Swift-2/Data.playground)



An idiomatic `Data`, representing any buffer (contiguous or discontiguous) of

numeric elements. Part `NSData`, part `dispatch_data_t`, `Data` is useful for

low-level byte-based APIs in Swift, such as crypto and string parsing.



Create one with an array:



```swift

let data = Data(array: [ 0x48, 0x65, 0x6c, 0x6c, 0x6f, 0x2c, 0x20, 0x57, 0x6f, 0x72, 0x6c, 0x64, 0x21 ])

```



And enumerate through it in constant time:



```swift

for byte in data {

	...

}

```



Made with lots of help from [@a2](https://github.com/a2).



#### [Fixing `dispatch_block_t`](https://github.com/zwaldowski/ParksAndRecreation/blob/master/Swift-2/DispatchBlock.playground)



Even though it's been fixed in 2.1, Swift 2.0 has a rather ugly bug with wrapped `dispatch_block_t` types. Fix it with a C few tricks and a rational `DispatchBlock` type.