algal

/// Save image in an in-memory URL
func toURL(image:UIImage) -> NSURL
{
  let img  = image
  let imgData:NSData = UIImagePNGRepresentation(img)
  let dataFormatString = "data:image/png;base64,%@"
  let dataString = String(format: dataFormatString, imgData.base64EncodedStringWithOptions(.allZeros))
  let dataURL = NSURL(string: dataString)!
  return dataURL
}

algal

/**
Adds views to containerView, along with constraints to stack them vertically
and fill horozintally.
*/
func addVerticallyStackedViews(views:[UIView], toView containerView:UIView) -> [NSLayoutConstraint]
{
  for v in views {
    v.setTranslatesAutoresizingMaskIntoConstraints(false)
    containerView.addSubview(v)
  }

algal

import UIKit

// known-good: Swift 3

/**
 Abstract superclass for quickly defining a `UICollectionViewCell` subclass that wraps a
 specific `UIView` subclass. The resulting `UICollectionViewCell` will hug the wrapped view
 with layout constraints, so that both the cell and the wrapped view can influence
 each other's size via the normal Auto Layout mechanism.
 To use, override the class function `wrappedViewType` and the computed property

algal

// code from: http://stackoverflow.com/questions/2451223/uibutton-how-to-center-an-image-and-a-text-using-imageedgeinsets-and-titleedgei/24294816#24294816

extension UIButton {
  func centerLabelVerticallyWithPadding(spacing:CGFloat) {
    // update positioning of image and title
    let imageSize = self.imageView.frame.size
    self.titleEdgeInsets = UIEdgeInsets(top:0,
                                        left:-imageSize.width,
                                        bottom:-(imageSize.height + spacing),
                                        right:0)

algal

// in a playground, pause execution wait until the condition pred is true
func waitUntilTrue(@autoclosure pred:()->Bool, secondsUntilTimeout duration:NSTimeInterval = 25)
{
  let previousPlayGroundRunStatus = XCPExecutionShouldContinueIndefinitely()
  XCPSetExecutionShouldContinueIndefinitely(continueIndefinitely: true)
  
  let start = NSDate()
  while true {
    if pred() {
      NSLog("condition met.")

algal

// works as of Swift 1.2, 2015-08-29

// https://developer.apple.com/library/ios/technotes/tn2232/_index.html#//apple_ref/doc/uid/DTS40012884-CH1-SECNSURLSESSION

class NSURLSessionAllowBadCertificateDelegate : NSObject, NSURLSessionDelegate
{
  func URLSession(session: NSURLSession, didReceiveChallenge challenge: NSURLAuthenticationChallenge, completionHandler: (NSURLSessionAuthChallengeDisposition, NSURLCredential!) -> Void)
  {
    if challenge.protectionSpace.authenticationMethod == NSURLAuthenticationMethodServerTrust
    {

algal

// Swift 1.2
// synchronous JSON download

import XCPlayground

// my goodness all this complexity is just for an unconditional synchronous
// get in a playground on HTTP or HTTPS and decoding to JSON. sad.

public func waitUntilTrue(@autoclosure pred:()->Bool, secondsUntilTimeout duration:NSTimeInterval = 25)
{

algal

import UIKit

//: # Paragraphs, lines, breaks, and spacing in attributed strings

/*:
The cocoa text system lets you separately adjust line spacing and paragraph spacing.

This playground investigates a few questions concerning these spacing configurations and text layout:

1. Do empty UILabels collapse to zero height?

algal

//: Playground - noun: a place where people can play

import UIKit

/*:

This playground shows a bug in how `NSAttributedString.boundingRectWithSize(_:options:context:)` handles attributed strings containing the LINE SEPARATOR character when the .UsesDeviceMetrics option is not included.

When the `.UsesDeviceMetrics` option is set, the function is supposed to return the bounding rect where the height is what is required to bound the particular glyphs in the string.

algal

let v = UIView()
// use `performSelector` to workaround that the method is private
// use `takeRetainedValue` to get an AnyObject
// use the forced cast because we know it's a string
let s = v.performSelector("recursiveDescription").takeRetainedValue() as! String
// convert the string to a fixed width font, so the quicklook is useful
NSAttributedString(string: s, attributes: [UIFontDescriptorFeatureSettingsAttribute:[UIFontFeatureTypeIdentifierKey:kMonospacedTextSelector]])