UIKit & Foundation Extensions

Date.swift

extension Date {
  func add(_ value: Int, _ component: Calendar.Component) -> Date! {
    let calendar = Calendar.current
    return calendar.date(byAdding: component, value: value, to: self)
  }

  func subtract(_ value: Int, _ component: Calendar.Component) -> Date! {
    let calendar = Calendar.current
    return calendar.date(byAdding: component, value: -value, to: self)
  }

  private func gregorianOnly(closure: (_ calendar: Calendar) -> Date!) -> Date {
    let calendar = Calendar.current
    switch calendar.identifier {
    case .gregorian:
      return closure(calendar)
    default:
      print("Calculation intended for use only with a Gregorian calendar")
      return closure(Calendar(identifier: .gregorian))
    }
  }

  var beginningOfYear: Date! {
    return gregorianOnly { calendar in
      let currentMonthComponents = calendar.dateComponents([.year], from: self)
      return calendar.date(from: currentMonthComponents)
    }
  }

  var endOfYear: Date! {
    return beginningOfYear.add(1, .year).subtract(1, .second)
  }

  var beginningOfMonth: Date! {
    return gregorianOnly { calendar in
      let currentMonthComponents = calendar.dateComponents([.year, .month], from: self)
      return calendar.date(from: currentMonthComponents)
    }
  }

  var endOfMonth: Date! {
    return beginningOfMonth.add(1, .month).subtract(1, .second)
  }

  var beginningOfWeek: Date! {
    return gregorianOnly { calendar in
      var currentDateComponents = calendar.dateComponents([.year, .weekOfYear], from: self)
      currentDateComponents.weekday = 1
      return calendar.date(from: currentDateComponents)
    }
  }

  var endOfWeek: Date! {
    return beginningOfWeek.add(1, .weekOfYear).subtract(1, .second)
  }

  var beginningOfDay: Date! {
    return gregorianOnly { calendar in
      let currentDateComponents = calendar.dateComponents([.year, .month, .day], from: self)
      return calendar.date(from: currentDateComponents)
    }
  }

  var endOfDay: Date! {
    return beginningOfDay.add(1, .day).subtract(1, .second)
  }

  var beginningOfHour: Date! {
    return gregorianOnly { calendar in
      let currentDateComponents = calendar.dateComponents([.year, .month, .day, .hour], from: self)
      return calendar.date(from: currentDateComponents)
    }
  }

  var endOfHour: Date! {
    return beginningOfHour.add(1, .hour).subtract(1, .second)
  }

  var midday: Date! {
    return gregorianOnly { calendar in
      var currentDateComponents = calendar.dateComponents([.year, .month, .day], from: self)
      currentDateComponents.hour = 12
      return calendar.date(from: currentDateComponents)
    }
  }

  var noon: Date! {
    return midday
  }

  var midnight: Date! {
    return beginningOfDay
  }

  var yesterday: Date! {
    return subtract(1, .day)
  }

  var tomorrow: Date! {
    return add(1, .day)
  }
}

UIColor.swift

// Interesting Libraries:
// https://github.com/yannickl/DynamicColor
// https://github.com/SwiftGen/SwiftGen

// Custom Colors
extension UIColor {
  static let charcoal = UIColor(red: 0.05, green: 0.05, blue: 0.05, alpha: 1.0)
  static let mint = UIColor(red: 0.5, green: 0.9, blue: 0.7, alpha: 1.0)
}

// Convenience initializers with terser RGB & RGBA syntax
extension UIColor {
  convenience init(rgb: Int...) {
    let redPart: CGFloat = CGFloat(rgb[0]) / 255
    let greenPart: CGFloat = CGFloat(rgb[1]) / 255
    let bluePart: CGFloat = CGFloat(rgb[2]) / 255
    self.init(red: redPart, green: greenPart, blue: bluePart, alpha: CGFloat(1.0))
  }

  convenience init(rgba: Int...) {
    let redPart: CGFloat = CGFloat(rgba[0]) / 255
    let greenPart: CGFloat = CGFloat(rgba[1]) / 255
    let bluePart: CGFloat = CGFloat(rgba[2]) / 255
    let alphaPart: CGFloat = CGFloat(rgba[3]) / 100
    self.init(red: redPart, green: greenPart, blue: bluePart, alpha: alphaPart)
  }
}

UIImage.swift

extension UIImage {
  static func from(color: UIColor, size: CGSize? = nil) -> UIImage? {
    let defaultSize = CGSize(width: 1, height: 1)
    let rect = CGRect(origin: .zero, size: (size ?? defaultSize))

    // Start drawing context; defer end
    UIGraphicsBeginImageContext(rect.size)
    defer { UIGraphicsEndImageContext() }

    // Fill with given color
    guard let context = UIGraphicsGetCurrentContext() else { return nil }
    context.setFillColor(color.cgColor)
    context.fill(rect)

    return UIGraphicsGetImageFromCurrentImageContext()
  }
}

UIImageView.swift

extension UIImageView {
  static func from(color: UIColor, size: CGSize? = nil) -> UIImageView {
    let defaultSize = CGSize(width: 1, height: 1)
    let image = UIImage.from(color: color, size: (size ?? defaultSize))
    return UIImageView(image: image)
  }
}