I’ll send out a beta invitation to everybody on the TableFlip Newsletter this week. If you want to help me find quirks in the app and overall make it more usable, this is your chance!

Everyone who reports an issue will get a free license when the beta ends. Also, I’ll invite interested folks in batches, so you may not get your hands on the app this time but maybe in 2 weeks.

→ Join the Beta List

Tell your friends and in general everybody who’s using Markdown and/or deals with lots of tabular data in their work.

All 3 amazingly useful objc.io books are 30% off this week. Grab all three of them in a bundle and save even more.

If you use my link, I’ll even get a small kickback thanks to their affiliate program. I wholeheartedly recommend you take at least the time to read the samples. The team updates their ebooks regularly, and you’ll get a Swift 3.0 edition later this year, too.

When parameter lists grow or two kinds of parameters seem to go together a lot, it’s time use the extract parameter object refactoring for greater good – then you can even specify sensible defaults.

This is a typical way to pass a set of options to an objects during initialization in a language like Swift. In languages like JavaScript or Ruby, dictionaries of key–value pairs can work just as well. Using dictionaries in Swift for this can be a pain, though.

Now Soroush wrote about a way that uses the Then microframework as a replacement for configuaration dictionaries. This way you don’t have to promote every property to the initializer’s list of parameters. Here’s a before and after, where you can see that without then you have to write a lot of repeating boilerplate:

// Before

struct FieldData {
    let title: String
    let placeholder: String
    let keyboardType: UIKeyboardType
    let secureEntry: Bool
    let autocorrectType: UITextAutocorrectionType
    let autocapitalizationType: UITextAutocapitalizationType

    init(title: String,
        placeholder: String = "",
        keyboardType: UIKeyboardType = .Default,
        secureEntry: Bool = false,
        autocorrectType: UITextAutocorrectionType = .None,
        autocapitalizationType: UITextAutocapitalizationType = .None)
        {
            self.title = title
            self.placeholder = placeholder
            self.keyboardType = keyboardType
            self.secureEntry = secureEntry
            self.autocorrectType = autocorrectType
            self.autocapitalizationType = autocapitalizationType
    }
}

let fieldData = FieldData(title: "Password", secureEntry: true)

Now with then, making non-mandatory properties mutable and getting rid of the boilerplate:

// After

struct FieldData {
    let title: String
    var placeholder = ""
    var keyboardType = UIKeyboardType.Default
    var secureEntry = false
    var autocorrectType = UITextAutocorrectionType.No
    var autocapitalizationType = UITextAutocapitalizationType.None

    init(title: String) {
        self.title = title
    }
}

let fieldData = FieldData(title: "Password").then({
    $0.secureEntry = true
})

That’s a Swift alternative to Ruby’s hash-based option initializers. There, the dictionary’s key is used as the setter’s name which is then invoked like so:

class Example
  attr_reader :name, :age
  
  def initialize(args)
    args.each do |k,v|
      instance_variable_set("@#{k}", v) unless v.nil?
    end
  end
end

e1 = Example.new :name => 'foo', :age => 33
#=> #<Example:0x3f9a1c @name="foo", @age=33>

Understanding Uncle Bob’s Principles of Object-Oriented Design (which resulted in the SOLID principles) is super important to really grasp the use of design patterns (like MVVM) and architectural patterns (like VIPER). It’s like the grammar for crafting proper object-oriented software.

And now here’s the good news: there is a Swift playground (and Markdown file to read online) that illustrates all the principles by Uncle Bob: The Principles of OOD in Swift 2.2

Check it out, take notes, and keep the principles close to your heart. They may save your life someday.