…create a domain-specific language and compactly express complex values. In this chapter, you will implement a result builder for making fancy attributed strings…

…model the whole thing like this: struct Domains: Decodable { let data: [Domain] } struct Domain: Decodable { let attributes: Attributes } struct Attributes: Decodable { let name: String let description: String let level: String } These types store only the attributes that you care about. The types are Decodable because their properties are Decodable…

…works: var number = 2 number **= exponent The value number is modified by the **= operator in-place. Mini-exercises Implement a custom multiplication operator for strings so that the following code works: let baseString = "abc" let times = 5 var multipliedString = baseString ** times Implement the corresponding multiplication assignment operator so that…

…safety. Failable Initializers When you try to initialize an object from external input, it may fail. For example, if you’re converting a String into an Int, there is no guarantee it’ll work. let value = Int("3") // Optional(3) let failedValue = Int("nope") // nil In “Swift Apprentice: Fundamentals - Chapter…

…tutorials, most of which an editor scrutinizes before you see them. Create a new playground and add the following code: class Tutorial { let title: String var editor: Editor? init(title: String) { self.title = title print("Hello tutorial \(title)!") } deinit { print("Goodbye tutorial \(title)!") } } This class models a tutorial. In addition…

Decodable protocols. Literally: typealias Codable = Encodable & Decodable Automatic Encoding and Decoding Many of Swift’s types are codable out of the box: Int, String, Date, Array and many other types from the Standard Library and the Foundation framework. If you want your type to be codable, the simplest…

…already seen pattern matching in action. In “Swift Apprentice: Fundamentals - Chapter 4: Advanced Control Flow”, you used a switch statement to match numbers and strings in different cases. That’s a simple example, but there’s a lot more to explore on the topic. You’ll dive deep into…

June 2, 2014, as "2014-06-02". You could enforce this validation by applying a @ValidatedDate annotation as follows: struct Order { @ValidatedDate var orderPlacedDate: String @ValidatedDate var shippingDate: String @ValidatedDate var deliveredDate: String } To achieve this, you define this property wrapper: @propertyWrapper public struct ValidatedDate { private var storage: Date…

…already know and have used — it’s merely a concrete type accessed through a protocol. Put this into a playground: protocol Pet { var name: String { get } } struct Cat: Pet { var name: String } In this code, the Pet protocol says that pets must have a name. Then, you defined a concrete…

…vastly. Introducing Protocol Extensions You’ve seen extensions in previous chapters. They let you add additional methods and computed properties to a type: extension String { func shout() { print(uppercased()) } } "Swift is pretty cool".shout() Here, you’re extending the String type to add a new method. You can extend…

…keep track of your paint. Start with a simple color and paint abstraction: struct Color: CustomStringConvertible { var red, green, blue: Double var description: String { "r: \(red) g: \(green) b: \(blue)" } } // Preset colors extension Color { static let black = Color(red: 0, green: 0, blue: 0) static let white = Color…

…banking library by extending the behavior of BasicAccount to make a CheckingAccount: class CheckingAccount: BasicAccount { private let accountNumber = UUID().uuidString class Check { let account: String var amount: Dollars private(set) var cashed = false func cash() { cashed = true } init(amount: Dollars, from account: CheckingAccount) { self.amount = amount self.account = account.accountNumber } } } CheckingAccount…