Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

iOS Enumerations and Optionals in Swift Introduction to Optionals Initializing Optional Values

Posted by Aryaman Dhingra
Aryaman Dhingra
3,536 Points

How to unwrap optionals in initializers?

I can't figure out how to unwrap optionals that are inside initializers. Please help.

optionals.swift 
struct Book {
    let title: String
    let author: String
    let price: String?
    let pubDate: String?

    init?(dictionary: [String: String]) {
        self.title = dictionary["title"]
        self.author = dictionary["author"]
        let pubDate = dictionary["pubDate"]
        let price = dictionary["price"]
        self.pubDate = pubDate
        self.price = price


    }

}

1 Answer

Brandon Mahoney
.a{fill-rule:evenodd;}techdegree seal-36
Brandon Mahoney
iOS Development with Swift Techdegree Graduate 30,149 Points

Don't forget you need to use dict and not dictionary as per the instructions. Also you its title and author you need to be worried about in case they are not there.

With if let:

struct Book {
    let title: String
    let author: String
    let price: String?
    let pubDate: String?

    init?(dict: [String: String]) {
      if let title = dict["title"], let author = dict["author"] {
        self.title = title
        self.author = author
        self.price = dict["price"]
        self.pubDate = dict["pubDate"]
      } else {
          return nil
      }
    }
}

With a guard let:

struct Book {
    let title: String
    let author: String
    let price: String?
    let pubDate: String?

    init?(dict: [String: String]) {
      guard let title = dict["title"], let author = dict["author"] else {
          return nil
      }

      self.title = title
      self.author = author
      self.price = dict["price"]
      self.pubDate = dict["pubDate"]
    }
}