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

Vladislav Kobyakov
Vladislav Kobyakov
9,439 Points
Posted by Vladislav Kobyakov
Vladislav Kobyakov
9,439 Points

What's the solution?

I was trying to make the init method as in the example from the previous video but still didn't get a few things. I compared the non-optional stored properties such as "title" and "author" to "nil" value as shown in the example before, but I do not really understand why do we compare a non-optional value to nil if it is never equal to nil since we know for sure that they exist?

Anyway, I couldn't really get how to make the init method at all in this exercise because an init method shouldn't return anything (unless it's "init?" and returns nil) like in this example. The code that I've written compiles but still doesn't pass the criteria.

I have feeling that the code that I've written is semantically completely wrong. Can someone please help me with it?

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

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

1 Answer

Heath Robertson
Heath Robertson
3,158 Points

Hey. Here's my solution:

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"]

    }

}

I think you are supposed to use a guard statement, because you can initialise title and author first, because they will never be nil, then continue with the other parameters, checking if they are nil or not. The challenge probably wants you to use guard instead of if let, even though both work. In this case though, using guard is much cleaner. Hope that helped and made sense... :)