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

Posted by Pino Gatto
Pino Gatto
2,463 Points

Options task Help

Hey all, thanks for the help.

I am getting a compile error telling me that pattern of type 'String" cannot match type 'String?' in my guard statement

Any help would be greatly appreciated.

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

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

        self.price = dict["price"]
        self.pubDate = dict["pubDate"]

    }

}

2 Answers

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

When you use self in your guard let you are trying to create the constant all over again. You want to create a new constant and then assign the original constant that value.

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

I guess an easier way for you to understand what is happening is to see it with the guard let names changed.

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

        self.title = bookTitle
        self.author = bookAuthor
        self.price = dict["price"]
        self.pubDate = dict["pubDate"]
    }
Pino Gatto
Pino Gatto
2,463 Points
Pino Gatto
Pino Gatto
2,463 Points

Hi Brandon, Thank you...

I literally, just re-wrote in Xcode realizing that with guard let, I was re-creating the constant as you stated.

Appreciate the response