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11,257 PointsError says variables title and author are optional strings, but they aren't
I don't understand how the user can get more than one key out a dictionary. Please help!
struct Book {
let title: String
let author: String
let price: String?
let pubDate: String?
init? (dict: [String: String]) {
self.title = dict["title"]
self.author = dict["author"]
guard let price = dict["price"], let pubDate = dict["pubDate"] else {
return nil
}
self.price = price
self.pubDate = pubDate
}
}
1 Answer
Ben Shockley
6,094 PointsThey are optionals, because it's referring to the "title" and "author" being retrieved from the dictionary. A dictionary always returns and optional, so you have to unwrap it to get to it.
This is what you want your initializer to look like.
struct Book {
let title: String
let author: String
let price: String?
let pubDate: String?
init? (dict: [String: String]) {
if dict.isEmpty {
return nil
}
self.title = dict["title"]!
self.author = dict["author"]!
self.price = dict["price"]
self.pubDate = dict["pubDate"]
}
}
First you want to check and make sure the dictionary isn't nil, so you check it with the isEmpty
function. If it is nil, then you return nil
. If it isn't empty, then you So you use the bang operator !
to unwrap the value from the dictionary and set the constant to that value. You don't need to unwrap price and pubDate because they are being assigned to an optional constant, so it doesn't matter if they are nil or not. Does this make sense?