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iOS Parsing JSON Using Codable Parsing to Non-Primitive Types Parsing Dates

Posted by Nicholas Whitfield
Nicholas Whitfield
5,154 Points

I'm getting a "Date string does not match format expected by formatter." error when I type in the code in xCode

I set the type of the publishDate variable to "Date" like it says in the video, and the only thing that works is 

decoder.dateDecodingStrategy = .iso8061

When I use the code 

let formatter = DateFormatter()
formatter.dateFormat = "MMMM dd, yyyy"
decoder.dateDecodingStrategy = .formatted(formatter)

I get the error

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

Can you post all of your code please.

Nicholas Whitfield
Nicholas Whitfield
5,154 Points

ok, whole code

import Foundation

let json = """
{
    "title": "Harry Potter and the sorcerer's stone",
    "url": "https:\\/\\/openlibrary.org\\/books\\/OL26331930M\\/Harry_Potter_and_the_sorcerer's_stone",
    "publish_date": "1997-06-26T00:00:00+0000",
    "text": "VGhpcyBpc24ndCByZWFsbHkgdGhlIGNvbnRlbnRzIG9mIHRoZSBib29r",
    "rating": 4.9

}
""".data(using: .utf8)!

struct Book: Codable {
    let title: String
    let url: URL
    let publishDate: Date
    private let text: Data
    let rating: Double

    var contents: String {
        return text.stringDescription
    }
}

let decoder = JSONDecoder()
decoder.keyDecodingStrategy = .convertFromSnakeCase
//decoder.dateDecodingStrategy = .iso8601

let formatter = DateFormatter()
formatter.dateFormat = "MMMM dd, yyyy"
decoder.dateDecodingStrategy = .formatted(formatter)
decoder.dataDecodingStrategy = .base64
decoder.nonConformingFloatDecodingStrategy = .convertFromString(positiveInfinity: "+Infinity", negativeInfinity: "-Infinity", nan: "NaN")

let potter = try! decoder.decode(Book.self, from: json)

potter.title
potter.url
potter.publishDate
potter.contents
potter.rating

1 Answer

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

Yes your dates format does not match. You missed the part about changing it. He was demonstrating changing the format received forcing you to use a custom formatter.

let json = """
{
    "title": "Harry Potter and the sorcerer's stone",
    "url": "https:\\/\\/openlibrary.org\\/books\\/OL26331930M\\/Harry_Potter_and_the_sorcerer's_stone",
    "publish_date": "June 26, 1997",

    "text": "VGhpcyBpc24ndCByZWFsbHkgdGhlIGNvbnRlbnRzIG9mIHRoZSBib29r",
    "rating": 4.9

}
""".data(using: .utf8)!
Nicholas Whitfield
Nicholas Whitfield
5,154 Points

Dang, how did I miss that. Thanks dude!

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

Yeah no problem.