Error Decoding Date with Swift

Question

For example my JSON looks like so:

{ 
   createdAt = "2018-06-13T12:38:22.987Z"  
}

My Struct looks like so:

struct myStruct {
    let createdAt: Date
}

Decode like so:

let decoder = JSONDecoder()
decoder.dateDecodingStrategy = .iso8601

When I am decoding I get this error:

failed to decode, dataCorrupted(Swift.DecodingError.Context(codingPath: [CodingKeys(stringValue: "results", intValue: nil), _JSONKey(stringValue: "Index 0", intValue: 0), CodingKeys(stringValue: "createdAt", intValue: nil)], debugDescription: "Expected date string to be ISO8601-formatted.", underlyingError: nil))

I understand it says that the string was expected to be ISO8601 formatted, but isn't it?

JSONDecoder includes the option to provide a custom DateFormatter object. Create a custom DateFormatter with the desired format. Use your sample date string to test it, and then install it in the JSONDecoder. — Duncan C
@farhan note that it is Swift naming convention to name your structures starting with an uppercase letter you might also be interested in stackoverflow.com/questions/46458487/… — Leo Dabus

rmaddy rmaddy · Accepted Answer · 2018-06-13T22:38:13

The standard ISO8601 date format doesn't include fractional seconds so you need to use a custom date formatter for the date decoding strategy.

let dateFormatter = DateFormatter()
dateFormatter.locale = Locale(identifier: "en_US_POSIX")
dateFormatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSSZ"

let decoder = JSONDecoder()
decoder.dateDecodingStrategy = .formatted(dateFormatter)

Error Decoding Date with Swift

1 Answers