Decoding JSON From API - Swift 5

Question

I am not that great at building structs for JOSN decoding yet so was hoping for some help. I have the following JSON

{
    "computer": {
        "location": {
            "username": "john.smith",
            "realname": "john smith",
            "real_name": "johnsmith",
            "email_address": "[email protected]",
            "position": "somePosition",
            "phone": "123-456-7890",
            "phone_number": "123-456-7890",
            "department": "",
            "building": "",
            "room": "someRoom01"
        }
    }
}

I have created the following Structs to hold it:

struct ComputerRecord: Codable {
        public let locationRecord: Location
    }

    struct Location: Codable {
        public let record: Record
    }

    struct Record: Codable {
        public let username: String
        public let realname: String
        public let real_name: String
        public let email_address: String
        public let position: String
        public let phone: String
        public let phone_number: String
        public let department: String
        public let building: String
        public let room: String
    }

When I try and decode it and use it like this (part of a larger function w\ completion handler):

do {
    let decoder = JSONDecoder()
    let computer = try decoder.decode(jssComputerRecord.self, from: data)

    if  computer.locationRecord.record.username == nameToCheck {
        usernameSet(true, response, error)
    } else {
          print("In the else")
          usernameSet(false, response, error)
      }
} catch {
      print(error)
      usernameSet(false, response, error)
  }

I hit the catch and get this error:

keyNotFound(CodingKeys(stringValue: "locationRecord", intValue: nil), Swift.DecodingError.Context(codingPath: [], debugDescription: "No value associated with key CodingKeys(stringValue: \"locationRecord\", intValue: nil) (\"locationRecord\").", underlyingError: nil))

I assume this is an error in the way I have constructed the Structs to decode into as if I print a string version of the data, I get the JSON shown above.

Note: I have anonymized the record but left the exact structure intact.

Any help on this would be great.

Thanks,

Ludeth (Ed)

vadian · Accepted Answer · 2019-06-09 15:38:09Z

The most significant rule is:

The name of the struct member must match the JSON key unless you map keys with CodingKeys

To conform to the naming convention I added the snake_case conversion

struct ComputerRecord: Codable {
    public let computer: Computer
}

struct Computer: Codable {
    public let location: Record
}

struct Record: Codable {
    public let username: String
    public let realname: String
    public let realName: String
    public let emailAddress: String
    public let position: String
    public let phone: String
    public let phoneNumber: String
    public let department: String
    public let building: String
    public let room: String
}

do {
    let decoder = JSONDecoder()
    decoder.keyDecodingStrategy = .convertFromSnakeCase
    let result = try decoder.decode(ComputerRecord.self, from: data)

    if result.computer.location.username == nameToCheck {
        usernameSet(true, response, error)
    } else {
        print("In the else")
        usernameSet(false, response, error)
    }
} catch {
      print(error)
      usernameSet(false, response, error)
  }

Vadian has the answer here. This is also great info for me! I had no idea about the name matching. The SnakeCase is also a great tip. Marked as answered. Thanks a lot for taking the time to share your expertise. This site has helped me learn stuff like this that I did not pick up from a book or just learn on my own lol.

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