Unlocking JSON with various structures using Swift

Question

Unlocking JSON with various structures using Swift

I am dealing with json data that follows a consistent structure from a nosql database (PK, SK, attributes). The content of the attributes section varies depending on the value of SK.

For instance:

[
  {
    "PK": "POLL#1544693DF0E88EC-3225-410E-B156-D13781B238F6",
    "SK": "#METADATA#1544693DF0E88EC-3225-410E-B156-D13781B238F6",
    "attributes": {
      "latitude": "53.34589121858683",
      "longitude": "-6.272215191675388",
      "max_choices": 50,
      "number": "1544693",
      "poll_open": false,
    }
  },
  {
    "PK": "POLL#1544693DF0E88EC-3225-410E-B156-D13781B238F6",
    "SK": "CHOICE#00a6ec5c-acc1-40f1-a087-31160d2cfc65",
    "attributes": {
      "distance": 790.95097525,
      "latitude": 53.3416,
      "price": "€€",
      "categories": [
        {
          "title": "Ramen",
          "alias": "ramen"
        }
      ],
      "vote_count": 0,
      "longitude": -6.26274
    }
  }
]

I am facing challenges trying to decode this without encountering errors. I have spent hours stuck on this problem.

I have set up the following struct:

struct Result: Codable {
    var PK: String
    var SK: String
    var attributes: String
}

However, when I attempt to decode, I receive the error message:

typeMismatch(Swift.String, Swift.DecodingError.Context(codingPath: [_JSONKey(stringValue: "Index 0", intValue: 0), CodingKeys(stringValue: "attributes", intValue: nil)], debugDescription: "Expected to decode String but found a dictionary instead.", underlyingError: nil))

All I want is to decode 'attributes' as a generic string and then parse it later based on the value of SK once I figure out how to properly handle it. Why does this seem so complex?

json swift decode codable

Answer 1

Answer №1

Are you currently in need of specific attributes, or are you solely interested in the primary key (PK) and sort key (SK)? If you don't require it, simply omit

var attributes: String

it from your struct. This will prevent a decoding error, allowing the successful decoding of the other two parameters, albeit without the attributes data. Since Swift cannot handle attributes as a string due to its dictionary-like nature, proper struct definition is crucial. You could approach this by defining nested structs like so:

struct Result: Codable {
var PK: String
var SK: String
var attributes: Attributes
}

struct Attributes: Codable {
var latitude: String
var longitude: String
// add any other expected attributes here
}

The important thing is to only include attributes that you know will be present; otherwise, an error may occur.

Answer 2

Are you currently in need of specific attributes, or are you solely interested in the primary key (PK) and sort key (SK)? If you don't require it, simply omit

var attributes: String

it from your struct. This will prevent a decoding error, allowing the successful decoding of the other two parameters, albeit without the attributes data. Since Swift cannot handle attributes as a string due to its dictionary-like nature, proper struct definition is crucial. You could approach this by defining nested structs like so:

struct Result: Codable {
var PK: String
var SK: String
var attributes: Attributes
}

struct Attributes: Codable {
var latitude: String
var longitude: String
// add any other expected attributes here
}

The important thing is to only include attributes that you know will be present; otherwise, an error may occur.

Answer 3

Answer №2

To properly handle this scenario, you should utilize JSONSerialization instead of Codable. If you prefer to stick with the same struct, make the following adjustments:

struct Result {
    var primaryKey: String
    var secondaryKey: String
    var attributes: [String: Any]
}

Then, proceed to decode the JSON data as shown below:

var result: Result?
do {
    if let jsonDict = try JSONSerialization.jsonObject(with: data) as? [String: Any],
       let pk = jsonDict["primaryKey"] as? String,
       let sk = jsonDict["secondaryKey"] as? String,
       let attributes = jsonDict["attributes"] as? [String: Any] {
        result = Result(primaryKey: pk, secondaryKey: sk, attributes: attributes)
    }
} catch {
    print(error)
}

Further refinement may be needed for the "attributes" property in Result to enhance its usability, but that is a separate matter.

Answer 4

To properly handle this scenario, you should utilize JSONSerialization instead of Codable. If you prefer to stick with the same struct, make the following adjustments:

struct Result {
    var primaryKey: String
    var secondaryKey: String
    var attributes: [String: Any]
}

Then, proceed to decode the JSON data as shown below:

var result: Result?
do {
    if let jsonDict = try JSONSerialization.jsonObject(with: data) as? [String: Any],
       let pk = jsonDict["primaryKey"] as? String,
       let sk = jsonDict["secondaryKey"] as? String,
       let attributes = jsonDict["attributes"] as? [String: Any] {
        result = Result(primaryKey: pk, secondaryKey: sk, attributes: attributes)
    }
} catch {
    print(error)
}

Further refinement may be needed for the "attributes" property in Result to enhance its usability, but that is a separate matter.

Unlocking JSON with various structures using Swift

Answer №1

Answer №2

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