Swift: post only specific codable objects - swift

Question

I am trying to work out how to upload only certain values via a put request. Essentially, I have an app whereby when the user accesses a specific screen, there are a bunch of fields, some of whose values will be pre-populated from an API (precisely which values are already populated is unpredictable). Any blank fields are editable and the user can put their own values in and upload them via a put request. However, I only want to upload new values (that were essentially 'nil' in the original API response). I do not want to override the values that came with the initial response and 're-upload' them. Here is the codable struct which essentially represents the body of the request:
struct UpdateRequest: Codable {
let total: Double?
let discrep: Double?
let percent: Double?
let pre: Double?
let target: Double?
let req: Double?
let dep: Double?
}
So all values are optional.
Here is my update method which is called once the user has completed the 'blanks' and pressed a specific button:
func updateVals() {
let args = ["id": viewModel.id]
guard let body = convertValues() else { return }
API.client.post(.order, with: args, using: .put, posting: body, expecting: MessageResponse.self) { (success, response) in
switch success {
case .failure:
DispatchQueue.asyncMain {
let viewController = WarningViewController.detailsUpdatedFailure()
self.present(viewController, animated: true, completion: nil)
}
case .success:
DispatchQueue.asyncMain {
let viewController = WarningViewController.detailsUpdatedSuccess()
self.present(viewController, animated: true, completion: nil)
}
}
}
}
}
And here is convertedValues() :
func convertValues() -> UpdateRequest? {
// In here I have a bunch of logic to convert values to specific units which is not relevant to this question
{
return UpdateRequest(
total: convertedTotal
discrep: convertedDiscrep
percent: convertedPercent
pre: convertedPre
target: convertedTarget
req: convertedReq
dep: convertedDep
)
}
return nil
}
However, if 'total' for example was in the initial API response I do not want to upload it to this request - as this end point is essentially the same as the 'get' endpoint from which I am populating these initial values.
Obviously I can write logic to check if the values were in the response, but how can I only upload new values to this UpdateRequest without uploading 'nil' values for the ones I don't need?

Answer 1

All you need to do is to override encode(to:) in UpdateRequest and use encodeIfPresent since that method will not include values that are nil.
func encode(to encoder: Encoder) throws {
var container = encoder.container(keyedBy: CodingKeys.self)
try container.encodeIfPresent(total, forKey: .total)
try container.encodeIfPresent(discrep, forKey: .discrep)
//... and so on
}
Example with only total set
let req = UpdateRequest(total: 123.5, discrep: nil, percent: nil, pre: nil, target: nil, req: nil, dep: nil)
do {
let data = try JSONEncoder().encode(req)
print(String(data: data, encoding: .utf8))
} catch {
print(error)
}
outputs
Optional("{\"total\":123.5}")