Swift - Using PATCH Method to update receive errors - json

Question

I am fairly new using API's and been trying to use the API with Airtable. I got the Update API to work with the Rested app. Now I am trying to build my app and utilize the data in the database. The code I am using is:
func requestUpdate(completion: #escaping (Result<Codable, Error>) -> Void) {
let url = URL(string: baseURL)
var request = URLRequest(url: url!)
request.addValue(authorizationToken, forHTTPHeaderField: "Authorization")
request.addValue("application/json", forHTTPHeaderField: "Content-Type")
request.httpMethod = "PATCH"
do {
let jsonEncoder = try JSONEncoder().encode(test)
request.httpBody = jsonEncoder
} catch {
print("Error")
}
let task = URLSession.shared.dataTask(with: request) {data, response, error in
print("Error: \(String(describing: error))")
print(response as Any)
}
task.resume()
}
This is the Data structure I am using to send to the API:
let test: Dictionary<String, Any> = [
"records": [
"id": "recG5MIwZ6Tp3OczR",
"fields": [
"Goods": "Other",
"Paid": 1,
"Sold": 69,
"Weight": 2,
"ETA": 2
]
]
]
The basic structure I need is
'{
"records": [
{
"id": "a id number",
"fields": {
"Goods": "Test 1",
"Paid": 200,
"Sold": 500,
"Weight": 120,
"ETA": 40
}
},
{
"id": "a id number",
"fields": {
"Goods": "Test 2",
"Paid": 150,
"Sold": 0,
"Weight": 10,
"ETA": 7
}
}
]
}'
I even tried creating some simple structs to duplicate this but kept getting an error of Invalid Top-level error in json. Which I am still investigating the error.
I get the error: Status Code: 422, Headers {...} I have only ever used GET method. I am pretty positive I am missing some code with the conversion and all. I think my error could also be with the JSON conversion. Either way I am lost an not sure where to go. Any guidance would be helpful.

Answer 1

When you want to encode a Dictionary<String, Any> into JSON you better use JSONSerialisation.
Alternatively, create an appropriate encodable struct for your "patch spec" (the Dictionary<String, Any>):
struct Spec: Encodable {
...
}
and then use JSONEncoder to encode the value to JSON.
Either way, in your PATCH request you assign the encoded patch spec value (a Data) the httpBody parameter from the patch request - as you have already done.
When you receive a result, you perform the mandatory error checks, and if you got a valid response data whose content type is "application/json", you again have two ways to decode it into a value representation:
Having an appropriate struct which represents the JSON from the response which also conforms to Decodable, then you can use JSONDecoder to decode the data into the value.
Otherwise, you can use JSONSerialisation and try to decode the JSON into either an Array<Any> or Dictionary<String, Any> object.
So, basically you have two approaches to decode/encode JSON. I would prefer to use JSONDecoder/JSONEncoder since it provides type safe values, and you have it much easier to deal with them, instead when having a Dictionary<String, Any>.
How to make your custom structs conform to Decodable and Encodable protocol is a different topic and there are numerous questions and answers to this. If you come to a point where you got stuck there, please ask a specific question.
How to make a proper PATCH request is also a different topic. However, the backend should already have defined a proper API for this.
While not always an easy read, the definitive bible for all HTTP related questions are the various "RFC" from the "Internet Engineering Task Force (IETF)". For a deep dive into a PATCH request you find the specification here:
PATCH Method for HTTP