Codable: Process one key manually - ios

Question

I get JSON from API and most of the keys are decoded out of the box.
Example API response:
[
{ "href":"http:\/\/audiomachine.com\/",
"description":"Audiomachine",
"extended":"Music for videos",
"shared":"yes",
"toread":"no",
"tags":"creative video music"
},
{ "href": "https:\/\/www.root.cz\/clanky\/nekricte-na-disky-zvuk-i-ultrazvuk-je-muze-poskodit-nebo-zmast-cidla\/",
"description":"Nek\u0159i\u010dte na disky: zvuk i\u00a0ultrazvuk je m\u016f\u017ee po\u0161kodit nebo zm\u00e1st \u010didla - Root.cz",
"extended":"Added by Chrome Pinboard Extension",
"shared":"yes",
"toread":"no",
"tags":"root.cz ril hardware webdev"
},
{ "href": "https:\/\/www.premiumbeat.com\/blog\/10-apple-motion-tutorials-every-motion-designer-watch\/",
"description":"10 Apple Motion Tutorials Every Motion Designer Should Watch",
"extended":"For people used to working with FCPX, sometimes learning Apple Motion can be much easier than learning After Effects. While the two programs are different, there\u2019s certainly a lot of overlap in terms of functionality and creative potential. The following ten Apple Motion tutorials are great examples of just that.\r\n\r\nWhether you are someone new to Apple Motion or a seasoned veteran looking to up your skills, here are ten must watch Apple Motion tutorials.",
"shared":"yes",
"toread":"no",
"tags":"apple apple_motion video creative effects"
}
]
I store the each item in following struct.
struct Link: Codable {
let href: URL
let description: String
var tags: String
}
which is then decoded with something like
URLSession.shared.dataTask(with:url!, completionHandler: {(data, response, error) in
guard let data = data, error == nil else { return }
do {
let decoder = JSONDecoder()
let decodedData = try decoder.decode([Link].self, from: data)
From API data I use href, description and tags. Tags is a bit troublemaker, because I want to use it in code as an Array of Strings, but in the JSON it is retrieved as a String containing all the tags separated by space. As this is my first project, I use to learn iOS development, I have almost no idea how to solve this.
I was able to get close by googling computed properties, so it could be something like
struct Link: Codable {
let href: URL
let description: String
var tags: String {
return tagsFromServer.components(separatedBy: " ")
}
}
, but I have two problems with this solution.
I have strong feeling, this closure would be called every time the code access .tags. I would rather do it once upon the JSON retrieval and after that just read product of that.
I have absolutely no idea how to pass "the original tags I've got from server" / tagsFromServer to the closure.
I would be grateful for filling up my gaps in terminology or a nice video tutorial on this topic, also.

Answer 1

I recommend to write a custom initializer, decode tags as String and split it:
struct Link: Decodable {
let href: URL
let description: String
let tags: [String]
private enum CodingKeys: String, CodingKey { case href, description, tags }
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
href = try container(URL.self, forKey: .href)
description = try container(String, forKey: .description)
let tagsFromServer = try container(String.self, forKey: .tags)
tags = tagsFromServer.components(separatedBy: " ")
}
}
Alternatively you can use the computed property but then you have to add the CodingKeys
struct Link: Decodable {
let href: URL
let description: String
let tagsFromServer : String
private enum CodingKeys: String, CodingKey { case href, description, tagsFromServer = "tags" }
var tags: [String] {
return tagsFromServer.components(separatedBy: " ")
}
}