Nested struct for UITableView Swift/JSON - json

Question

I need to display topic and description in a UITableView.
struct Topics: Decodable {
let subtopics: [subTopic]
struct subTopic: Decodable {
var topic = ""
var description = ""
}
}
The data for the TableView is fetched with a URL post request and assigned inside a do/try/catch block.
let Topics = Topics()
excerpt from URLRequest:
self.Topics = try JSONDecoder().decode(Topics.self, from: data)
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "topicCell") as! topicCell
var subTopic = Topics?.subtopics[indexPath.row]
cell.topicLabel?.text = subTopic.topic
cell.descriptionTextView?.text = subTopic.description
return cell
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return Topics?.subtopics.count
}
Sample JSON:
{"subtopics":[{"topic":"Computer Science", "description":"beginner course"},{"topic":"Data Analysis", "description":"beginner course"}]}

Answer 1

You give the the variable the same name as the struct.
let Topics = Topics()
Don't do that. It is confusing and can cause unexpected behavior.
There is a reason for the naming convention to name variables lowercase and structs/classes uppercase.
For less confusion name the top object different for example
struct Response: Decodable {
let subtopics: [SubTopic]
struct SubTopic: Decodable {
let topic, description : String
}
}
The default values (and variables) in SubTopic make no sense.
My next recommendation is to omit the top object and declare the data source array
var subTopics = [Response.SubTopic]()
and assign
let response = try JSONDecoder().decode(Response.self, from: data)
self.subTopics = response.subtopics
This will clean up the table view code and gets rid of the ugly optionals
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "topicCell") as! topicCell
let subTopic = subTopics[indexPath.row]
cell.topicLabel?.text = subTopic.topic
cell.descriptionTextView?.text = subTopic.description
return cell
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return subTopics.count
}