Reddit: JSON Parsing in swift 3 - ios

Question

I'm trying to find a way to parse through some Json data on reddit and display the information in a table view. (https://api.reddit.com).
So far this is what my code looks like:
var names: [String] = []
var comment: [String] = []
override func viewDidLoad() {
super.viewDidLoad()
let url = URL(string: "https://api.reddit.com")
do{
let reddit = try Data(contentsOf: url!)
let redditAll = try JSONSerialization.jsonObject(with: reddit, options: JSONSerialization.ReadingOptions.mutableContainers) as! [String : AnyObject]
if let theJSON = redditAll["children"] as? [AnyObject]{
for child in 0...theJSON.count-1 {
let redditObject = theJSON[child] as! [String : AnyObject]
names.append(redditObject["name"] as! String)
}
}
print(names)
}
catch{
print(error)
}
}
//Table View
func numberOfSections(in tableView: UITableView) -> Int {
return 1
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return names.count
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: cellId, for: indexPath)
//Configure cells...
cell.textLabel?.text = names[indexPath.row]
cell.detailTextLabel?.text = comments[indexPath.row]
return cell
}
I know for a fact, the information is actually coming through the "redditALL" constant but i'm not sure what i'm doing incorrect after the JSONSerialization.
Also, i would really appreciate it if there was some kind of link to help me understand JSON Parsing in swift better, Thanks.

Answer 1

First of don't use Data(contentsOf:) to get JSON from URL because it will block your Main thread instead of that use URLSession.
Now to retrieve your children array you need to first access data dictionary because children is inside it. So try like this way.
let url = URL(string: "https://api.reddit.com")
let task = Session.dataTask(with: url!) { data, response, error in
if error != nil{
print(error.)
}
else
{
if let redditAll = (try? JSONSerialization.jsonObject(with: reddit, options: []) as? [String : Any],
let dataDic = redditAll["data"] as? [String:Any],
let children = dataDic["children"] as? [[String:Any]] {
for child in children {
if let name = child["name"] as? String {
names.append(name)
}
}
DispatchQueue.main.async {
self.tableView.reloadData()
}
}
}
}
task.resume()

Answer 2

JSON parsing in Swift (Foundation) is dirt-simple. You call JSONSerialization.jsonObject(with:) and you get back an "object graph". Usually it's a dictionary or array containing other objects. You have to know about the format of the data you're getting in order to cast the results to the proper types and walk the object graph. If you cast wrong your code will fail to run as expected. You should show us your JSON data. It's likely there is a mismatch between your JASON and your code.