Cannot find 'posts' in scope error in SwiftUI - swift

Question

I'm getting an error saying cannot find 'posts' in scope. I've been trying to check for a solution online however didn't come across which would solve this.
ContentView.swift
struct ContentView: View {
var body: some View {
NavigationView{
List(posts) { //error on this line
post in
Text(post.title)
}
.navigationBarTitle("Hacker News")
}
}
}
struct Results: Decodable {
let hits: [Post]
}
struct Post: Decodable, Identifiable {
var id: String {
return objectId
}
let objectId: String
let title: String
let url: String
let points: Int
}
class NetworkManager {
func fetchData() {
if let url = URL(string: "https://hn.algolia.com/api/v1/search?tags=front_page"){
let session = URLSession(configuration: .default)
let task = session.dataTask(with: url) { (data, response, error) in
if error == nil{
let decoder = JSONDecoder()
if let safeData = data{
do {
let results=try decoder.decode(Results.self, from: safeData)
} catch {
print(error)
}
}
}
}
task.resume()
}
}
}

Answer 1

Cannot find 'posts' in scope
This means that you didn't create any variable called posts.
Also note that your code produces a warning in NetworkManager as well:
Initialization of immutable value 'results' was never used; consider
replacing with assignment to '_' or removing it
This is because the data fetched by NetworkManager isn't used anywhere.
In short, the problem is that NetworkManager isn't connected with / used by ContentView in any way.
A possible solution is to make NetworkManager an ObservableObject and create a #Published property of type [Post]:
class NetworkManager: ObservableObject { // make ObservableObject
#Published var posts = [Post]() // create `posts` here
func fetchData() {
if let url = URL(string: "https://hn.algolia.com/api/v1/search?tags=front_page") {
let session = URLSession(configuration: .default)
let task = session.dataTask(with: url) { data, response, error in
if error == nil {
let decoder = JSONDecoder()
if let safeData = data {
do {
let results = try decoder.decode(Results.self, from: safeData)
DispatchQueue.main.async {
self.posts = results.hits // assign fetched data to `posts`
}
} catch {
print(error)
}
}
}
}
task.resume()
}
}
}
Now you need to use NetworkManager in ContentView:
struct ContentView: View {
#StateObject private var networkManager = NetworkManager() // or `#ObservedObject` for iOS 13
var body: some View {
NavigationView {
List(networkManager.posts) { post in // use `posts` from `networkManager`
Text(post.title)
}
.navigationBarTitle("Hacker News")
}
.onAppear {
networkManager.fetchData() // fetch data when the view appears
}
}
}
Also you have a typo in objectId -> it should be objectID:
struct Post: Decodable, Identifiable {
var id: String {
return objectID
}
let objectID: String
let title: String
let url: String
let points: Int
}
If you don't want to change the name, you can use CodingKeys instead:
struct Post: Decodable, Identifiable {
enum CodingKeys: String, CodingKey {
case objectId = "objectID", title, url, points
}
var id: String {
return objectId
}
let objectId: String
let title: String
let url: String
let points: Int
}