SwiftUI NavigationLink cannot find 'json' in scope - json

Question

I'm new to SwiftUI and have worked through the server requests and JSON. I now need to programmatically transition to a new view which is where I get stuck with a "Cannot find 'json' in scope" error on the NavigationLink in ContentView.swift. I've watched videos and read articles but nothing quite matches, and everything I try just seems to make things worse.
JSON response from server
{"status":{"errno":0,"errstr":""},
"data":[
{"home_id":1,"name":"Dave's House","timezone":"Australia\/Brisbane"},
{"home_id":2,"name":"Mick's House","timezone":"Australia\/Perth"},
{"home_id":3,"name":"Jim's House","timezone":"Australia\/Melbourne"}
]}
JSON Struct file
import Foundation
struct JSONStructure: Codable {
struct Status: Codable {
let errno: Int
let errstr: String
}
struct Home: Codable, Identifiable {
var id = UUID()
let home_id: Int
let name: String
let timezone: String
}
let status: Status
let data: [Home]
}
ContentView file
import SwiftUI
struct ContentView: View {
#State private var PushViewAfterAction = false
var body: some View {
NavigationLink(destination: ListView(json: json.data), isActive: $PushViewAfterAction) {
EmptyView()
}.hidden()
Button(action: {
Task {
await performAnAction()
}
}, label: {
Text("TEST")
.padding()
.frame(maxWidth: .infinity)
.background(Color.blue.cornerRadius(10))
.foregroundColor(.white)
.font(.headline)
})
}
func performAnAction() {
PushViewAfterAction = true
return
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
ListView file
import SwiftUI
struct ListView: View {
#State var json: JSONStructure
var body: some View {
VStack {
List (self.json.data) { (home) in
HStack {
Text(home.name).bold()
Text(home.timezone)
}
}
}.onAppear(perform: {
guard let url: URL = URL(string: "https://... ***removed*** ") else {
print("invalid URL")
return
}
var urlRequest: URLRequest = URLRequest(url: url)
urlRequest.httpMethod = "POST"
URLSession.shared.dataTask(with: urlRequest, completionHandler: { (data, response, error) in
// check if response is okay
guard let data = data, error == nil else { // check for fundamental networking error
print((error?.localizedDescription)!)
return
}
let httpResponse = (response as? HTTPURLResponse)!
if httpResponse.statusCode != 200 { // check for http errors
print("httpResponse Error: \(httpResponse.statusCode)")
return
}
// convert JSON response
do {
self.json = try JSONDecoder().decode(JSONStructure.self, from: data)
} catch {
print(error.localizedDescription)
print(String(data: data, encoding: String.Encoding.utf8)!)
}
print(json)
if (json.status.errno != 0) {
print(json.status.errstr)
}
print("1. \(json.data[0].name)), \(json.data[0].timezone)")
print("2. \(json.data[1].name)), \(json.data[1].timezone)")
}).resume()
})
}
}
struct ListView_Previews: PreviewProvider {
static var previews: some View {
ListView()
}
}
I've tried to keep the code to a minimum for clarity.

Answer 1

It's because there is no "json" in ContentView, you need to pass json object to ListView, but since you load json in ListView, then you need to initialize json in ListView like:
struct ListView: View {
#State var json: JSONStructure = JSONStructure(status: JSONStructure.Status(errno: 0, errstr: ""), data: [JSONStructure.Home(home_id: 0, name: "", timezone: "")])
var body: some View {
and remove it form NavigationLink in ContentView like:
NavigationLink(destination: ListView(), isActive: $PushViewAfterAction) {
or you could build your JSONStructure to accept optional like:
import Foundation
struct JSONStructure: Codable {
struct Status: Codable {
let errno: Int?
let errstr: String?
init() {
errno = nil
errstr = nil
}
}
struct Home: Codable, Identifiable {
var id = UUID()
let home_id: Int?
let name: String?
let timezone: String?
init() {
home_id = nil
name = nil
timezone = nil
}
}
let status: Status?
let data: [Home]
init() {
status = nil
data = []
}
}
but then you need to check for optionals or provide default value like:
struct ListView: View {
#State var json: JSONStructure = JSONStructure()
var body: some View {
VStack {
List (self.json.data) { (home) in
HStack {
Text(home.name ?? "Could not get name").bold()
Text(home.timezone ?? "Could not get timeZone")
}
}
}.onAppear(perform: {
guard let url: URL = URL(string: "https://... ***removed*** ") else {
print("invalid URL")
return
}
var urlRequest: URLRequest = URLRequest(url: url)
urlRequest.httpMethod = "POST"
URLSession.shared.dataTask(with: urlRequest, completionHandler: { (data, response, error) in
// check if response is okay
guard let data = data, error == nil else { // check for fundamental networking error
print((error?.localizedDescription)!)
return
}
let httpResponse = (response as? HTTPURLResponse)!
if httpResponse.statusCode != 200 { // check for http errors
print("httpResponse Error: \(httpResponse.statusCode)")
return
}
// convert JSON response
do {
self.json = try JSONDecoder().decode(JSONStructure.self, from: data)
} catch {
print(error.localizedDescription)
print(String(data: data, encoding: String.Encoding.utf8)!)
}
print(json)
if (json.status?.errno != 0) {
print(json.status?.errstr)
}
print("1. \(json.data[0].name)), \(json.data[0].timezone)")
print("2. \(json.data[1].name)), \(json.data[1].timezone)")
}).resume()
})
}
}