我是 SwiftUI 的新手，已經處理過服務器請求和 JSON。我現在需要以編程方式轉換到一個新視圖，這是我在 ContentView.swift 中的 NavigationLink 上遇到“無法在范圍內找到‘json’”錯誤的地方。我看過視頻和文章，但沒有什么完全匹配的，我嘗試的一切似乎都讓事情變得更糟。
來自服務器的 JSON 回應
{"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 結構檔案
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]
}
內容視圖檔案
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()
}
}
串列視圖檔案
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()
}
}
為了清楚起見，我試圖將代碼保持在最低限度。
uj5u.com熱心網友回復：
是因為ContentView中沒有“json”，所以需要將json物件傳遞給ListView，但是既然是在ListView中加載json，那么就需要在ListView中像這樣初始化json：
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 {
并將其從 ContentView 中的 NavigationLink 中洗掉，例如：
NavigationLink(destination: ListView(), isActive: $PushViewAfterAction) {
或者你可以構建你的 JSONStructure 來接受可選的，比如：
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 = []
}
}
但隨后您需要檢查選項或提供默認值，例如：
結構串列視圖：查看{
@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()
})
}
}
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