我正在编写一个应用程序，需要查看本地JSON文件，然后将其版本与我在网站上托管的版本进行比较。如果它们不匹配，请从网上下载并保存到本地。如果它们确实匹配，则继续并使用本地JSON文件。这个版本信息在JSON文件中。
以前，我的应用程序只需分析在线数据并直接使用。然后它将使用JSON数据填充UITableView。现在我正在使用本地文件，UITableView没有被填充，我不确定如何修复它。通过阅读新函数，我认为我的问题是我没有使用JSONDecoder（），而是使用JSONSerialization（），因此我不能将它指向我想要的特定元数据。
18年6月26日编辑（下面是我的BonusListViewController.swift文件）：
//
// BonusListViewController.swift
// Tour of Honor
//
// Created by Tommy Craft on 6/6/18.
// Copyright © 2018 Tommy Craft. All rights reserved.
//
import UIKit
import os.log
import Foundation
class BonusListViewController: UITableViewController {
var bonuses = [JsonFile.JsonBonuses]()
let defaults = UserDefaults.standard
override func viewDidLoad() {
super.viewDidLoad()
// MARK: Data Structures
// Settings Struct
struct Constants {
struct RiderData {
let riderNumToH = "riderNumToH"
let pillionNumToH = "pillionNumToH"
}
struct RallyData {
let emailDestinationToH = "emailDestinationToH"
}
}
//MARK: Check for updated JSON file
checkJSON()
//MARK: Trigger JSON Download
/*
downloadJSON {
print("downloadJSON Method Called")
}
*/
}
// MARK: - Table View Configuration
// MARK: Table view data source
override func numberOfSections(in tableView: UITableView) -> Int {
print("Found \(bonuses.count) sections.")
return bonuses.count
}
override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
print("Found \(bonuses.count) rows in section.")
return bonuses.count
}
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = UITableViewCell(style: .default, reuseIdentifier: nil)
cell.textLabel?.text = bonuses[indexPath.section].name.capitalized
return cell
}
override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
performSegue(withIdentifier: "showDetail", sender: self)
}
// MARK: - Table View Header
override func tableView(_ tableView: UITableView, heightForHeaderInSection section: Int) -> CGFloat {
return 30
}
override func tableView(_ tableView: UITableView, titleForHeaderInSection section: Int) -> String? {
return bonuses[section].state
}
override func tableView(_ tableView: UITableView, heightForFooterInSection section: Int) -> CGFloat {
return 3
}
// MARK: Functions
// MARK: - Download JSON from ToH webserver
func downloadJSON(completed: @escaping () -> ()) {
let url = URL(string: "http://tourofhonor.com/BonusData.json")
URLSession.shared.dataTask(with: url!) { [weak self] (data, response, error) in
if error == nil {
do {
let posts = try JSONDecoder().decode(JsonFile.self, from: data!)
DispatchQueue.main.async {
completed()
}
print("Downloading Updated JSON (Version \(posts.meta.version))")
print(posts.bonuses.map {$0.bonusCode})
print(posts.bonuses.map {$0.state})
self?.bonuses = posts.bonuses
self?.defaults.set("downloadJSON", forKey: "jsonVersion") //Set version of JSON for comparison later
DispatchQueue.main.async {
//reload table in the main queue
self?.tableView.reloadData()
}
} catch {
print("JSON Download Failed")
}
}
}.resume()
}
func checkJSON() {
//MARK: Check for updated JSON file
let defaults = UserDefaults.standard
let hostedJSONFile = "http://tourofhonor.com/BonusData.json"
let jsonURL = URL(string: hostedJSONFile)
var hostedJSONVersion = ""
let jsonData = try! Data(contentsOf: jsonURL!)
let jsonFile = try! JSONSerialization.jsonObject(with: jsonData, options: .mutableContainers) as! [String : Any]
let metaData = jsonFile["meta"] as! [String : Any]
hostedJSONVersion = metaData["version"] as! String
let localJSONVersion = defaults.string(forKey: "jsonVersion")
if localJSONVersion != hostedJSONVersion {
print("L:\(localJSONVersion!) / H:\(hostedJSONVersion)")
print("Version Mismatch: Retrieving lastest JSON from server.")
updateJSONFile()
} else {
//Retrieve the existing JSON from documents directory
print("L:\(localJSONVersion!) / H:\(hostedJSONVersion)")
print("Version Match: Using local file.")
let fileURL = defaults.url(forKey: "pathForJSON")
do {
let localJSONFileData = try Data(contentsOf: fileURL!, options: [])
let myJson = try JSONSerialization.jsonObject(with: localJSONFileData, options: .mutableContainers) as! [String : Any]
//Use my downloaded JSON file to do stuff
print(myJson)
DispatchQueue.main.async {
//reload table in the main queue
self.tableView.reloadData()
}
} catch {
print(error)
}
}
}
func updateJSONFile() {
print("updateJSONFile Method Called")
let hostedJSONFile = "http://tourofhonor.com/BonusData.json"
let jsonURL = URL(string: hostedJSONFile)
let itemName = "BonusData.json"
let defaults = UserDefaults.standard
do {
let directory = try FileManager.default.url(for: .documentDirectory, in: .userDomainMask, appropriateFor:nil, create:false)
let fileURL = directory.appendingPathComponent(itemName)
let jsonData = try Data(contentsOf: jsonURL!)
let jsonFile = try JSONSerialization.jsonObject(with: jsonData, options: .mutableContainers) as? [String : Any]
let metaData = jsonFile!["meta"] as! [String : Any]
let jsonVersion = metaData["version"]
print("JSON VERSION ", jsonVersion!)
try jsonData.write(to: fileURL, options: .atomic)
defaults.set(fileURL, forKey: "pathForJSON") //Save the location of your JSON file to UserDefaults
defaults.set(jsonVersion, forKey: "jsonVersion") //Save the version of your JSON file to UserDefaults
DispatchQueue.main.async {
//reload table in the main queue
self.tableView.reloadData()
}
} catch {
print(error)
}
}
// MARK: - Navigation
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if let destination = segue.destination as? BonusDetailViewController {
destination.bonus = bonuses[(tableView.indexPathForSelectedRow?.row)!]
}
}
}
下面是JsonFile.swift：
import Foundation
struct JsonFile: Codable {
struct Meta: Codable {
let fileName: String
let version: String
}
struct JsonBonuses: Codable {
let bonusCode: String
let category: String
let name: String
let value: Int
let city: String
let state: String
let flavor: String
let imageName: String
}
let meta: Meta
let bonuses: [JsonBonuses]
}
这是因为在我的更新版本中没有使用JSONDecoder（）还是因为我走错了路？另外，如何让这个新数据与UITableView一起工作？
最佳答案
首先，您错误地解析了JSON值。您需要首先了解JSON格式。转到JSON文件链接，并对其进行分析。如果它以“{”开头，那么它就是一个字典，如果它以“[”开头，那么它就是一个数组。在你的例子中，它是一个字典，然后是字符串（“meta”，“counds”）键。所以，我们知道我们的钥匙是弦。接下来，我们来看看我们的价值观。对于“meta”，我们有一个String:String字典；对于“奖金”，我们有一系列字典。
因此，我们的JSON格式是[String:Any]，或者可以编写Dictionary<String, Any>。
下一步是访问字典中的这些值。
func updateJSONFile() {
print("updateJSONFile Method Called")
let hostedJSONFile = "http://tourofhonor.com/BonusData.json"
let jsonURL = URL(string: hostedJSONFile)
let itemName = "BonusData.json"
let defaults = UserDefaults.standard
do {
let directory = try FileManager.default.url(for: .documentDirectory, in: .userDomainMask, appropriateFor:nil, create:false)
let fileURL = directory.appendingPathComponent(itemName)
let jsonData = try Data(contentsOf: jsonURL!)
let jsonFile = try JSONSerialization.jsonObject(with: jsonData, options: .mutableContainers) as? [String : Any]
let metaData = jsonFile!["meta"] as! [String : Any]
let jsonVersion = metaData["version"]
print("JSON VERSION ", jsonVersion!)
try jsonData.write(to: fileURL, options: .atomic)
defaults.set(fileURL, forKey: "pathForJSON") //Save the location of your JSON file to UserDefaults
defaults.set(jsonVersion, forKey: "jsonVersion") //Save the version of your JSON file to UserDefaults
DispatchQueue.main.async {
//reload table in the main queue
self.tableView.reloadData()
}
} catch {
print(error)
}
}
然后，当您访问本地保存的文件时，您必须再次解析JSON以检查版本：
func checkJSON() {
//MARK: Check for updated JSON file
let defaults = UserDefaults.standard
let hostedJSONFile = "http://tourofhonor.com/BonusData.json"
let jsonURL = URL(string: hostedJSONFile)
var hostedJSONVersion = ""
let jsonData = try! Data(contentsOf: jsonURL!)
let jsonFile = try! JSONSerialization.jsonObject(with: jsonData, options: .mutableContainers) as! [String : Any]
let metaData = jsonFile["meta"] as! [String : Any]
hostedJSONVersion = metaData["version"] as! String
let localJSONVersion = defaults.string(forKey: "jsonVersion")
if localJSONVersion != hostedJSONVersion {
print("\(localJSONVersion) : \(hostedJSONVersion)")
updateJSONFile()
} else {
//Retrieve the existing JSON from documents directory
print("\(localJSONVersion) : \(hostedJSONVersion)")
print("Local JSON is still the latest version")
let fileUrl = defaults.url(forKey: "pathForJSON")
do {
let localJSONFileData = try Data(contentsOf: fileUrl!, options: [])
let myJson = try JSONSerialization.jsonObject(with: localJSONFileData, options: .mutableContainers) as! [String : Any]
//Use my downloaded JSON file to do stuff
DispatchQueue.main.async {
//reload table in the main queue
self.tableView.reloadData()
}
} catch {
print(error)
}
}
}
不要忘记在Info.plist文件中允许任意加载，因为JSON文件托管在没有https的网站上。
关于json - 读取本地JSON文件并使用它来填充UITableView，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/50942306/