这里我创建了带有labelName和labelUsername的表视图, 我已经下载了Json数据并将其保存在名为Details的核心数据实体中,其中包含属性名称和用户名。 这里的表格视图在线显示其数据... 但是如何在离线状态下在表格视图中显示提取的数据..
请在代码中帮助我......
import UIKit
import CoreData
struct JsonData {
var nameS: String
var usernameS: String
init(name: String, username: String) {
self.nameS = name
self.usernameS = username
}
}
class ViewController: UIViewController {
@IBOutlet weak var tableView: UITableView!
let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
var iteamsArray = [JsonData]()
override func viewDidLoad() {
downloadJson()
}
func downloadJson(){
let urlStr = "https://jsonplaceholder.typicode.com/users"
let url = URL(string: urlStr)
URLSession.shared.dataTask(with: url!, completionHandler: {(data, response, error) in
guard let respData = data else {
return
}
guard error == nil else {
print("error")
return
}
do{
let jsonObj = try JSONSerialization.jsonObject(with: data!, options: .allowFragments) as! [[String: Any]]
for items in jsonObj {
let nameJson = items["name"] as? String
let usernameJson = items["username"] as? String
let coreData = NSEntityDescription.insertNewObject(forEntityName: "Details", into: self.context) as! Details
coreData.name = nameJson
coreData.username = usernameJson
self.iteamsArray.append(JsonData(name: nameJson!, username: usernameJson!))
}
try self.context.save()
//fetching from core data
let fetchRequest : NSFetchRequest<Details> = Details.fetchRequest()
let details = try self.context.fetch(fetchRequest)
if details.count > 0 {
for detail in details as [NSManagedObject] {
let nameCore = detail.value(forKey: "name")
let usernameCore = detail.value(forKey: "username")
}
}
DispatchQueue.main.async {
self.tableView.reloadData()
}
}
catch {
print("catch error")
}
}).resume()
}
}
// MARK: - TableView
extension ViewController: UITableViewDataSource, UITableViewDelegate {
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return iteamsArray.count
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "JsonCell", for: indexPath) as! JsonTableViewCell
let aData = iteamsArray[indexPath.row]
cell.labelName.text = aData.nameS
cell.labelUsername.text = aData.usernameS
cell.selectionStyle = .none
return cell
}
}
答案 0 :(得分:1)
首先忘记自定义结构。使用NSManagedObject
类作为数据源数组。
var iteamsArray = [Details]()
在viewDidLoad
首先获取数据,如果数组为空,则从Web服务加载
override func viewDidLoad() {
let fetchRequest : NSFetchRequest<Details> = Details.fetchRequest()
do {
iteamsArray = try self.context.fetch(fetchRequest)
if iteamsArray.isEmpty {
downloadJson()
} else {
self.tableView.reloadData()
}
} catch { print(error) }
}
在downloadJson()
替换
self.iteamsArray.append(JsonData(name: nameJson!, username: usernameJson!))
与
self.iteamsArray.append(coreData)
并删除这些行
//fetching from core data
let fetchRequest : NSFetchRequest<Details> = Details.fetchRequest()
let details = try self.context.fetch(fetchRequest)
if details.count > 0 {
for detail in details as [NSManagedObject] {
let nameCore = detail.value(forKey: "name")
let usernameCore = detail.value(forKey: "username")
}
}
在cellForRow
中直接从NSManagedObject
对象获取值
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "JsonCell", for: indexPath) as! JsonTableViewCell
let aData = iteamsArray[indexPath.row]
cell.labelName.text = aData.name
cell.labelUsername.text = aData.userName
cell.selectionStyle = .none
return cell
}