我刚学习Swift，遇到了些麻烦。我需要将这个数组保存为JSON文件，并存储在iPhone的文档文件夹中。
var levels = ["unlocked", "locked", "locked"]
然后稍后能够将其读入另一个数组中。请问有人可以告诉我如何做到这一点吗？或者提供实现此操作的确切代码。
编辑： 我找到了一个示例。以下是他们如何设置数据：
"[ {"person": {"name":"Dani","age":"24"}}, {"person": {"name":"ray","age":"70"}} ]"
然后您可以通过以下方式访问它：
if let item = json[0]
{ if let person = item["person"]
{ if let age = person["age"]
{ println(age) } } }
但我需要能够从保存在“文档”文件夹中的文件中进行相同的操作。
如果你像我一样，不喜欢为了这种琐事使用全新的第三方框架，那么在这里，我用原生的Swift提供了解决方案。从在“文档”文件夹中创建.json文件到将JSON写入其中。
let documentsDirectoryPathString = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true).first!
let documentsDirectoryPath = NSURL(string: documentsDirectoryPathString)!
let jsonFilePath = documentsDirectoryPath.URLByAppendingPathComponent("test.json")
let fileManager = NSFileManager.defaultManager()
var isDirectory: ObjCBool = false
// creating a .json file in the Documents folder
if !fileManager.fileExistsAtPath(jsonFilePath.absoluteString, isDirectory: &isDirectory) {
let created = fileManager.createFileAtPath(jsonFilePath.absoluteString, contents: nil, attributes: nil)
if created {
print("File created ")
} else {
print("Couldn't create file for some reason")
}
} else {
print("File already exists")
}
// creating an array of test data
var numbers = [String]()
for var i = 0; i < 100; i++ {
numbers.append("Test\(i)")
}
// creating JSON out of the above array
var jsonData: NSData!
do {
jsonData = try NSJSONSerialization.dataWithJSONObject(numbers, options: NSJSONWritingOptions())
let jsonString = String(data: jsonData, encoding: NSUTF8StringEncoding)
print(jsonString)
} catch let error as NSError {
print("Array to JSON conversion failed: \(error.localizedDescription)")
}
// Write that JSON to the file created earlier
let jsonFilePath = documentsDirectoryPath.URLByAppendingPathComponent("test.json")
do {
let file = try NSFileHandle(forWritingToURL: jsonFilePath)
file.writeData(jsonData)
print("JSON data was written to teh file successfully!")
} catch let error as NSError {
print("Couldn't write to file: \(error.localizedDescription)")
}
jsonFilePath.path而不是jsonFilePath.absoluteString。 - newDeveloperArray保存为json文件下面是Swift 3 / iOS 10代码示例，展示了如何将一个Array实例转换为json数据，并使用FileManager和JSONSerialization将其保存到iPhone文档目录中的json文件中：
func saveToJsonFile() {
// Get the url of Persons.json in document directory
guard let documentDirectoryUrl = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first else { return }
let fileUrl = documentDirectoryUrl.appendingPathComponent("Persons.json")
let personArray = [["person": ["name": "Dani", "age": "24"]], ["person": ["name": "ray", "age": "70"]]]
// Transform array into data and save it into file
do {
let data = try JSONSerialization.data(withJSONObject: personArray, options: [])
try data.write(to: fileUrl, options: [])
} catch {
print(error)
}
}
/*
Content of Persons.json file after operation:
[{"person":{"name":"Dani","age":"24"}},{"person":{"name":"ray","age":"70"}}]
*/
作为替代方案，您可以实现使用流的以下代码：
func saveToJsonFile() {
// Get the url of Persons.json in document directory
guard let documentDirectoryUrl = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first else { return }
let fileUrl = documentDirectoryUrl.appendingPathComponent("Persons.json")
let personArray = [["person": ["name": "Dani", "age": "24"]], ["person": ["name": "ray", "age": "70"]]]
// Create a write-only stream
guard let stream = OutputStream(toFileAtPath: fileUrl.path, append: false) else { return }
stream.open()
defer {
stream.close()
}
// Transform array into data and save it into file
var error: NSError?
JSONSerialization.writeJSONObject(personArray, to: stream, options: [], error: &error)
// Handle error
if let error = error {
print(error)
}
}
/*
Content of Persons.json file after operation:
[{"person":{"name":"Dani","age":"24"}},{"person":{"name":"ray","age":"70"}}]
*/
Array下面是Swift 3 / iOS 10代码示例，演示如何从iPhone文档目录中的json文件获取数据，并使用FileManager和JSONSerialization将其转换为Array实例：
/*
Content of Persons.json file:
[{"person":{"name":"Dani","age":"24"}},{"person":{"name":"ray","age":"70"}}]
*/
func retrieveFromJsonFile() {
// Get the url of Persons.json in document directory
guard let documentsDirectoryUrl = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first else { return }
let fileUrl = documentsDirectoryUrl.appendingPathComponent("Persons.json")
// Read data from .json file and transform data into an array
do {
let data = try Data(contentsOf: fileUrl, options: [])
guard let personArray = try JSONSerialization.jsonObject(with: data, options: []) as? [[String: [String: String]]] else { return }
print(personArray) // prints [["person": ["name": "Dani", "age": "24"]], ["person": ["name": "ray", "age": "70"]]]
} catch {
print(error)
}
}
作为替代方案，您可以实现以下使用流的代码：
/*
Content of Persons.json file:
[{"person":{"name":"Dani","age":"24"}},{"person":{"name":"ray","age":"70"}}]
*/
func retrieveFromJsonFile() {
// Get the url of Persons.json in document directory
guard let documentsDirectoryUrl = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first else { return }
let fileUrl = documentsDirectoryUrl.appendingPathComponent("Persons.json")
// Create a read-only stream
guard let stream = InputStream(url: fileUrl) else { return }
stream.open()
defer {
stream.close()
}
// Read data from .json file and transform data into an array
do {
guard let personArray = try JSONSerialization.jsonObject(with: stream, options: []) as? [[String: [String: String]]] else { return }
print(personArray) // prints [["person": ["name": "Dani", "age": "24"]], ["person": ["name": "ray", "age": "70"]]]
} catch {
print(error)
}
}
Array 保存成 json 文件以及如何读取 json 文件并获取其中的 Swift Array 。JSONSerialization方法来处理流。谢谢。 - Imanou Petit在 Swift 4 中，这个功能已经内置于 JSONEncoder 中。
let pathDirectory = getDocumentsDirectory()
try? FileManager().createDirectory(at: pathDirectory, withIntermediateDirectories: true)
let filePath = pathDirectory.appendingPathComponent("levels.json")
let levels = ["unlocked", "locked", "locked"]
let json = try? JSONEncoder().encode(levels)
do {
try json!.write(to: filePath)
} catch {
print("Failed to write JSON data: \(error.localizedDescription)")
}
func getDocumentsDirectory() -> URL {
let paths = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
return paths[0]
}
您正在尝试编码的对象必须符合Encodable协议。
阅读 苹果公司官方指南，了解如何扩展现有对象以使其可编码。
我建议您使用SwiftyJSON框架。请学习其文档，并学习如何将字符串写入文件（提示：NSFileHandle）。
像下面的代码一样，但您确实需要学习SwiftyJSON和NSFileHandle，以了解如何将JSON数据序列化到文件中，以及从文件解析JSON数据。
let levels = ["unlocked", "locked", "locked"]
let json = JSON(levels)
let str = json.description
let data = str.dataUsingEncoding(NSUTF8StringEncoding)!
if let file = NSFileHandle(forWritingAtPath:path) {
file.writeData(data)
}
以下是Isuru在Swift 4.2中的答案。这个代码可以在playground中使用：
let documentsDirectoryPathString = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true).first!
let documentsDirectoryPath = NSURL(string: documentsDirectoryPathString)!
let jsonFilePath = documentsDirectoryPath.appendingPathComponent("test.json")
let fileManager = FileManager.default
var isDirectory: ObjCBool = false
// creating a .json file in the Documents folder
if !fileManager.fileExists(atPath: (jsonFilePath?.absoluteString)!, isDirectory: &isDirectory) {
let created = fileManager.createFile(atPath: jsonFilePath!.absoluteString, contents: nil, attributes: nil)
if created {
print("File created ")
} else {
print("Couldn't create file for some reason")
}
} else {
print("File already exists")
}
// creating an array of test data
var numbers = [String]()
for i in 0..<100 {
numbers.append("Test\(i)")
}
// creating JSON out of the above array
var jsonData: NSData!
do {
jsonData = try JSONSerialization.data(withJSONObject: numbers, options: JSONSerialization.WritingOptions()) as NSData
let jsonString = String(data: jsonData as Data, encoding: String.Encoding.utf8)
print(jsonString as Any)
} catch let error as NSError {
print("Array to JSON conversion failed: \(error.localizedDescription)")
}
// Write that JSON to the file created earlier
// let jsonFilePath = documentsDirectoryPath.appendingPathComponent("test.json")
do {
let file = try FileHandle(forWritingTo: jsonFilePath!)
file.write(jsonData as Data)
print("JSON data was written to teh file successfully!")
} catch let error as NSError {
print("Couldn't write to file: \(error.localizedDescription)")
}
这里是通用的 Swift 解决方案
我创建了一个通用类，可以轻松实现此功能
//
// OfflineManager.swift
//
//
// Created by Prashant on 01/05/18.
// Copyright © 2018 Prashant. All rights reserved.
//
import UIKit
class OfflineManager: NSObject {
static let sharedManager = OfflineManager()
let LocalServiceCacheDownloadDir = "LocalData"
// Replace case as your naming
enum WSCacheKeys {
case CampignList .
case CampignDetail(id:String)
case ScreenShotList
var value:String {
switch self {
case .CampignList:
return "CampignList"
case .CampignDetail(let id):
return id
case .ScreenShotList :
return "ScreenShotList"
}
}
}
func getBaseForCacheLocal(with fileName:String) -> String? {
let filePath = FileManager.default.getDocumentPath(forItemName: self.LocalServiceCacheDownloadDir)
if FileManager.default.directoryExists(atPath: filePath) {
return filePath.stringByAppendingPathComponent(fileName)
} else {
if FileManager.default.createDirectory(withFolderName: self.LocalServiceCacheDownloadDir) {
return filePath.stringByAppendingPathComponent(fileName)
}
}
return nil
}
//------------------------------------------------------------
@discardableResult
func cacheDataToLocal<T>(with Object:T,to key:WSCacheKeys) -> Bool {
let success = NSKeyedArchiver.archiveRootObject(Object, toFile: getBaseForCacheLocal(with: key.value)!)
if success {
print( "Local Data Cached\(String(describing: getBaseForCacheLocal(with: key.value)))")
} else {
print("Error")
}
return success
}
//------------------------------------------------------------
func loadCachedDataFromLocal<T>(with key:WSCacheKeys ) -> T? {
return NSKeyedUnarchiver.unarchiveObject(withFile: getBaseForCacheLocal(with: key.value)!) as? T
}
//------------------------------------------------------------
func removeAllCacheDirs () {
do {
try FileManager.default.removeItem(atPath: self.getBaseForCacheLocal(with: "")!)
} catch {
print("error in remove dir \(error.localizedDescription)")
}
}
//--------------------------------------------------------------------------------
}
扩展 FileManager的范畴。public var getDocumentDirectoryPath: String {
let documentDirectory = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0]
return documentDirectory
}
public func getDocumentPath(forItemName name: String)-> String {
return getDocumentDirectoryPath.stringByAppendingPathComponent(name)
}
public func directoryExists(atPath filePath: String)-> Bool {
var isDir = ObjCBool(true)
return FileManager.default.fileExists(atPath: filePath, isDirectory: &isDir )
}
public func createDirectory(withFolderName name: String)-> Bool {
let finalPath = getDocumentDirectoryPath.stringByAppendingPathComponent(name)
return createDirectory(atPath: finalPath)
}
这里是字符串扩展的方法
public func stringByAppendingPathComponent(_ path: String) -> String {
let fileUrl = URL.init(fileURLWithPath: self)
let filePath = fileUrl.appendingPathComponent(path).path
return filePath
}
OfflineManager.sharedManager.cacheDataToLocal(with: object as! [String:Any], to: .CampignList)
DispatchQueue.global().async {
// GET OFFLINE DATA
if let object:[String:Any] = OfflineManager.sharedManager.loadCachedDataFromLocal(with: .CampignList) {
do {
let data = try JSONSerialization.data(withJSONObject: object, options: [])
let object = try CampaignListResponse.init(data: data)
self.arrCampignList = object.data ?? []
DispatchQueue.main.async {
self.tableVIew.reloadData()
}
} catch {
}
}
}
WSCacheKeys，就像我正在获取一些活动列表一样。