如何在Swift中將數組保存為json文件？

Question

我是新手，我很難解決這個問題。 所以我需要做的是將此數組保存為iphone文檔文件夾中的json文件。

var levels = ["unlocked", "locked", "locked"]

然后才能將它讀回另一個數組。 有人可以告訴我該怎么做？ 或提供完成此操作的確切代碼。

編輯：我找到了一個例子。 這是他們設置數據的方式：

 "[ {"person": {"name":"Dani","age":"24"}}, {"person": {"name":"ray","age":"70"}} ]" 

你可以這樣訪問它：

 if let item = json[0] 
   { if let person = item["person"] 
     { if let age = person["age"] 
      { println(age) } } }

但我需要能夠從保存在文檔文件夾中的文件中執行相同的操作。

Answer 1

如果你像我一樣不喜歡使用全新的第三方框架只是為了這樣一件小事，那么這就是我在vanilla Swift中的解決方案。 從在Documents文件夾中創建.json文件到將JSON寫入其中。

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)")
}

Answer 2

＃1。 將Swift Array保存為json文件

以下Swift 3 / iOS 10代碼顯示了如何使用FileManager和JSONSerialization將Array實例轉換為json數據並將其保存到位於iPhone文檔目錄中的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"}}]
*/

作為替代方案，您可以實現以下使用流的代碼：

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"}}]
*/

---

＃2。 從json文件中獲取Swift Array

以下Swift 3 / iOS 10代碼顯示了如何從位於iPhone文檔目錄中的json文件中獲取數據，並使用FileManager和JSONSerialization將其轉換為Array實例：

/*
 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)
    }
}

作為替代方案，您可以實現以下使用流的代碼：

/*
 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)
    }
}

---

位於Github的Save-and-read-JSON-from-Playground repo中的Playground顯示了如何將Swift Array保存到json文件以及如何讀取json文件並從中獲取Swift Array 。

Answer 3

我建議你使用SwiftyJSON框架。 研究它的文檔，另外學習如何將字符串寫入文件（提示： NSFileHandle ）

類似下面的代碼，但你真的需要學習SwiftyJSON和NSFileHandle來學習如何將JSON數據序列化到文件並解析文件中的JSON數據

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)
} 

Answer 4

在Swift 4中，這已經內置了JSONEncoder 。

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]
}

您嘗試編碼的對象必須符合Encodable協議。

閱讀Apple關於如何擴展現有對象以使其可編碼的官方指南 。

Answer 5

這是通用的Swift解決方案

我創建了通用類，可以輕松完成

//
//  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)")
        }

    }

    //--------------------------------------------------------------------------------


}

這是一些extension FileManager輔助方法

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)
}

這是String擴展的方法

public func stringByAppendingPathComponent(_ path: String) -> String {
    let fileUrl = URL.init(fileURLWithPath: self)
    let filePath = fileUrl.appendingPathComponent(path).path
    return filePath
}

如何使用它 ？

要保存

   OfflineManager.sharedManager.cacheDataToLocal(with: object as! [String:Any], to: .CampignList)

要讀取數據

    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 {
            }
        }
      }

注意：您可以為json的類型定義自己的WSCacheKeys ，就像我正在獲取一些廣告系列列表一樣

Answer 6

這是Isuru在Swift 4.2中的答案。 這適用於游樂場：

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)")
}