Swift Playgrounds 4.3保存JSON文件遇权限问题，求解决方法

问题背景 #

在macOS 13系统上使用Swift Playgrounds 4.3保存JSON文件到本地时，遇到权限不足或文件找不到的问题，具体场景如下：

1. 自定义路径写入报错 #

尝试直接写入/Users/la/JSON目录时触发权限错误：

import Foundation

struct Driver: Codable { 
    let name: String
    let ownsCar: Bool
    let license_code: String?
    
    init(name: String, ownsCar: Bool, license_code: String? = nil) {
        self.name = name
        self.ownsCar = ownsCar
        self.license_code = license_code
    }
}

class Drivers {
    let filePathURL = URL(fileURLWithPath: "/Users/la/JSON/JSONTestFile.json")
    
    var data: Driver = Driver(name: "Picard", ownsCar: true)
    
    func readFromFile(filePathURL: URL) throws {
        let readData = try Data(contentsOf: filePathURL)
        self.data = try JSONDecoder().decode(Driver.self, from: readData)
    }
    
    func writeToFile(filePathURL: URL) throws {
        let jsonData = try JSONEncoder().encode(self.data)
        try jsonData.write(to: filePathURL)
    }
    
}
let drivers: Drivers = Drivers()
do {
    try drivers.writeToFile(filePathURL: drivers.filePathURL )
}
catch {
    print("Error saving file at path: \(drivers.filePathURL) with error: \(error)")
}

错误信息：

Error saving file at path: file:///Users/la/JSON/JSONTestFile.json
with error: Error Domain=NSCocoaErrorDomain Code=513 "You don’t have
permission to save the file “JSONTestFile.json” in the folder “JSON”."
UserInfo={NSFilePath=/Users/la/JSON/JSONTestFile.json,
NSUnderlyingError=0x7f88474252b0 {Error Domain=NSPOSIXErrorDomain
Code=1 "Operation not permitted"}}

2. 旧版Shared Playground Data路径不可用 #

尝试使用playgroundSharedDataDirectory时触发API不可用错误：

import Foundation
import PlaygroundSupport
import Swift

struct Driver: Codable {
    let name: String
    let ownsCar: Bool
    let license_code: String?
    
    init(name: String, ownsCar: Bool, license_code: String? = nil) {
        self.name = name
        self.ownsCar = ownsCar
        self.license_code = license_code
    }
}

class Drivers {
  let filePathURL = URL(fileURLWithPath: "/Users/la/Documents/Shared Playground Data/JSONTestFile.json")
  //  print (playgroundSharedDataDirectory)
   // let filePathURL = playgroundSharedDataDirectory.appendingPathComponent("JSONTestFile.json")
    
    var data: Driver = Driver(name: "Picard", ownsCar: true)
    
    func readFromFile(filePathURL: URL) throws {
        let readData = try Data(contentsOf: filePathURL)
        self.data = try JSONDecoder().decode(Driver.self, from: readData)
    }
    
    func writeToFile(filePathURL: URL) throws {
        let jsonData = try JSONEncoder().encode(self.data)
        try jsonData.write(to: filePathURL)
    }
    
}
let drivers: Drivers = Drivers()
do {
    try drivers.writeToFile(filePathURL: drivers.filePathURL )
}
catch {
    print("Error saving file at path: \(drivers.filePathURL) with error: \(error)")
}

报错内容：
'playgroundSharedDataDirectory' is unavailable: playgroundSharedDataDirectory is not supported in Swift Playgrounds

3. DocumentDirectory写入无报错但找不到文件 #

使用系统DocumentDirectory路径时，代码无报错但无法定位生成的文件：

let fileName = "JSONTestFile.json"

let docDirectory = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0]

let outputFileUrl = docDirectory.appendingPathComponent(fileName)

func documentDirectoryURL() -> URL {
    let paths = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
    return paths[0]
}

func filePathURL() -> URL {
    return documentDirectoryURL().appendingPathComponent(fileName)
}

解决方案 #

1. 理解沙箱限制 #

macOS版Swift Playgrounds运行在沙箱环境中，默认仅能访问自身容器内的文件，无法直接读写系统自定义目录或旧版Shared Playground路径，这是系统安全机制的要求。

2. 写入Playgrounds专属可读写目录 #

Swift Playgrounds 4.x的可读写目录位于其容器内的Documents文件夹，以下是修改后的完整可运行代码：

import Foundation

struct Driver: Codable {
    let name: String
    let ownsCar: Bool
    let license_code: String?
    
    init(name: String, ownsCar: Bool, license_code: String? = nil) {
        self.name = name
        self.ownsCar = ownsCar
        self.license_code = license_code
    }
}

class Drivers {
    var data: Driver = Driver(name: "Picard", ownsCar: true)
    
    // 获取Playgrounds容器内的Documents路径
    private func getDocumentsURL() -> URL {
        let containerURL = FileManager.default.containerURL(forSecurityApplicationGroupIdentifier: "com.apple.swiftplaygrounds")!
        return containerURL.appendingPathComponent("Documents")
    }
    
    func writeToFile() throws {
        let filePath = getDocumentsURL().appendingPathComponent("JSONTestFile.json")
        // 确保目录存在
        try FileManager.default.createDirectory(at: getDocumentsURL(), withIntermediateDirectories: true)
        let jsonData = try JSONEncoder().encode(data)
        try jsonData.write(to: filePath)
        print("文件已保存到：\(filePath)")
    }
    
    func readFromFile() throws {
        let filePath = getDocumentsURL().appendingPathComponent("JSONTestFile.json")
        let readData = try Data(contentsOf: filePath)
        data = try JSONDecoder().decode(Driver.self, from: readData)
        print("读取的数据：\(data)")
    }
}

let drivers = Drivers()
do {
    try drivers.writeToFile()
    // 可选：验证读取功能
    try drivers.readFromFile()
} catch {
    print("操作失败：\(error)")
}

3. 找到生成的文件 #

运行代码后，通过以下步骤定位文件：

• 在Swift Playgrounds中打开目标项目
• 点击顶部菜单栏Playground -> Show in Finder
• 在Finder中右键点击playground文件，选择Show Package Contents
• 导航到Contents -> Documents，即可找到保存的JSONTestFile.json

4. 手动选择路径（绕过沙箱） #

如果需要将文件保存到自定义位置，可使用系统文件选择器让用户主动授权，代码如下：

import Foundation
import AppKit

func saveFileWithPanel(data: Data, fileName: String) {
    let savePanel = NSSavePanel()
    savePanel.title = "保存JSON文件"
    savePanel.nameFieldStringValue = fileName
    savePanel.allowedContentTypes = [.json]
    
    if savePanel.runModal() == .OK {
        do {
            try data.write(to: savePanel.url!)
            print("文件已保存到：\(savePanel.url!)")
        } catch {
            print("保存失败：\(error)")
        }
    }
}

// 使用示例
let driver = Driver(name: "Picard", ownsCar: true)
let jsonData = try! JSONEncoder().encode(driver)
saveFileWithPanel(data: jsonData, fileName: "JSONTestFile.json")

注意：此方案需要导入AppKit框架，运行时会弹出系统保存对话框，用户选择路径后即可完成保存。

内容的提问来源于stack exchange，提问作者iPadawan