Swift 3：无法将数据写入 plist 文件

Question

我正在尝试使用一个名为 Data.plist 的文件来存储一些简单的非结构化数据，并将该文件放在我的应用程序的根文件夹中。为了使读取/写入此文件变得简单，我创建了以下 DataManager 结构。它可以毫无问题地读取 Data.plist 文件，但不能将数据写入文件。我不确定问题出在哪里，有人能发现哪里可能出错了吗？

struct DataManager {

    static var shared = DataManager()        

    var dataFilePath: String? {        
        return Bundle.main.path(forResource: "Data", ofType: "plist")
    }

    var dict: NSMutableDictionary? {
        guard let filePath = self.dataFilePath else { return nil }
        return NSMutableDictionary(contentsOfFile: filePath)
    }

    let fileManager = FileManager.default

    fileprivate init() {

        guard let path = dataFilePath else { return }
        guard fileManager.fileExists(atPath: path) else {
            fileManager.createFile(atPath: path, contents: nil, attributes: nil) // create the file
            print("created Data.plist file successfully")
            return
        }
    }

    func save(_ value: Any, for key: String) -> Bool {
        guard let dict = dict else { return false }

        dict.setObject(value, forKey: key as NSCopying)
        dict.write(toFile: dataFilePath!, atomically: true)

        // confirm
        let resultDict = NSMutableDictionary(contentsOfFile: dataFilePath!)
        print("saving, dict: \(resultDict)") // I can see this is working

        return true
    }

    func delete(key: String) -> Bool {
        guard let dict = dict else { return false }
        dict.removeObject(forKey: key)
        return true
    }

    func retrieve(for key: String) -> Any? {
        guard let dict = dict else { return false }

        return dict.object(forKey: key)
    }
}

Answer 1

您无法修改应用程序包中的文件。因此，您使用Bundle.main.path(forResource:ofType:) 获得的所有文件都是可读但不可写的。

如果您想修改此文件，您需要先将其复制到应用的文档目录中。

let initialFileURL = URL(fileURLWithPath: Bundle.main.path(forResource: "Data", ofType: "plist")!)
let documentDirectoryURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).last!
let writableFileURL = documentDirectoryURL.appendingPathComponent("Data.plist", isDirectory: false)

do {
    try FileManager.default.copyItem(at: initialFileURL, to: writableFileURL)
} catch {
    print("Copying file failed with error : \(error)")
}

// You can modify the file at writableFileURL