ios - swift 4 : Adding dictionaries to Plist

Question

所以，我有一个空的 plist，我试图在 plist 中创建这些值

使用这段代码:

 let dictionary:[String:String] = ["key1" : "value1", "key2":"value2", "key3":"value3"]

let documentDirectoryURL =  FileManager().urls(for: .documentDirectory, in: .userDomainMask).first!
let fileURL = documentDirectoryURL.appendingPathComponent("dictionary.plist")
if NSKeyedArchiver.archiveRootObject(dictionary, toFile: fileURL.path) {
    print(true)
}

if let loadedDic = NSKeyedUnarchiver.unarchiveObject(withFile: fileURL.path) as? [String:String] {
    print(loadedDic)   // "["key1": "value1", "key2": "value2", "key3": "value3"]\n"
}

这里一切都很好，但问题是，当我在我的 xcode 项目中单击 plist 时，它是空的，这些值只被打印而没有插入到 plist

Answer 1

NSKeyedUnarchiver 是保存属性列表的错误方式。

有一个专用结构PropertyListSerialization 来加载和保存属性列表。

首先声明一个计算属性plistURL

var plistURL : URL {
    let documentDirectoryURL =  try! FileManager.default.url(for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: false)
    return documentDirectoryURL.appendingPathComponent("dictionary.plist")
}

以及加载和保存的两种方法

func savePropertyList(_ plist: Any) throws
{
    let plistData = try PropertyListSerialization.data(fromPropertyList: plist, format: .xml, options: 0)
    try plistData.write(to: plistURL)
}


func loadPropertyList() throws -> [String:String]
{
    let data = try Data(contentsOf: plistURL)
    guard let plist = try PropertyListSerialization.propertyList(from: data, format: nil) as? [String:String] else {
        return [:]
    }
    return plist
}

创建字典并保存

do {
    let dictionary = ["key1" : "value1", "key2":"value2", "key3":"value3"]
    try savePropertyList(dictionary)
} catch {
    print(error)
}

要更新一个值，读取它，更新值并保存回来

do {
    var dictionary = try loadPropertyList()
    dictionary.updateValue("value4", forKey: "key4")
    try savePropertyList(dictionary)
} catch {
    print(error)
}