Question

我正在尝试保存我的struct数组。我读了我能找到的关于这个主题的所有帖子。最后，我使用了一个示例并将其剥离了一点，但它不起作用。它没有保存，因此无法回读：

    func path() -> String {
        return URL(fileURLWithPath: "/Volumes/MacOS/fasttemp/Test.TXT").absoluteString
    }

    struct Movie {
        let name: String
        let releaseYear: Int
    }

    protocol Dictionariable {
        func dictionaryRepresentation() -> NSDictionary
        init?(dictionaryRepresentation: NSDictionary?)
    }

    extension Movie: Dictionariable {
        func dictionaryRepresentation() -> NSDictionary {
            let representation: [String: AnyObject] = [
                "name": name as AnyObject,
                "releaseYear": releaseYear as AnyObject
            ]
            return representation as NSDictionary
        }

        init?(dictionaryRepresentation: NSDictionary?) {
            guard let values = dictionaryRepresentation else {return nil}
            if let name = values["name"] as? String,
                let releaseYear = values["releaseYear"] as? Int {
                self.name = name
                self.releaseYear = releaseYear
            } else {
                return nil
            }
        }
    }

    func extractStructureFromArchive<T: Dictionariable>() -> T? {
        guard let encodedDict = NSKeyedUnarchiver.unarchiveObject(withFile: path()) as? NSDictionary else {return nil}
        return T(dictionaryRepresentation: encodedDict)
    }

    func archiveStructure<T: Dictionariable>(structure: T) {
        let encodedValue = structure.dictionaryRepresentation()
        NSKeyedArchiver.archiveRootObject(encodedValue, toFile: path())
    }

    func extractStructuresFromArchive<T: Dictionariable>() -> [T] {
        guard let encodedArray = NSKeyedUnarchiver.unarchiveObject(withFile: path()) as? [AnyObject] else {return []}
        return encodedArray.map{$0 as? NSDictionary}.flatMap{T(dictionaryRepresentation: $0)}
    }

    func archiveStructureInstances<T: Dictionariable>(structures: [T]) {
        let encodedValues = structures.map{$0.dictionaryRepresentation()}
        NSKeyedArchiver.archiveRootObject(encodedValues, toFile: path())
    }

    let movies = [
        Movie(name: "Avatar", releaseYear: 2009),
        Movie(name: "The Dark Knight", releaseYear: 2008)
    ]

    // this fails!
    archiveStructureInstances(structures: movies)

    let someArray: [Movie] = extractStructuresFromArchive()

    print("\(someArray[0].name)")

没有创建文件。该文件夹存在。它出什么问题了？我正在使用XCode 8.2.1和Swift 3。

补充：我从另一个问题/答案中提取了这个例子。我还将它从3个减少到2个结构成员。我为Swift 3更新了它。但它仍然不起作用！这就是我要问的原因。

Answer 1

您的path错了。您不归档到文件。你必须使用一个目录。

将path()方法更改为此from this answer)：

func path() -> String {
    let documentsPath = NSSearchPathForDirectoriesInDomains(FileManager.SearchPathDirectory.documentDirectory, FileManager.SearchPathDomainMask.userDomainMask, true).first
    let path = documentsPath! + "/Movie"
    return path
}

您的代码按预期打印Avatar。

试图保存struct array：失败

1 个答案: