Question

我有一个班级来处理我的应用程序中的简单笔记创建者。目前，使用一组自定义Note对象存储注释。当应用程序关闭时如何保存此数组的内容，并在重新打开应用程序时再次加载它们？我已经尝试了NSUserDefaults，但我无法弄清楚如何保存数组，因为它不仅仅是由字符串组成。

代码：

Note.swift

class Note {
    var contents: String

    // an automatically generated note title, based on the first line of the note
    var title: String {
        // split into lines
        let lines = contents.componentsSeparatedByCharactersInSet(NSCharacterSet.newlineCharacterSet()) as [String]
        // return the first
        return lines[0]
    }

    init(text: String) {
        contents = text
    }


}

        var notes = [
    Note(text: "Contents of note"),]

Answer 1

有不同的方法。

NSCoding

最简单的方法是采用NSCoding，让Note继承自NSObject并使用NSKeyedArchiver和NSKeyedUnarchiver来写入/来自应用中的文件＆＃39; s沙箱。

以下是一个简单的例子：

final class Feedback : NSObject, NSCoding {
    private static let documentsPath = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)[0]

    let content : String
    let entry : EntryId
    let positive : Bool
    let date : NSDate


    init(content: String, entry: EntryId, positive : Bool, date :NSDate = NSDate()) {
        self.content = content
        self.entry = entry
        self.positive = positive
        self.date = date

        super.init()
    }

    @objc init?(coder: NSCoder) {
        if let c = coder.decodeObjectForKey("content") as? String,
            let d = coder.decodeObjectForKey("date") as? NSDate {
                let e = coder.decodeInt32ForKey("entry")
                let p = coder.decodeBoolForKey("positive")
                self.content = c
                self.entry = e
                self.positive = p
                self.date = d
        }
        else {
            content = ""
            entry = -1
            positive = false
            date = NSDate()
        }
        super.init()
        if self.entry == -1 {
            return nil
        }
    }

    @objc func encodeWithCoder(aCoder: NSCoder) {
        aCoder.encodeBool(self.positive, forKey: "positive")
        aCoder.encodeInt32(self.entry, forKey: "entry")
        aCoder.encodeObject(content, forKey: "content")
        aCoder.encodeObject(date, forKey: "date")
    }

    static func feedbackForEntry(entry: EntryId) -> Feedback? {
        let path = Feedback.documentsPath.stringByAppendingString("/\(entry).feedbackData")
        if let success = NSKeyedUnarchiver.unarchiveObjectWithFile(path) as? Feedback {
            return success
        }
        else {
            return nil
        }

    }

    func save() {
        let path = Feedback.documentsPath.stringByAppendingString("/\(entry).feedbackData")
        let s = NSKeyedArchiver.archiveRootObject(self, toFile: path)
        if !s {
            debugPrint("Warning: did not save a Feedback for \(self.entry): \"\(self.content)\"")
        }
    }
}

核心数据

更高效但更复杂的解决方案是使用Core Data，Apple的ORM-Framework - 其使用范围超出了SO答案的范围。

在应用启动之间保留数据

1 个答案:

NSCoding

核心数据

进一步阅读