ios - 在应用程序启动之间保留数据

Question

我有一个类可以在我的应用程序中处理一个简单的笔记创建者。目前，笔记是使用自定义笔记对象数组存储的。如何在应用程序关闭时保存此数组的内容并在应用程序重新打开时再次加载它们？我试过 NSUserDefaults，但我不知道如何保存数组，因为它不仅仅是由字符串组成。

代码:

注意.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

对此有不同的方法。

NS编码

最简单的是采用NSCoding，让Note继承NSObject，使用NSKeyedArchiver和NSKeyedUnarchiver 用于向/从应用沙箱中的文件写入数据。

这是一个简单的例子:

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，即 Apple 的 ORM 框架 - 它的用法超出了 SO 答案的范围。

延伸阅读

• NSHipster article
• Archiving programming guide
• Core Data programming guide