Writing swift dictionary to file

dictionary, nsdictionary, plist, swift

Solution

Anyway, when you want to store `MyOwnType` to file, `MyOwnType` must be a subclass of `NSObject` and conforms to `NSCoding` protocol. like this:

class MyOwnType: NSObject, NSCoding {

    var name: String

    init(name: String) {
        self.name = name
    }

    required init(coder aDecoder: NSCoder) {
        name = aDecoder.decodeObjectForKey("name") as? String ?? ""
    }

    func encodeWithCoder(aCoder: NSCoder) {
        aCoder.encodeObject(name, forKey: "name")
    }
}

Then, here is the `Dictionary`:

var dict = [Int : [Int : MyOwnType]]()
dict[1] = [
    1: MyOwnType(name: "foobar"),
    2: MyOwnType(name: "bazqux")
]

So, here comes your question:

Writing swift dictionary to file

You can use `NSKeyedArchiver` to write, and `NSKeyedUnarchiver` to read:

func getFileURL(fileName: String) -> NSURL {
    let manager = NSFileManager.defaultManager()
    let dirURL = manager.URLForDirectory(.DocumentDirectory, inDomain: .UserDomainMask, appropriateForURL: nil, create: false, error: nil)
    return dirURL!.URLByAppendingPathComponent(fileName)
}

let filePath = getFileURL("data.dat").path!

// write to file
NSKeyedArchiver.archiveRootObject(dict, toFile: filePath)

// read from file
let dict2 = NSKeyedUnarchiver.unarchiveObjectWithFile(filePath) as [Int : [Int : MyOwnType]]

// here `dict2` is a copy of `dict`

But in the body of your question:

how can I write/read it to/from a plist file in swift?

In fact, `NSKeyedArchiver` format is binary plist. But if you want that dictionary as a value of plist, you can serialize `Dictionary` to `NSData` with `NSKeyedArchiver`:

// archive to data
let dat:NSData = NSKeyedArchiver.archivedDataWithRootObject(dict)

// unarchive from data
let dict2 = NSKeyedUnarchiver.unarchiveObjectWithData(data) as [Int : [Int : MyOwnType]]

Problem

There are limitations with writing NSDictionaries into files in swift. Based on what I have learned from api docs and this stackoverflow answer, key types should be NSString, and value types also should be NSx type, and Int, String, and other swift types might not work. The question is that if I have a dictionary like: `Dictionary<Int, Dictionary<Int, MyOwnType>>`, how can I write/read it to/from a plist file in swift?

Original source

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