What is difference between NSDictionary vs Dictionary in Swift?

Question

I\'m learning Swift, and I can see Dictionary in it.
But there are lots of examples that are using NSDictionary with Swift.
What\'s the

Answer 1

Consider this example

    let dataArray = NSMutableArray()

    let d0 = ["code":"AA","name":"American Airlines"]
    let d1 = ["code":"BA","name":"British Airlines"]
    let d2 = ["code":"DA","name":"Delta Airlines"]

    dataArray.addObject(d0)
    dataArray.addObject(d1)
    dataArray.addObject(d2)

later...

let d0 = dataArray.objectAtIndex(0) as! [String:String]
let lbl = UILabel() 
lbl.text = d0["code"] // no xcode warnings

Using NSDictionary in swift

let d0 = dataArray.objectAtIndex(0) as! NSDictionary 

Now you need to coerce the dictionary value into shape.

lbl1.text = d0["name"] as! String

From experience - when dealing with json responses - I've used NSDictionary as it's loosely typed and I can't guaranteed to know exactly what it contains - just that is valid json. There's a growing library of native swift tools to handle this use case, I suggest looking here https://github.com/search?q=json+NSDictionary+swift&type=Code&utf8=%E2%9C%93

In this case - you need to hack around data with the 'if let' dance.

if let results = json["result"] as? NSDictionary

lastly - NSMutableDictionary is more on par with Dictionary as you won't be able to mutate the key / value pairs on a NSDictionary.

eg.

results["code"] = 100 // <-- BOOM

the work around -

let mResults = NSMutableDictionary(dictionary:results)

mResults["code"] = NSNumber(100) // <-- OK

which begs the clarification - you can only stick NSObjects (NSNumbers / NSArrays / NSCount/NSSet) inside the NSMutableDictionaries. The Swift Dictionary gets around this.