Optional Values in NSMutableDictionary - ios

Question

I'm new to Swift, very experienced in Objective-C.
In my app, I am receiving data from a server and mapping it to an NSMutableDictionary. The reason I am using an NSMutableDictionary is that the values are not consistent coming from the server, it's a mix of strings and numbers. And that appears to break a Swift Dictionary that expects only one type of value.
Sometimes the server is not sending a value that the NSMutableDictionary is expecting and it crashes the app.
In my research, it appears that I have to check every object to see if the value exists in Swift before setting it into the NSMutableDictionary.
This is my current code:
let userDictionary:NSMutableDictionary = [
"name": data.objectForKey("name") as! String,
... // many more values
This crashes if there is no "name" value in the response from the server.
It appears the solution would be:
if let nameValue = data.objectForKey("name") as! String {
//not sure what to do in here since the var is assigned as I need
}
// ... check many more values
let userDictionary:NSMutableDictionary = [
"name": nameValue,
// ... assign many more values that I checked above
This seems like a lot of extra code to check every single value from the server. Is there a simpler solution?
Thank you for your time.
#Matt below. Here is the code in detail (took out some of the values in the userDictionary for brevity). I'm taking data from Facebook, adding additional info and saving it to Firebase:
//check all of the values
var birthdayValue:String? = "";
if let value:String? = data.objectForKey("birthday") as? String {
birthdayValue = value;
}
let userDictionary:NSMutableDictionary = [
"name": data.objectForKey("name") as! String,
"birthday": birthdayValue!,
"email": data.objectForKey("email") as! String,
"firstName": data.objectForKey("first_name") as! String,
"lastName": data.objectForKey("last_name") as! String,
"description": "",
"distance": 50,
"facebookID": data.objectForKey("id") as! String,
"location":[ 37.12314, -122.49182 ], //TODO: Get location
"points" : 0,
"rating" : 1,
"school" : "",
]
//we need to convert the FB profile pic to a base 64 string and add it here
let imagePath:String = "https://graph.facebook.com/\(data.objectForKey("id") as! String)/picture?width=375&height=667"
self.getDataFromUrl(NSURL(string: imagePath)!) { (imageData, response, error) -> Void in
//convert the data to base 64
let imgString:String = self.convertDataToBase64(imageData);
let images:Array<String> = [imgString];
userDictionary.setValue(images, forKey: "profilePics")
//save the user to Firebase
userRef.childByAppendingPath(data.objectForKey("id") as! String).setValue(userDictionary)
self.currentUserID = (data.objectForKey("id")) as! String
}

Answer 1

Swift actually support multiple types in a dictionary. The following is legal.
let arr: [NSObject: AnyObject] = [1: "hello", "a": 19, 2: "Swift"]
And you can store optional object in the dictionary:
let arr: [NSObject: AnyObject?] = [1: "hello", "a": 19, 2: nil]
And yes, you might need to check the existence of the value if you do care about it. Instead of if, I would use guard to make sure you can use the variable later.
guard let nameValue = data.objectForKey("name") as? String else {
return
}
// Now you can safely use nameValue.

Answer 2

In my app, I am receiving data from a server and mapping it to an NSMutableDictionary
There is no need for this at all. The data is coming to you as a dictionary (at least I presume it is; if it weren't, you could hardly be calling objectForKey, it seems to me). So now just proceed to use it. There is nothing to "map".
For example, suppose that data is the result of calling NSJSONSerialization's JSONObjectWithData:options: on an original NSData d. And suppose what you expect this to serialize to is a dictionary. So after you've said
var data = try! NSJSONSerialization.JSONObjectWithData(
d, options:[]) as! [NSObject:AnyObject]
...you are finished: that's a mutable dictionary and you are off to the races.

Answer 3

If your data is a mix of strings and numbers you could perhaps try to store it as AnyObject in the dictionary, e.g. [String: AnyObject]
Then you could just try to save your data like this:
var userDictionary: [String: AnyObject] = [:]
userDictionary["name"] = data.objectForKey("name")
And when you need to access it:
if let name = userDictionary["name"] as? String {
// Do something with name
}
If you don't want to save it as AnyObject I'd suggest you create a struct instead.

Answer 4

as! is a force downcast, which causes an exception if this downcast isn't possible (which obviously is the case if the value is nil). as?, on the other hand, only downcasts where possible, and results in nil otherwise (which sounds like what you want).
let userDictionary:NSMutableDictionary = [
"name": data.objectForKey("name") as? String,
... // many more values
]
This should work.
Edit: Never mind, this would only work if you'd use a native Swift dictionary. It's still useful to know about the difference between as? and as!, though.