Nested JSON to Array in Swift

Question

There are already posts talking about this, but I am still not able to figure out my problem.

I am accessing my database and am converting the response into a JSON object - that part is working fine. Here is the code for that. joArray now has the data I need.

//Convert data to json object
let joArray : NSArray
do {
    joArray = try JSONSerialization.jsonObject(with: data, options: []) as! NSArray
}
catch  {
    print(responseString)
    print("error trying to convert data to JSON")
    return
 }

If I print out joArray . . .

print(joArray)

. . . this is what I get.

(
        {
        FirstName = Bob;
    },
        {
        FirstName = Bill;
    }
)

How can I put this data into a swift array so that it looks like this?

let FirstNameArray = ["Bob", "Bill"]

FirstName will always be in the same position, but there will be varying numbers of users (Bob, Bill, Mary, etc.).

Hard to jugde without knowing the exact JSON. Your print-out is most like only a small part of it. You get an array of dictionaries. You have to (flat)map the array to your desired format. Side-note: Do not use NSArray in Swift. You defeat the strong type system by throwing away the crucial type information. Use native Array — vadian
– vadian, Commented Dec 5, 2016 at 18:12

ganzogo · Accepted Answer · 2016-12-05 20:55:42Z

2

You will make life easier for yourself if you use a native Swift array instead. So, start by changing your array definition:

let joArray: [[String: Any]]
do {
  joArray = try JSONSerialization.jsonObject(with: data, options: []) as! [[String: Any]]
} catch {
  // etc...
}

Now, it's straightforward to construct the required array:

let FirstNameArray = swiftArray.flatMap { $0["FirstName"] }

You should use flatMap, rather than map, because the given array item might not have a property called "FirstName".

answered Dec 5, 2016 at 20:55

ganzogo

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