Fetch all values for a particular key from a Dictionary in Swift

Question

I have a array of dictionary like this.

let arr = [["EmpName"   :   "Alex",     "Designation"   :   "Jr. Developer"],
           ["EmpName"   :   "Bob",     "Designation"   :   "Sr. Developer"],
           ["EmpName"   :   "Claire",  "Designation"   :   "Jr. Developer"],
           ["EmpName"   :   "David",   "Designation"   :   "Project Manager"]]

Now I want to fetch only the EmpName objects from this. How do I do this in swift? I basically want an array which have the following values.

["Alex", "Bob", "Claire", "David"]

This is what I do now. But I wonder if I could do that in a single like by using filter or map...

var employees = [String]()
    for empRecord in arr {
        employees.append(empRecord["EmpName"]!)
    }

Answer 1

A simple way is to use flatMap:

let employees = arr.flatMap { $0["EmpName"] }

Result:

["Alex", "Bob", "Claire", "David"]

flatMap in Swift is like map but it also safely unwraps optionals, which is what we need here since Swift dictionaries always return Optionals.