Iterating Through a Dictionary in Swift

Question

Dictionaries in Swift (and other languages) are not ordered. When you iterate through the dictionary, there's no guarentee that the order will match the initialization order. In this example, Swift processes the "Square" key before the others. You can see this by adding a print statement to the loop. 25 is the 5th element of Square so largest would be set 5 times for the 5 elements in Square and then would stay at 25.

let interestingNumbers = [
    "Prime": [2, 3, 5, 7, 11, 13],
    "Fibonacci": [1, 1, 2, 3, 5, 8],
    "Square": [1, 4, 9, 16, 25]
]
var largest = 0
for (kind, numbers) in interestingNumbers {
    println("kind: \(kind)")
    for number in numbers {
        if number > largest {
            largest = number
        }
    }
}
largest

This prints:

kind: Square
kind: Prime
kind: Fibonacci

let dict : [String : Any] = ["FirstName" : "Maninder" , "LastName" : "Singh" , "Address" : "Chandigarh"]
dict.forEach { print($0) }

Result would be

("FirstName", "Maninder") ("LastName", "Singh") ("Address", "Chandigarh")

This is a user-defined function to iterate through a dictionary:

func findDic(dict: [String: String]) {
    for (key, value) in dict {
        print("\(key) : \(value)")
    }
}

findDic(dict: ["Animal": "Lion", "Bird": "Sparrow"])
// prints…
// Animal : Lion 
// Bird : Sparrow

Here is an alternative for that experiment (Swift 3.0). This tells you exactly which kind of number was the largest.

let interestingNumbers = [
"Prime": [2, 3, 5, 7, 11, 13],
"Fibonacci": [1, 1, 2, 3, 5, 8],
"Square": [1, 4, 9, 16, 25],
]

var largest = 0
var whichKind: String? = nil

for (kind, numbers) in interestingNumbers {
    for number in numbers {
    if number > largest {
        whichKind = kind
        largest = number
    }
  }
}

print(whichKind)
print(largest)

OUTPUT:
Optional("Square")
25

If you want to iterate over all the values:

dict.values.forEach { value in
    // print(value)
}

You can also use values.makeIterator() to iterate over dict values, like this:

for sb in sbItems.values.makeIterator(){
  // do something with your sb item..
  print(sb)
}

You can also do the iteration like this, in a more swifty style:

sbItems.values.makeIterator().forEach{
  // $0 is your dict value..
  print($0) 
}

sbItems is dict of type [String : NSManagedObject]