Swift Language Modifying Dictionaries


Example

Add a key and value to a Dictionary

var books = [Int: String]()
//books = [:]
books[5] = "Book 5"
//books = [5: "Book 5"]
books.updateValue("Book 6", forKey: 5)
//[5: "Book 6"]

updateValue returns the original value if one exists or nil.

let previousValue = books.updateValue("Book 7", forKey: 5)
//books = [5: "Book 7"]
//previousValue = "Book 6"

Remove value and their keys with similar syntax

books[5] = nil
//books [:]
books[6] = "Deleting from Dictionaries"
//books = [6: "Deleting from Dictionaries"]
let removedBook = books.removeValueForKey(6)
//books = [:]
//removedValue = "Deleting from Dictionaries"