Swift Programming: The Big Nerd Ranch Guide

Adding and Removing Values

Now that you have seen how to update a value, let’s look at how you can update the key-value pairs in your dictionary by adding or removing a value. Begin by adding a value.

Listing 10.6  Adding a value

import Cocoa

var movieRatings = ["Donnie Darko": 4, "Chungking Express": 5, "Dark City": 4]
print("I have rated \(movieRatings.count) movies.")
let darkoRating = movieRatings["Donnie Darko"]
movieRatings["Dark City"] = 5
movieRatings
let oldRating: Int? = movieRatings.updateValue(5, forKey: "Donnie Darko")
if let lastRating = oldRating {
     print(lastRating)
}
movieRatings["The Cabinet of Dr. Caligari"] = 5

Here, you add a new key-value pair to your dictionary using this syntax: movieRatings["The Cabinet ...