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iOS Enumerations and Optionals in Swift Introduction to Optionals Nil Values in Collections

Lana Wong
Lana Wong
3,968 Points
Posted by Lana Wong
Lana Wong
3,968 Points

What is wrong with my If/let statement in dealing with this dictionary?

INSTRUCTIONS: In the editor, you have a pretty complex dictionary representing a movie. It contains a nested dictionary, which itself contains an array of Strings as a value.

Your job is to assign the string containing the value for the lead actor (which for the sake of the example is at position 0 in the array) to the variable leadActor.

Since dictionaries return optional values, you will have to use an if let statement to unwrap each consecutive operation.

optionals.swift 
let movieDictionary = ["Spectre": ["cast": ["Daniel Craig", "Christoph Waltz", "LÊa Seydoux", "Ralph Fiennes", "Monica Bellucci", "Naomie Harris"]]]

var leadActor: String = lead

// Enter code below

if let theMovie = movieDictionary["Spectre"], let people = theMovie["cast"], let lead = people["Daniel Craig"]{
return(lead)
}

1 Answer

wwyattw
wwyattw
10,389 Points

First of all, you should keep leadActor empty because we will assign a value to it after unwrapping the dictionary.. In the first optional binding, you unwrapped the dictionary with key "Spectre", at the second binding, you untapped another dictionary with key "cast". At this point you already have access to an array of names. so the last let lead = people isn't needed. Also you use return when there is a value to return to, in this case. you can assign any value from the array to leadActor.

Here is my answer.

if let theMovie = movieDictionary["Spectre"], let people = theMovie["cast"] { leadActor = people[0] }