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iOS Swift Basics (retired) Collections What is a Dictionary?

Matthew Grant
Matthew Grant
3,703 Points
Posted by Matthew Grant
Matthew Grant
3,703 Points

Unsure about how to pass Part 2 of Dictionary task

I've been tinkering my code for about half an hour but I have hit a roadblock on how to pass part 2 of the dictionary task.

This is my code at the moment:

let currencies = [ "US": "Dollar", "UK": "Pound", "JP": "Yen"] let ukCurrency = currencies.removeValueForKey("UK")

The error message I receieve on Xcode is:

Playground execution failed: <EXPR>:13:18: error: immutable value of type '[String : String]' only has mutating members named 'removeValueForKey' let ukCurrency = currencies.removeValueForKey("UK")

If you know how to resolve please reply to post.

Thank you :).

4 Answers

Damian Adams
Damian Adams
21,351 Points
Damian Adams
Damian Adams
21,351 Points

The problem with the code challenge in particular is that it won't permit you to change your dictionary type from a constant to a variable, obstructing you from being able to assign a removed key value to your new ''ukCurrency'' constant because the dictionary you're working on is immutable.

I hope they can fix this soon, or maybe I'm missing something.

George Blizzard
George Blizzard
Courses Plus Student 285 Points

This gave me the correct answer, but I don't understand why this is correct and let ukCurrency = currencies.removeValueForKey("UK") is incorrect. The example shown in the video uses that code; let ukCurrency = currencies["UK"] is never demonstrated.

Michael Liendo
Michael Liendo
15,326 Points
Michael Liendo
Michael Liendo
15,326 Points

hello :) the error message is saying that your dictionary named ukCurrency is a constant...so it can't be changed, yet your trying to remove a member using the 'removeValueForKey' method.

In other words, your dictionary is immutable, you have to make it mutable, hope that helps!

Taylor Smith
seal-mask
.a{fill-rule:evenodd;}techdegree seal-36
Taylor Smith
iOS Development Techdegree Graduate 14,153 Points
Taylor Smith
.a{fill-rule:evenodd;}techdegree seal-36
Taylor Smith
iOS Development Techdegree Graduate 14,153 Points

everything Michael Liendo said. but for us common folk, instead of using "let currencies" use "var currencies." let makes it a constant which can't be changed. var makes it a variable which can be changed. :)