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

Alexander Batalov
Alexander Batalov
21,887 Points
Posted by Alexander Batalov
Alexander Batalov
21,887 Points

It seems to be an error in Swift basics / what is dictionary? code challenge

If I understand correctly you can not change the value in a dictionary when it defined as a constant. The challenge requires me to create a constant like that:

let currencies = ["US" : "Dollar", "UK" : "Pound", "JP" : "Yen"]

and then assign new value for UK key, so here is what I did:

let currencies = ["US" : "Dollar", "UK" : "Pound", "JP" : "Yen"]
let ukCurrency = "Bitcoin"
currencies["UK"] = ukCurrency

I've got an error: ( Bummer! Your code could not be compiled. Please click on "Preview" to view the compiler errors. )

swift_lint.swift:5:1: error: '@lvalue $T5' is not identical to '(String, String)'
currencies["UK"] = ukCurrency
^

When I played with it in playground I figured out that currencies should be a variable. And It runs perfect. 

var currencies = ["US" : "Dollar", "UK" : "Pound", "JP" : "Yen"]
let ukCurrency = "Bitcoin"
currencies["UK"] = ukCurrency

currencies // => ["UK": "Bitcoin", "JP": "Yen", "US": "Dollar"]

4 Answers

Robert Bojor
PLUS
Robert Bojor
Courses Plus Student 29,439 Points
Robert Bojor
Robert Bojor
Courses Plus Student 29,439 Points

Hi Alexander,

It looks like you did a different version of the challenge since the current challenge asks you to create the currencies constant, and then in step 2 assign the value of the UK key to another constant called "ukCurrency". Other than that there's no more points...

let currencies = ["US":"Dollar", "UK":"Pound", "JP":"Yen"]
let ukCurrency = currencies["UK"]

Maybe they've changed it in the meantime...

Stone Preston
Stone Preston
42,016 Points
Stone Preston
Stone Preston
42,016 Points

robert is correct. task 2 states: Assign the value for key "UK" to a constant named ukCurrency.. it does not ask you to modify the dictionary. It asks you to use a value from the dictionary and assign that to a variable. its fine for the dictionary to be a constant, it does not need to be a variable

Alexander Batalov
Alexander Batalov
21,887 Points
Alexander Batalov
Alexander Batalov
21,887 Points

Oh... :) Sorry. I misunderstood the question. Thank you guys!

Myers Carpenter
Myers Carpenter
6,421 Points
Myers Carpenter
Myers Carpenter
6,421 Points

The reason it won't compile is that you are trying modify a constant. If you had wrote let currencies as var currencies you could compile the code.

But like Stone said, that's not what the challenge asked you do do.