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

Posted by Ingrid Stevens
Ingrid Stevens
1,651 Points

According to the problem, both currencies and ukCurrency need to be constants, however ukCurrency is changing currencies

According to the problem, both currencies and ukCurrency need to be constants (let), however ukCurrency is changing currencies and making it so that there is a mutable error. If you were to let the challenge accept currencies as a var, it would be compiled correctly, but then you get the error of "let currencies needs to be defined".

This is what it wants: let currencies = ["US":"Dollar", "UK":"Pound", "JP":"Yen"]

let ukCurrency = currencies.removeValueForKey("UK")

This is what works:

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

let ukCurrency = currencies.removeValueForKey("UK")

Treehouse, can you fix this so I can correctly answer the question?

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

let ukCurrency = currencies.removeValueForKey("UK")

2 Answers

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

you misinterpreted what the task is asking you to do.

task 2 states: Assign the value for key "UK" to a constant named ukCurrency.

you dont change the value assigned to the key "UK", you assign the value of that key to a new constant:

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

let ukCurrency = currencies["UK"] // ukCurrency now has a value of "Pound"
// currencies remains unchanged, with a value of [ "US": "Dollar", "UK": "Pound", "JP": "Yen"]

this does not modify the currencies dict at all, you just access a value from it. nothing in the dictionary changes. you are basically saying "give me the value that corresponds to this key, and assign that value to this constant". it doesnt change anything about the dictionary itself

Ingrid Stevens
Ingrid Stevens
1,651 Points
Ingrid Stevens
Ingrid Stevens
1,651 Points

Thanks. I just reread the problem and realized that it was asking for the value of UK. Solved it and came back here.

But thanks again for your quick response!