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iOS Enumerations and Optionals in Swift Objects and Optionals Enumerations With Raw Values

Gavin Hobbs
Gavin Hobbs
5,205 Points
Posted by Gavin Hobbs
Gavin Hobbs
5,205 Points

Coin, Coins, coin, and coins--What's the difference?

I'm having a hard time figuring out what for coin in coins is doing and referring to. Could someone possibly explain this?

enum Coin: Double {
    case penny = 0.01
    case nickel = 0.05
    case dime = 0.10
    case quarter = 0.25
}

let coins: [Coin] = [.penny, .nickel, .dime, .dime, .quarter, .quarter, .quarter]

func sum (having coins: [Coin]) -> Double {
    var total: Double = 0

    for coin in coins {
        total += coin.rawValue
    }

    return total
}

sum(having: coins)

Thanks!

  • Gavin

2 Answers

Greg Kaleka
Greg Kaleka
39,021 Points
Greg Kaleka
Greg Kaleka
39,021 Points

Hi Gavin,

There's a lot going on here. I've renamed things - let me know if this helps:

enum CoinType: Double {
    case penny = 0.01
    case nickel = 0.05
    case dime = 0.10
    case quarter = 0.25
}

let myOwnCoinArray: [CoinType] = [.penny, .nickel, .dime, .dime, .quarter, .quarter, .quarter]

func sum (having passedInValueThatCanBeAnyCoinArray: [CoinType]) -> Double {
    var total: Double = 0

    for specificCoin in passedInValueThatCanBeAnyCoinArray {
        total += specificCoin.rawValue
    }

    return total
}

sum(having: myOwnCoinArray)

Note: this is ridiculous, and you would never name things like this... but hopefully it helps illustrate what's what.

Cheers :beers:

-Greg

Jennifer Nordell
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Jennifer Nordell
Treehouse Teacher
Jennifer Nordell
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Jennifer Nordell
Treehouse Teacher

Hi there! I'm guessing we can agree that coins is a constant that contains an array of enum values. This for loop is saying for every item in this array, we're going to assign it to a temporary variable named coin. The first iteration of the loop, coin will be equal to .penny and we get the raw value of that which is 0.01 and add it to sum. This will keep a running count. Our second iteration, coin will be equal to .nickel as it moves on to the next item and we add the raw value of that, 0.05. At this point, sum is equal to 0.06. This will continue until we run out of items in the coins array. You could have named that variable coin just about anything, but we named it something that makes sense. It might be helpful for you to think of it instead as individualCoin. Then we could say for individualCoin in coins.

Hope that clarifies things! :sparkles: