Swift return string from Array

Question

I'm trying to get a random name from this Array as a string instead of a number.

I.E: The array normally returns a random number 0 through 9, I'd rather have it return the string that 0 through 9 represents like Preston or James instead of the number itself.

The code below is broken, but I hope it lets you see what I'm trying to do.

 var firstName : [String] = ["Preston", "Ally", "James", "Justin", "Dave", "Bacon", "Bossy",     "Edward", "Edweird" ]

var standardIdent = "First Name:\(firstName[random(0...9)]) Last Name:\(lastName[random(0...5)]) \n Age:\(rand())"
println(standardIdent)

Thank you for your help!

Rob · Accepted Answer · 2018-09-03 17:13:49Z

2

You should not use arc4random() with % operator. That introduces a modulo bias.

In Swift 4.2 and later, you should use randomElement():

let firstNames = ["Preston", "Ally", "James", "Justin", "Dave", "Bacon", "Bossy", "Edward", "Edweird"]
let randomFirstName = firstNames.randomElement()!

Or, if the array could possibly be empty, don't use the forced unwrapping operator, but instead do:

guard let randomFirstName = firstNames.randomElement() else {
    print("array was empty")
    return
}

In Swift versions prior to 4.2, you should:

You should generally use arc4random_uniform, not arc4random, to eliminate modulo bias.
You should probably use the count of the items in the array to determine the range of possible index values.

Thus:

guard firstNames.count > 0 else { ... }
let index = Int(arc4random_uniform(UInt32(firstNames.count)))
let randomFirstName = firstNames[index]

edited Sep 3, 2018 at 17:13

answered Dec 18, 2014 at 14:27

Rob

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Dániel Nagy · Accepted Answer · 2014-12-18 14:18:53Z

1

You should use arc4random like:

let firstRandom = Int(arc4random() % 10)
let secondRandom = Int(arc4random() % 6)
var standardIdent = "First Name:\(firstName[firstRandom]) Last Name:\(lastName[secondRandom]) \n Age:\(rand())"

answered Dec 18, 2014 at 14:18

Dániel Nagy

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Thorsten Karrer · Accepted Answer · 2014-12-18 14:32:38Z

1

Even better: use arc4random_uniform to avoid modulo bias:

var firstName : [String] = ["Preston", "Ally", "James", "Justin", "Dave", "Bacon", "Bossy", "Edward", "Edweird" ]

var lastName : [String] = ["Miller", "Jones", "Jackson", "Smith"]

let firstRandom = Int(arc4random_uniform(UInt32(firstName.count)))
let secondRandom = Int(arc4random_uniform(UInt32(lastName.count)))
var standardIdent = "First Name:\(firstName[firstRandom]) Last Name:\(lastName[secondRandom]) \n Age:\(rand())"

answered Dec 18, 2014 at 14:32

Thorsten Karrer

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