Random number with user defined range

Question

I am teaching myself Swift and am stuck with a Random function.

What I want to achieve: User is able to specify the min and max of the Range.

Code I have now for the button, where I believe I am declaring the text as an integer:

@IBAction func generateNumbers(sender: AnyObject) {

    let minRange:Int? = Int(lowValue.text!)
    let maxRange:Int? = Int(highValue.text!)

    func randomNumber(range: Range<Int> = minRange...maxRange) -> Int {
        let min = range.startIndex
        let max = range.endIndex
        return Int(arc4random_uniform(UInt32(max - min))) + min
    }
}

Obviously minRange and maxRange aren't valid integers for the Range, I am just wondering where I'm going wrong.

Thanks in advance for any assistance.

"Optionals". Very important. :) Read this: developer.apple.com/library/ios/documentation/Swift/Conceptual/… — Eric Aya
– Eric Aya, Commented Jun 19, 2016 at 13:45

Luca Angeletti · Accepted Answer · 2016-06-19 14:47:24Z

2

You are almost there

The problem is that

let minRange:Int? = Int(lowValue.text!)
let maxRange:Int? = Int(highValue.text!)

are defined as optionals.

While here

func randomNumber(range: Range<Int> = minRange...maxRange) -> Int {

you need minsRange and maxRange to be non optional.

So you could use the guard let statement to safely perform the needed unwrappings

@IBAction func generateNumbers(sender: AnyObject) {

    guard let
        lowText = lowValue.text,
        highText = highValue.text,
        minRange = Int(lowText),
        maxRange = Int(highText)
    else {
        print("Couldn't find valid integers inside lowValue and highValue UITextFields. So I'm giving up...")
        return
    }

    func randomNumber(range: Range<Int> = minRange...maxRange) -> Int {
        let min = range.startIndex
        let max = range.endIndex
        return Int(arc4random_uniform(UInt32(max - min))) + min
    }
}

Invoking randomNumber

Of course don't forget to finally invoke your function randomNumber(1...10)

Update

@IBAction func generateNumbers(sender: AnyObject) {

    guard let
        lowText = lowValue.text,
        highText = highValue.text,
        minRange = Int(lowText),
        maxRange = Int(highText)
        else {
            print("Couldn't find valid integers inside lowValue and highValue UITextFields. So I'm giving up...")
            return
    }

    let result = Int(arc4random_uniform(UInt32(minRange - maxRange))) + minRange

}

edited Jun 19, 2016 at 14:47

answered Jun 19, 2016 at 13:44

Luca Angeletti

59.6k13 gold badges127 silver badges153 bronze badges

Sign up to request clarification or add additional context in comments.

6 Comments

Peter G Over a year ago

Thanks so much I will try this now! :)

Peter G Over a year ago

Unfortunately I receive this error: Command /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swiftc failed with exit code 1

Luca Angeletti Over a year ago

@PeterG: interesting error. I think the problem is about the default parameter value used into randomNumber. Infact providing an explicitt value randomNumber(1...100) seems to solve the error. If you want I can provide you a workaround.

Peter G Over a year ago

I can get it working in Playground like this: let lowValue = "10" let highValue = "50" let minRange:Int? = Int(lowValue) let maxRange:Int? = Int(highValue) func randomNumber(range: Range<Int> = minRange!...maxRange!) -> Int { let min = range.startIndex let max = range.endIndex return Int(arc4random_uniform(UInt32(max - min))) + min } let results = randomNumber()

Luca Angeletti Over a year ago

@PeterG: it is working only because you removed the parent function (which seems to be the problem). In your code you are using ! which I suggest you to avoid. Just take a look at the updated section in my answer.

|

vacawama · Accepted Answer · 2016-06-19 15:02:26Z

1

As others have identified, your minRange and maxRange are Optionals. They need to be Int, not Int? in order to form the range.

Also, you should avoid using ! to unwrap the text fields, just in case they're nil.

If you have some reasonable defaults for minRange and maxRange (such as 1 and 10), you could use the nil coalescing operator to unwrap your text fields and replace the values with defaults if the text fields can't be converted to an Int:

@IBAction func generateNumbers(sender: AnyObject) {

    let minRange = Int(lowValue.text ?? "") ?? 1
    let maxRange = Int(highValue.text ?? "") ?? 10

    func randomNumber(range: Range<Int>) -> Int {
        let min = range.startIndex
        let max = range.endIndex
        return Int(arc4random_uniform(UInt32(max - min))) + min
    }

    // test
    let results = randomNumber(minRange...maxRange)
    self.field1.text = String(results)
}

Note: The compiler is not happy with using the values minRange and maxRange to set the default value for range, so I added them to the call of randomNumber.

There is another potential gotcha here as well. You can't form a range if minRange is larger than maxRange, so you should check for that as well:

var minRange = Int(lowValue.text ?? "") ?? 1
var maxRange = Int(highValue.text ?? "") ?? 10
if minRange > maxRange {
    // Swap 'em
    (minRange, maxRange) = (maxRange, minRange)
}

Why even torture yourself in creating the range anyway? Since randomNumber is declared inside of generateNumbers you can just use minRange and maxRange:

@IBAction func generateNumbers(sender: AnyObject) {

    var minRange = Int(lowValue.text ?? "") ?? 1
    var maxRange = Int(highValue.text ?? "") ?? 10
    if minRange > maxRange {
        // Swap 'em
        (minRange, maxRange) = (maxRange, minRange)
    }

    func randomNumber() -> Int {
        return Int(arc4random_uniform(UInt32(maxRange - minRange))) + minRange
    }

    //test
    let results = randomNumber()
    self.field1.text = String(results)
}

edited Jun 19, 2016 at 15:02

answered Jun 19, 2016 at 13:51

vacawama

155k32 gold badges283 silver badges315 bronze badges

6 Comments

Peter G Over a year ago

This looks like a nice and simple way to do it, thank you. However, it kept coming up with an error requesting I insert a ; separator, which didn't work either.

vacawama Over a year ago

Which line specifically requested the ;?

Peter G Over a year ago

Actually just copy pasting your code in only resulted in an error at run. So I'm probably doing something wrong. Command /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/u‌sr/bin/swiftc failed with exit code 1

vacawama Over a year ago

Make sure all of your @IBOutlets are wired up.

vacawama Over a year ago

Check out my latest update. You don't even need to bother creating the range.

|

Collectives™ on Stack Overflow

Random number with user defined range

2 Answers 2

You are almost there

Invoking randomNumber

Update

6 Comments

6 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

You are almost there

Invoking randomNumber

Update

6 Comments

6 Comments

Your Answer

Sign up or log in

Post as a guest

Related