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iOS Build a Simple iPhone App with Swift Improving Our User Interface Adding a Pop of Color

Posted by Ludwing Najera
Ludwing Najera
4,596 Points

App "fatal error" when clicking "show another fun fact" button. It's supposed to change background color!

My FunFact app crashes with this message in the console "fatal error: Array index out of range (lldb)"

It has a breakpoint on these two lines.

view.backgroundColor = colorWheel.randomColor()

And

return factsArray[randomNumber]

10 Answers

Stone Preston
Stone Preston
42,016 Points

your var randomNumber needs to be Int(unsignedRandomNumber) not Int(unsignedColorsArray):

func randomColor() -> UIColor {
    var unsignedColorsArray = UInt32(colorsArray.count)
    var unsignedRandomNumber = arc4random_uniform (unsignedColorsArray)
    // cast the unsignedRandomNumber to an Int, not unsignedColorsArray
    var randomNumber = Int(unsignedRandomNumber)

    return colorsArray[randomNumber]
}
Stone Preston
Stone Preston
42,016 Points
Stone Preston
Stone Preston
42,016 Points

post the randomColor method thats implemented in the colorWheel class

Ludwing Najera
Ludwing Najera
4,596 Points
Ludwing Najera
Ludwing Najera
4,596 Points

here

func randomColor() -> UIColor {
    var unsignedColorsArray = UInt32(colorsArray.count)
    var unsignedRandomNumber = arc4random_uniform (unsignedColorsArray)
    var randomNumber = Int(unsignedColorsArray)

    return colorsArray[randomNumber]
}
Ludwing Najera
Ludwing Najera
4,596 Points
Ludwing Najera
Ludwing Najera
4,596 Points

when i do that, i get another error saying "Expected declaration"

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

it could be the fact you have a space after the arc4random_uniform method name, try removing that and making sure you spelled everything correctly

func randomColor() -> UIColor {
    var unsignedColorsArray = UInt32(colorsArray.count)
    // remove the space
    var unsignedRandomNumber = arc4random_uniform(unsignedColorsArray)
    // cast the unsignedRandomNumber to an Int, not unsignedColorsArray
    var randomNumber = Int(unsignedRandomNumber)

    return colorsArray[randomNumber]
}
Ludwing Najera
Ludwing Najera
4,596 Points
Ludwing Najera
Ludwing Najera
4,596 Points

i removed the space and the error still lingers

Stone Preston
Stone Preston
42,016 Points

post your full code for the struct

Ludwing Najera
Ludwing Najera
4,596 Points
Ludwing Najera
Ludwing Najera
4,596 Points

struct ColorWheel {

let colorsArray = [
    UIColor(red: 90/255.0, green: 187/255.0, blue: 181/255.0, alpha: 1.0), //teal color
    UIColor(red: 222/255.0, green: 171/255.0, blue: 66/255.0, alpha: 1.0), //yellow color
    UIColor(red: 223/255.0, green: 86/255.0, blue: 94/255.0, alpha: 1.0), //red color
    UIColor(red: 239/255.0, green: 130/255.0, blue: 100/255.0, alpha: 1.0), //orange color
    UIColor(red: 77/255.0, green: 75/255.0, blue: 82/255.0, alpha: 1.0), //dark color
    UIColor(red: 105/255.0, green: 94/255.0, blue: 133/255.0, alpha: 1.0), //purple color
    UIColor(red: 85/255.0, green: 176/255.0, blue: 112/255.0, alpha: 1.0), //green color
]


func randomColor() -> UIColor {
    var unsignedColorsArray = UInt32(colorsArray.count)
    var unsignedRandomNumber = arc4random_uniform(unsignedColorsArray)
    var randomNumber = Int(unsignedRandomNumber)

    return colorsArray[randomNumber]

}

Ludwing Najera
Ludwing Najera
4,596 Points
Ludwing Najera
Ludwing Najera
4,596 Points

okay i fixed it so i never closed the struct brackets and thats what was causing the problems

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

you are missing the closing brace of your function:

struct ColorWheel {

    let colorsArray = [
        UIColor(red: 90/255.0, green: 187/255.0, blue: 181/255.0, alpha: 1.0), //teal color
        UIColor(red: 222/255.0, green: 171/255.0, blue: 66/255.0, alpha: 1.0), //yellow color
        UIColor(red: 223/255.0, green: 86/255.0, blue: 94/255.0, alpha: 1.0), //red color
        UIColor(red: 239/255.0, green: 130/255.0, blue: 100/255.0, alpha: 1.0), //orange color
        UIColor(red: 77/255.0, green: 75/255.0, blue: 82/255.0, alpha: 1.0), //dark color
        UIColor(red: 105/255.0, green: 94/255.0, blue: 133/255.0, alpha: 1.0), //purple color
        UIColor(red: 85/255.0, green: 176/255.0, blue: 112/255.0, alpha: 1.0), //green color
    ]


    func randomColor() -> UIColor {
        var unsignedColorsArray = UInt32(colorsArray.count)
        var unsignedRandomNumber = arc4random_uniform(unsignedColorsArray)
        var randomNumber = Int(unsignedRandomNumber)

        return colorsArray[randomNumber]

  // add the closing brace
  }
}
Ludwing Najera
Ludwing Najera
4,596 Points
Ludwing Najera
Ludwing Najera
4,596 Points

yeah i fixed that and it worked

Stone Preston
Stone Preston
42,016 Points

cool