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iOS Build a Simple iPhone App with Swift Creating a Data Model Finishing Up Our Model

ronald greti
ronald greti
800 Points
Posted by ronald greti
ronald greti
800 Points

Cannot assign to currentIndex in self

I added code to avoid asking the SAME question (random no) twice as follows...

import Foundation


//var currentIndex = 0

struct FactBook {

    var currentIndex = 0

    //stored propeties...
    //------------------------------------------------------------------------------------------------------

    let factsArray = [  "Ants stretch when they wake up in the morning.",
                        "Ostriches can run faster than horses.",
                        "Olympic gold medals are actually made mostly of silver.",
                        "You are born with 300 bones; by the time you are an adult you will have 206.",
                        "It takes about 8 minutes for light from the Sun to reach Earth.",
                        "Some bamboo plants can grow almost a meter in just one day.",
                        "The state of Florida is bigger than England.",
                        "Some penguins can leap 2-3 meters out of the water.",
                        "On average, it takes 66 days to form a new habit.",
                        "Mammoths still walked the earth when the Great Pyramid was being built."
                     ]

    //methods...
    //------------------------------------------------------------------------------------------------------

    func randomFact() -> String {

        var randomIndex: Int
        do {
            var unsignedArrayCount = UInt32(factsArray.count)
            var unsignedRandomNumber = arc4random_uniform(unsignedArrayCount)
            randomIndex = Int(unsignedRandomNumber)
        } while currentIndex == randomIndex
        currentIndex = randomIndex
        println("the index is \(randomIndex)")

        return factsArray[randomIndex]
    }
}

However, this does not work, seems the var currentIndex = randomIndex is causing a problem? I have tried adding self. in from but that does not work either? If I place the var currentIndex = 0 outside the struct it works, but then this makes the var global?
ronald greti
ronald greti
800 Points
ronald greti
ronald greti
800 Points

It turns oh that the function needs to be a 'mutating' function ...

    mutating func randomFact() -> String {

        var randomIndex: Int
        do {
            var unsignedArrayCount = UInt32(factsArray.count)
            var unsignedRandomNumber = arc4random_uniform(unsignedArrayCount)
            randomIndex = Int(unsignedRandomNumber)
        } while currentIndex == randomIndex
        currentIndex = randomIndex
        println("index is \(randomIndex)")

        return factsArray[randomIndex]
    }
}

Then you have to instantiate into a variable using a 'var' and not 'let'

var factBook = FactBook()