Generate list of unique random numbers in Swift from range

I would like to write a function which should return list of integer. Integer list size and max Random number will be defined by user, which user will pass through function parameter. My special requirement is, integer into list can not be redundant.
My approach using Array:

func getRandomNumbers(maxNumber: Int, listSize: Int)-> [Int]{
    var randomNumbers = [Int]()
    for _ in 1...listSize{
        let randomNumber = Int(arc4random_uniform(UInt32(listSize)))
        randomNumbers.append(randomNumber)
    }
    return randomNumbers
}

Problem: Sometimes i am getting duplicate values with this approach.
I know swift Set doesn't hold duplicate value.

My approach using Set:

func getRandomNumbers(maxNumber: Int, listSize: Int)-> Set<Int>{
    var randomNumbers = Set<Int>()
    for _ in 1...listSize{
        let randomNumber = Int(arc4random_uniform(UInt32(listSize)))
        randomNumbers.insert(randomNumber)
    }
    return randomNumbers
} 

Problem: Sometimes Set size is less then user defined size.