Checking if randomNumber has already been generated

[coltonbswapp]

Howdy guys,

I am trying to finish get through the Matching card game - but am hitting some stumbling blocks when it comes to the random number generating. Chris alluded to this in the video, by using a while loop to get completely unique sets of numbers.

I cannot for the life of me, figure out how this is down.

Any help is appreciated.
As you can see I started to make another empty array, as well as a while loop but I keep getting to a spot where I don’t know how to proceed.

[mikaelacaron]

To have only unique values show here’s the steps I’d follow:

1. Get a random number
2. Use a for loop to check if that number has been used already
   3a. If it hasn’t, use that number
   3b. If it has, generate a new number. (Keep repeating until you find a unique number)

4a. Add this number to your used numbers array

[roosterboy]

I would do pretty much what @MikaelaCaron suggested, but use a Set<Int> instead of an Array. For this particular purpose it almost certainly won’t matter much, but with larger amounts of data using a Set will gain you better performance because testing whether a Set contains an item is faster than testing an Array. Also, you won’t need a loop to do the test.

[Ayse_Dibek]

Hi, I am also stuck here. And unfortunately the responses above didn’t help me

Check screenshot - compared to the example in the lesson when he’s inputting an integer back into an int array, for the card game we’re putting in a Card type into an array that accepts Card types. So when I try to use a WHILE LOOP - if generatedCards.contains(cardOne) == false { does not work. It gives an error that says: “Referencing instance method ‘contains’ on ‘Sequence’ requires that ‘Card’ conform to ‘Equatable’”

How do we resolve this?

Thank you!!!

[roosterboy]

In order to be able to compare two objects, you have to have some way of determining if they are equal or not. Thus the Equatable protocol. Int conforms to Equatable; Card does not. So you can compare integers but you can’t compare Cards. That’s why Chris used a generatedNumbersArray = [Int]() in the video.

So you have two options for fixing this:

1. Make Card conform to Equatable. This can be done by giving Card an == method and then adding : Equatable to the class definition. Something like this:

class Card: Equatable {
    var imageName = ""
    var isFlipped = false
    
    static func == (lhs: Card, rhs: Card) -> Bool {
        lhs.imageName == rhs.imageName
    }
}

2. Don’t store the generated Card objects, store the random Ints like Chris does in his video.

[Ayse_Dibek]

Thank you so much @roosterboy!!