swift ios adding constraints for several subviews with a loop - ios

Question

I am newcomer in swift and tried to learn how to add several subviews and their constraints using a loop. I tried to follow some answer to similar questions but it is not working. Could you help me with my code? Thank you in advance.
Here is my code:
let card = UIView()
let view2 = UIView()
view2.backgroundColor = UIColor.greenColor()
view2.translatesAutoresizingMaskIntoConstraints = false
view.addSubview(view2)
let leftSideConstraint3 = NSLayoutConstraint(item: view2, attribute: .Left, relatedBy: .Equal, toItem: view, attribute: .Left, multiplier: 1, constant: 0.0)
let topConstraint3 = NSLayoutConstraint(item: view2, attribute: .Top, relatedBy: .Equal, toItem: view, attribute: .Top, multiplier: 1, constant: 0.0)
let widthConstraint3 = NSLayoutConstraint(item: view2, attribute: .Width, relatedBy: .Equal, toItem: view, attribute: .Width, multiplier: 1, constant: 0.0)
let heightConstraint3 = NSLayoutConstraint(item: view2, attribute: .Height, relatedBy: .Equal, toItem: view, attribute: .Height, multiplier: 1, constant: 0.0)
view.addConstraints([leftSideConstraint3, topConstraint3, heightConstraint3, widthConstraint3])
var cards = [UIView](count: 16, repeatedValue: card) // array with 16 cards
card.layer.borderWidth = 3
card.layer.borderColor = UIColor.blackColor().CGColor
card.backgroundColor = UIColor.orangeColor()
var columnCounter:Int = 0
var rowCounter:Int = 0
//Loop through each card in the array
for index in 0...cards.count-1 {
// place the card in the view and turn off translateAutoresizingMask
let thisCard = cards[index]
thisCard.translatesAutoresizingMaskIntoConstraints = false
view2.addSubview(thisCard)
//set the height and width constraints
let widthConstraint = NSLayoutConstraint(item: thisCard, attribute: .Width, relatedBy: .Equal, toItem: view2, attribute: .Width, multiplier: 0.25, constant: 0)
let heightConstraint = NSLayoutConstraint(item: thisCard, attribute: .Height, relatedBy: .Equal, toItem: view2, attribute: .Height, multiplier: 0.25, constant: 0)
view2.addConstraints([heightConstraint, widthConstraint])
//set the horizontal position
if (columnCounter > 0) {
// card is not in the first column
let cardOnTheLeft = cards[index-1]
let leftSideConstraint = NSLayoutConstraint(item: thisCard, attribute: .Left, relatedBy: .Equal, toItem: cardOnTheLeft, attribute: .Right, multiplier: 1, constant: 0)
//add constraint to the contentView
view2.addConstraint(leftSideConstraint)
} else {
//card is in the first column
let leftSideConstraint = NSLayoutConstraint(item: thisCard, attribute: .Left, relatedBy: .Equal, toItem: view2, attribute: .Left, multiplier: 1, constant: 0)
//add constraint to the contentView
view2.addConstraint(leftSideConstraint)
}
//set the vertical position
if (rowCounter > 0) {
// card is not in the first row
let cardOnTop = cards[index-4]
let topConstraint = NSLayoutConstraint(item: thisCard, attribute: .Top, relatedBy: .Equal, toItem: cardOnTop, attribute: .Bottom, multiplier: 1, constant: 0)
// add constraint to the contentView
view2.addConstraint(topConstraint)
} else {
//card is in the first row
let topConstraint = NSLayoutConstraint(item: thisCard, attribute: .Top, relatedBy: .Equal, toItem: view2, attribute: .Top, multiplier: 1, constant: 0)
//add constraint to the contentView
view2.addConstraint(topConstraint)
}
//increment the column counter
columnCounter = columnCounter+1
//if the column counter reaches the fifth column reset it and increase the row counter
if (columnCounter >= 4) {
columnCounter = 0
rowCounter = rowCounter+1
}
} // end of the loop

Answer 1

This creates an array with 16 references to the same card.
var cards = [UIView](count: 16, repeatedValue: card)
Replace it with:
var cards = (1...16).map { _ in UIView() }
which will result in an array with 16 unique UIViews.