CODEWITHSUNDEEP
swiftfor-loopmultidimensional-arrayappend
tore
tore

Reputation: 689

How do I properly create a multidimensional array in swift?

I have created a multidimensional array, but as soon as I try to add values to it at specific indexes it crashes with an index out of range message. I think it has to do with the way I initialise the array - that I have to be more specific about what it can store etc. At this thread: Filling the Multidimensional Array in Swift it was suggested that I should initialise the array like this (obviously modified for my purposes):

var array: [[Int]] = Array(count:N, repeatedValue:Array(count:N, repeatedValue:0))

But I didn't get it to work, nor understood it properly. Below is the code I have. It crashes on the last code line.

    var multiArray = [[Tile]]()

    var gb = gameBoard.frame.width/4

    for xItem in 0...3 { //DRAW TILE ON X AXIS

        for yItem in 0...3 { //DRAW TILE ON Y AXIS
            //CREATES A VARIABLE FOR TILE WITH PROPERTIES
            tileView = Tile(frame: CGRect(x: (CGFloat(xItem) * gb), y: (CGFloat(yItem) * gb), width: gb, height: gb))

            gameBoard.addSubview(tileView) //DRAWS TILE ONTO PARENT VIEW
            multiArray[xItem][yItem] = tileView   //CRASHES HERE WHEN TRYING TO ADD TO INDEX
        }
    }

Upvotes: 0

Views: 114

Answers (1)

vacawama
vacawama

Reputation: 154563

You are really creating an array of arrays. You can't access indices that aren't created yet, so instead just create one column at a time and append items to it and then append each column array to the the multiArray:

var multiArray = [[Tile]]()

var gb = gameBoard.frame.width/4

for xItem in 0...3 { //DRAW TILE ON X AXIS
    var col = [Tile]()

    for yItem in 0...3 { //DRAW TILE ON Y AXIS
        //CREATES A VARIABLE FOR TILE WITH PROPERTIES
        tileView = Tile(frame: CGRect(x: (CGFloat(xItem) * gb), y: (CGFloat(yItem) * gb), width: gb, height: gb))

        gameBoard.addSubview(tileView) //DRAWS TILE ONTO PARENT VIEW
        col.append(tileView)
    }

    multiArray.append(col)
}

The method you mentioned for initializing a multiArray works best if your array is filled with value types (such as Int or Double) and you have a reasonable default value (such as 0). It doesn't work as well if your array will be holding class instances. You could make your array [[Tile?]] and initialize it with nil values, but then you'd have to deal with unwrapping the optionals later. The append method is best for your case.

Upvotes: 2

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