Initializing Two Dimensional User-defined Arrays in Swift

Question

I am very new to Swift and this problem has got me stumped. I am trying to create a two-dimensional map. In init of my Map class, I need to create a two-dimensional array of another class called Grid.

This is what I have right now:

class Map: NSObject {
    var squares: [[Grid]]
    let MAXROWS = 200
    let MAXCOLUMNS = 200

    override init(){
         for r in 0...MAXROWS{
             for c in 0...MAXCOLUMNS{
                squares[r][c].append
            }
        }
    }

At the append function, it creates an error:

value of type "Grid" has no member "append"

How do I do this correctly?

Sander Saelmans · Accepted Answer · 2019-02-11 21:34:14Z

3

Or if you don't like raw loops:

override init(){
    self.squares = Array<[Grid]>(
        repeating: Array<Grid>(
            repeating: Grid(),
            count: MAXCOLUMNS),
        count: MAXROWS
    )
}

edit: Like Alain T metnioned, this only works if Grid is a struct, otherwise the same instance would be used throughout the 2d array. This is because classes are passed by reference, and in this case, the same reference would be used every single time.

edited Feb 11, 2019 at 21:34

answered Feb 11, 2019 at 18:12

Sander Saelmans

8614 silver badges14 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

vikingosegundo Over a year ago

Hey Sander. Nice one! MM

Alain T. Over a year ago

This will produce rows with the same instance of the Grid() object in each column (given that Grid is a class). i.e. column 1 and column 2 of row 1 will be the same instance rather than two distinct instances of Grid.

Alain T. · Accepted Answer · 2019-02-11 20:13:07Z

0

You could also do it like this (because Grid is a class):

squares = (0..<MAXROWS).map{_ in (0..<MAXCOLUMNS).map{_ in Grid()}}

This uses the ranges as a means to "generate" the desired number of elements in the array. The map() function returns an entry for each generated number. Entries for rows are arrays of columns each containing a new instance of a Grid object. The "_ in" inside the map() closures tells the compiler that we are not actually using the value produced by the ranges.

edited Feb 11, 2019 at 20:13

answered Feb 11, 2019 at 19:09

Alain T.

42.2k4 gold badges36 silver badges57 bronze badges

Comments

Masoud Roosta · Accepted Answer · 2019-02-11 21:14:08Z

0

try it:

class Map: NSObject {
var squares: [[Grid]]
let MAXROWS = 200
let MAXCOLUMNS = 200

override init(){
     for r in 0...MAXROWS{
        squares.append([])
         for c in 0...MAXCOLUMNS{
            squares[r].append(Grid())
        }
    }
}

answered Feb 11, 2019 at 21:14

Masoud Roosta

4759 silver badges19 bronze badges

1 Comment

Rachel Zuhl Over a year ago

I used this answer, however it generated an error because c is unused. I switched it from c to _ like it said and it no longer generates errors right there.

Collectives™ on Stack Overflow

Initializing Two Dimensional User-defined Arrays in Swift

3 Answers 3

2 Comments

Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

2 Comments

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related