{"id":1066,"date":"2014-11-30T20:45:18","date_gmt":"2014-12-01T02:45:18","guid":{"rendered":"http:\/\/dev.iachieved.it\/iachievedit\/?p=1066"},"modified":"2018-12-24T08:42:16","modified_gmt":"2018-12-24T14:42:16","slug":"multidimensional-arrays-in-swift","status":"publish","type":"post","link":"https:\/\/dev.iachieved.it\/iachievedit\/multidimensional-arrays-in-swift\/","title":{"rendered":"Multidimensional Arrays in Swift"},"content":{"rendered":"

Updated on 12\/24\/2018<\/b> for \"Swift.<\/p>\n

Swift 4.2<\/h3>\n

The format for defining a 3-dimensional array in Swift 4.2 has changed!<\/p>\n

\nlet a:[[[Int]]] = [[[Int]]](repeating:[[Int]](repeating:[Int](repeating:1, count:3), count:3), count:3)\n<\/pre>\n
Enumerating still works as follows:<\/p>\n
\nfor (i,plane) in a.enumerated() {\n  for (j,row) in plane.enumerated() {\n    for (k,cell) in row.enumerated() {\n      print(\"m[\\(i),\\(j),\\(k)] = \\(cell)\")\n    }\n  }\n}\n<\/pre>\n
Updated on 5\/12\/2018<\/b> for \"Swift.<\/p>\n
Swift 4.0<\/h3>\n
The format for defining a 3-dimensional array in Swift 4.0 has not changed, and can still be accomplished with a variation of:<\/p>\n
\nlet a:[[[Int]]] = [[[Int]]](count:3, repeatedValue:[[Int]](count:3, repeatedValue:[Int](count:3, repeatedValue:1)))\n<\/pre>\n
What has changed is the enumerate()<\/code> method has been renamed to enumerated()<\/code>:<\/p>\n
\nfor (i,plane) in a.enumerated() {\n  for (j,row) in plane.enumerated() {\n    for (k,cell) in row.enumerated() {\n      print(\"m[\\(i),\\(j),\\(k)] = \\(cell)\")\n    }\n  }\n}\n<\/pre>\n
Updated on 1\/24\/2016<\/b> to support \"Swift, including removing C-style for<\/code> loops and postfix increment operators.<\/p>\n
Editor’s note:<\/b>  If you’re looking to branch out with Swift on a Linux system, check out our latest series of articles Swift on Linux<\/a> and More Swift on Linux<\/a>.<\/p>\n
File this in the “Well I’ll be damned” category.  While working on another project (I’m interested in a hybrid OS X and iOS project for generating Mandelbrot<\/a> images) I came across the need to store Mandelbrot “escape values” in a two-dimensional array (e.g., a matrix).  This matrix will be the basis for drawing the Mandelbrot plot, which each cell value being mapped to a color.<\/p>\n
Of course I’m writing this code in Swift so I looked up how to declare a multidimensional array in the Swift Standard Library Reference<\/a>.<\/p>\n
Let’s take a look at the syntax for a unidimensional array, and yes, we’re using the “sugar” version of the syntax:<\/p>\n
class MyClass {\n  var anArray:[Int]\n\n  init() {\n    self.anArray = [3,4,5]\n  }\n\n  func dump() {\n    print(anArray)\n  }\n\n}<\/pre>\n
Simple enough.  If we wanted to prefill our array with ones, we can do that with the (count:c, repeatedValue:v)<\/code> construct:<\/p>\n
\nself.anArray = [Int](count:10, repeatedValue:1)\n<\/pre>\n
The syntax may look out of place but it’s not really:  [Int]<\/code> is<\/i> the name of the object we want to construct (an array of Int<\/code>s) and we’re providing constructor arguments.  It would be no different than writing self.anArray = IntegerArray(count:10, repeatedValue:1)<\/code> if IntegerArray<\/code> provided us with an array of integers.<\/p>\n
Now enter the multidimensional array syntax.  For an array of arrays of integers we would write:<\/p>\n
\nvar anArray:[[Int]]\n<\/pre>\n
The Swift reference also provides for basic initialization.  Here we create a 3×3 identity matrix:<\/p>\n
\nself.anArray = [[1,0,0], [0,1,0], [0,0,1]]\n<\/pre>\n
We’ll use this again in a basic class:<\/p>\n
\nclass MyClass {\n  \n  var anArray:[[Int]]\n  \n  init() {\n    self.anArray = [[1,0,0], [0,1,0], [0,0,1]]\n  }\n  \n  func dump() {\n    for (i,row) in anArray.enumerate() {\n      for (j,cell) in row.enumerate() {\n        print(\"m[\\(i),\\(j)] = \\(cell)\")\n      }\n    }\n  }\n  \n}\n\nlet m = MyClass()\nm.dump()\n<\/pre>\n
Executing this in the Playground gives us<\/p>\n
\nm[0,0] = 1\nm[0,1] = 0\nm[0,2] = 0\nm[1,0] = 0\nm[1,1] = 1\nm[1,2] = 0\nm[2,0] = 0\nm[2,1] = 0\nm[2,2] = 1\n<\/pre>\n
which is what we would expect.<\/p>\n
Now, I want to store information in a larger array (say 175 by 100), and want to initialize each element to zero.  Here is the syntax:<\/p>\n
\nself.anArray = [[Int]](count:175, repeatedValue:[Int](count:100, repeatedValue:0))\n<\/pre>\n
Take a step back and let it soak in and it makes perfect sense.  A two dimensional array is an array of arrays, so it stands to reason that the repeatedValue<\/code> of the outer array will itself be an array.  The repeatedValue<\/code> of the inner array will be the base type you are storing in each cell.<\/p>\n
Finally, a 3x3x3 array with each cell initialized to 1.<\/p>\n
\nlet a:[[[Int]]] = [[[Int]]](count:3, repeatedValue:[[Int]](count:3, repeatedValue:[Int](count:3, repeatedValue:1)))\n<\/pre>\n
Swift 3.0<\/h2>\n
As mentioned in our Moving to Swift 3.0<\/a> post, the array initializer signature has changed from (count:repeatedValued:)<\/code> to (repeating:count:)<\/code>.  No sweat, let’s update our 3x3x3 array declaration:<\/p>\n
\nlet a = [[[Int]]](repeating:[[Int]](repeating:[Int](repeating:1,count:3), count:3), count:3)\n<\/pre>\n
Cake.<\/p>\n","protected":false},"excerpt":{"rendered":"
Updated on 12\/24\/2018 for . Swift 4.2 The format for defining a 3-dimensional array in Swift 4.2 has changed! let a:[[[Int]]] = [[[Int]]](repeating:[[Int]](repeating:[Int](repeating:1, count:3), count:3), count:3) Enumerating still works as follows: for (i,plane) in a.enumerated() { for (j,row) in plane.enumerated() { for (k,cell) in row.enumerated() { print(“m[\\(i),\\(j),\\(k)] = \\(cell)”) } } } Updated on 5\/12\/2018 […]<\/p>\n","protected":false},"author":1,"featured_media":3108,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[5],"tags":[],"class_list":["post-1066","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-swift"],"_links":{"self":[{"href":"https:\/\/dev.iachieved.it\/iachievedit\/wp-json\/wp\/v2\/posts\/1066"}],"collection":[{"href":"https:\/\/dev.iachieved.it\/iachievedit\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/dev.iachieved.it\/iachievedit\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/dev.iachieved.it\/iachievedit\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/dev.iachieved.it\/iachievedit\/wp-json\/wp\/v2\/comments?post=1066"}],"version-history":[{"count":17,"href":"https:\/\/dev.iachieved.it\/iachievedit\/wp-json\/wp\/v2\/posts\/1066\/revisions"}],"predecessor-version":[{"id":2608,"href":"https:\/\/dev.iachieved.it\/iachievedit\/wp-json\/wp\/v2\/posts\/1066\/revisions\/2608"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/dev.iachieved.it\/iachievedit\/wp-json\/wp\/v2\/media\/3108"}],"wp:attachment":[{"href":"https:\/\/dev.iachieved.it\/iachievedit\/wp-json\/wp\/v2\/media?parent=1066"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/dev.iachieved.it\/iachievedit\/wp-json\/wp\/v2\/categories?post=1066"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/dev.iachieved.it\/iachievedit\/wp-json\/wp\/v2\/tags?post=1066"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}