Multidimensional arrays in Swift

Question

Edit  As Adam Washington points out  as from Beta 6  this code works as is  so the question is no longer relevant    I am trying to create and iterate through a two dimensional array   var array   Array count NumColumns  repeatedValue Array count NumRows  repeatedValue Double      array 0  0    1 array 1  0    2 array 2  0    3 array 0  1    4 array 1  1    5 array 2  1    6 array 0  2    7 array 1  2    8 array 2  2    9  for column in 0   2       for row in 0   2           println  column    column  row    row  value   array column  row               However  this is the output I get   column  0 row  0 value 3 0 column  0 row  1 value 6 0 column  0 row  2 value 9 0 column  1 row  0 value 3 0 column  1 row  1 value 6 0 column  1 row  2 value 9 0 column  2 row  0 value 3 0 column  2 row  1 value 6 0 column  2 row  2 value 9 0   It looks as if the last column in the row is overwriting the other column values   Am I declaring it wrong   Edit  Perhaps a picture from the Playground would help

User · Answer

Using http   blog trolieb com trouble-multidimensional-arrays-swift  as a start  I added generics to mine   class Array2DTyped lt T gt    var cols Int  rows Int var matrix  T   init cols Int  rows Int  defaultValue T       self cols   cols     self rows   rows     matrix   Array count cols rows repeatedValue defaultValue     subscript col Int  row Int  - gt  T       get          return matrix cols   row   col            set          matrix cols   row   col    newValue          func colCount   - gt  Int       return self cols    func rowCount   - gt  Int       return self rows

User · Answer

Your problem may have been due to a deficiency in an earlier version of Swift or of the Xcode Beta  Working with Xcode Version 6 0  6A279r  on August 21  2014  your code works as expected with this output    column  0 row  0 value 1 0 column  0 row  1 value 4 0 column  0 row  2 value 7 0 column  1 row  0 value 2 0 column  1 row  1 value 5 0 column  1 row  2 value 8 0 column  2 row  0 value 3 0 column  2 row  1 value 6 0 column  2 row  2 value 9 0   I just copied and pasted your code into a Swift playground and defined two constants   let NumColumns   3  NumRows   3

User · Answer

You are creating an array of three elements and assigning all three to the same thing  which is itself an array of three elements  three Doubles    When you do the modifications you are modifying the floats in the internal array

User · Answer

For future readers  here is an elegant solution 5x5    var matrix     Int   repeating   Int  repeating  0  count  5   count  5   and a dynamic approach   var matrix     Int        creates an empty matrix var row    Int       fill this row matrix append row     add this row

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var array  Int         1 2 3   4 5 6   7 8 9    for first in array       for second in first           println  value   second              To achieve what you re looking for you need to initialize the array to the correct template and then loop to add the row and column arrays   var NumColumns   27 var NumRows   52 var array   Array lt Array lt Int gt  gt    var value   1  for column in 0  NumColumns       var columnArray   Array lt Int gt        for row in 0  NumRows           columnArray append value              array append columnArray     println  array   array

User · Answer

Your original logic for creating the matrix is indeed correct  and it even works in Swift 2  The problem is that in the print loop  you have the row and column variables reversed  If you change it to   for row in 0   2     for column in 0   2       print  column    column  row    row  value   array column  row              you will get the correct results  Hope this helps

User · Answer

As stated by the other answers  you are adding the same array of rows to each column  To create a multidimensional array you must use a loop  var NumColumns   27 var NumRows   52 var array   Array lt Array lt Double gt  gt    for column in 0  NumColumns       array append Array count NumRows  repeatedValue Double

[arrays] Multidimensional arrays in Swift

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