How initiate a multidimensional array?

Bodevinaat

I see lots of documentation about arrays but it all seem one dimensional array. How about multidim?
Var MyArray(-1,-1) does not seem to work.

Garry

ObjoBasic doesn’t currently support Xojo-style multidimensional array declarations like:

Var MyArray(-1, -1) As String

That syntax is specific to Xojo’s built-in multidimensional arrays. ObjoBasic’s array model is deliberately a little different: arrays are generic, dynamic, zero-based objects, and multidimensional data is represented as an array of arrays.

So for a 2D array/grid you would write:

Var grid As Array(Of Array(Of Integer)) = [[1, 2], [3, 4]]

Print(grid[0][1]) # 2
Print(grid[1][0]) # 3

The access pattern is:

grid[row][column]

not:

grid(row, column)

The reason for this design is that it keeps arrays consistent with the rest of ObjoBasic’s object model. A “2D array” is still just normal arrays containing normal arrays, so the usual array methods, typing rules, and iteration behaviour all still apply. It also allows ragged arrays naturally, where different rows can have different lengths.

That said, your question showed that the ergonomics and discoverability could be better, especially for users coming from Xojo. I’ve made some improvements for the next release:

Var grid As Array(Of Array(Of String)) = Array.Grid(Of String)(3, 4, "")

grid[1][2] = "Hello"
Print(grid[1][2]) # Hello

Array.Grid(rows, columns, defaultValue) creates a rectangular array of arrays with independent row arrays, so appending/resizing one row won’t accidentally affect the others.

I’ve also improved the compiler error for Var MyArray(-1, -1) so it now explains the ObjoBasic equivalent instead of just failing with a generic parser error.

https://feedback.objo.dev/feature/378

Bodevinaat

OK, looks like Delphi's approach to arrays. So the declaration of an array needs a pair of round brackets() but to access the array you need the Delphi style square[] brackets. All clear.

Thanks Gary

Garry

You're welcome.

One small clarification: the parentheses in Array(Of Integer) are not dimension brackets. They are the generic type syntax. ObjoBasic arrays are not pre-dimensioned in the declaration like Xojo-style arrays.

So you either initialise with an array literal:

Var grid As Array(Of Array(Of Integer)) = [[1, 2], [3, 4]]

or, in the next release, with:

Var grid = Array.Grid(Of Integer)(rows, columns, 0)

Access is then always with square brackets:

grid[row][column]

I’ll make sure the docs call this out more clearly for users coming from Xojo or Delphi.