To declare multidimensional dynamic arrays, use iterated array of ... constructions. For example,
type TMessageGrid = array of array of string;
var Msgs: TMessageGrid;
declares a two-dimensional array of strings. To instantiate this array, call SetLength with two integer arguments. For example, if I and J are integer-valued variables,
SetLength(Msgs,I,J);
allocates an I-by-J array, and Msgs[0,0] denotes an element of that array.
You can create multidimensional dynamic arrays that are not rectangular. The first step is to call SetLength, passing it parameters for the first n dimensions of the array. For example,
var Ints: array of array of Integer;
SetLength(Ints,10);
allocates ten rows for Ints but no columns. Later, you can allocate the columns one at a time (giving them different lengths); for example
SetLength(Ints[2], 5);
makes the third column of Ints five integers long. At this point (even if the other columns haven’t been allocated) you can assign values to the third column—for example, Ints[2,4] := 6.
The following example uses dynamic arrays (and the IntToStr function declared in the SysUtils
unit) to create a triangular matrix of strings.
var
A : array of array of string;
I, J : Integer;
begin
SetLength(A, 10);
for I := Low(A) to High(A) do
begin
SetLength(A[I], I);
for J := Low(A[I]) to High(A[I]) do
A[I,J] := IntToStr(I) + ',' + IntToStr(J) + ' ';
end;
end;