Question

I’m developing class to represent special kind of matrix:

type   DifRecord = record     Field: String;     Number: Byte;     Value: smallint;   end;  type   TData = array of array of MainModule.DataRecord;  type   TDifference = array of DifRecord;  type   TFogelMatrix = class   private     M: Byte;     N: Byte;     Data: ^TData;     DifVector: ^TDifference;     procedure init();    public     constructor Create(Rows, Cols: Byte);     destructor Destroy;   end; 

Now in constructor I need to reserve memory for Data and DifVector class members. I use pointers to array of records, as you see. So, the main question is, how can I correctly reserve memory? I suppose I can not use something like that:
new(Data);
new(DifVector);
cause I`m loosing the main idea – to reserve memory space, as much as I want to, at run-time. Thanks for comments.

Answer 1

Since you’re using dynamic arrays, array of, then you should use SetLength to specify the length of the array, which can be done dynamically.

ie. like this:

SetLength(Data, 100); 

This will not reserve 100 bytes, but will reserve enough space to hold 100 elements of whatever type the array holds.

Change your declarations for the arrays to simple arrays:

Data: TData; DifVector: TDifference; 

and use it with SetLength, it should do the trick.