Delphi dynamic array

Question

I'm using Delphi 10.0 Seattle.

Suppose I have a record like this:

TmyRecord = record
  a,b : string;
  ar  : array of string
end;

And a variable like this:

v : array of TmyRecord;

and some code like this:

SetLength(v,2);
SetLength(v[0].ar,3);
SetLength(v[1].ar,2);
SetLength(v[0].ar[0],10);
SetLength(v[0].ar[1],5);
SetLength(v[0].ar[2],7);
...
v[0].ar[0][0] := 'aaaa';
v[0].ar[0][1] := 'bbbb';
....
v[1].ar[1][0] := 'xxxx';

Will this statement:

SetLength(v,0);

free all of the occupied memory, or do I have to free it manually?

Dalija Prasnikar · Accepted Answer · 2021-07-01 08:11:59Z

6

Dynamic array memory is automatically managed by Delphi and is released when they go out of scope.

If you need to release array memory sooner you can explicitly clear the array v and that will automatically release all memory including the ones occupied by ar member of your record.

You don't have to do anything else.

There are several ways to clear the dynamic array in Delphi:

Setting array length to 0 is one way to clear the array.

SetLength(v,0);

You can also clear v array by setting it to nil

v := nil;

or by using the intrinsic Finalize:

Finalize(v);

All of these have identical meaning.

edited Jul 1, 2021 at 8:11

answered Dec 12, 2016 at 11:57

Dalija Prasnikar♦

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1 Comment

Uli Gerhardt Over a year ago

Normally (e.g. if v is a local variable) I'd clear it by doing nothing (simply letting it fall out of scope).

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