Set dynamic array of records to nil: frees all content?

[alogrep 0]

type
  name_struct= record
   fname: string;
   lname : string;
end;
arec= record
   names : array of name_struct ;
   age: array of integer;
end;

type
records = array of arec;

setlength(records,100);
for x :=0 to 99 do
  load each records[x]

When I do

  records:=Nil, does it free all "names" (and fname, lname) of all recs as well as the recods array itself?

[DelphiUdIT 178]

The record generally doesn't need to be freed.

 

The array should not to be freed setting a nil, you must use:   

 

EDIT1: MY FAULT, like @David Heffernan  said in the next post setting a nil is right.

 

EDIT: Of course only with dynamic arrays !!!

 

SetLength(records, 0);

Every single elements of the array must be released if necessary.
In you case you must release ALL arrays inside the record structure:

 

EDIT2: I FORGOT ALWAYS, AND ALSO THAT IS NOT NECESSARY LIKE @Remy Lebeau  later explained.

 

for var i :=  Low(records) to High(records) do
  begin
 	SetLength(records[i].names, 0);
 	SetLength(records[i].age, 0);
  end;

 

Integral type and string doesn't need to be released in Delphi, this include all numerical type and string. All others types should be released before resizing the array.

//Example
var A: array of integer;
	B: array of string;
	C: array of TComponent;

SetLength(A, 9);
A[0] := 1;
A[1] := 2;
..... // Do something with A[]
SetLenght(A, 0); //OK, right

SetLength(B, 9);
B[0] := 'Ola';
B[1] := 'Bye';
..... // Do something with B[]
SetLength(B, 0); //OK, right

SetLength(C, 9);
C[0] := TEdit.Create(self);
C[1] := TLabel.Create(self);
..... // Do something with C[]
SetLength(C, 0); // NOOOOO, wrong


SetLength(C, 9);
C[0] := TEdit.Create(self);
C[1] := TLabel.Create(self);
//release every single element
for var compo in C do
  begin
    if Assigned(compo) then
      FreeAndNil(compo);
  end;
SetLength(C, 0); // OK, right

 

Edited March 6 by DelphiUdIT

[David Heffernan 2347]

37 minutes ago, DelphiUdIT said:

The array should not to be freed setting a nil, you must use

Wrong. Setting a dynamic array to nil is identical to setting length to 0 and identical to passing it to Finalize. 

[David Heffernan 2347]

56 minutes ago, alogrep said:

When I do

  records:=Nil, does it free all "names" (and fname, lname) of all recs as well as the recods array itself?

Yes. 

[Remy Lebeau 1403]

20 hours ago, alogrep said:

When I do

  records:=Nil, does it free all "names" (and fname, lname) of all recs as well as the recods array itself?

In this example, yes. Like strings, dynamic arrays are also reference-counted. When you nil a reference to a dynamic array, its refcount is decremented. When its refcount falls to 0, its contents are finalized as needed (to release their references, etc), and the array is freed from memory.

Edited March 6 by Remy Lebeau

[DelphiUdIT 178]

11 hours ago, David Heffernan said:

Wrong. Setting a dynamic array to nil is identical to setting length to 0 and identical to passing it to Finalize. 

Thanks, I really didn't know this.