Adrian Maier wrote:
On 10/31/07, Joao Morais <[EMAIL PROTECTED]> wrote:
Adrian Maier wrote:
On 10/31/07, Matt Emson <[EMAIL PROTECTED]> wrote:
Adrian Maier wrote:
Hello,
I'm seeking for advice about which is the best way to hold an array of
class instances
I need to access the elements using its position (like a regular
array) , and also i'd like
the structure to grow when I add more elements
TObjectList
I am aware that TObjectList is one of the possible ways.
But I was hoping to get a better understanding about the purpose of these
various classes or types of array , and more importantly what are the
drawbacks .
Is there really no wiki page , tutorial, anything that provides an overview of
the collections and types of arrays that FPC has ?
You can use dynamic arrays, they work like an ansi string:
var
VArray: array of TSomeClass;
begin
SetLength(VArray, 10);
// now you have VArray[0] .. VArray[9];
SetLength(VArray, 20);
// now you have [0] .. [19];
// Length(VArray) = 20
// for I := 0 to Pred(Length(VArray)) is a valid statement
They are reference counted, just like ansi strings, ie don't worry about
memory leakages.
The detail that is not crystal clear to me is : after the first SetLength
and i set the first 3 elements, is it *guaranteed* that the
second SetLength leaves those first 3 elements untouched?
I don't use dyn array realocation by myself, but seeing this piece of
code I'd assume yes:
procedure TFPList.SetCapacity(NewCapacity: Integer);
begin
If (NewCapacity < FCount) or (NewCapacity > MaxListSize) then
Error (SListCapacityError, NewCapacity);
if NewCapacity = FCapacity then
exit;
ReallocMem(FList, SizeOf(Pointer)*NewCapacity);
FCapacity := NewCapacity;
end;
--
Joao Morais
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