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Magnus Jungsbluth · Guest

Hi,

is there any easy approach to load BO's properties when they are needed
withouth much causing overhead?
My Objects use an Attribute-approach:
i.e. TIntegerAttribute
- prop Value
- function IsNul: Boolean

so I could easily add an "loaded" flag that is checked, when "Value" is
accessed .... BUT
My problem ist how to define which Fields should be loaded if I use lets say
5 properties in an operation I want them to be loaded all at once(if
persisted from database), so I don't have 5 issued selects.
The only way I can imageine is to add methods to my BO that take care of
this
i.e. BO.LoadAdressProps, BO.LoadAccountInfo, BO.LoadDescriptiveProps...

So. is there any easy pattern to solve this ?

best regards,
Magnus

Dan Downs · Guest

Here's how I've done it in the past:

TSomeAttribClass = class;

TMyClass = class
protected
FPropVar : TSomeAttribClass;
function GetSomeAttribClass: TSomeAttribClass;
procedure SetSomeAttribClass(const Value: TSomeAttribClass);
public
constructor Create;
published
property PropVar : TSomeAttribClass read GetSomeAttribClass write
SetSomeAttribClass;
end;

constructor TMyClass.Create;
begin
FPropVar := nil;
end;

function TMyClass.GetSomeAttribClass: TSomeAttribClass;
begin
if Assigned(FPropVar) then
begin
Result := FPropVar;
exit;
end;
FPropVar := TSomeAttribClass.Create;
FPropVar.LoadSomethingFromSomewhereSomehow;
Result := FPropVar;
end;

procedure TMyClass.SetSomeAttribClass(const Value: TSomeAttribClass);
begin
if Value = nil then
// Handle nil case
if Value <> FPropVar then
FPropVar.Assign(Value);
end;

It can be a bit tendious, but it can be applied to nearly every property.

DD

John Herbster · Guest