TList.Add and iterating

rbuser

Hello,

Please ,could you give me some advise:

I'm trying to make a loop to iterate trough
variables (objects) and trying to use TList
to store pointers to objects.

Here is my basic example ( RAP ):

var
i: Integer;
myList: TList;

Var1: TppVariable;
Var2: TppVariable;
Var3: TppVariable;

begin

myList := TList.Create;

myList.Add(Var1);
myList.Add(Var2);
myList.Add(Var3);

for i := 0 to myList.Count -1 do
begin

if myList.Items[i] is TppVariable then
begin
TppVariable(myList.Items[i].Value) := 'test123'; {PROBLEM IS HERE}
end;
end;

myList.Free;
end; {END}


This code works without errors but the problem is that in RAP language
that TList.Add seems to make a new instance of parameter and does not
store the pointer/reference. So, I cannot "see" the real variable
(Var1,Var2,Var3 etc.) in that loop.
That situation works correctly with Delphi TList, but not with RAP.

Thanks

Gunnar

nicocizik

Hi Gunnar,

You need to instantiate each variable object before using them. Your
current code contains three empty (nil) objects. Also if you plan to
view these variables on a report, you will need to assign their Band
property.

...
begin

myList := TList.Create;

Var1 := TppVariable.Create(nil);
Var2 := TppVariable.Create(nil);
Var3 := TppVariable.Create(nil);

Var1.Band := Report.DetailBand;
Var2.Band := Report.DetailBand;
Var3.Band := Report.DetailBand;

...

//Don't need to free variables if Band prop is assigned.
//Var1.Free;
//Var2.Free;
//Var3.Free;

myList.Free;

end;

rbuser

Hi Nico,

Thanks for the example, but still
there is something I am doing wrong probably. Here is the
real situation with the real variable in Report SummaryBeforePrint event:

procedure SummaryBeforePrint;
var
VarList: TList;
begin

{Following is the real variable, designed in summary band}
myRealVariable.Value := 'First value'; {this works OK of course}

{now into TList}
VarList := TList.Create;
VarList.Add(myRealVariable);
TppVariable(VarList.Items[0]).Value := 'Other value'; {still no luck}

end;

Still nothing, myRealVariable shows 'First value' on printout.

Gunnar

nicocizik

Hi Gunnar,

My first suggestion would be to get this working in Delphi first, then
move the code to RAP. This way you can trace the variable value and
event timing to find issues.

Variable values should not be calculated inside events other than the
OnCalc event. If you are simply trying to alter some text for the
summary band, I suggest using a label.

http://www.digital-metaphors.com/rbWiki/Delphi_Code/Calculations/Overview