Title: Getting the controls used by fields
Question: How to know what controls are used to edit the fields in a dataset linked with a datasource?
Answer:
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Getting the controls used by fields
by Rubem Nascimento da Rocha - cartouche@ig.com.br
Manaus, AM - Brazil (2002 August)
(Check it out the sample project inside Sample.zip)
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The data aware VCL has a very interesting feature to ensure separate bussiness
logic from visual interface. When we're working with data-aware controls and
dataset components, we can force the focus to a specific field using then
FocusControl TField's method. However, in some cases, this is not enough. Even
if this method was called from a data module, sometimes the focus is not
directed to the control used to edit the field (e.g., a TDBGrid).
I've noted this a long time ago, and then I've created a very good function to
use on my dataset maintenance forms, and others where it's applicable, to find
what control is used to edit a specific field in a dataset linked with a
datasource. With the function source code, you can extend this idea to, for
instance, write functions to control all the controls used by a datasource and
set the focus to the exact control used by a specific field.
I hope you enjoy it!
[]s
//----------------------------------------------------------------------------
// GetControlField - Given a window control (TForm, TPanel, etc.), a data
// source (TDataSource) and a field name, this function will try to find and
// return which control is used to edit the field contents, even a grid.
//
// by Rubem Nascimento da Rocha (Manaus-AM/Brazil) - cartouche@ig.com.br
//----------------------------------------------------------------------------
type
THackDBGrid = class(TCustomDBGrid);
function GetControlField(AOwner: TWinControl;
ADataSource: TDataSource; ADataField: String): TWinControl;
const
PropDataSource = 'DataSource';
PropDataField = 'DataField';
var
I: Integer;
Found: Boolean;
RefWinControl: TWinControl;
CurrControl: TControl;
PropInfo: PPropInfo;
PropValue: String;
Stack: TStringList; // recurse engine
AuxObject: TObject;
function GridHasField: Boolean;
var
_Field, _Qty: Integer;
_AName: String;
begin
Result := False;
with THackDBGrid(CurrControl) do
begin
_Qty := DataLink.FieldCount;
for _Field := 0 to _Qty - 1 do
begin
_AName := UpperCase(DataLink.Fields[_Field].FieldName);
Result := (_AName = UpperCase(ADataField));
if Result then Break;
end;
end;
end;
begin
Found := False;
RefWinControl := AOwner;
I := Pred(RefWinControl.ControlCount);
Result := NIL;
Stack := TStringList.Create;
try
while ((I = 0) or (Stack.Count 0)) and (not Found) do
begin
// Check if control will be only checked checado or if all your
// child controls, one-by-one, will do
CurrControl := RefWinControl.Controls[I];
if CurrControl is TWinControl then
if TWinControl(CurrControl).ControlCount 0 then
begin
Stack.AddObject(IntToStr(I), RefWinControl);
RefWinControl := TWinControl(CurrControl);
I := Pred(RefWinControl.ControlCount);
Continue;
end;
PropInfo := GetPropInfo(CurrControl.ClassInfo, PropDataSource);
if Assigned(PropInfo) then
begin
AuxObject := TObject(GetOrdProp(CurrControl, PropInfo));
// check if control is a data-aware grid
if CurrControl is TCustomDBGrid then
Found := GridHasField
else
begin
PropInfo := GetPropInfo(PTypeInfo(CurrControl.ClassInfo),
PropDataField);
if Assigned(PropInfo) then
begin
// ... check if property has the search value
PropValue := GetStrProp(CurrControl, PropInfo);
Found := (TDataSource(AuxObject) = ADataSource) and
(UpperCase(PropValue) = UpperCase(ADataField));
end;
end;
end;
while (Pred(I) = -1) and (Stack.Count 0) do
begin
I := StrToInt(Stack[Pred(Stack.Count)]);
RefWinControl := TWinControl(Stack.Objects[Pred(Stack.Count)]);
Stack.Delete(Pred(Stack.Count));
end;
Dec(I);
if Found then
result := TWinControl(CurrControl);
end;
finally
Stack.Free;
end;
end;
//----------------------------------------------------------------------------