Transforming online listview object - Delphi - delphi

I wonder how caught a row of a listview and transform object.
I carry an .xml file and play in a listview , after loading this file you need to double-click in a row, take all of the data line and throw in a LabelEdit , as shown in the code below .
procedure TForm1.LstbxDadosDblClick(Sender: TObject);
begin
if Assigned(TMensagem(LstbxDados.Items.Objects[LstbxDados.ItemIndex])) then
begin
with TMensagem(LstbxDados.Items.Objects[LstbxDados.ItemIndex]) do
begin
EdtPara.Text := Para;
EdtDe.Text := De;
EdtCabecalho.Text := Cabecalho;
EdtCorpo.Text := Corpo;
end;
end;
end;
TMensagem = class
private
FCorpo: String;
FCabecalho: String;
FPara: String;
FDe: String;
public
property Para : String read FPara write FPara;
property De : String read FDe write FDe;
property Cabecalho: String read FCabecalho write FCabecalho;
property Corpo : String read FCorpo write FCorpo;
end;

Many ways to edit an object where the current object can change at any time (like with a double click). Here is one of the easiest: save when the current object changes and save at the very end. Here is a quick and dirty solution.
Add a member to the form or global in the implementation section
FLastMensagem: TMensagem;
May want to initialize to nil on create or initialization (left to you). Now in the event save data when the TMensagem object changes
procedure TForm1.LstbxDadosDblClick(Sender: TObject);
var
LNewMensagem: TMensagem;
begin
LNewMensagem := TMensagem(LstbxDados.Items.Objects[LstbxDados.ItemIndex]));
if Assigned(LNewMensagem) then
begin
// When we switch, capture the dialog before updating it
if Assigned(FMensagem) and (LNewMensagem <> FLastMensagem) then
begin
FLastMensagem.Para := EdtPara.Text;
FLastMensagem.De := EdtDe.Text;
FLastMensagem.Cabecalho := EdtCabecalho.Text;
FLastMensagem.Corpo := EdtCorpo.Text;
end;
EdtPara.Text := LNewMensagem.Para;
EdtDe.Text := LNewMensagem.De;
EdtCabecalho.Text := LNewMensagem.Cabecalho;
EdtCorpo.Text := LNewMensagem.Corpo;
//Set the last dblclicked
FLastMensagem := LNewMensagem
end;
end;
Of course the very last edit needs to be saved, that you can do in say a form close (not sure what your full design is). For example
procedure TForm1.FormClose(Sender: TObject; var Action: TCloseAction);
begin
if Assigned(FLastMensagem) then
begin
FLastMensagem.Para := EdtPara.Text;
FLastMensagem.De := EdtDe.Text;
FLastMensagem.Cabecalho := EdtCabecalho.Text;
FLastMensagem.Corpo := EdtCorpo.Text;
end;
end;

Related

How to make the same button run different code everytime it is clicked?

I am currently doing a school project, I am making a Credit Card machine. I need the 'Enter Button' to
run different code when it is clicked. The first click must get the card number from an edit ps... (I clear the edit once the card number has been retrieved), and the second click must get the pin from the same edit.
How would I do this?
procedure TfrmMainMenu.btbtnEnterClick(Sender: TObject);
var
sCvv,sPin:string;
begin
iCount2:=0;
sCardNumber:=lbledtCardInfo.Text;
if (Length(sCardNumber)<>16) AND (iCount2=0) then
begin
ShowMessage('Card number has to 16 digits,please try again!!');
end
else
begin
Inc(iCount2);
lbledtCardInfo.clear;
lbledtCardInfo.EditLabel.Caption:='Enter Pin' ;
btbtnEnter.Enabled:=false;
end; //if
if iCount2=2 then
begin
btbtnEnter.Enabled:=true;
sPin:=lbledtCardInfo.Text;
ShowMessage(sPin);//returns a blank
end;
You could try to do everything in a single event handler. There are several different ways to handle that. However, a different solution would be to use separate event handlers for each task, and then each task can assign a new handler for the next click to perform, eg:
procedure TfrmMainMenu.FormCreate(Sender: TObject);
begin
// you can set this at design-time if desired...
btbtnEnter.OnClick := GetCCNumber;
end;
procedure TfrmMainMenu.GetCCNumber(Sender: TObject);
begin
sCardNumber := lbledtCardInfo.Text;
if Length(sCardNumber) <> 16 then
begin
ShowMessage('Card number has to 16 digits,please try again!!');
Exit;
end;
lbledtCardInfo.Clear;
lbledtCardInfo.EditLabel.Caption := 'Enter Pin' ;
btbtnEnter.OnClick := GetCCPin;
end;
procedure TfrmMainMenu.GetCCPin(Sender: TObject);
var
sPin: string;
begin
sPin := lbledtCardInfo.Text;
if Length(sPin) <> 4 then
begin
ShowMessage('Card Pin has to 4 digits,please try again!!');
Exit;
end;
ShowMessage(sPin);
...
lbledtCardInfo.Clear;
lbledtCardInfo.EditLabel.Caption := 'Enter Number' ;
btbtnEnter.OnClick := GetCCNumber;
end;
A variation of this would be to create multiple buttons that overlap each other in the UI, and then you can toggle their Visible property back and forth as needed, eg:
procedure TfrmMainMenu.FormCreate(Sender: TObject);
begin
// you can set this at design-time if desired...
btbtnCCPinEnter.Visible := False;
btbtnCCNumEnter.Visible := True;
end;
procedure TfrmMainMenu.btbtnCCNumEnterClick(Sender: TObject);
begin
sCardNumber := lbledtCardInfo.Text;
if Length(sCardNumber) <> 16 then
begin
ShowMessage('Card number has to 16 digits,please try again!!');
Exit;
end;
lbledtCardInfo.Clear;
lbledtCardInfo.EditLabel.Caption := 'Enter Pin' ;
btbtnCCNumEnter.Visible := False;
btbtnCCPinEnter.Visible := True;
end;
procedure TfrmMainMenu.btbtnCCPinEnterClick(Sender: TObject);
var
sPin: string;
begin
sPin := lbledtCardInfo.Text;
if Length(sPin) <> 4 then
begin
ShowMessage('Card Pin has to 4 digits,please try again!!');
Exit;
end;
ShowMessage(sPin);
...
lbledtCardInfo.Clear;
lbledtCardInfo.EditLabel.Caption := 'Enter Number' ;
btbtnCCPinEnter.Visible := False;
btbtnCCNumEnter.Visible := True;
end;
Notice that you test iCount2 = 0 immediately after setting iCount2 := 0. Thus, that test will always be True. Furthermore, the later test iCount2 = 2 will always be False because the value starts at 0 and you only have one Inc in between.
Instead try the following.
Add two string fields FCardNumber and FPin to your form class:
private
FCardNumber: string;
FPin: string;
Also create an enumerated type TEntryStage = (esCardNumber, esPin) and add a field of this type. This will make your code look like this:
private
type
TEntryStage = (esCardNumber, esPin);
var
FCardNumber: string;
FPin: string;
FEntryStage: TEntryStage;
In Delphi, class fields (class member variables) are always initialized, so FEntryStage will be esCardNumber (=TEntryStage(0)) when the form is newly created.
Add a TLabeledEdit (I see you use those) and a TButton; name them eInput and btnNext, respectively. Let the labeled edit's caption be Card number: and the caption of the button be Next.
Now add the following OnClick handler to the button:
procedure TForm1.btnNextClick(Sender: TObject);
begin
case FEntryStage of
esCardNumber:
begin
// Save card number
FCardNumber := eInput.Text;
// Prepare for the next stage
eInput.Clear;
eInput.EditLabel.Caption := 'Pin:';
FEntryStage := esPin;
end;
esPin:
begin
// Save pin
FPin := eInput.Text;
// Just do something with the data
ShowMessageFmt('Card number: %s'#13#10'Pin: %s', [FCardNumber, FPin]);
end;
end;
end;
You might notice that you cannot trigger the Next button using Enter, which is very annoying. To fix this, do
procedure TForm1.eInputEnter(Sender: TObject);
begin
btnNext.Default := True;
end;
procedure TForm1.eInputExit(Sender: TObject);
begin
btnNext.Default := False;
end;
Much better!

Checking the items checked in a CheckListBox

As my first instance of the question was too broad, I am going to try and reword this so it is more understandable.
I want to be able to change the visibility of a label based on an item in a check box list being checked. I have a loop that goes through my check box list.
procedure TFrmSettings.CheckBoxSelected;
var
i : Integer;
begin
for i := 0 to CblRequiredFields.Items.Count - 1 do
begin
if CblRequiredFields.Checked[i] then
begin
FrmVReg.ReqFields(CblRequiredFields.Items.Strings[i]);
end;
end;
end;
Here is just a part of the ReqFields procedure as it would be too long to put into this Q.
procedure TFrmVReg.ReqFields(ChkStr : String);
begin
if ChkStr = 'Gender' then
begin
lblGenderReq.Visible := True;
end
else
begin
lblGenderReq.Visible := False;
end;
The problem I keep having is I can either only have one label active at one time or have it where a label will not disappear when it is deselected.
I hope I have reworded this to a point that it isn't as broad as the previous question.
If the FrmVReg form exists before the creation of the FrmSettings you can maintain a lisk of key-value pairs (checbox name and label object) in the CblRequiredFields list directly.
The labels visibility can be synchronized with the CblRequiredFieldschecks using the OnClickCheck event of the TCheckListBox object.
procedure TFrmSettings.CblRequiredFieldsClickCheck(Sender: TObject);
begin
TLabel(CblRequiredFields.Items.Objects[CblRequiredFields.ItemIndex]).Visible := CblRequiredFields.Checked[CblRequiredFields.ItemIndex];
end;
procedure TFrmSettings.FormCreate(Sender: TObject);
begin
CblRequiredFields.AddItem('Gender', FrmVReg.lblGenderReq);
CblRequiredFields.AddItem('Age', FrmVReg.lblAgeReq);
. . .
end;
If the above can't be applied, you can modify the ReqFields method like this:
procedure TFrmVReg.ReqFields(ChkStr: String; Checked: Boolean);
begin
if ChkStr = 'Gender' then
lblGenderReq.Visible := Checked
else if ChkStr = 'Age' then
lblAgeReq.Visible := Checked
//else if . . .
end;
... calling it accordingly with its new signature:
for i := 0 to CblRequiredFields.Items.Count - 1 do
FrmVReg.ReqFields(CblRequiredFields.Items.Strings[i], CblRequiredFields.Checked[i]);

WebBrowser component navigation through multiple pages does not work

Trying to navigate using WebBrowser component automatically through code it doesn't work. The navigation includes the login page and after that some other pages. The first page button login works fine. On second page the next button needed an application.processmessages before executing to make it work. On the next/third page I cannot make automatically the next button to work.
CODE:
//CLICK BUTTON
function clickForm1(WebBrowser: TWebBrowser; FieldName: string): Boolean;
var
i, j: Integer;
FormItem: Variant;
begin
Result := False;
//no form on document
if WebBrowser.OleObject.Document.all.tags('FORM').Length = 0 then
begin
Exit;
end;
//count forms on document
for I := 0 to WebBrowser.OleObject.Document.forms.Length - 1 do
begin
FormItem := WebBrowser.OleObject.Document.forms.Item(I);
for j := 0 to FormItem.Length - 1 do
begin
try
//when the fieldname is found, try to fill out
if FormItem.Item(j).Name = FieldName then
begin
FormItem.Item(j).click;
Result := True;
end;
except
Exit;
end;
end;
end;
end;
//SEARCH INSIDE THE MEMO
procedure TForm2.Button7Click(Sender: TObject);
var
i: Integer;
a: string;
begin
Memo1.Lines.Add('');
Memo1.Lines.Text := ' ' + Memo1.Lines.Text;
for i := 0 to Length(Memo1.Lines.Text) - Length(edit7.Text) do
begin
a := Copy(Memo1.Lines.Text, i, Length(edit7.Text));
if CheckBox1.Checked = True then //FIND CASE Sensitive
begin
if a = edit7.Text then
begin
find := True;
x := 2;
Memo1.Lines.Text := Copy(Memo1.Lines.Text, 2, Length(Memo1.Lines.Text) - 1);
Memo1.SetFocus;
Memo1.SelStart := i - 2;
Memo1.SelLength := Length(edit7.Text);
break;
end;
end
else
begin
if lowercase(a) = lowercase(edit7.Text) then
begin
Memo1.Lines.Text := Copy(Memo1.Lines.Text, 2, Length(Memo1.Lines.Text) - 1);
find := True;
x := 2;
Memo1.SetFocus;
Memo1.SelStart := i - 2;
Memo1.SelLength := Length(edit7.Text);
break;
end;
end;
end;
end;
//HTML TO MEMO
procedure TForm2.Button6Click(Sender: TObject);
var
iall : IHTMLElement;
begin
if Assigned(WebBrowser1.Document) then
begin
iall := (WebBrowser1.Document AS IHTMLDocument2).body;
while iall.parentElement <> nil do
begin
iall := iall.parentElement;
end;
memo1.Text := iall.outerHTML;
end;
end;
procedure TForm2.WebBrowser1DocumentComplete(ASender: TObject;
const pDisp: IDispatch; var URL: OleVariant);
var
Document: IHtmlDocument2;
CurWebrowser : IWebBrowser;
TopWebBrowser: IWebBrowser;
WindowName : string;
ovElements: OleVariant;
i: Integer;
begin
CurWebrowser := pDisp as IWebBrowser;
TopWebBrowser := (ASender as TWebBrowser).DefaultInterface;
if CurWebrowser=TopWebBrowser then
begin
button6.Click; // HTML TO MEMO
TRY
button7.Click; //SEARCH LOGIN FORM
if find=true then Begin
clickForm1(WebBrowser1, 'move'); //CLICK LOGIN BUTTON
End Else begin Null; End;
FINALLY find:=false; END;
TRY
button8.Click; //SEARCH HOME (AFTER LOGIN) FORM
if find1=true then Begin
Application.ProcessMessages;//NEEDED IN ORDER THE BUTTON TO BE PRESSED.
clickForm1(WebBrowser1, 'refresh'); //CLICK NEXT PAGE BUTTON
End;
FINALLY find1:=false;END;
TRY
button9.Click; //SEARCH WORKLIST FORM
if find2=true then Begin
clickForm1(WebBrowser1, 'next'); //CLICK NEW FORM BUTTON
End;
FINALLY find2:=false;END;
end;
end;
I'm not sure how much you know about working with Event Handlers in code.
Objects like Forms and WebBrowsers typically have one or more event properties that are used to define what happens when the event occurs. So, an event property is a property of an object that can hold the information necessary to invoke (call) a procedure (or function, but not usually) of the same object or another one. The procedure to call has to have the right "signature" for the type definition of the event. If it does then an "event handler" can be assigned to the event property in code, as I'll show below.
One can use event properties and event-handling code in Delphi in a simple way, without knowing any of this, just by going to the Events tab of the Object Inspector and double-clicking next to one of the event names. What that actually does is to create a new handler procedure and to assign it to the corresponding event property of the object (well, not quite, actually that assignment is done at run-time when the host form is loaded).
What I mean by "signature" is the routine type (procedure or function) and its list of parameters, and their types, in its definition.
So, for a WebBrowser, the signature of the OnDocumentComplete event is
procedure (Sender: TObject; const pDisp: IDispatch; var URL: OLEVariant);
The clever thing is that you can assign the OnDocumentComplete property to
any procedure of an object that has the exact same signature. The event type for the WB's OnDocumentComplete is defined in the import unit ShDocVw, btw
So, let's suppose you write three methods that contain the code you want to run
when the WB completes loading URLs A, B and C, respectively:
procedure TForm1.DocCompleteA(Sender: TObject; const
pDisp: IDispatch; var URL: OLEVariant);
begin
// Do your stuff for arrival at site/page A here
// Then update NavigationOK flag to reflect if you succeeded or failed
if NavigationOK then begin
WebBrowser1.OnDocumentComplete := DocCompleteB;
// Now navigate to site/page B
end
else
WebBrowser1.OnDocumentComplete := Nil;
end;
procedure TForm1.DocCompleteB(Sender: TObject; const
pDisp: IDispatch; var URL: OLEVariant);
begin
end;
procedure TForm1.DocCompleteC(Sender: TObject; const
pDisp: IDispatch; var URL: OLEVariant);
begin
end;
Then, you can assign the WB's OnDocumentComplete property to each of them in turn,
with something like the code at the end of DocCompleteA which updates the WB's OnDocumentComplete to the code needed for B, and so on, in turn. The NavigationOK variable is just a flag to indicate that our navigation stays "on course" as it progresses. If it gets set to false because something went wrong, we set the WB's OnDocumentComplete to Nil, so that it does nothing next time the event occurs.
Then, you can kick off the whole "tour" of sites with something like this:
procedure TForm1.NavigateSites;
begin
NavigationOK := True;
WebBrowser1.OnDocumentComplete := DocCompleteA;
WebBrowser1.Navigate(...); // Navigate to site A
end;
Of course, you don't have to do the updating of the WB's OnDocumentComplete property and navigation to the next URL in the current DocCompleteX. In fact, it's probably clearer if you do those if a higher level procedure like the NavigateSites one, and more easily maintainable, which can be important if you're navigating others' sites, which are apt to be changed without any prior warning.

dynamically create forms using a STRING

I have 5 forms created at design time. I need to dynamically create an instance of each form and put on a tab.
My question: If the form names are in an array of strings and I call my procedure like this:
ShowForm(FormName[3]);// To show the 3rd form on a tab page.
How can I define and create the new instance for each form?
This is what I have for now:
procedure TForm1.ShowFormOnTab(pProcName:String);
var
NewForm: TfrmSetupItemCategories;//***HERE IS MY PROBLEM***
NewTab: TTabSheet;
FormName: String;
begin
NewTab := TTabSheet.Create(PageControl1);
NewTab.PageControl:= PageControl1;
NewTab.Caption:='hi';
PageControl1.ActivePage := NewTab;
if pProcName='ProcfrmSetupItemCategories' Then
begin
NewForm:=TfrmSetupItemCategories.Create(NewTab);
NewTab.Caption := NewForm.Caption;
end;
if pProcName='ProcfrmZones' Then
begin
NewForm:=TfrmZones.Create(NewTab);
NewTab.Caption := NewForm.Caption;
end;
.
.
.
end;
the line that reads "HERE IS MY PROBLEM" is where I need help. I can't reuse NewForm as a variable with a second form in this way...
Note: My problem is NOT the tab. Rather it's creating a new instance of the form using the same variable name.
Declare the NewForm variable as TForm:
var
NewForm: TForm;
begin
NewForm := TMyForm.Create(Tab1); //compiles OK
NewForm := TMyOtherForm.Create(Tab2); //also compiles OK
end;
I'm assuming TMyForm and TMyOtherForm both are derivatives of TForm.
DRY
You can also reduce your repeating code using a class reference variable, like this:
procedure TForm1.ShowFormOnTab(pProcName:String);
var
NewForm: TForm;
ClassToUse: TFormClass;
NewTab: TTabSheet;
FormName: String;
begin
NewTab := TTabSheet.Create(PageControl1);
NewTab.PageControl:= PageControl1;
NewTab.Caption:='hi';
PageControl1.ActivePage := NewTab;
if pProcName='ProcfrmSetupItemCategories' then
ClassToUse := TfrmSetupItemCategories
else if pProcName='ProcfrmZones' then
ClassToUse := TfrmZones
else
ClassToUse := nil;
if Assigned(ClassToUse) then
begin
NewForm := ClassTouse.Create(NewTab);
NewTab.Caption := NewForm.Caption;
//if you access custom properties or methods, this is the way:
if NewForm is TfrmZones then
TfrmZones(NewForm).ZoneInfo := 'MyInfo';
end;
end;
Register your classes and then create the forms from a string
As Sir Rufo points in his comment, you can even go further registering your classes (I'm not sure if this can be done in Lazarus, that exercise is up to you).
First, register the form classes you want to instantiate from the class name, previous to any call to your ShowFormOnTab method, for example:
procedure TMainForm.FormCreate(Sender: TObject);
begin
RegisterClass(TfrmSetupItemCategories);
RegisterClass(TfrmZones);
//and other classes
end;
Then, you can change the code to get the class reference from the class name string:
procedure TForm1.ShowFormOnTab(pProcName:String);
var
NewForm: TForm;
ClassToUse: TFormClass;
ClassNameToUse: string;
NewTab: TTabSheet;
FormName: String;
begin
NewTab := TTabSheet.Create(PageControl1);
NewTab.PageControl:= PageControl1;
NewTab.Caption:='hi';
PageControl1.ActivePage := NewTab;
//get rid of 'Proc' and add the T
//or even better, pass directly the class name
ClassNameToUse := 'T' + Copy(pProcName, 5, MaxInt);
ClassToUse := TFormClass(FindClass(ClassNameToUse));
if Assigned(ClassToUse) then
begin
NewForm := ClassTouse.Create(NewTab);
NewTab.Caption := NewForm.Caption;
//if you access custom properties or methods, this is the way:
if NewForm is TfrmZones then
TfrmZones(NewForm).ZoneInfo := 'MyInfo';
end;
end;
That way, the code remains the same for any number of classes.
For more info about this, take a look at Creating a Delphi form from a string in delphi.about.com.
Declare your variable as an ancestor type:
var
NewForm: TForm;
or
var
NewForm: TCustomForm;
Drawback: you'll need to cast the variable to the specific class if you want to call any methods of your form that you have declared yourself.
Use a 'soft' cast if you want to have the compiler check that NewForm is actually a TMyForm at runtime:
(NewForm as TMyForm).MyMethod;
When you are absolutely sure that NewForm is a TMyForm (like when you just created it), you can also use a 'hard' cast:
TMyForm(NewForm).MyMethod;
With registered classes, in the initialization of the used forms, you could shorten it to
Function CreateAndDock(pc:TPageControl;const FormName:String):Boolean;
begin
Result := false;
if Assigned(GetClass(FormName)) and GetClass(FormName).InheritsFrom(TCustomForm) then
With TFormClass( GetClass(FormName)).Create(pc.Owner) do
begin
ManualDock(pc);
Show;
Result := true;
end;
end;
procedure TForm4.Button1Click(Sender: TObject);
begin
ShowMessage(IntToStr(Integer(CreateAndDock(pagecontrol1,'TDockForm'))));
ShowMessage(IntToStr(Integer(CreateAndDock(pagecontrol1,'TNotExists'))));
end;

Remove and Replace a visual component at runtime

Is it possible to, for instance, replace and free a TEdit with a subclassed component instantiated (conditionally) at runtime? If so, how and when it should be done? I've tried to set the parent to nil and to call free() in the form constructor and AfterConstruction methods but in both cases I got a runtime error.
Being more specific, I got an Access violation error (EAccessViolation). It seems François is right when he says that freeing components at frame costruction messes with Form controls housekeeping.
This more generic routine works either with a Form or Frame (updated to use a subclass for the new control):
function ReplaceControlEx(AControl: TControl; const AControlClass: TControlClass; const ANewName: string; const IsFreed : Boolean = True): TControl;
begin
if AControl = nil then
begin
Result := nil;
Exit;
end;
Result := AControlClass.Create(AControl.Owner);
CloneProperties(AControl, Result);// copy all properties to new control
// Result.Left := AControl.Left; // or copy some properties manually...
// Result.Top := AControl.Top;
Result.Name := ANewName;
Result.Parent := AControl.Parent; // needed for the InsertControl & RemoveControl magic
if IsFreed then
FreeAndNil(AControl);
end;
function ReplaceControl(AControl: TControl; const ANewName: string; const IsFreed : Boolean = True): TControl;
begin
if AControl = nil then
Result := nil
else
Result := ReplaceControlEx(AControl, TControlClass(AControl.ClassType), ANewName, IsFreed);
end;
using this routine to pass the properties to the new control
procedure CloneProperties(const Source: TControl; const Dest: TControl);
var
ms: TMemoryStream;
OldName: string;
begin
OldName := Source.Name;
Source.Name := ''; // needed to avoid Name collision
try
ms := TMemoryStream.Create;
try
ms.WriteComponent(Source);
ms.Position := 0;
ms.ReadComponent(Dest);
finally
ms.Free;
end;
finally
Source.Name := OldName;
end;
end;
use it like:
procedure TFrame1.AfterConstruction;
var
I: Integer;
NewEdit: TMyEdit;
begin
inherited;
NewEdit := ReplaceControlEx(Edit1, TMyEdit, 'Edit2') as TMyEdit;
if Assigned(NewEdit) then
begin
NewEdit.Text := 'My Brand New Edit';
NewEdit.Author := 'Myself';
end;
for I:=0 to ControlCount-1 do
begin
ShowMessage(Controls[I].Name);
end;
end;
CAUTION: If you are doing this inside the AfterConstruction of the Frame, beware that the hosting Form construction is not finished yet.
Freeing Controls there, might cause a lot of problems as you're messing up with Form controls housekeeping.
See what you get if you try to read the new Edit Caption to display in the ShowMessage...
In that case you would want to use
...ReplaceControl(Edit1, 'Edit2', False)
and then do a
...FreeAndNil(Edit1)
later.
You have to call RemoveControl of the TEdit's parent to remove the control. Use InsertControl to add the new control.
var Edit2: TEdit;
begin
Edit2 := TEdit.Create(self);
Edit2.Left := Edit1.Left;
Edit2.Top := Edit2.Top;
Edit1.Parent.Insertcontrol(Edit2);
TWinControl(Edit1.parent).RemoveControl(Edit1);
Edit1.Free;
end;
Replace TEdit.Create to the class you want to use, and copy all properties you need like I did with Left and Top.
You can actually use RTTI (look in the TypInfo unit) to clone all the matching properties. I wrote code for this a while back, but I can't find it now. I'll keep looking.

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