creating a frame at runtime

[JIMSMITH 0]

I have 5 frames that I want to create at runtime.  The frames are descended from tframe2 or tframe3 how can I create this and allow the type (tframe2 or tframe3) to be specified in a variable.? So the object will be specified in a variable and the type will be in a variable as well.  So tframe2 and tframe3 will be defined and created at runtime, but the actual frame and descendant from type would be in a variable.

[Remy Lebeau 1403]

TFrame has a virtual constructor, so you can use a meta class variable for this task, eg:

type
  TFrameClass = class of TFrame;

var
  Frame: TFrame;
  FrameClass: TFrameClass;
begin
  ...
  if SomeCondition then
    FrameClass := TFrame2;
  else
    FrameClass := TFrame3;

  Frame := FrameClass.Create(Owner);
  ...
end;

 

 

Edited October 17 by Remy Lebeau

[Lars Fosdal 1792]

Note that the Frame instance should have its parent set to Owner as well.

 

[Der schöne Günther 316]

Don't forget to set the Name property of your frame to something unique.

Otherwise, it will throw a runtime exception when you have several components with identical name in the same container.

[havrlisan 25]

1 hour ago, Der schöne Günther said:

Don't forget to set the Name property of your frame to something unique.

Otherwise, it will throw a runtime exception when you have several components with identical name in the same container.

Or to an empty string. It's the safest and easiest way, in my opinion.

Edited October 17 by havrlisan

[Der schöne Günther 316]

Didn't even know that was possible. Thanks.

[Uwe Raabe 2059]

2 minutes ago, Der schöne Günther said:

Didn't even know that was possible.

It is even possible at design time. Setting an empty name to a component will remove the corresponding field in the class. It is often used with TLabel instances that only exist to display some static text, but won't be accessed in the code. It reduces code cluttering a bit.

[Remy Lebeau 1403]

9 minutes ago, Uwe Raabe said:

It is even possible at design time. Setting an empty name to a component will remove the corresponding field in the class. It is often used with TLabel instances that only exist to display some static text, but won't be accessed in the code. It reduces code cluttering a bit.

Interesting! I never thought of that. I learned something new today 😁 I'll definitely have to play with this in my projects.

Edited October 17 by Remy Lebeau

[Typer2 0]

When using frame inheritance, be aware that running Delphi at high DPI can cause issues, which might negatively affect the layout and functionality of your frames.

 

To avoid these issues, you can run Delphi in DPI-unaware mode:

"C:\Program Files (x86)\Embarcadero\Studio\23.0\bin\bds.exe" /highdpi:unaware

[tgbs 14]

2 hours ago, Uwe Raabe said:

It is even possible at design time. Setting an empty name to a component will remove the corresponding field in the class. It is often used with TLabel instances that only exist to display some static text, but won't be accessed in the code. It reduces code cluttering a bit.

This can be a problem in a multilingual project

[mvanrijnen 123]

2 hours ago, tgbs said:

This can be a problem in a multilingual project

In that case, the text is not static 😉

 

[Lars Fosdal 1792]

21 hours ago, Der schöne Günther said:

set the Name property of your frame to something unique

I use a global function GetNextInstanceNumber to get and increment a integer variable and just set the name to Self.ClassName+'_'+GetNextInstanceNumber.ToString;