Application.MainForm v Self v Nil??

[Ian Branch 121]

Hi Team,

When creating a form in code..   i.e.  MyForm := TMyForm.Create(xxx);

If the code the creation is happening is in the MainForm's code, what are the Pros and Cons of xxx being 'Application.MainForm', 'Self' and 'Nil' please??

Does it matter??

 

Regards & TIA,

Ian

[Uwe Raabe 1891]

Sorry, but I don't understand your question.

[Ian Branch 121]

Hi Uwe,

Apologies.

In my MainForm I create subforms depending on the menu selection.

I currently use the format MyForm := TMyForm.Create(nil);  Just an old habit/practice.

I have seen variously 'Application.MainForm', 'Self' and 'Nil' in the .Create().

I am curious, if the subform creation is from the MainForm's code, what are the Pros and/or Cons of using 'Application.MainForm', 'Self' or 'Nil' in the .Create()??

Is Application.MainForm the same as Self in this context?

 

HTH.

 

Regards,

Ian

[Attila Kovacs 617]

you could start here https://docwiki.embarcadero.com/RADStudio/Sydney/en/Components_and_Ownership

[Uwe Raabe 1891]

Application.MainForm is set with the first TForm created with Application.CreateForm.

[Ian Branch 121]

Hi Team,

Thank you for your inputs.

This link gave me the insight I was after.  https://www.thoughtco.com/tform-createaowner-aowner-1057563

 

Regards,

Ian

[Remy Lebeau 1263]

23 hours ago, Ian Branch said:

I am curious, if the subform creation is from the MainForm's code, what are the Pros and/or Cons of using 'Application.MainForm', 'Self' or 'Nil' in the .Create()??

The only thing that matters is whether you assign a nil Owner (ie, you are responsible for freeing the sub-Form when you are done using it) or assign a non-nil Owner (ie, the Owner will free the sub-Form when the Owner itself is freed).  WHO the Owner is when non-nil is largely irrelevant, as long as the Owner outlives the usage of the sub-Form.

23 hours ago, Ian Branch said:

Is Application.MainForm the same as Self in this context?

Yes.

[Ian Branch 121]

Tks Remy.