Delphi What is the Free Property in DelphiVCL.Application?

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What is the Free Property in DelphiVCL.Application?
By Muhammad Azizul Hakim July 19, 2021

Use the Free property or DelphiVCL.Application.Free to destroy an object and free its associated memory, if necessary.

Use Free to destroy an object. Free automatically calls the destructor if the object reference is not nil. Any object instantiated at run time that does not have an owner should be destroyed by a call to Free, so that it can be properly disposed of and its memory released. Unlike Destroy, Free is successful even if the object is nil; if the object was never initialized, Free would not result in an error.

What happens if we call the Free method on a component?​

When you call Free for a component, it calls Free for all components that it owns—that is, all components in its component list. Since a form owns all the controls and other components that are created on it in design mode, those components are automatically freed when the form is freed. By default, all forms are owned by the Application object; when the application terminates, it frees the Application object, which frees all forms. For objects that are not components, or for components created with a nil owner, be sure to call Free after you are finished with them; otherwise, the allocated memory will not be usable until after the application terminates.

Be careful how you use the Free method​

Warning: Never explicitly free a component within one of its own event handlers or the event handler of a component it owns or contains. For example, do not free a button or the form that owns the button in its OnClick event handler.

To free a form, call its Release method, which destroys the form and releases the memory allocated for it after all its event handlers and those of the components it contains are through executing.

Note: In C++ code, do not use Free to destroy an object. Use the delete keyword.

Examining the properties and methods of DelphiVCL.Application.Free​

Let’s browse all the methods and built-in properties of the DelphiVCL.Application.Free using dir() command:

import DelphiVCL
 
dir(DelphiVCL.Application.Free)

See the responses in our Windows command prompt:

You can also read short information about the DelphiVCL.Application.Free using the print() command:

print(DelphiVCL.Application.Free)
print(DelphiVCL.Application.Free.__doc__)

See the responses in our Windows command prompt: