Re: event and OOP

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#110

From: Alisdair Meredith [TeamB]
Date: Wed, 27 Oct 2004 14:00

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fwang11 wrote:

> It does. The ButtonClick() event handler is called from Button object
> to Form object.

No, the button objects stores a callback object, of a special BCB type
called a __closure.  If such an object is stored in its OnClick
property, it asks it to perform its action.

When the form loads, it sets various properties of the Button object it
owns, such as Caption, Top and Left.  It may also set a value for the
OnClick property, by making the appropriate callback object.

So the button knows nothing about the form, all it knows is the
callback.  The callback is created by the form, and typically points to
a bound member function in itself.  That is OK though, as the form has
the info to do this, not the button.

AlisdairM(TeamB)

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Subject: Re: event and OOP
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