Event Types Are closure Types (C++)
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Because an event is a pointer to an event handler, the type of the event property must be a closure type. Similarly, any code to be used as an event handler must be an appropriately typed method of a class.
To be compatible with an event of a given type, an event-handler method must have the same number and type of parameters, in the same order, passed in the same way.
C++Builder defines closures for all its standard events. When you create your own events, you can use an existing closure if that is appropriate, or define one of your own.