# Explicit downcasting from a MovieClip subclass

**URL:** <https://forum.kirupa.com/t/explicit-downcasting-from-a-movieclip-subclass/173869>\
**Category:** flash\
**Created:** [December 30, 2005, 12:48pm UTC](https://forum.kirupa.com/t/explicit-downcasting-from-a-movieclip-subclass/173869 "2005-12-30T12:48:06Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![ilazarte](https://avatars.discourse-cdn.com/v4/letter/i/94ad74/32.png) [@ilazarte](https://forum.kirupa.com/u/ilazarte)\
**Post date:** [December 30, 2005, 12:48pm UTC](https://forum.kirupa.com/t/explicit-downcasting-from-a-movieclip-subclass/173869/1 "2005-12-30T12:48:06Z")

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sorry, title should read:  
Explicit downcasting **to** a MovieClip subclass (from a MovieClip)

Class MovieSubclass extends MovieClip{  
…  
}

function doSomething( m:MovieSubclass ) {  
…  
}

* * *

var mc:MovieClip = MovieClip(new MovieSubclass());  
… mc.duplicateMovieClip(…);  
… mc.attachMovie(…);  
doSomething( MovieSubClass(mc) );

The last line, doSomething doesn’t get a valid call because the cast of MovieClip to its subclass doesn’t work. How can I get a valid downcast of MovieClip? Workarounds welcome.