# Undefined property in DisplayObject

**URL:** <https://forum.kirupa.com/t/undefined-property-in-displayobject/290615>\
**Category:** Uncategorized\
**Created:** [June 17, 2009, 7:26am UTC](https://forum.kirupa.com/t/undefined-property-in-displayobject/290615 "2009-06-17T07:26:25Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![samroni](https://avatars.discourse-cdn.com/v4/letter/s/2acd7d/32.png) [@samroni](https://forum.kirupa.com/u/samroni)\
**Post date:** [June 17, 2009, 7:26am UTC](https://forum.kirupa.com/t/undefined-property-in-displayobject/290615/1 "2009-06-17T07:26:25Z")

</div>

Hi People,

> var container:MovieClip = new MovieClip();  
> addChild(container);

var clip:MovieClip = new MovieClip();  
clip.name = “myclip”;

container.addChild(clip);

trace(container.getChildByName(“myclip”)); //output: [object MovieClip]

trace(container.getChildByName(“myclip”).numChildren);

//output: 1119: Access of possibly undefined property numChildren through a reference with static type flash.display: DisplayObject.  
can anyone explain why numchildren give me error?

i googled it, others said this error can be fix with casting, but im not sure.