<p>I am trying to link the as3corelib library to use their JSON functionality following <a href="http://www.mikechambers.com/blog/2006/03/28/tutorial-using-json-with-flex-2-and-actionscript-3/" rel="nofollow noreferrer">this tutorial</a>. But am having trouble compiling it. My command looks like:</p>

<pre>
mxmlc --strict=true -library-path+=as3corelib.swc --file-specs  myapp.mxml
</pre>

<p>But I am getting this error:</p>

<pre>
_divided_mx_managers_SystemManager.as(13): col: 14 Error: Interface method getVisibleApplicationRect in namespace mx.managers:ISystemManager not implemented by
class _divided_mx_managers_SystemManager.

public class _divided_mx_managers_SystemManager
</pre>

<p>What is the problem?</p>

<p><em>Update: Is this because I am using Flex 3? The tutorial seems to be for Flex 2. If so, what do I need to do for Flex 3?</em></p>

Are you using the flex Gubmo sdk?
Looks like the method it's complaining about is in an interface that's part of Gumbo.
If so, then as3corelib probably won't work with it.