JSON property is not defined - JSONUtil.as:65

[jimplouplou]

Hello, i have just started a new project with your API.
I try to run this example :

<esri:Map>
<esri:ArcGISTiledMapServiceLayer url="http://server.arcgisonline.com/ArcGIS/rest/services/World_Street_Map/MapServer"/>
</esri:Map>

I have Flex 4.5.1 and agslib-3.1-2012-12-12.swc
I soon as i run my very simple app, i have this error :

ReferenceError: Error #1065: The property JSON is not defined.
at com.esri.ags.utils::JSONUtil$/decode()
at com.esri.ags.tasks::BaseTask/handleResultEvent()
at mx.rpc::AsyncResponder/result()
at mx.rpc::AsyncToken/http://www.adobe.com/2006/flex/mx/internal::applyResult()
at mx.rpc.events::ResultEvent/http://www.adobe.com/2006/flex/mx/internal::callTokenResponders()
at HTTPOperation/http://www.adobe.com/2006/flex/mx/internal::dispatchRpcEvent()
at mx.rpc::AbstractInvoker/http://www.adobe.com/2006/flex/mx/internal::resultHandler()
at mx.rpc::Responder/result()
at mx.rpc::AsyncRequest/acknowledge()
at DirectHTTPMessageResponder/completeHandler()
at flash.events::EventDispatcher/dispatchEventFunction()
at flash.events::EventDispatcher/dispatchEvent()
at flash.net::URLLoader/onComplete()

Do you know what i have to do to resolve this ?
Thanks

[RobertScheitlin__GISP · Accepted solution]

Jim,

   The reason is because if you read the minimum requirements you will find that the 3.x line of the AGS Flex API requires Adobe Flex SDK 4.6 as a minimum.

http://resources.arcgis.com/en/help/flex-api/concepts/index.html#//017p0000000m000000#GUID-6D1447E1-...

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