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June 9, 2009

Top Flex Interview Questions

  • s it possible to make httpService Requests synchronous?

      Other Solution:

        I use a single HTTPService instance, and a single result handler. The send() method returns an AsyncToken, which is a dynamic object to which you add most any kind of property you want. The result handler function can access this AsyncToken and read those proerties. I typically set a “callId”, which is a string that identifies the call, and sometimes a “nextaction” property when I invoke a dataservice call. In the result handler, I use a switch statement to conditionally work with those properties to determine the next appropriate processing step, which obviously can include another dataservice call. The switch statement can get pretty long, but is easy to understand, debug and modify. With a single breakpoint, I can monitor every result.

  • I need to load an image from flickr into my application. Do I need a crossdomain.xml file on flickr?

      NO, file is already there we need to register IP address to flicker’s crossdomain.xml.

      A cross-domain policy file is an XML file that provides a way for the server to indicate that its data and documents are available to SWF files served from other domains. Any SWF file that is served from a domain that the server’s policy file specifies is permitted to access data or assets from that server. When a Flash document attempts to access data from another domain, Flash
      Player attempts to load a policy file from that domain. If the domain of the Flash document that is attempting to access the data is included in the policy file, the data is automatically accessible. The default policy file is named crossdomain.xml and resides at the root directory of the server that is serving the data. The following example policy file permits access to Flash
      documents that originate from,, * and



      If you want to access Flickr from Flex/Flash, you have to use Flickr API. And to use their API, you have to register with Flickr. While registering, they will ask you where you are going to host your application that will use the API. There you need to mention the URL/domain name of your website and they will add the website to their list of allowed domains in
      their crossdomain.xml

  • How to create application which fetches images from flickr using a keyword?

      What is the difference between httpService and DataService?

      Data Services :

      services-config.xml configuration file is required at compile time if the flex application is using FDS.

      A Flex data service is an object you insert in an MXML file to communicate with the business layer of a multi-tier application. Specifically, you can use Flex data services to interact with the following RPC Services:

      • Web services :

        • use raw HTTP requests
        • use named services or raw URLs and connect to an HTTP proxy using text-based query parameters or XML
      • HTTP services :

        • use the SOAP protocol
        • use named services or raw URLs and connect to an HTTP proxy using text-based query parameters or XML
      • Remote objects :

        • uses AMF3
        • example: server-based Java objects.
        • specifies named or unnamed sources and connects to an Action Message Format (AMF) gateway.
        • data is transferred in a binary format.
        • data move across the network more quickly.
        • data deserialized more rapidly than text-based formats such as XML.
        • performance gains, particularly where large sets of data are involved.
        • The remoting service, which runs on your server, automatically marshalls data between AMF and your server-side language (e.g., PHP, Java, C#). As a result, you can directly call methods on your PHP objects without having to write an XML REST interface or create web service interfaces.
  • What is the difference between “mx.rpc.http.HTTPService” and “mx.rpc.http.mxml.HTTPService”
    • mx.rpc.http.HTTPService

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