the reason why Dan said you need to be carefull with creating delegates in your
command's constructor is because the creation of remote services sometimes
seems to be a very expensive operation, it might run over multiple frames so
you might not be able to rely on defining your remote services before defining
your front controller in one MXML file, since this will be compiled to one
ActionScript block, which runs in one frame.
So,
<!-- the ServiceLocator where we specify the remote services -->
<business:Services id="services" />
<!-- the FrontController, containing Commands specific to this appliation -->
<control:Controller id="controller" />
can yield to the problem that remote services are not defined when the
constructors of the commands in your FrontController run. This is why we
initialise business delegates in each command's execute method. Commands are
stateless anyway, and creating instance variables currently can have side
effects in this version of Cairngorm.
Best,
Alex
--
Alex Uhlmann
Software Engineer
iteration::two
-----Original Message-----
From: [email protected] [mailto:[EMAIL PROTECTED] Behalf Of flexcoding
Sent: 31 August 2005 22:19
To: [email protected]
Subject: [flexcoders] Re: CAIRNGORM 0.99 QUESTION
Hi,
Thanks for the reply. You must be a very experienced programmer
because you just looked at the suggestion and found the problem it
will create two steps down. I have experienced the same problem that
you mentioned below if I use recommended <mx:Application> tag
instead of <cairngorm:CairngormApplication> tag, but I had to spend
considerable time to nail down the cause, which I believe, and like
you said, is that the ServiceLocator.getInstance() is failing
because it hasn't been initialized yet.
1. How can I ensure that my services are created before my front
controller in the Index?
2. Does this approach of creating delegates in Command Constructor
has any advantage/disadvantage?
Thanks & Regards,
Rohit Chhabra.
--- In [email protected], "Daniel Harfleet"
<[EMAIL PROTECTED]> wrote:
> Hi,
>
> you would need to be carefull, because the command instances are
> created once only at creation of the FrontController. By creating a
> delegate instance, you are using the ServiceLocator to look up the
> remote object, however, if your service locator hasn't been
> initialized yet, you may get a no service found error. So make
sure
> your services are created before you front controller if you are
going
> to take this approach.
>
>
>
> --- In [email protected], "flexcoding" <[EMAIL PROTECTED]>
wrote:
> > Is it OK to have a constructor in the Command classes and have
> > delegate initialized there rather than doing it in every time
> > execute method is called?
> >
> > So Could the code of LoginCommand of sample code that came with
> > CAIRNGORM 0.99 be changed to:
> >
> > class org.nevis.cairngorm.samples.login.commands.LoginCommand
> > implements Command, Responder
> > {
> > private var delegate: CustomerDelegate;
> >
> > public function LoginCommand ()
> > {
> > delegate = new CustomerDelegate( this );
> > }
> >
> > public function execute( event:Event ) : Void
> > {
> > var loginVO : LoginVO = LoginVO( event.data );
> > delegate.login( loginVO );
> > }
> >
> > //---------------------------------------------------------------
----
> > ------
> >
> > public function onResult( event : Object ) : Void
> > {
> > ModelLocator.workflowState =
> > ModelLocator.VIEWING_LOGGED_IN_SCREEN;
> >
> > var loginDate : Date = Date( event.result );
> > ModelLocator.loginDate = loginDate;
> > }
> >
> > //---------------------------------------------------------------
----
> > ------
> >
> > public function onFault( event : Object ) : Void
> > {
> > ModelLocator.statusMessage = "Your username or password
was
> > wrong, please try again.";
> > }
> > }
> >
> > from
> >
> > /*
> >
> > Copyright 2005 iteration::two Ltd
> >
> > Licensed under the Apache License, Version 2.0 (the "License");
> > you may not use this file except in compliance with the License.
> > You may obtain a copy of the License at
> >
> > http://www.apache.org/licenses/LICENSE-2.0
> >
> > Unless required by applicable law or agreed to in writing,
software
> > distributed under the License is distributed on an "AS IS" BASIS,
> > WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
> > implied.
> > See the License for the specific language governing permissions
and
> > limitations under the License.
> >
> > @ignore
> > */
> > import org.nevis.cairngorm.business.Responder;
> > import org.nevis.cairngorm.commands.Command;
> > import org.nevis.cairngorm.control.Event;
> > import
org.nevis.cairngorm.samples.login.business.CustomerDelegate;
> > import org.nevis.cairngorm.samples.login.vo.LoginVO;
> > import org.nevis.cairngorm.samples.login.model.ModelLocator;
> >
> > /**
> > * @version $Revision: 1.4 $
> > */
> > class org.nevis.cairngorm.samples.login.commands.LoginCommand
> > implements Command, Responder
> > {
> >
> > public function execute( event:Event ) : Void
> > {
> > var delegate: CustomerDelegate = new CustomerDelegate(
> > this );
> > var loginVO : LoginVO = LoginVO( event.data );
> > delegate.login( loginVO );
> > }
> >
> > //---------------------------------------------------------------
----
> > ------
> >
> > public function onResult( event : Object ) : Void
> > {
> > ModelLocator.workflowState =
> > ModelLocator.VIEWING_LOGGED_IN_SCREEN;
> >
> > var loginDate : Date = Date( event.result );
> > ModelLocator.loginDate = loginDate;
> > }
> >
> > //---------------------------------------------------------------
----
> > ------
> >
> > public function onFault( event : Object ) : Void
> > {
> > ModelLocator.statusMessage = "Your username or password
was
> > wrong, please try again.";
> > }
> > }
--
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