Confusion about observer design pattern

Hi all,
I have a case related to observer design pattern and I feel a bit confusion.
Suppose there is a gui class which consists of 2 buttons connect and disconnect to the network and a socket class handling these two operations. Then socket class will inform the gui class if the operation is success or not. By applying the observer design pattern. gui class is observer and socket class is obserable. however I feel confusion as observer will send a command e.g. connect to observable.

dophine wrote:
my confusion is that the observer is the event source not the listernerIt is an observer but it also takes another role: the controller of the observable.
kind regards,
Jos

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Observer Design Pattern: Looking for redesign ABAP OO code example

Hello folks,
I am looking for an example for ABAP OO code that has been redesigned by applying the Observer Design Pattern. I would be very interested in both the code before as well as the code after the pattern is being applied.
Thanks in advance and kind regards, Alex

Observer can be implemented using the EVENTS.
I had recently implemented the observer at one of my client's place. I had screen with so many ALVs. One ALV was kind of editable and other were just showing the information of the current row as well as some total information. So, initially I started with the Main ALV and SUB(1 and 2) for other ALVs. Now, when I need to refresh my ALVs based on the main ALV data, I had to explicitly update the data of the each Sub ALV. The code was kind of static and requirement was not yet fixed.
Later on we need to add one more ALV on the same screen. It was easy to change the existing method where I was doing the explicit refresh of each ALV. But I thought of using the Events.
I created an event REFRESH_DETAILS for main ALV. so, when data gets changed (which I was catching by DATA_CHANGED event of ALV), I raise the event.
RAISE EVENT REFRESH_DETAILS
exporting new_data = it_Data.
In Sub ALVs, I created the event handler method to handle the event REFRESH_DETAILS of the main ALV.
methods: handle_refresh_details
for event REFRESH_DETAILS of ZCL_MAIN_ALV.
I also had to register the Handler.
SET HANDLER me->handle_refresh_details FOR ALL INSTANCES.
I'll soon write a post on my [ABAP Help blog|http://help-abap.zevolving.com/] with all the details.
Regards,
Naimesh Patel

When I use SmartSync Notifier/ Observer design pattern

Hi all,
I have development a simple SmartSync Application with S01 syncBO type.
I not use SmartSync Notifier/ Observer design pattern for read the local syncbo and local delta.
When I have to use and I have to implement the SmartSync Notifier/ Observer design pattern ?

Hi Rocco,
<b>SmartSync uses Notifier/Observer design pattern for applications to access inbox/outbox. Application has a read-access to the passed SyncBoOutDelta instance during the notification</b>
The usage of this API depending upon your custom requirement. If u want to monitor the number of new records(for example sales or like thAT) u have created in the client device , then that delta records will be there in the Smart Sync Outbox. If u want to monitor this new records then u have to use the API related with (Outbox - SyncBoOutDelta)..
Then comes the Inbox.The new records came from the Server will be there in the inbox of the MI client. This new records may be the response of number of new records u ahve created in the client device . If u want to monitor the number of new records that has downloaded to the MI client , then u have to make use of the SmartSyncInboxDelta..
Using this APIs , u can also find out the errors happened during the particular synchronization. For this APIs are also available...
refer these helps also..
SyncBoChange
This interface is the base interface to describe SyncBo delta change. Application should not use the interface directly, instead, use its sub interfaces - SyncBoInDelta, SyncBoOutDelta.
http://media.sdn.sap.com/public/html/submitted_docs/MI/MDK_2.5/content/javadoc/com/sap/ip/me/api/smartsync/SyncBoChange.html
SyncBoInDelta
http://media.sdn.sap.com/public/html/submitted_docs/MI/MDK_2.5/content/javadoc/com/sap/ip/me/api/smartsync/SyncBoInDelta.html
SyncBoInDelta is used to apply SyncBo delta data from backend to client. The SyncBoInDelta could may be a delta data from either the backend or other devices, or a response to the previously uploaded SyncBoOutDelta from the client, which can be distinguisehd by the SyncReply information included within the SyncBoInDelta
SyncBoOutDelta
SmartSync uses Notifier/Observer design pattern for applications to access inbox/outbox. Application has a read-access to the passed SyncBoOutDelta instance during the notification
http://media.sdn.sap.com/public/html/submitted_docs/MI/MDK_2.5/content/javadoc/com/sap/ip/me/api/smartsync/SyncBoOutDelta.html
Regards
Kishor Gopinathan

Observer/Observable design pattern

Is there a way to implement the Observer/Observable pattern in a pure java FX 1.2 desktop Application?
And if yes how ? :)

You can use the real stuff, as shown in some threads (eg. in [Cannot bind a string array|http://forums.sun.com/thread.jspa?threadID=5425718] I show an example).
This is necessary only to bind Java variables to JavaFX code.
Now, as said above, in pure JavaFX code, you use binding. And the 'on replace' facility is useful too, as changes trigger actions.

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Hello,
I have read the available "How To", Using EJBs in Web Dynpro Applications where the author mentions that one should use a Command Bean (according to J2EE Design Patterns) so that one can invoke business methods in a Session Bean from our Web Dynpro Application. Well, although, I have read some available articles in the internet about J2EE design patterns, I still have some questions about command beans and its usage in Web Dynpro applications.
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King Regards

I have the same problem.
Does anyone know the solution?
Thanks
Davide

What is command design pattern? what is the problem that it solves?

Hi i have been reading few articles on command design pattern but was unable to understand what it is and what problem does it solve. As far as my understanding goes if there is a pre specified method in an object that could execute and perform the necessary activities then it is called as command design pattern. Why is it named as command design pattern, it is because in a shell we use commands to retrieve output. For example when we type "dir" in dos command prompt it returns the list of files. so here we have to remember a preexisting exe file named "dir" which does something when used. So here like we call it command because when "dir" is passed to the computers it returns something that is expected. may be the computer obeys the command issued and return something back. So like wise if there is a method that is defined as as the command, for example in struts framework the action class must have a method "execute()" which is called by the framework to execute the necessary action mapped to it. So if there is a predefined method like "execute" in struts then the object is said to be followed command design pattern. So what actually does it solve?
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See here for a longer version of this incident.

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bye for now
sat

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Try the Patterns and OO Design forum.

Design patterns,about value object ,how?why?could you give me a soluttion

design patterns,about value object ,how?why?could you give me a soluttion
use value object in ejb,thanks
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Hai
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Question about design pattern - business delegate: repost

hi guys
i have got a question to ask about the delegate pattern. usually, we use it to decouple between presentation client and businessservice tiers. for instance, the service tier has an session ejb, and delegate wrapps the ejb. and the web client calls delegate to access service. is the delegate only used by the presentation tier? within the service tier, we can have many ejbs that work together to get tasks done. do we still use delegates in the service tier? what is ur suggestion? thanks

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Confusion about observer design pattern

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