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• abstract method signature, inheritance, and "Do" naming convention

  - by T. Webster

  I'm learning about design patterns and in examples of code I've seen a convention where the abstract class declares a method, for example: public abstract class ServiceBase { ... public virtual object GetSomething(); and then protected abstract object DoGetSomething(); My question is on why these two methods exist, since they appear to serve the same purpose. Is this so that the base class GetSomething() method logic cannot be overridden by inherited classes? But then again, the method is marked virtual, so it can be overridden anyway. What is the usefulness here in requiring derived class implementers to implement the abstract method when the virtual method can be called anyway?

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• Build a JavaScript wrapper for a rails-generated XML API?

  - by Thor Thurn

  I am working with a large website written in Ruby on Rails. Thanks to the support for REST in Rails 2, the site's business logic is all accessible via a consistent XML API. Now I want to be able to easily write one or more JavaScript frontends to the site that interact with the generated Rails XML API. Ideally, an automated wrapper for the API could be created in JavaScript, since this would minimize the effort required in writing XML processing code for the more than 500 API functions. How, then, can I automatically generate a wrapper around a given XML API in JavaScript so that it's more pleasant to work with? I've worked with solutions of this nature for Java that generate classes and methods to wrap an API, so my current thinking is that I want something of that nature for JavaScript. I'd be open to an alternative take on the problem, though.

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• Detecting/Repairing NSConnection failure

  - by anthony

  I would like to use NSConnection/NSDistributedObject for interprocess communication. I would like the client to be able to handle the case where the server is only occasionally reachable. How can I determine if sending a message to the NSConnection will fail or has failed? Currently if my server (the process that has vended the remote object) dies, the client will crash if it sends a selector to the remote object. Ideally I'd like to have a wrapper for the remote object that can lazily instantiate (or reinstantiate) the connection, and return a default value in the case where the connection could not be instantiated, or the connection has failed. I don't really know the correct way to do this using objective c. Here's some pseudocode representing this logic: if myConnection is null: instantiate myConnection if MyConnection is null: return defaultValue try return [myConnection someMethod] catch myConnection = null return defaultValue

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• Why acegi (Spring Security) converts password to uppercase before comparing ?

  - by Tony

  One of my colleague in QA team reported a bug to me, the bug said that can't change password to lowercase, otherwise login is rejected,using number or uppercase is all fine. The login system was implemented using acegi 1.0 (now called Spring Security). This was a very strange bug,changing password is done by encrypting the user input string into MD5 string, I implemented this without using anything related acegi, I don't if the is the origin cause of the problem. When the login is rejected, through debugging, I find that, the user input is converted into uppercase by acegi when passing to the acegi comparing logic. At first, I didn't believe this, when I checkout the acegi source and debugging with it, I find it does convert both username and password to uppercase (source code line 121), Can you tell me why it does this? This can cause password encoding mismatch!

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• net c# lock statement in data access layer

  - by Pedro Rivera

  I saw a code where they have the data access layer like this: public class CustomerDA{ private static readonly object _sync = new object(); private static readonly CustomerDA _mutex = new CustomerDA(); private CustomerDA(){ } public CustomerDA GetInstance(){ lock(_sync){ return _mutex; } } public DataSet GetCustomers(){ //database SELECT //return a DataSet } public int UpdateCustomer(some parameters){ //update some user } } public class CustomerBO{ public DataSet GetCustomers(){ //some bussiness logic return CustomerDA.GetInstance().GetCustomers(); } } I was using it, but start thinking... "and what if had to build a facebook like application where there are hundreds of thousands of concurrent users? would I be blocking each user from doing his things until the previous user ends his database stuff? and for the Update method, is it useful to LOCK THREADS in the app when database engines already manage concurrency at database server level?" Then I started to think about moving the lock to the GetCustomers and UpdateCustomer methods, but think again: "is it useful at all?"

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• When to use POJO and When to use SLSB

  - by user83795

  we are using EJB3 in our application. Our design aim is to separate persistence layer from Business Layer. So we have developed XXXbean classes to be used as SLSB and XXXRepository classes to be used as persistence classes. We also have POJO that implement reusable NON business logic(get list of countries etc) and we call then service/helper Classes. We use EJB3 JPA (using Hibernate provider) and Repository classes has all the methods for CRUD operation and the get methods for data access. Currently XXXRepository classes are all POJO and we instantiate these classes directly from the bean XXXClasses or from the service Objects. Should the XXXRepository classes be SLSB ? what would be the benefits and pitfalls of converting them to SLSB?

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• How are dll's loaded by the CLR?

  - by priehl

  My assumption was always that the CLR loaded all of the dlls it needed on startup of the app domain. However, I've written an example that makes me question this assumption. I start up my application and check to see how many modules are loaded. Process[] ObjModulesList; ProcessModuleCollection ObjModulesOrig; //Get all modules inside the process ObjModulesList = Process.GetProcessesByName("MyProcessName"); // Populate the module collection. ObjModulesOrig = ObjModulesList[0].Modules; Console.WriteLine(ObjModulesOrig.Count.ToString()); I then repeate the exact same code and my count is different. The additional dll is C:\WINNT\system32\version.dll. I'm really confused as to why the counts would be different. Could someone please elaborate on what the clr is doing and how it's loading these thing, and by what logic it's doing so?

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• Which design pattern should I be using?

  - by Gabriel

  Here's briefly what I'm trying to do. The user supplies me with a link to a photo from one of several photo-sharing websites (such as Flickr, Zooomr, et. al). I then do some processing on the photo using their respective APIs. Right now, I'm only implementing one service, but I will most likely add more in the near future. I don't want to have a bunch of if/else or switch statements to define the logic for the different websites (but maybe that's necessary?) I'd rather just call GetImage(url) and have it get me the image from whatever service the url's domain is from. I'm confused how the GetImage function and classes should be designed. Maybe I need the strategy pattern? I'm still reading and trying to understand the various design patterns and how I could make one fit in this case. I'm doing this in C#, but this question is language-agnostic.

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• What class should manage/control the CALayers in my view using proper MVC?

  - by wanderlust

  I have a ViewController with a view (UIView). I need to handle touches, run some logic, check against model data, and and add and remove sublayers to the view based on those touches. Then I need to update the model based on the results. Should I have: ViewController - manage touches, get/set model data, add/remove sublayers UIView CALayer Sublayers or Controller (NSObject) - get/set data ViewController - manage touches, add/remove sublayers UIView CALayer Sublayers or Controller (NSObject) - get/set data CustomView - manage touches, add/remove sublayers CALayer Sublayers Or is it something else all together? No matter what I try, it "feels" awkward. SVN is my friend. Can you guys help a girl (with architectural issues) out?

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• ASP.NET handling button click event before OnPreInit

  - by Phillykins

  Hello, I have a data access layer, a business logic layer and a presentation layer (ie. the pages themselves). I handle the OnPreInit event and populate collections required for the page. All the data comes from an SQL server database and I do not use caching. I handle a button click event to grab values from a form and insert a new object into the database. The problem is that by the time I handle the click event, the collections have already been populated, so the new item which has been inserted into the database has not been retrieved. What is the accepted solution to this? I could insert the new object directly into the collection and re-bind the GridView, but the SQL query selects only a set of objects and the new object could fall outside of this set. Thanks!

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• rails, rest, render different action with responds to

  - by Sam

  Maybe my logic is not restful or know if this is how you would do it but this is what I am trying to do. I'm getting a category inside a category controller and then once I get that category I want to return to an index page in a different controller but keep that @category and the Category.busineses. Before rest I would have just done this: render :controller = "businesses" and it would have rendered the view of the index action in that controller. now in my respond_to block I have this format.html {redirect_to(business_path)} # index.html.erb format.xml { render :xml => @businesses } but of course with a render it looses the instance variable and starts with a new action. So what I want to do is render the action instead of redirecting to that action. is this possible?

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• [C#] Async threaded tcp server

  - by mark_dj

  I want to create a high performance server in C# which could take about ~10k clients. Now i started writing a TcpServer with C# and for each client-connection i open a new thread. I also use one thread to accept the connections. So far so good, works fine. The server has to deserialize AMF incoming objects do some logic ( like saving the position of a player ) and send some object back ( serializing objects ). I am not worried about the serializing/deserializing part atm. My main concern is that I will have a lot of threads with 10k clients and i've read somewhere that an OS can only hold like a few hunderd threads. Are there any sources/articles available on writing a decent async threaded server ? Are there other possibilties or will 10k threads work fine ? I've looked on google, but i couldn't find much info about design patterns or ways which explain it clearly

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• Service Layer Pattern - Could we avoid the service layer on a specific case?

  - by lidermin

  Hi, we are trying to implement an application using the Service Layer Pattern cause our application needs to connect to other multiple applications too, and googling on the web, we found this link of a demonstrative graphic for the "right" way of apply the pattern: martinfowler.com - Service Layer Pattern But now we have a question: what if our system needs to implement some business logic, only for our application (like some maintenance data for the system itself) that we don't need to share with other systems. Based on this graphic: As it seems, it will be unnecesary to implement a service layer just for that; it will be more practical to avoid the service layer, and just go from User Interface to the Business Layer (for example). What should be the right way in this case to implement the Service Layer Pattern? What do you suggest us for a scenario like the one I told you? Thanks in advance.

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• MySQL triggers cannot update rows in same table the trigger is assigned to. Suggested workaround?

  - by Cory House

  MySQL doesn't currently support updating rows in the same table the trigger is assigned to since the call could become recursive. Does anyone have suggestions on a good workaround/alternative? Right now my plan is to call a stored procedure that performs the logic I really wanted in a trigger, but I'd love to hear how others have gotten around this limitation. Edit: A little more background as requested. I have a table that stores product attribute assignments. When a new parent product record is inserted, I'd like the trigger to perform a corresponding insert in the same table for each child record. This denormalization is necessary for performance. MySQL doesn't support this and throws: Can't update table 'mytable' in stored function/trigger because it is already used by statement which invoked this stored function/trigger. A long discussion on the issue on the MySQL forums basically lead to: Use a stored proc, which is what I went with for now. Thanks in advance!

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• How to set the content of the $script_for_layout in cakephp?

  - by sipiatti

  Hi, I am learning cakephp in an autodidact manner and I am a complete newbie :) I am creating a simple application. Some logic work so now I going to dive into designing views and layouts. I read the docs and the tutorial but I could not find where to set the content of $script_for_layout. Especially I want to set a $html-css to create link in pages to the stylesheet. I found out that I could do it in directly in the layout template but I would like to create the same link in all pages/views/layouts to the stylesheet so I hope there is a simple way, and avoid to do this in all layouts and/or controllers

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• Missunderstanding js variables

  - by meo

  I have a little problem: slideHelpers.total = 4 for (i=1;i <= slideHelpers.total; i++) { $('<a href="#">' + i + '</a>').bind('click', function(){ alert('go to the ' + i + ' slide')}).appendTo('.slideaccess') } the alert gives out 5 what is logic, because when the function click triggers i is actually 5. But i would like to have the same i as in my <a> tag. What is the best way to handle this? I could put i in the data() of the <a> tag for example but i am sure there is a easier way.

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• Upper Bound in FOR loop does not get altered in loop,Why?

  - by Vineet

  Hi ALL, I am trying to change the value of upper bound in For loop ,but the Loop is running till the upper bound which was defined in the starting. According to logic loop should go infinite, since value of v_num is always one ahead of i,But loop is executing three time.Please explain This is the code DECLARE v_num number:=3; BEGIN FOR i IN 1..v_num LOOP v_num:=v_num+1; DBMS_OUTPUT.PUT_LINE(i ||' '||v_num); END LOOP; END; Ouput Coming 1 4 2 5 3 6

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• GUI designers! - got suggestions for a GUI modelling diagram language?

  - by naugtur

  Refering to this question I asked a while ago: UI functionality modeling languages It looks like there is no good-enough solution. I decided to develop one. (and prepare a set of elements for DIA or something) I'm sure it will require a good insight in peoples' experiences and problems in designing functionally complicated GUIs. I've got some ideas already, but I'd like to hear from You what You'd expect from a GUI functionality modelling language. Clarification: It's functionality modelling, so it's not about where I put a button. It's about objects that have some events binded, and the interface behaviour logic. If You think (just as I do) that UML is far from useful for such purposes - feel free to put Your expectations here. I'll try to meet them. ( not necessarily in person;) ) Remember - there is no such thing as a wrong answer to this question

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• Small methods - Small sprocs

  - by Berlioz

  Uncle Bob recommends having small methods. Do stored procedures have an ideal size? Or can they run on for 100's and 100's of lines long? Also does anyone have anything to say about where to place business logic. If located in stored procedures, the database is being used as data processing tier. If you read Adam Machanic, his bias is toward the database, does that imply long stored procedures that only the author of the sproc understands, leaving maintainers to deal with the mess? I guess there is two inter-related questions, somehow. Thanks in advance for responding to a fuzzy question(s).

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• mysql: select ... where id = any value. is it possible?

  - by Syom

  look at this table please table |id| |name| |order| i must get the rows, where name = something and order = somevalue so i write select `id` from `table` where `name` = 'something' and `order` = 'somevalue' but depend on php logic, sometimes i need to get all rows, where name = somethimg, independently of order value. i don't want to change the query structure, because in practise there are many number of fields, and possible count of queries will became very big. so i want to save the structure of query, and when i need to select just by name, i want to write something like this select `id` from `table` where `name` = 'something' and `order` = any value is it possible? maybe the question is incomprehensible, at least i tried;) sorry for bad english thanks

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• Calling UITableViews delegate methods directly.

  - by RickiG

  Hi I was looking for a way to call the edit method directly. - (void)tableView:(UITableView *)theTableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath I have all my logic for animating manipulated cells, removing from my model array etc. in this method. It is getting called when a user swipes, adds or rearranges, but I would like to call it manually/directly as a background thread changes my model. I have constructed an NSIndexPath like so: NSIndexPath *path = [NSIndexPath indexPathForRow:i inSection:1]; I just can't figure out how to call something like: [self.tableview commitEditingStyle:UITableViewCellEditingStyleDelete forRowAtIndexPath:path]; Do I need to gain access to the methods of this plain style UITableView in another way? Thanks:)

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• What is the best way to interoperably serialize a message?

  - by iwein

  I'm considering message serialization support for spring-integration. This would be useful for various wire level transports to implement guaranteed delivery, but also to allow interoperability with other messaging systems (e.g. through AMQP). The fundamental problem that arises is that a message containing Java object in it's payload and headers should be converted to a byte[] and/or written to a stream. Java's own serialization is clearly not going to cut it because that is not interoperable. My preference would be to create an interface that allows the user to implement the needed logic for all Objects that take part in serialization. Is this a sensible idea and what would the interface look like? Is there a standard interoperable way to serialize Objects that would make sense in this context?

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• Testing a (big) collection retrieved from a db

  - by Bas

  I'm currently doing integration testing on a live database and I have the following sql statement: var date = DateTime.Parse("01-01-2010 20:30:00"); var result = datacontext.Repository<IObject>().Where(r => r.DateTime > date).First(); Assert.IsFalse(result.Finished); I need to test if the results retrieved from the statement, where the given date is less then the date of the object, have Finished set to False. I do not know how many results I get back and currently I'm getting the first object of the list and check if that object has Finished set to false. I know testing only the first item of the list is not valid testing, as a solution for that I could iterate through the list and check all items on Finished, but putting logic in a Test is kinda going against the concept of writing 'good' tests. So my question is: Does anyone have a good solution of how to properly test the results of this list?

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• Is JavaFx suitable for creating online multiplayer board/card games?

  - by Piniu

  In JavaFx i can easy create animations, moving pieces etc., but as far as i see there is better to write program logic and communication in java. Worst i see at the moment is calling javafx part as a result of data incoming from server. Is there any convenient way to do it or its better to change to other technology (flex, qt?) assuming it is not important if program will run in browser or outside as a standalone application? I just started to learn javafx but can drop it and move to other technology and consider c++ + wxWidgets or Qt which im more comforatable with.

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• How to manually manage Core Data relationships when deleting

  - by Simon

  I have a Core Data entity, which contains a relationship to another entity. Under certain circumstances, I need to delete the managed objects in the relationship, and at other times no action needs to be taken. I have the Delete Rule on the entity is No Action because of this manual management. The problem I have is, where is the best place to enforce these rules? I cannot see any suitable messages to override on NSManagedObject (something that might notify the object it has been deleted and should clear up its relationships). I would rather not do it higher up in the application logic, because the entity objects can get deleted from array controllers and at different points in the applications, making it necessary to stuff relationship update code at all those levels.

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