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• Design pattern suggestion

  - by Avinash

  Following is the problem statement. There are n numbers of match strings, If event A occurs and then in certain period of time event B occurs then I do not raise alarm. but if B do not occurs then i have to raise alarm. There can be multiple chain of events which defines whether to raise alarm or not.

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• Database design -- does it respect 3rd NF?

  - by Flavius

  Hi I have the following relations (tables) in a relational model Person person_id, first_name, last_name, address Student person_id, matr_nr Teacher person_id, salary Lecture lecture_id, lect_name, lect_description Attendees lecture_id, person_id, date I'm wondering about the functional dependencies of Student and Teacher. Do these tables respect the 3rd normal form? Which should be the primary keys of these tables?

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• Design best practice - best way to handle user selection

  - by user1457227

  I'm an experienced developer (WPF) moving over to Android development. My question: an app I am developing allows the user to browse their local storage (such as SDCARD) and select a file. Now, should I simply create a new Activity (after the user has made a selection) to handle what I want to have the app do with that chosen file, -or- is the better approach to pass the path/name of the selected file back to the main Activity and let IT launch the next Activity? In other words, is the better practice to have the main Activity launch other (support) activities, or is it perfectly ok and normal to have one activity chain to another and on and on? Thanks!

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• Design pattern: Polymorphism for list of objects

  - by ziang

  Suppose I have a class A, and A1, A2 inherits from A. There are 2 functions: List<A1> getListA1(){...} List<A2> getListA2(){...} Now I want to do something similar to both A1 and A2 in another function public void process(List<A>){...} If I want to pass the instance of either ListA1 or ListA2, of course the types doesn't match because the compiler doesn't allow the coercion from List< A1 to List< A. I can't do something like this: List<A1> listA1 = getListA1(); List<A> newList = (List<A>)listA1; //this is not allowed. So what is the best approach to the process()? Is there any way to do it in a universal way rather than write the similar code to both List and List?

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• Best Design Pattern to Implement while Mapping Actions in MVC

  - by FidEliO

  What could be the best practices of writing the following case: We have a controller which based on what paths users take, take different actions. For example: if user chooses the path /path1/hello it will say hello. If a user chooses /path1/bye?name="Philipp" it will invoke sayGoodBye() and etc. I have written a switch statement inside the controller which is simple, however IMO not efficient. What are the best way to implement this, considering that paths are generally String. private void takeAction() { switch (path[1]) { case "hello": //sayHello(); break; case "bye": //sayBye(); break; case "case3": //Blah(); break; ... } }

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• Database design: one huge table or separate tables?

  - by littlegreen

  Currently I am designing a database for use in our company. We are using SQL Server 2008. The database will hold data gathered from several customers. The goal of the database is to acquire aggregate benchmark numbers over several customers. Recently, I have become worried with the fact that one table in particular will be getting very big. Each customer has approximately 20.000.000 rows of data, and there will soon be 30 customers in the database (if not more). A lot of queries will be done on this table. I am already noticing performance issues and users being temporarily locked out. My question, will we be able to handle this table in the future, or is it better to split this table up into smaller tables for each customer?

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• Which design pattern fits - strategy makes sense ?

  - by user554833

  --Bump *One desperate try to get someone's attention I have a simple database table that stores list of users who have subscribed to folders either by email OR to show up on the site (only on the web UI). In the storage table this is controlled by a number(1 - show on site 2- by email). When I am showing in UI I need to show a checkbox next to each of folders for which the user has subscribed (both email & on site). There is a separate table which stores a set of default subscriptions which would apply to each user if user has not expressed his subscription. This is basically a folder ID and a virtual group name. But, Email subscriptions do not count for applying these default groups. So if no "on site" subscription apply default group. Thats the rule. How about a strategy pattern here (Pseudo code) Interface ISubscription public ArrayList GetSubscriptionData(Pass query object) Public class SubscriptionWithDefaultGroup Implement ArrayList GetSubscriptionData(Pass query object) Public class SubscriptionWithoutDefaultGroup Implement ArrayList GetSubscriptionData(Pass query object) Public class SubscriptionOnlyDefaultGroup Implement ArrayList GetSubscriptionData(Pass query object) does this even make sense? I would be more than glad for receive any criticism / help / notes. I am learning. Cheers

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• basic database design table on rails

  - by runcode

  I am confuse on a concept. I am doing this on rails. Is that Entity set equal to a table in the database? Is that Relationship set equal to a table in the database? Let say we have Entity set "USER" and Entity set "POST" and Entity set "COMMENT" User- can post many posts and comments as they want Post- belong to users Comments-belong to posts ,users, so comment is weak entity. SCHEMA ====== USER -id -name POST -id -user_id(FK) -comment_id (FK) COMMENT -id -user_id (FK) -post_id (FK) so USER,POST,COMMENT are tables I think. And what else is a table? And do I need a table for the relationship??

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• Decorator Design Pattern Use With Service Objects (wSingleton)

  - by Dustin

  I'm working on a project where I need to add some functionality to a service object and using a decorator to add it in seems like a good fit. However, I've only ever used decorators with simple beans, never on a singleton like a service object. Has anyone ever done this before and what are the pros and cons? In this case I don't think creating a subclass will work so a decorator seems to be a good fit. What are your thoughts on doing this?

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• [Design Pattern] Real cases you use Factory (method) pattern and the benefits

  - by Ricky

  Hi folks: Can you provide practices about leveraging Factory (method) pattern? And the benefit you got greatly. Thanks.

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• Database design to hold multiple iteration measurements

  - by Valder

  Hi All. I am new to sqlite and SQL in general. I am keen to switch from flat-files to sqlite for holding some measurement information. I need a tip on how to better layout the database, since I have zero experience with this. I have a ~10000 unique statistic counters that are collected before and after each test iteration. Max number of iterations are 10, though it could be less. I was thinking the following: CREATE TABLE stat_names(stat_id, stat_name); CREATE TABLE stats_per_iteration(stat_id, before_iter_1, after_iter_1, before_iter_2, after_iter_2, ...); stat_names table would hold mapping of a full counter to a uniq stat_id. stats_per_iteration table would hold mesurement data 1 + 10 * 2 columns. stat_names.stat_id = stats_per_iteration.stat_id OR maybe I should have a separate table for each iteration? Which would results in 1 + 10 tables in database. Thanks!

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• Policies Array Class-Design wrapper

  - by PT

  Hi, i want to write an wrapper for different Array Classes with different Policies. For example: typedef ArrayType<useValArray,StdAllocator> Array; // one global assignment I want to use the class like a blitz++ Array for example: Array<double,2> x(2,2); //maps the Array to an Valarray or to a Blitz++ Array Array<double,2> x2(5,6); is this Posible? Which technics i need to realise that?

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• UI Design - design pattern for city/country drop down? (ASP.NET MVC)

  - by JK

  What is the best way to do a city/country dropdown pair in ASP.NET MVC? I see lots of places with country above city, but that's unnatural: in real life we write city/country. I've used city, then country, but the problem is that the user then has to go backwards after changing the country. The other problem is what do you do about cities/countries not in your list? If city/country are both drop downs, then the user cant type their own city if it is missing. But if you have a dropdown and a textbox, that makes it unwieldy (you end up with 4 controls to enter 2 pieces of data). Are there any examples websites where the city/country dropdown pair are done in a very useable and clear manner?

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• sports league database design

  - by John

  Hello, I'm developing a database to store statistics for a sports league. I'd like to show several tables: - league table that indicates the position of the team in the current and previous fixture - table that shows the position of a team in every fixture in the championship I have a matches table: Matches (IdMatch, IdTeam1, IdTeam2, GoalsTeam1, GoalsTeam2) Whith this table I can calculate the total points of every team based on the matches the team played. But every time I want to show the league table I have to calculate the points. Also I have a problem to calculate in which position classified a team in the last 10 fixtures cause I have to make 10 queries. To store the league table for every fixture in a database table is another approach, but every time I change a match already played I have to recalculate every fixture from there... Is there a better approach for this problem? Thanks

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• database design help for game / user levels / progress

  - by sprugman

  Sorry this got long and all prose-y. I'm creating my first truly gamified web app and could use some help thinking about how to structure the data. The Set-up Users need to accomplish tasks in each of several categories before they can move up a level. I've got my Users, Tasks, and Categories tables, and a UserTasks table which joins the three. ("User 3 has added Task 42 in Category 8. Now they've completed it.") That's all fine and working wonderfully. The Challenge I'm not sure of the best way to track the progress in the individual categories toward each level. The "business" rules are: You have to achieve a certain number of points in each category to move up. If you get the number of points needed in Cat 8, but still have other work to do to complete the level, any new Cat 8 points count toward your overall score, but don't "roll over" into the next level. The number of Categories is small (five currently) and unlikely to change often, but by no means absolutely fixed. The number of points needed to level-up will vary per level, probably by a formula, or perhaps a lookup table. So the challenge is to track each user's progress toward the next level in each category. I've thought of a few potential approaches: Possible Solutions Add a column to the users table for each category and reset them all to zero each time a user levels-up. Have a separate UserProgress table with a row for each category for each user and the number of points they have. (Basically a Many-to-Many version of #1.) Add a userLevel column to the UserTasks table and use that to derive their progress with some kind of SUM statement. Their current level will be a simple int in the User table. Pros & Cons (1) seems like by far the most straightforward, but it's also the least flexible. Perhaps I could use a naming convention based on the category ids to help overcome some of that. (With code like "select cats; for each cat, get the value from Users.progress_{cat.id}.") It's also the one where I lose the most data -- I won't know which points counted toward leveling up. I don't have a need in mind for that, so maybe I don't care about that. (2) seems complicated: every time I add or subtract a user or a category, I have to maintain the other table. I foresee synchronization challenges. (3) Is somewhere in between -- cleaner than #2, but less intuitive than #1. In order to find out where a user is, I'd have mildly complex SQL like: SELECT categoryId, SUM(points) from UserTasks WHERE userId={user.id} & countsTowardLevel={user.level} groupBy categoryId Hmm... that doesn't seem so bad. I think I'm talking myself into #3 here, but would love any input, advice or other ideas.

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• Help Desk Database Design

  - by user237244

  The company I work at has very specific and unique needs for a help desk system, so none of the open source systems will work for us. That being the case, I created a custom system using PHP and MySQL. It's far from perfect, but it's infinitely better than the last system they were using; trust me! It meets most of our needs quite nicely, but I have a question about the way I have the database set up. Here are the main tables: ClosedTickets ClosedTicketSolutions Locations OpenTickets OpenTicketSolutions Statuses Technicians When a user submits a help request, it goes in the "OpenTickets" table. As the technicians work on the problem, they submit entries with a description of what they've done. These entries go in the "OpenTicketSolutions" table. When the problem has been resolved, the last technician to work on the problem closes the ticket and it gets moved to the "ClosedTickets" table. All of the solution entries get moved to the "ClosedTicketSolutions" table as well. The other tables (Locations, Statuses, and Technicians) exist as a means of normalization (each location, status, and technician has an ID which is referenced). The problem I'm having now is this: When I want to view a list of all the open tickets, the SQL statement is somewhat complicated because I have to left join the "Locations", "Statuses", and "Technicians" tables. Fields from various tables need to be searchable as well. Check out how complicated the SQL statement is to search closed tickets for tickets submitted by anybody with a first name containing "John": SELECT ClosedTickets.*, date_format(ClosedTickets.EntryDate, '%c/%e/%y %l:%i %p') AS Formatted_Date, date_format(ClosedDate, '%c/%e/%y %l:%i %p') AS Formatted_ClosedDate, Concat(Technicians.LastName, ', ', Technicians.FirstName) AS TechFullName, Locations.LocationName, date_format(ClosedTicketSolutions.EntryDate, '%c/%e/%y') AS Formatted_Solution_EntryDate, ClosedTicketSolutions.HoursSpent AS SolutionHoursSpent, ClosedTicketSolutions.Tech_ID AS SolutionTech_ID, ClosedTicketSolutions.EntryText FROM ClosedTickets LEFT JOIN Technicians ON ClosedTickets.Tech_ID = Technicians.Tech_ID LEFT JOIN Locations ON ClosedTickets.Location_ID = Locations.Location_ID LEFT JOIN ClosedTicketSolutions ON ClosedTickets.TicketNum = ClosedTicketSolutions.TicketNum WHERE (ClosedTickets.FirstName LIKE '%John%') ORDER BY ClosedDate Desc, ClosedTicketSolutions.EntryDate, ClosedTicketSolutions.Entry_ID One thing that I'm not able to do right now is search both open and closed tickets at the same time. I don't think a union would work in my case. So I'm wondering if I should store the open and closed tickets in the same table and just have a field indicating whether or not the ticket is closed. The only problem I can forsee is that we have so many closed tickets already (nearly 30,000) so the whole system might perform slowly. Would it be a bad idea to combine the open and closed tickets?

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• What Design Pattern To Replace 'CurrentStep' Variable

  - by Rob P.

  Tried to search but didn't know how to phrase it. I've got some code that is essentially... Private CurMajorStep as Integer = 0 Private CurMinorStep as Integer = 0 Public Sub PerformNextStep() Select Case iMajorStep Case 0 ThingOne() Case 1 ThingTwo() Case 2 ThingThree() Case 3 ThingFour() Case 4 AnythingElse() Case 5 Finish() End Select End Sub And then, in some of those, the CurMinorStep keeps track of the current state of that particular 'step'. I hope that all makes sense. The code is messy and I know it's going to be problematic to maintain. Can someone point me to a clean OO pattern to handle this?

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• Data access layer design

  - by Sam

  I have a web app and a console application accessing a db. The db has 2 tables (A, B) one of which (A) is specific to the web app. When writing a data access layer, what is the best way to do it? Technically data access layer should provide access to all the data accessible. In doing so, methods to interact with A are exposed to the console application if we have single access layer. Does creating 2 access layers to 2 table in the same database makes any sense? What is a good way to do it?

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• Database Design Question

  - by Soo

  Ok SO, I have a user table and want to define groups of users together. The best solution I have for this is to create three database tables as follows: UserTable user_id user_name UserGroupLink group_id member_id GroupInfo group_id group_name This method keeps the member and group information separate. This is just my way of thinking. Is there a better way to do this? Also, what is a good naming convention for tables that link two other tables?

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• C++: How to design a utility class?

  - by Martijn Courteaux

  Hi, The title says it all. But I don't know if I should go for static methods, just a header, a class, or something else? What would be best practice? But, I don't want to have an instance of a utility class. I want to add functions like: Uint32 MapRGB (int r, int g, int b); const char* CopyString(const char* char); // etc. You know: utility methods...

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• View Mobile Websites in Windows with Safari 4 Developer Tools

  - by Matthew Guay

  Want to try out mobile websites designed for the iPhone and other mobile devices on your PC?  Safari 4 for Windows lets you do this easily with their developer tools. By default, Safari will show standard desktop websites.  But by making a simple change, you can switch it to work like Safari Mobile on the iPhone or iPod Touch. Getting Started First make sure you have Safari 4 for Windows installed.  You can download Safari directly (link below) and install it as usual.   Or if you already have another Apple program installed, such as QuickTime or iTunes, then you can install it from Apple Software update.  Simply enter apple software update in the Start menu search box. And then select Safari 4 from the list of new software available.  Click Install to automatically download and install Safari. Accept the license Agreement, and then Safari will automatically install. Once this is finished, Safari will be ready to use. View Mobile Sites in Safari First, we need to enable the developer tools.  Click the gear icon on the toolbar, and select Preferences. Click the Advanced tab, and then check the box that says “Show Develop menu in menu bar”. Once you’ve closed your settings box, click the page icon, select Develop, then User Agent, and then choose one of the Mobile Safari settings.  In our test we chose Mobile Safari 3.1.2 – iPhone. To make your browser emulate a mobile device better, you can hide the bookmarks and tab bar to have a more streamlined interface. Click the Gear icon, and select “Hide Bookmarks Bar”, and then repeat and click “Hide Tab Bar”. You can also shrink your window to be closer to the size of a mobile device screen.  Once you’ve done these things, Safari should look similar to this screenshot.  Here we have loaded Google.com, and you can see it in its iPhone-style interface. Simply enter any website into the address bar, and it will load in its mobile interface if it has one.  Here is Google’s other mobile offerings, right inside Windows. Gmail loads messages with the default iPhone interface. One especially interesting mobile site is Apple’s online iPhone User Guide.  When loaded in Safari with the iPhone setting, it loads with a very nice mobile UI that works just like an iPhone app.  In fact, you can even click and drag to scroll, just like you would with your finger on an iPhone. Conclusion Even if you do not have a Smartphone, you can still preview what websites will look like on them with this trick. Not all sites will work of course, but it’s fun to play around with different sites that have mobile versions. Links: Safari 4 Download Apple iPhone online user guide Similar Articles Productive Geek Tips Make Safari Stop Crashing Every 20 Seconds on Windows VistaCustomize Safari for Windows ToolbarSave Screen Space by Hiding the Bookmarks Toolbar in Safari for WindowsEdit Text in a Webpage with Internet Explorer 8Keep Websites From Using Tiny Fonts in Safari TouchFreeze Alternative in AutoHotkey The Icy Undertow Desktop Windows Home Server – Backup to LAN The Clear & Clean Desktop Use This Bookmarklet to Easily Get Albums Use AutoHotkey to Assign a Hotkey to a Specific Window Latest Software Reviews Tinyhacker Random Tips Revo Uninstaller Pro Registry Mechanic 9 for Windows PC Tools Internet Security Suite 2010 PCmover Professional Windows Media Player 12: Tweak Video & Sound with Playback Enhancements Own a cell phone, or does a cell phone own you? Make your Joomla & Drupal Sites Mobile with OSMOBI Integrate Twitter and Delicious and Make Life Easier Design Your Web Pages Using the Golden Ratio Worldwide Growth of the Internet

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• Logging WebSocket Frames using Chrome Developer Tools, Net-internals and Wireshark (TOTD #184)

  - by arungupta

  TOTD #183 explained how to build a WebSocket-driven application using GlassFish 4. This Tip Of The Day (TOTD) will explain how do view/debug on-the-wire messages, or frames as they are called in WebSocket parlance, over this upgraded connection. This blog will use the application built in TOTD #183. First of all, make sure you are using a browser that supports WebSocket. If you recall from TOTD #183 then WebSocket is combination of Protocol and JavaScript API. A browser supporting WebSocket, or not, means they understand your web pages with the WebSocket JavaScript. caniuse.com/websockets provide a current status of WebSocket support in different browsers. Most of the major browsers such as Chrome, Firefox, Safari already support WebSocket for the past few versions. As of this writing, IE still does not support WebSocket however its planned for a future release. Viewing WebSocket farmes require special settings because all the communication happens over an upgraded HTTP connection over a single TCP connection. If you are building your application using Java, then there are two common ways to debug WebSocket messages today. Other language libraries provide different mechanisms to log the messages. Lets get started! Chrome Developer Tools provide information about the initial handshake only. This can be viewed in the Network tab and selecting the endpoint hosting the WebSocket endpoint. You can also click on "WebSockets" on the bottom-right to show only the WebSocket endpoints. Click on "Frames" in the right panel to view the actual frames being exchanged between the client and server. The frames are not refreshed when new messages are sent or received. You need to refresh the panel by clicking on the endpoint again. To see more detailed information about the WebSocket frames, you need to type "chrome://net-internals" in a new tab. Click on "Sockets" in the left navigation bar and then on "View live sockets" to see the page. Select the box with the address to your WebSocket endpoint and see some basic information about connection and bytes exchanged between the client and the endpoint. Clicking on the blue text "source dependency ..." shows more details about the handshake. If you are interested in viewing the exact payload of WebSocket messages then you need a network sniffer. These tools are used to snoop network traffic and provide a lot more details about the raw messages exchanged over the network. However because they provide lot more information so they need to be configured in order to view the relevant information. Wireshark (nee Ethereal) is a pretty standard tool for sniffing network traffic and will be used here. For this blog purpose, we'll assume that the WebSocket endpoint is hosted on the local machine. These tools do allow to sniff traffic across the network though. Wireshark is quite a comprehensive tool and we'll capture traffic on the loopback address. Start wireshark, select "loopback" and click on "Start". By default, all traffic information on the loopback address is displayed. That includes tons of TCP protocol messages, applications running on your local machines (like GlassFish or Dropbox on mine), and many others. Specify "http" as the filter in the top-left. Invoke the application built in TOTD #183 and click on "Say Hello" button once. The output in wireshark looks like Here is a description of the messages exchanged: Message #4: Initial HTTP request of the JSP page Message #6: Response returning the JSP page Message #16: HTTP Upgrade request Message #18: Upgrade request accepted Message #20: Request favicon Message #22: Responding with favicon not found Message #24: Browser making a WebSocket request to the endpoint Message #26: WebSocket endpoint responding back You can also use Fiddler to debug your WebSocket messages. How are you viewing your WebSocket messages ? Here are some references for you: JSR 356: Java API for WebSocket - Specification (Early Draft) and Implementation (already integrated in GlassFish 4 promoted builds) TOTD #183 - Getting Started with WebSocket in GlassFish Subsequent blogs will discuss the following topics (not necessary in that order) ... Binary data as payload Custom payloads using encoder/decoder Error handling Interface-driven WebSocket endpoint Java client API Client and Server configuration Security Subprotocols Extensions Other topics from the API

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• Why represent shopping carts and order invoices differently in a domain model?

  - by Todd

  I've built some shopping cart systems in the past, but I always designed them such that the final order invoice is just a shopping cart that has been marked as "purchased". All the logic for adding/removing/changing items in a cart is also the logic for the order. All data is stored in the same tables in the database. But it seems this is not the proper way to design an e-commerce site.. Can someone explain the benefit of separating the shopping cart from invoices in the domain model? It seems to me this would lead to a lot of duplicated code, an extra set of tables in the database, and make it harder to maintain in the event the system need to start accommodating more complicated orders (like specifying selected options for an item which may or may not change the price/availability/shipping time of the order). I'm assuming I just haven't seen the light, as every book and other example I see seems to separate these two seemingly similar concerns -- but I can't find any explanation as to the benefit of doing such! It's also the case in the systems that I design that changes are often made after the initial order is confirmed. It's not uncommon for items to be removed, replaced, or added afterwards (but prior to fulfillment).

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• How should I handle expected errors? eg. "username already exists"

  - by Pheter

  I am struggling to understand how I should design the error handling parts of my code. I recently asked a similar question about how I should go about returning server error codes to the user, eg. 404 errors. I learnt that I should handle the error from within the current part of the application; seem's simple enough. However, what should I do when I can't handle the error from the current link in the chain? For example, I may have a class that is used to manage authentication. One of it's methods could be createUser($username, $password). Within that function, I need to determine if the username already exists. If this is true, how should I alert the calling code about this? Returning null instead of a user object is one way. But how do I then know what caused the error? How should I handle errors in such a way that calling code can easily find out what caused the error? Is there a design pattern commonly used for this kind of situation?

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• What's the "correct way" to organize this project?

  - by user571747

  I'm working on a project that allows multiple users to submit large data files and perform operations on them. The "backend" which performs these operations is written in Perl while the "frontend" uses PHP to load HTML template files and determines which content to deliver. Data is stored in a database (MySQL, SQLite, Oracle) and while there is data which has not yet been acted upon, Perl adds it to a running queue which delivers data to other threads based on system load. In addition, there may be pre- and post-processing of the data before and after the main Perl script operates (the specifications are unclear) so I may want to allow these processors to be user-selectable plugins. I had been writing this project in a more procedural fashion but I am quickly realizing the benefit of separating concerns as to limit the scope one change has on the rest of the project. I'm quite unexperienced with design patterns and am curious what the best way to proceed is. I've heard MVC thrown around quite a bit but I am unsure of how to apply it. Specifically, what are some good options to structure this code (in terms of design patterns and folder hierarchy)? How can I achieve this with both PHP and Perl while minimizing duplicated code between languages? Should I keep my PHP files in the top level so I don't have ugly paths in the URL? Also, if I want to provide interchangeable databases, does each table need its own DAO implementation?

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