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  • XML Socket and Regular Socket in Flash/Flex does not send message immediately.

    - by kramer
    I am trying to build a basic RIA where my Flex application client opens an XML socket, sends the xml message "people_list" to server, and prints out the response. I have ruby at the server side and I have successfully set up the security policy stuff. The ruby xml server, successfully accepts the connections from Flex, successfully detects when they are closed and can also send messages to client. But; there is a problem... It cannot receive messages from flex client. The messages sent from flex client are queued and sent as one package when the socket is closed. Therefore, the whole wait-for-request-then-reply thing is not working... This is also -kinda- mentioned in the XMLSocket.send() document, where it is stated that the messages are sent async so; they may be delivered at any time in future. But; I need them to be synced, flushed or whatever. This is the server side code: require 'socket' require 'observer' class Network_Reader_Ops include Observable @@reader_listener_socket = UDPSocket.new @@reader_broadcast_socket = UDPSocket.new @@thread_id def initialize @@reader_broadcast_socket.setsockopt(Socket::SOL_SOCKET, Socket::SO_BROADCAST, 1) @@reader_broadcast_socket.setsockopt(Socket::SOL_SOCKET, Socket::SO_REUSEADDR, 1) @@reader_listener_socket.setsockopt(Socket::SOL_SOCKET, Socket::SO_REUSEADDR, 1) @@reader_broadcast_socket.bind('', 50050) @@reader_listener_socket.bind('', 50051) @@thread_id = Thread.start do loop do begin text, sender = @@reader_listener_socket.recvfrom_nonblock 1024 print("Knock response recived: ", text) notify_observers text rescue Errno::EAGAIN retry rescue Errno::EWOULDBLOCK retry end end end end def query @@reader_broadcast_socket.send("KNOCK KNOCK", 0, "255.255.255.255", 50050) end def stop Thread.kill @@thread_id end end class XMLSocket_Connection attr_accessor :connection_id def update (data) connection_id.write(data+"\0") end end begin # Set EOL for Flash $/ = '\x00' xml_socket = TCPServer.open('', '4444') security_policy_socket = TCPServer.open('', '843') xml_socket.setsockopt(Socket::SOL_SOCKET, Socket::SO_REUSEADDR, 1) security_policy_socket.setsockopt(Socket::SOL_SOCKET, Socket::SO_REUSEADDR, 1) a = Thread.start do network_ops = nil loop { accepted_connection = xml_socket.accept print(accepted_connection.peeraddr, " is accepted\n") while accepted_connection.gets incoming = $_.dump print("Received: ", incoming) if incoming == "<request>readers on network</request>" then network_ops = Network_Reader_Ops.new this_con = XMLSocket_Connection.new this_con.connection_id = accepted_connection network_ops.add_observer this_con network_ops.query end end if not network_ops.nil? then network_ops.delete_observer this_con network_ops.stop network_ops = nil end print(accepted_connection, " is gone\n") accepted_connection.close } end b = Thread.start do loop { accepted_connection = security_policy_socket.accept Thread.start do current_connection = accepted_connection while current_connection.gets if $_ =~ /.*policy\-file.*/i then current_connection.write("<cross-domain-policy><allow-access-from domain="*" to-ports="*" /></cross-domain-policy>\0") end end current_connection.close end } end a.join b.join rescue puts "FAILED" retry end And this is the flex/flash client side code: UPDATE: I have also tried using regular socket and calling flush() method but; the result was same. private var socket:XMLSocket = new XMLSocket(); protected function stopXMLSocket():void { socket.close(); } protected function startXMLSocket():void { socket.addEventListener(DataEvent.DATA, dataHandler); socket.connect(xmlSocketServer_address, xmlSocketServer_port); socket.send("<request>readers on network</request>"); } protected function dataHandler(event:DataEvent):void { mx.controls.Alert.show(event.data); } How do I achieve the described behaviour?

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  • How much abstraction is too much?

    - by Daniel Bingham
    In an Object Oriented Program: How much abstraction is too much? How much is just right? I have always been a nuts and bolts kind of guy. I understood the concept behind high levels of encapsulation and abstraction, but always felt instinctively that adding too much would just confuse the program. I always tried to shoot for an amount of abstraction that left no empty classes or layers. And where in doubt, instead of adding a new layer to the hierarchy, I would try and fit something into the existing layers. However, recently I've been encountering more highly abstracted systems. Systems where everything that could require a representation later in the hierarchy gets one up front. This leads to a lot of empty layers, which at first seems like bad design. However, on second thought I've come to realize that leaving those empty layers gives you more places to hook into in the future with out much refactoring. It leaves you greater ability to add new functionality on top of the old with out doing nearly as much work to adjust the old. The two risks of this seem to be that you could get the layers you need wrong. In this case one would wind up still needing to do substantial refactoring to extend the code and would still have a ton of never used layers. But depending on how much time you spend coming up with the initial abstractions, the chance of screwing it up, and the time that could be saved later if you get it right - it may still be worth it to try. The other risk I can think of is the risk of over doing it and never needing all the extra layers. But is that really so bad? Are extra class layers really so expensive that it is much of a loss if they are never used? The biggest expense and loss here would be time that is lost up front coming up with the layers. But much of that time still might be saved later when one can work with the abstracted code rather than more low level code. So when is it too much? At what point do the empty layers and extra "might need" abstractions become overkill? How little is too little? Where's the sweet spot? Are there any dependable rules of thumb you've found in the course of your career that help you judge the amount of abstraction needed?

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  • Any one like me who still believes in AspNet Web forms? Or has evryone switched to MVC

    - by The_AlienCoder
    After years mastering Aspnet webforms I recently decided to try out ASpnet MVC. Naturally my first action was to google 'Aspnet webforms vs Aspnet MVC'. I hoped to get an honest comparison of the two development techniques and guidelines on when to use which one. ..But I was completely turned off by the MVC proponents. In almost every post on the net comparing the two 'platforms' the MVC camp is simply bashing webform developers like me. They go on and on about how wrong and stupid using webforms is. As if what we have been doing the past decade has been pointless - all those websites built(& still running), all those clever controls, the mighty gridview..ALL POINTLESS ! Karl Seguin especially with his stupid webforms rant really turned me off. If his intention was to convert people like me he did the oposite and made me defensive. If anything I am now convinced that the webforms approach is better. consider the following All the critical shortcomings of aspnet webforms have now been Addressed in visual studio 2010 with Aspnet 4.0.- Cleaner html, cleaner control IDs, friendly urls, leaner viewstate etc Why would any one want to implement the mighty gridview and other wonderful controls from scratch ? In MVC you have to do this yourself because ABSTRACTION IS PLAIN STUPID- Instead of writing loops why not just code using 1s and 0s then? A stateless web is a WEAKNESS so why would anyone want to get rid of viewstate? Everyone would like a better implementation but getting rid of it is a step backwards not forward. Unit testing is great but not a critical requirement for most web projects. I thought inline codes were dead with asp. But now they are back and fashionable - Thanks to MVC. I dont know about you people but codebehind was REVOLUTIONARY. Ive had the Ajax Update panel do so many wonderful things without writing a line of code so why demonise it? Ive succesfully implemented a chat client, IM client and Status bar using nothing but the update panel and script manager.Ofcourse you cant use it for everything but most of the time its appropriate. And finally the last word from JQUERY - 'Write less do more !' - That's what webforms is all about ! So Am I the only who still believes in webforms(and it getting better as Aspnet 4.0 has shown) or will it be dead and gone a few years from now like asp? I mean if inline coding is 'the future' why not just switch to PHP !

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  • Optimized .htaccess???

    - by StackOverflowNewbie
    I'd appreciate some feedback on the compression and caching configuration below. Trying to come up with a general purpose, optimized compression and caching configuration. If possible: Note your PageSpeed and YSlow grades Add configuration to your .htaccess Clear your cache Note your PageSpeed and YSlow grades to see if there are any improvements (or degradations) NOTE: Make sure you have appropriate modules loaded. Any feedback is much appreciated. Thanks. # JavaScript MIME type issues: # 1. Apache uses "application/javascript": http://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x/conf/mime.types # 2. IIS uses "application/x-javascript": http://technet.microsoft.com/en-us/library/bb742440.aspx # 3. SVG specification says it is text/ecmascript: http://www.w3.org/TR/2001/REC-SVG-20010904/script.html#ScriptElement # 4. HTML specification says it is text/javascript: http://www.w3.org/TR/1999/REC-html401-19991224/interact/scripts.html#h-18.2.2.2 # 5. "text/ecmascript" and "text/javascript" are considered obsolete: http://www.rfc-editor.org/rfc/rfc4329.txt #------------------------------------------------------------------------------- # Compression #------------------------------------------------------------------------------- <IfModule mod_deflate.c> AddOutputFilterByType DEFLATE application/xhtml+xml AddOutputFilterByType DEFLATE application/xml AddOutputFilterByType DEFLATE application/atom+xml AddOutputFilterByType DEFLATE text/css AddOutputFilterByType DEFLATE text/html AddOutputFilterByType DEFLATE text/plain AddOutputFilterByType DEFLATE text/xml # The following MIME types are in the process of registration AddOutputFilterByType DEFLATE application/xslt+xml AddOutputFilterByType DEFLATE image/svg+xml # The following MIME types are NOT registered AddOutputFilterByType DEFLATE application/mathml+xml AddOutputFilterByType DEFLATE application/rss+xml # Deal with JavaScript MIME type issues AddOutputFilterByType DEFLATE application/javascript AddOutputFilterByType DEFLATE application/x-javascript AddOutputFilterByType DEFLATE text/ecmascript AddOutputFilterByType DEFLATE text/javascript </IfModule> #------------------------------------------------------------------------------- # Expires header #------------------------------------------------------------------------------- <IfModule mod_expires.c> # 1. Set Expires to a minimum of 1 month, and preferably up to 1 year, in the future # (but not more than 1 year as that would violate the RFC guidelines) # 2. Use "Expires" over "Cache-Control: max-age" because it is more widely accepted ExpiresActive on ExpiresByType application/pdf "access plus 1 year" ExpiresByType application/x-shockwave-flash "access plus 1 year" ExpiresByType image/bmp "access plus 1 year" ExpiresByType image/gif "access plus 1 year" ExpiresByType image/jpeg "access plus 1 year" ExpiresByType image/png "access plus 1 year" ExpiresByType image/svg+xml "access plus 1 year" ExpiresByType image/tiff "access plus 1 year" ExpiresByType image/x-icon "access plus 1 year" ExpiresByType text/css "access plus 1 year" ExpiresByType video/x-flv "access plus 1 year" # Deal with JavaScript MIME type issues ExpiresByType application/javascript "access plus 1 year" ExpiresByType application/x-javascript "access plus 1 year" ExpiresByType text/ecmascript "access plus 1 year" ExpiresByType text/javascript "access plus 1 year" # Probably better to explicitly declare MIME types than to have a blanket rule for expiration # Uncomment below if you disagree #ExpiresDefault "access plus 1 year" </IfModule> #------------------------------------------------------------------------------- # Caching #------------------------------------------------------------------------------- <IfModule mod_headers.c> <FilesMatch "\.(bmp|css|flv|gif|ico|jpg|jpeg|js|pdf|png|svg|swf|tif|tiff)$"> Header add Cache-Control "public" Header unset ETag Header unset Last-Modified FileETag none </FilesMatch> </IfModule>

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  • Strategy pattern and "action" classes explosion

    - by devoured elysium
    Is it bad policy to have lots of "work" classes(such as Strategy classes), that only do one thing? Let's assume I want to make a Monster class. Instead of just defining everything I want about the monster in one class, I will try to identify what are its main features, so I can define them in interfaces. That will allow to: Seal the class if I want. Later, other users can just create a new class and still have polymorphism by means of the interfaces I've defined. I don't have to worry how people (or myself) might want to change/add features to the base class in the future. All classes inherit from Object and they implement inheritance through interfaces, not from mother classes. Reuse the strategies I'm using with this monster for other members of my game world. Con: This model is rigid. Sometimes we would like to define something that is not easily achieved by just trying to put together this "building blocks". public class AlienMonster : IWalk, IRun, ISwim, IGrowl { IWalkStrategy _walkStrategy; IRunStrategy _runStrategy; ISwimStrategy _swimStrategy; IGrowlStrategy _growlStrategy; public Monster() { _walkStrategy = new FourFootWalkStrategy(); ...etc } public void Walk() { _walkStrategy.Walk(); } ...etc } My idea would be next to make a series of different Strategies that could be used by different monsters. On the other side, some of them could also be used for totally different purposes (i.e., I could have a tank that also "swims"). The only problem I see with this approach is that it could lead to a explosion of pure "method" classes, i.e., Strategy classes that have as only purpose make this or that other action. In the other hand, this kind of "modularity" would allow for high reuse of stratagies, sometimes even in totally different contexts. What is your opinion on this matter? Is this a valid reasoning? Is this over-engineering? Also, assuming we'd make the proper adjustments to the example I gave above, would it be better to define IWalk as: interface IWalk { void Walk(); } or interface IWalk { IWalkStrategy WalkStrategy { get; set; } //or something that ressembles this } being that doing this I wouldn't need to define the methods on Monster itself, I'd just have public getters for IWalkStrategy (this seems to go against the idea that you should encapsulate everything as much as you can!) Why? Thanks

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  • Some questions about writing on ASP.NET response stream

    - by vtortola
    Hi, I'm making tests with ASP.NET HttpHandler for download a file writting directly on the response stream, and I'm not pretty sure about the way I'm doing it. This is a example method, in the future the file could be stored in a BLOB in the database: public void GetFile(HttpResponse response) { String fileName = "example.iso"; response.ClearHeaders(); response.ClearContent(); response.ContentType = "application/octet-stream"; response.AppendHeader("Content-Disposition", "attachment; filename=" + fileName); using (FileStream fs = new FileStream(Path.Combine(HttpContext.Current.Server.MapPath("~/App_Data"), fileName), FileMode.Open)) { Byte[] buffer = new Byte[4096]; Int32 readed = 0; while ((readed = fs.Read(buffer, 0, buffer.Length)) > 0) { response.OutputStream.Write(buffer, 0, readed); response.Flush(); } } } But, I'm not sure if this is correct or there is a better way to do it. My questions are: When I open the url with the browser, appears the "Save File" dialog... but it seems like the server has started already to push data into the stream before I click "Save", is that normal? If I remove the line"response.Flush()", when I open the url with the browser, ... I see how the web server is pushing data but the "Save File" dialog doesn't come up, (or at least not in a reasonable time fashion) why? When I open the url with a WebRequest object, I see that the HttpResponse.ContentLength is "-1", although I can read the stream and get the file. What is the meaning of -1? When is HttpResponse.ContentLength going to show the length of the response? For example, I have a method that retrieves a big xml compresed with deflate as a binary stream, but in that case... when I access it with a WebRequest, in the HttpResponse I can actually see the ContentLength with the length of the stream, why? What is the optimal length for the Byte[] array that I use as buffer for optimal performance in a web server? I've read that is between 4K and 8K... but which factors should I consider to make the correct decision. Does this method bloat the IIS or client memory usage? or is it actually buffering the transference correctly? Sorry for so many questions, I'm pretty new in web development :P Cheers.

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  • Best practices concerning view model and model updates with a subset of the fields

    - by Martin
    By picking MVC for developing our new site, I find myself in the midst of "best practices" being developed around me in apparent real time. Two weeks ago, NerdDinner was my guide but with the development of MVC 2, even it seems outdated. It's an thrilling experience and I feel privileged to be in close contact with intelligent programmers daily. Right now I've stumbled upon an issue I can't seem to get a straight answer on - from all the blogs anyway - and I'd like to get some insight from the community. It's about Editing (read: Edit action). The bulk of material out there, tutorials and blogs, deal with creating and view the model. So while this question may not spell out a question, I hope to get some discussion going, contributing to my decision about the path of development I'm to take. My model represents a user with several fields like name, address and email. All the names, in fact, on field each for first name, last name and middle name. The Details view displays all these fields but you can change only one set of fields at a time, for instance, your names. The user expands a form while the other fields are still visible above and below. So the form that is posted back contains a subset of the fields representing the model. While this is appealing to us and our layout concerns, for various reasons, it is to be shunned by serious MVC-developers. I've been reading about some patterns and best practices and it seems that this is not in key with the paradigm of viewmodel == view. Or have I got it wrong? Anyway, NerdDinner dictates using FormCollection och UpdateModel. All the null fields are happily ignored. Since then, the MVC-community has abandoned this approach to such a degree that a bug in MVC 2 was not discovered. UpdateModel does not work without a complete model in your formcollection. The view model pattern receiving most praise seems to be Dedicated view model that contains a custom view model entity and is the only one that my design issue could be made compatible with. It entails a tedious amount of mapping, albeit lightened by the use of AutoMapper and the ideas of Jimmy Bogard, that may or may not be worthwhile. He also proposes a 1:1 relationship between view and view model. In keeping with these design paradigms, I am to create a view and associated view for each of my expanding sets of fields. The view models would each be nearly identical, differing only in the fields which are read-only, the views also containing much repeated markup. This seems absurd to me. In future I may want to be able to display two, more or all sets of fields open simultaneously. I will most attentively read the discussion I hope to spark. Many thanks in advance.

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  • Using commit monitors as a form of code review

    - by Jeff Dege
    I'm working in a small company - four developers, working on a variety of projects. We've been looking at what we can do as cost-effective methods of process improvement, and an idea came up. Given what we do, we often have single developers working on parts of a system, independently of the other developers. This can have a number of negative affects: A developer might not be fully aware of the context in which a change is being implemented, and make the change in a way that will meet the current customer's needs, but will break functionality that other customers depend on. A developer might make a change that breaks the current architectural design, introducing a dependency that will cause problems in future development. Other developers might not be aware of how the system has changed, in areas that they have not worked on. We've talked about doing code reviews, as a way of dealing with these issues. But we've not had much success when we tried. It takes a lot of time to prepare a change for a code review, and it takes everybody out of production while the review is being performed. And the benefits of any review we've tried has been minimal. We're using Subversion (with TortioseSVN) as our VCS. I've been looking at the SubVersion CommitMonitor tool, and wondering whether it might work as a sort of poor-man's code review. It lists every commit made on the repository, allowing someone to see the changes that have been made, the log messages made for that change, the files that were included in the change, and the specific lines in each file that were changed. Rather than scheduling a meeting, trying to get everybody together to review every change, we could just have every developer review every other developer's commits, at whatever time was convenient. This would keep every developer abreast of what changes were being made elsewhere in the system, and would have every change reviewed for customer conflicts and design consistency, at a fairly low cost. If someone saw a problem with the code that was being checked in, he could discuss it with the developer who did the commit, or more likely, schedule a meeting to discuss how the new feature could be implemented in a way that would not impact other users or screw up the architecture. Anyone else doing anything like this, using commit monitors for such a purpose?

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  • Sockets server design advice

    - by Rob
    We are writing a socket server in c# and need some advice on the design. Background: Clients (from mobile devices) connect to our server app and we leave their socket open so we can send data back down to them whenever we need to. The amount of data varies but we generally send/receive data from each client every few seconds, so it's quite intensive. The amount of simultaneous connections can range from 50-500 (and more in the future). We have already written a server app using async sockets and it works, however we've come across some stumbling blocks and we need to make sure that what we're doing is correct. We have a collection which holds our client states (we have no socket/connection pool at the moment, should we?). Each time a client connects we create a socket and then wait for them to send us some data and in receiveCallBack we add their clientstate object to our connections dictionary (once we have verified who they are). When a client object then signs off we shutdown their socket and then close it as well as remove them from our collection of clients dictionary. Presumably everything happens in the right order, everything works as expected. However, almost everyday it stops accepting connections, or so we think, either that or it connects but doesn't actually do anything past that and we can't work out why it's just stopping. There are few things that we'r'e unsure about 1) Should we be creating some kind of connection pool as opposed to just a dictionary of client sockets 2) What happens to the sockets that connect but then don't get added to our dictionary, they just linger around in memory doing nothing, should we create ANOTHER dictionary that holds the sockets as soon as they are created? 3) What's the best way of finding if clients are no longer connected? We've read some many methods but we're not sure of the best one to use, send data or read data, if so how? 4) If we loop through the connections dictonary to check for disposed clients, should we be locking the dictionary, if so how does this affect other clients objects trying to use it at the same time, will it throw an error or just wait? 5) We often get disposedSocketException within ReceiveCallBack method at random times, does this mean we are safe to remove that socket from the collection? We can't seem to find any production type examples which show any of this working. Any advice would be greatly received

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  • Custom property editors do not work for request parameters in Spring MVC?

    - by dvd
    Hello, I'm trying to create a multiaction web controller using Spring annotations. This controller will be responsible for adding and removing user profiles and preparing reference data for the jsp page. @Controller public class ManageProfilesController { @InitBinder public void initBinder(WebDataBinder binder) { binder.registerCustomEditor(UserAccount.class,"account", new UserAccountPropertyEditor(userManager)); binder.registerCustomEditor(Profile.class, "profile", new ProfilePropertyEditor(profileManager)); logger.info("Editors registered"); } @RequestMapping("remove") public void up( @RequestParam("account") UserAccount account, @RequestParam("profile") Profile profile) { ... } @RequestMapping("") public ModelAndView defaultView(@RequestParam("account") UserAccount account) { logger.info("Default view handling"); ModelAndView mav = new ModelAndView(); logger.info(account.getLogin()); mav.addObject("account", account); mav.addObject("profiles", profileManager.getProfiles()); mav.setViewName(view); return mav; } ... } Here is the part of my webContext.xml file: <context:component-scan base-package="ru.mirea.rea.webapp.controllers" /> <context:annotation-config/> <bean class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping"> <property name="mappings"> <value> ... /home/users/manageProfiles=users.manageProfilesController </value> </property> </bean> <bean id="users.manageProfilesController" class="ru.mirea.rea.webapp.controllers.users.ManageProfilesController"> <property name="view" value="home\users\manageProfiles"/> </bean> <bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter" /> However, when i open the mapped url, i get exception: java.lang.IllegalArgumentException: Cannot convert value of type [java.lang.String] to required type [ru.mirea.rea.model.UserAccount]: no matching editors or conversion strategy found I use spring 2.5.6 and plan to move to the Spring 3.0 in some not very distant future. However, according to this JIRA https://jira.springsource.org/browse/SPR-4182 it should be possible already in spring 2.5.1. The debug shows that the InitBinder method is correctly called. What am i doing wrong?

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  • How to optimize Core Data query for full text search

    - by dk
    Can I optimize a Core Data query when searching for matching words in a text? (This question also pertains to the wisdom of custom SQL versus Core Data on an iPhone.) I'm working on a new (iPhone) app that is a handheld reference tool for a scientific database. The main interface is a standard searchable table view and I want as-you-type response as the user types new words. Words matches must be prefixes of words in the text. The text is composed of 100,000s of words. In my prototype I coded SQL directly. I created a separate "words" table containing every word in the text fields of the main entity. I indexed words and performed searches along the lines of SELECT id, * FROM textTable JOIN (SELECT DISTINCT textTableId FROM words WHERE word BETWEEN 'foo' AND 'fooz' ) ON id=textTableId LIMIT 50 This runs very fast. Using an IN would probably work just as well, i.e. SELECT * FROM textTable WHERE id IN (SELECT textTableId FROM words WHERE word BETWEEN 'foo' AND 'fooz' ) LIMIT 50 The LIMIT is crucial and allows me to display results quickly. I notify the user that there are too many to display if the limit is reached. This is kludgy. I've spent the last several days pondering the advantages of moving to Core Data, but I worry about the lack of control in the schema, indexing, and querying for an important query. Theoretically an NSPredicate of textField MATCHES '.*\bfoo.*' would just work, but I'm sure it will be slow. This sort of text search seems so common that I wonder what is the usual attack? Would you create a words entity as I did above and use a predicate of "word BEGINSWITH 'foo'"? Will that work as fast as my prototype? Will Core Data automatically create the right indexes? I can't find any explicit means of advising the persistent store about indexes. I see some nice advantages of Core Data in my iPhone app. The faulting and other memory considerations allow for efficient database retrievals for tableview queries without setting arbitrary limits. The object graph management allows me to easily traverse entities without writing lots of SQL. Migration features will be nice in the future. On the other hand, in a limited resource environment (iPhone) I worry that an automatically generated database will be bloated with metadata, unnecessary inverse relationships, inefficient attribute datatypes, etc. Should I dive in or proceed with caution?

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  • Best way to handle multiple tables to replace one big table in Rails? (e.g. 'Books1', 'Books2', etc.

    - by mikep
    Hello, I've decided to use multiple tables for an entity (e.g. Books1, Books2, Books3, etc.), instead of just one main table which could end up having a lot of rows (e.g. just Books). I'm doing this to try and to avoid a potential future performance drop that could come with having too many rows in one table. With that, I'm looking for a good way to handle this in Rails, mainly by trying to avoid loading a bunch of unused associations. (I know that I could use a partition for this, but, for now, I've decided to go the 'multiple tables' route.) Each user has their books placed into a specific table. The actual book table is chosen when the user is created, and all of their books go into the same table. I'm going to split the adds across the tables. The goal is to try and keep each table pretty much even -- but that's a different issue. One thing I don't particularly want to have is a bunch of unused associations in the User class. Right now, it looks like I'd have to do the following: class User < ActiveRecord::Base has_many :books1, :books2, :books3, :books4, :books5 end class Books1 < ActiveRecord::Base belongs_to :user end class Books2 < ActiveRecord::Base belongs_to :user end class Books3 < ActiveRecord::Base belongs_to :user end I'm assuming that the main performance hit would come in terms of memory and possibly some method call overhead for each User object, since it has to load all of those associations, which in turn creates all of those nice, dynamic model accessor methods like User.find_by_. But for each specific user, only one of the book tables would be usable/applicable, since all of a user's books are stored in the same table. So, only one of the associations would be in use at any time and any other has_many :bookX association that was loaded would be a waste. For example, with a user.id of 2, I'd only need books3.find_by_author('Author'), but the way I'm thinking of setting this up, I'd still have access to Books1..n. I don't really know Ruby/Rails does internally with all of those has_many associations though, so maybe it's not so bad. But right now I'm thinking that it's really wasteful, and that there may just be a better, more efficient way of doing this. So, a few questions: 1) Is there's some sort of special Ruby/Rails methodology that could be applied to this 'multiple tables to represent one entity' scheme? Are there any 'best practices' for this? 2) Is it really bad to have so many unused has_many associations for each object? Is there a better way to do this? 3) Does anyone have any advice on how to abstract the fact that there's multiple book tables behind a single books model/class? For example, so I can call books.find_by_author('Author') instead of books3.find_by_author('Author'). Thank you!

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  • Automatically generate table of function pointers in C.

    - by jeremytrimble
    I'm looking for a way to automatically (as part of the compilation/build process) generate a "table" of function pointers in C. Specifically, I want to generate an array of structures something like: typedef struct { void (*p_func)(void); char * funcName; } funcRecord; /* Automatically generate the lines below: */ extern void func1(void); extern void func2(void); /* ... */ funcRecord funcTable[] = { { .p_func = &func1, .funcName = "func1" }, { .p_func = &func2, .funcName = "func2" } /* ... */ }; /* End automatically-generated code. */ ...where func1 and func2 are defined in other source files. So, given a set of source files, each of which which contain a single function that takes no arguments and returns void, how would one automatically (as part of the build process) generate an array like the one above that contains each of the functions from the files? I'd like to be able to add new files and have them automatically inserted into the table when I re-compile. I realize that this probably isn't achievable using the C language or preprocessor alone, so consider any common *nix-style tools fair game (e.g. make, perl, shell scripts (if you have to)). But Why? You're probably wondering why anyone would want to do this. I'm creating a small test framework for a library of common mathematical routines. Under this framework, there will be many small "test cases," each of which has only a few lines of code that will exercise each math function. I'd like each test case to live in its own source file as a short function. All of the test cases will get built into a single executable, and the test case(s) to be run can be specified on the command line when invoking the executable. The main() function will search through the table and, if it finds a match, jump to the test case function. Automating the process of building up the "catalog" of test cases ensures that test cases don't get left out (for instance, because someone forgets to add it to the table) and makes it very simple for maintainers to add new test cases in the future (just create a new source file in the correct directory, for instance). Hopefully someone out there has done something like this before. Thanks, StackOverflow community!

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  • How to detect page zoom level in all modern browsers?

    - by understack
    How can I detect page zoom level in all modern browsers? While this thread tells how to do it in IE7 and IE8, I can't find good solution for FF, Safari and Chrome. For FF one of the suggested solution FF stores page zoom level for future. So on first page load would I be able to get zoom level? Somewhere I read it works if you're changing zoom level on that page after its loaded. Is there a way to trap 'zoom' event? I need this because some of my calculations are based on no of pixels and they get changed on Zoom. Thanks. Modified sample given by tfl. This would alert different height based on zoom level. <html> <head> <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.3.1/jquery.min.js" type="text/javascript"/></script> <title></title> </head> <body> <div id="xy" style="border:1px solid #f00; width:100px;"> Lorem ipsum dolor sit amet, consectetur adipiscing elit. Pellentesque sollicitudin tortor in lacus tincidunt volutpat. Integer dignissim imperdiet mollis. Suspendisse quis tortor velit, placerat tempor neque. Cum sociis natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. Praesent bibendum auctor lorem vitae tempor. Nullam condimentum aliquam elementum. Nullam egestas gravida elementum. Maecenas mattis molestie nisl sit amet vehicula. Donec semper tristique blandit. Vestibulum adipiscing placerat mollis. </div> <div> <button onclick="alert($('#xy').height());">Show</button> </div> </body> </html>

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  • LINQ InsertOnSubmit Required Fields needed for debugging

    - by Derek Hunziker
    Hi All, I've been using the ADO.NET Strogly-Typed DataSet model for about 2 years now for handling CRUD and stored procedure executions. This past year I built my first MVC app and I really enjoyed the ease and flexibility of LINQ. Perhaps the biggest selling point for me was that with LINQ I didn't have to create "Insert" stored procedures that would return the SCOPE_IDENTITY anymore (The auto-generated insert statements in the DataSet model were not capable of this without modification). Currently, I'm using LINQ with ASP.NET 3.5 WebForms. My inserts are looking like this: ProductsDataContext dc = new ProductsDataContext(); product p = new product { Title = "New Product", Price = 59.99, Archived = false }; dc.products.InsertOnSubmit(p); dc.SubmitChanges(); int productId = p.Id; So, this product example is pretty basic, right, and in the future, I'll probably be adding more fields to the database such as "InStock", "Quantity", etc... The way I understand it, I will need to add those fields to the database table and then delete and re-add the tables to the LINQ to SQL Class design view in order to refresh the DataContext. Does that sound right? The problem is that any new fields that are non-null are NOT caught by the ASP.NET build processes. For example, if I added a non-null field of "Quantity" to the database, the code above would still build. In the DataSet model, the stored procedure method would accept a certain amount of parameters and would warn me that my Insert would fail if I didn't include a quantity value. The same goes for LINQ stored procedure methods, however, to my knowledge, LINQ doesn't offer a way to auto generate the insert statements and that means I'm back to where I started. The bottom line is if I used insert statements like the one above and I add a non-null field to my database, it would break my app in about 10-20 places and there would be no way for me to detect it. Is my only option to do a solution-side search for the keyword "products.InsertOnSubmit" and make sure the new field is getting assigned? Is there a better way? Thanks!

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  • PHP - static DB class vs DB singleton object

    - by Marco Demaio
    I don't want to create a discussion about singleton better than static or better than global, etc. I read dozens of questions about it on SO, but I couldn't come up with an answer to this SPECIFIC question, so I hope someone could now illuminate me buy answering this question with one (or more) real simple EXAMPLES, and not theoretical discussions. In my app I have the typical DB class needed to perform tasks on DB without having to write everywhere in code mysql_connect/mysql_select_db/mysql... (moreover in future I might decide to use another type of DB engine in place of mySQL so obviously I need a class of abstration). I could write the class either as a static class: class DB { private static $connection = FALSE; //connection to be opened //DB connection values private static $server = NULL; private static $usr = NULL; private static $psw = NULL; private static $name = NULL; public static function init($db_server, $db_usr, $db_psw, $db_name) { //simply stores connections values, withour opening connection } public static function query($query_string) { //performs query over alerady opened connection, if not open, it opens connection 1st } ... } or as a Singletonm class: class DBSingleton { private $inst = NULL; private $connection = FALSE; //connection to be opened //DB connection values private $server = NULL; private $usr = NULL; private $psw = NULL; private $name = NULL; public static function getInstance($db_server, $db_usr, $db_psw, $db_name) { //simply stores connections values, withour opening connection if($inst === NULL) $this->inst = new DBSingleton(); return $this->inst; } private __construct()... public function query($query_string) { //performs query over already opened connection, if connection is not open, it opens connection 1st } ... } Then after in my app if I wanto to query the DB i could do //Performing query using static DB object DB:init(HOST, USR, PSW, DB_NAME); DB::query("SELECT..."); //Performing query using DB singleton $temp = DBSingleton::getInstance(HOST, USR, PSW, DB_NAME); $temp->query("SELECT..."); My simple brain sees Singleton has got the only advantage to avoid declaring as 'static' each method of the class. I'm sure some of you could give me an EXAMPLE of real advantage of singleton in this specific case. Thanks in advance.

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  • Soon to be PhD in Computer Science - Which Path to Follow?

    - by mttr
    I am going to submit my PhD thesis within the next six months. My PhD is on managing the availabiity of large-scale distributed systems, so I have some experience actually building non-trivial systems (+ I have four years experience working as a programmer). I am now trying to figure out what I should do following the PhD. I enjoy research (a quick definition: identify problem, come up with solution, ask interesting questions, find ways to answer them, build system, experiment, contribute some new knowledge and publish). I also like teaching and supervising students. It would seem that a career in academia is the ideal thing to do (can work on non-trivial problems and contribute something of use to some or more people). However, a career in academia has two significant drawbacks. First, it can be difficult to gain access to real systems with real users which then display real problems. This creates the danger that you do work that seems important (to you and maybe to some of your colleagues), but is not really relevant to anything or anyone. Second, the pay is pretty sad. Apparently, you have to sacrifice this for the privilege of doing research. I enjoy programming, but don't just want to hack some web-based system for the rest of my life. That is, working in IT for a bank is not a future I see myself enjoying. I want to work on interesting problms (that's difficult to define clearly): things where you don't know how to start, that take some time to figure out and attack, that require a rigorous approach to demonstrate that the problem has been solved, and problems that need a solution in the real world. Give the experience of people on stackoverflow, what do you think suitable options are and why (or alternatively, what gaps in my thinking does the above reveal)? Is industrial research (aka IBM Research, Microsoft Research) the only alternative avenue to a career in academia? What other areas, companies, occupations, etc. could provide me with stimulating, inspiring work? Which regions, countries am I most likely to find such work? Please share your experience.

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  • NoSQL DB for .Net document-based database (ECM)

    - by Dane
    I'm halfway through coding a basic multi-tenant SaaS ECM solution. Each client has it's own instance of the database / datastore, but the .Net app is single instance. The documents are pretty much read only (i.e. an image archive of tiffs or PDFs) I've used MSSQL so far, but then started thinking this might be viable in a NoSQL DB (e.g. MongoDB, CouchDB). The basic premise is that it stores documents, each with their own particular indexes. Each tenant can have multiple document types. e.g. One tenant might have an invoice type, which has Customer ID, Invoice Number and Invoice Date. Another tenant might have an application form, which has Member Number, Application Number, Member Name, and Application Date. So far I've used the old method which Sharepoint (used?) to use, and created a document table which has int_field_1, int_field_2, date_field_1, date_field_2, etc. Then, I've got a "mapping" table which stores the customer specific index name, and the database field that will map to. I've avoided the key-value pair model in the DB due to volume of documents. This way, we can support multiple document types in the one table, and get reasonably high performance out of it, and allow for custom document type searches (i.e. user selects a document type, then they're presented with a list of search fields). However, a NoSQL DB might make this a lot simpler, as I don't need to worry about denormalizing the document. However, I've just got concerns about the rest of the data around a document. We store an "action history" against the document. This tracks views, whether someone emails the document from within the system, and other "future" functionality (e.g. faxing). We have control over the document load process, so we can manipulate the data however it needs to be to get it in the document store (e.g. assign unique IDs). Users will not be adding in their own documents, so we shouldn't need to worry about ACID compliance, as the documents are relatively static. So, my questions I guess : Is a NoSQL DB a good fit Is MongoDB the best for Asp.Net (I saw Raven and Velocity, but they're still kinda beta) Can I store a key for each document, and then store the action history in a MSSQL DB with this key? I don't need to do joins, it would be if a person clicks "View History" against a document. How would performance compare between the two (NoSQL DB vs denormalized "document" table) Volumes would be up to 200,000 new documents per month for a single tenant. My current scaling plan with the SQL DB involves moving the SQL DB into a cluster when certain thresholds are reached, and then reviewing partitioning and indexing structures.

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  • Can Hudson branch promotion get based on project stability?

    - by Wayne
    Hudson CI server displays stability "weather" which is cool. And it allows one project build to kick off based on the successful build of another. However, how can you make that secondary project dependent additionally on the stability of multiple builds of the first project? Specifically, project "stable_deploy" needs to only kick off to promote a version to "stable" if project "integrate" with version 8.3.4.1233 has built and tested successfully at least 8 times--in a row. Until then, it's still in integration mode. IMPORTANT: A significant caveat to this is that a single set of Hudson projects gets used as a "pipeline" to process each new version through to release. So a project may have built successfully 8 times in a rolw but the latest version 8.3.4.1233 may be only the 2 most recent builds. The builds prior to that may be an earlier version. We're open to completely reorganizing this but the pipeline idea seemed to greatly reduce the amount of manually project creation and deletion. Is there a better way to track version release "pipeline"? In particular, we will have multiple versions in this pipeline simultaneously in the future due to fixes or patches to older versions. We don't see how to do that yet, except to create new pipeline projects for each version which is a real hassle. Here's some background details: The TickZoom application has some very complete unit tests some of which simulates real time trading environments. Add to that TickZoom makes elaborate use of parallelization for leveraging multi-core computers. Needless to say, during development of a new version, there can be stability issues during integration testing which get uncovered by running the build and auto tests repeatedly. A version which builds and tests cleanly 8 times in a row without change plus has undergone some real world testing by users can be deemed "stable" and promoted to the stable branch. Our Hudson projects look like this: test - Only for testing a build, zero user visibility. integrate_deploy - Promotes a test project build to integrate branch and makes it available to public for UA testing. integrate - Repeatedly builds the integrate branch to determine if it's stable enough to promote to stable branch. This runs the builds and test hourly throughout every night. stable_deploy - Promotes an integrate project build to the stable branch and makes it public for users who want the latest and greatest. stable - Builds the stable branch once every night. After 2 weeks of successful builds (14 builds) it can go to "release candidate". And so on... it continues with "release candidate" and then "release".

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  • Register all GUI components as Observers or pass current object to next object as a constructor argu

    - by Jack
    First, I'd like to say that I think this is a common issue and there may be a simple or common solution that I am unaware of. Many have probably encountered a similar problem. Thanks for reading. I am creating a GUI where each component needs to communicate (or at least be updated) by multiple other components. Currently, I'm using a Singleton class to accomplish this goal. Each GUI component gets the instance of the singleton and registers itself. When updates need to be made, the singleton can call public methods in the registered class. I think this is similar to an Observer pattern, but the singleton has more control. Currently, the program is set up something like this: class c1 { CommClass cc; c1() { cc = CommClass.getCommClass(); cc.registerC1( this ); C2 c2 = new c2(); } } class c2 { CommClass cc; c2() { cc = CommClass.getCommClass(); cc.registerC2( this ); C3 c3 = new c3(); } } class c3 { CommClass cc; c3() { cc = CommClass.getCommClass(); cc.registerC3( this ); C4 c4 = new c4(); } } etc. Unfortunately, the singleton class keeps growing larger as more communication is required between the components. I was wondering if it's a good idea to instead of using this singleton, pass the higher order GUI components as arguments in the constructors of each GUI component: class c1 { c1() { C2 c2 = new c2( this ); } } class c2 { C1 c1; c2( C1 c1 ) { this.c1 = c1 C3 c3 = new c3( c1, this ); } } class c3 { C1 c1; C2 c2; c3( C1 c1, C2 c2 ) { this.c1 = c1; this.c2 = c2; C4 c4 = new c4( c1, c2, this ); } } etc. The second version relies less on the CommClass, but it's still very messy as the private member variables increase in number and the constructors grow in length. Each class contains GUI components that need to communicate through CommClass, but I can't think of a good way to do it. If this seems strange or horribly inefficient, please describe some method of communication between classes that will continue to work as the project grows. Also, if this doesn't make any sense to anyone, I'll try to give actual code snippets in the future and think of a better way to ask the question. Thanks.

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  • How to actually use Swing Application Framework?

    - by Joonas Pulakka
    Hello, I'd like to learn how to effectively use Swing Application Framework. Most of the the examples I've found are blog entries that just explain how to great it is to extend SingleFrameApplication and override its startup method, but that's about it. Sun's article is almost two years old, as is the project's own introduction, and there has apparently been some evolution since then. Are there any recent and thorough tutorials/HOWTOs available anywhere? There is JavaDoc of course, but it's hard to get the big picture from there. Any pointers are appreciated. Update: I realized that there's a mailing list archive at the project's site. While somewhat clumsy (compared to StackOverflow ;) it seems to be quite active. Still it's a pity that there are no real tutorials anywhere. The information is scattered here and there. Update 2: Let me clarify - I'm not having trouble using Swing (the widget toolkit) itself, I'm talking about its Application Framework, which is supposed to ease things like application lifecycle (startup, exit and whatever happens between them), action management etc. - that is, things that most Swing applications will need. It's cool to get such framework to be standard part of Java. The only problem is to learn how it's intended to be used. Update 3: For the interested, there was just some discussion at the project's forum regarding the current state and future of JSR 296. Shortly: the current version 1.03 is considered to be quite usable, but the API is not stable and it will change to the final version in Java 7. The package name will also change so Java 7 will not break current applications made on SAF. Update 4: Karsten Lentzsch stated at the above mentioned forum: "I doubt that it can be included in Java 7; and I'll vote against it.". I would rather not question the sincerity of this great guru, and it's certainly wise not to let anything flawed to slip into the core JDK, but frankly it's a strange situation - he is the author of JGoodies Swing Suite which is partly a commercial competitor of JSR 296, and he is sitting in the committee that will decide whether this JSR will be included to standard Java. It was the same thing with JSR 295 Beans Binding which I wrote about earlier. Given the current state of SAF, I think the best solution is to wrap the current implementation into a "homebrew" framework, which can then accommodate possible changes to the existing API.

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  • Which HTTP redirect status code is best for this REST API scenario?

    - by Aseem Kishore
    I'm working on a REST API. The key objects ("nouns") are "items", and each item has a unique ID. E.g. to get info on the item with ID foo: GET http://api.example.com/v1/item/foo New items can be created, but the client doesn't get to pick the ID. Instead, the client sends some info that represents that item. So to create a new item: POST http://api.example.com/v1/item/ hello=world&hokey=pokey With that command, the server checks if we already have an item for the info hello=world&hokey=pokey. So there are two cases here. Case 1: the item doesn't exist; it's created. This case is easy. 201 Created Location: http://api.example.com/v1/item/bar Case 2: the item already exists. Here's where I'm struggling... not sure what's the best redirect code to use. 301 Moved Permanently? 302 Found? 303 See Other? 307 Temporary Redirect? Location: http://api.example.com/v1/item/foo I've studied the Wikipedia descriptions and RFC 2616, and none of these seem to be perfect. Here are the specific characteristics I'm looking for in this case: The redirect is permanent, as the ID will never change. So for efficiency, the client can and should make all future requests to the ID endpoint directly. This suggests 301, as the other three are meant to be temporary. The redirect should use GET, even though this request is POST. This suggests 303, as all others are technically supposed to re-use the POST method. In practice, browsers will use GET for 301 and 302, but this is a REST API, not a website meant to be used by regular users in browsers. It should be broadly usable and easy to play with. Specifically, 303 is HTTP/1.1 whereas 301 and 302 are HTTP/1.0. I'm not sure how much of an issue this is. At this point, I'm leaning towards 303 just to be semantically correct (use GET, don't re-POST) and just suck it up on the "temporary" part. But I'm not sure if 302 would be better since in practice it's been the same behavior as 303, but without requiring HTTP/1.1. But if I go down that line, I wonder if 301 is even better for the same reason plus the "permanent" part. Thoughts appreciated!

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  • github like workflow on private server over ssh

    - by Jesse
    I have an server (available via ssh) on the internet that my friend and I use for working on projects together. We have started using git for source control. Our setup currently is as follows: Friend created repository on server with git init named project.friend.git I cloned project.friend.git on server to project.jesse.git I then cloned project.jesse.git on server to my local machine using git clone jesse@server:/git_repos/project.jesse.git I work on my local machine and commit to the local machine. When I want to push my changes to the project.jesse.git on server I use git push origin master. My friend is working on project.friend.git. When I want to get his changes I do pull jesse@server:/git_repos/project.friend.git. Everything seems to be working fine, however, I am now getting the following error when I do git push origin master: localpc:project.jesse jesse$ git push origin master Counting objects: 100, done. Delta compression using up to 2 threads. Compressing objects: 100% (76/76), done. Writing objects: 100% (76/76), 15.98 KiB, done. Total 76 (delta 50), reused 0 (delta 0) warning: updating the current branch warning: Updating the currently checked out branch may cause confusion, warning: as the index and work tree do not reflect changes that are in HEAD. warning: As a result, you may see the changes you just pushed into it warning: reverted when you run 'git diff' over there, and you may want warning: to run 'git reset --hard' before starting to work to recover. warning: warning: You can set 'receive.denyCurrentBranch' configuration variable to warning: 'refuse' in the remote repository to forbid pushing into its warning: current branch. warning: To allow pushing into the current branch, you can set it to 'ignore'; warning: but this is not recommended unless you arranged to update its work warning: tree to match what you pushed in some other way. warning: warning: To squelch this message, you can set it to 'warn'. warning: warning: Note that the default will change in a future version of git warning: to refuse updating the current branch unless you have the warning: configuration variable set to either 'ignore' or 'warn'. To jesse@server:/git_repos/project.jesse.git c455cb7..e9ec677 master -> master Is this warning anything I need to be worried about? Like I said, everything seems to be working. My friend is able to pull my changes in from my branch. I have the clone on the server so he can access it since he does not have access to my local machine. Is there something that could be done better? Thanks!

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  • Putting update logic in your migrations

    - by Daniel Abrahamsson
    A couple of times I've been in the situation where I've wanted to refactor the design of some model and have ended up putting update logic in migrations. However, as far as I've understood, this is not good practice (especially since you are encouraged to use your schema file for deployment, and not your migrations). How do you deal with these kind of problems? To clearify what I mean, say I have a User model. Since I thought there would only be two kinds of users, namely a "normal" user and an administrator, I chose to use a simple boolean field telling whether the user was an adminstrator or not. However, after I while I figured I needed some third kind of user, perhaps a moderator or something similar. In this case I add a UserType model (and the corresponding migration), and a second migration for removing the "admin" flag from the user table. And here comes the problem. In the "add_user_type_to_users" migration I have to map the admin flag value to a user type. Additionally, in order to do this, the user types have to exist, meaning I can not use the seeds file, but rather create the user types in the migration (also considered bad practice). Here comes some fictional code representing the situation: class CreateUserTypes < ActiveRecord::Migration def self.up create_table :user_types do |t| t.string :name, :nil => false, :unique => true end #Create basic types (can not put in seed, because of future migration dependency) UserType.create!(:name => "BASIC") UserType.create!(:name => "MODERATOR") UserType.create!(:name => "ADMINISTRATOR") end def self.down drop_table :user_types end end class AddTypeIdToUsers < ActiveRecord::Migration def self.up add_column :users, :type_id, :integer #Determine type via the admin flag basic = UserType.find_by_name("BASIC") admin = UserType.find_by_name("ADMINISTRATOR") User.all.each {|u| u.update_attribute(:type_id, (u.admin?) ? admin.id : basic.id)} #Remove the admin flag remove_column :users, :admin #Add foreign key execute "alter table users add constraint fk_user_type_id foreign key (type_id) references user_types (id)" end def self.down #Re-add the admin flag add_column :users, :admin, :boolean, :default => false #Reset the admin flag (this is the problematic update code) admin = UserType.find_by_name("ADMINISTRATOR") execute "update users set admin=true where type_id=#{admin.id}" #Remove foreign key constraint execute "alter table users drop foreign key fk_user_type_id" #Drop the type_id column remove_column :users, :type_id end end As you can see there are two problematic parts. First the row creation part in the first model, which is necessary if I would like to run all migrations in a row, then the "update" part in the second migration that maps the "admin" column to the "type_id" column. Any advice?

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  • Rails "NoMethodError" with sub-resources

    - by Tchock
    Hi. I'm a newbie Rails developer who is getting the following error when trying to access the 'new' action on my CityController: undefined method `cities_path' for #<#<Class:0x104608c18>:0x104606f08> Extracted source (around line #2): 1: <h1>New City</h1> 2: <%= form_for(@city) do |f| %> 3: <%= f.error_messages %> 4: 5: <div class="field"> As some background, I have a State model with many Cities. I'm getting this error after clicking on the following link coming from a State show page: <p>Add a city: <%= link_to "Add city", new_state_city_path(@state) %></p> When I run 'rake:routes' it says this is a legit route... For more background, here is the CityController 'new' action: def new @city = City.new respond_to do |format| format.html # new.html.erb format.xml { render :xml => @city } end end Here is the (complete) form in the view: <%= form_for(@city) do |f| %> <%= f.error_messages %> <div class="field"> <%= f.label :name %><br /> <%= f.text_field :name %> </div> <div class="actions"> <%= f.submit %> </div> <% end %> This initially made me think that it's a resources/routes issue since it came back with a mention of 'cities_path' (in fact, that's what another person posting to Stack Overflow had wrong (http://stackoverflow.com/questions/845315/rails-error-nomethoderror-my-first-ruby-app). However, that doesn't seem to be the case from what I can see. Here are how my resources look in my routes file: resources :states do resources :cities end I can get it working when they are not sub-resources, but I really need to keep them as sub-resources for my future plans with the app. Any help would be very much appreciated, since I've been racking my brains on this for more hours than I would care to admit... Thanks! (Not sure this matters at all, but I'm running the very latest version of Rails 3 beta2).

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