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• sudo apt-get install python.pip python-dev Gives Error

  - by user2539745

  I am learning Django from http://gettingstartedwithdjango.com/ and I have windows 7 32-bit. The tutorial asked to install virtualbox and vagrant(tutorial had precise64 and it had issues in my pc so I installed precise32) so I did it. Now the tutorial asked to do sudo apt-get install python-dev python.pip so I did it but it gave me this error > vagrant@precise32:~$ sudo apt-get install python.pip python-dev Reading package lists... Done Building dependency tree Reading state information... Done Note, selecting 'python-pip' for regex 'python.pip' Note, selecting 'python-pipeline' for regex 'python.pip' The following extra packages will be installed: libexpat1 libexpat1-dev libpython2.7 python-pkg-resources python-setuptools python-support python2.7 python2.7-dev python2.7-minimal Suggested packages: python-distribute python-distribute-doc python2.7-doc binfmt-support The following NEW packages will be installed: libexpat1-dev libpython2.7 python-dev python-pip python-pipeline python-pkg-resources python-setuptools python-support python2.7-dev The following packages will be upgraded: libexpat1 python2.7 python2.7-minimal 3 upgraded, 9 newly installed, 0 to remove and 63 not upgraded. Need to get 34.7 MB/35.7 MB of archives. After this operation, 42.0 MB of additional disk space will be used. Do you want to continue [Y/n]? y Err (http removed)us.archive.ubuntu.com/ubuntu/ precise-updates/main python2.7 i386 2.7 .3-0ubuntu3.1 404 Not Found [IP: 91.189.91.15 80] Err (http removed)us.archive.ubuntu.com/ubuntu/ precise-updates/main python2.7-minimal i386 2.7.3-0ubuntu3.1 404 Not Found [IP: 91.189.91.15 80] Err (http removed)us.archive.ubuntu.com/ubuntu/ precise-updates/main libpython2.7 i386 2.7.3-0ubuntu3.1 404 Not Found [IP: 91.189.91.15 80] Err (http removed)us.archive.ubuntu.com/ubuntu/ precise-updates/main python2.7-dev i386 2.7.3-0ubuntu3.1 404 Not Found [IP: 91.189.91.15 80] Failed to fetch (http removed)us.archive.ubuntu.com/ubuntu/pool/main/p/python2.7/python 2.7_2.7.3-0ubuntu3.1_i386.deb 404 Not Found [IP: 91.189.91.15 80] Failed to fetch (http removed)us.archive.ubuntu.com/ubuntu/pool/main/p/python2.7/python 2.7-minimal_2.7.3-0ubuntu3.1_i386.deb 404 Not Found [IP: 91.189.91.15 80] Failed to fetch (http removed)us.archive.ubuntu.com/ubuntu/pool/main/p/python2.7/libpyt hon2.7_2.7.3-0ubuntu3.1_i386.deb 404 Not Found [IP: 91.189.91.15 80] Failed to fetch (http removed)us.archive.ubuntu.com/ubuntu/pool/main/p/python2.7/python 2.7-dev_2.7.3-0ubuntu3.1_i386.deb 404 Not Found [IP: 91.189.91.15 80] E: Unable to fetch some archives, maybe run apt-get update or try with --fix-mis sing? Please help what should I do ??

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• Maven Assembly Plugin - install the created assembly

  - by Walter White

  I have a project that simply consists of files. I want to package those files into a zip and store them in a maven repository. I have the assembly plugin configured to build the zip file and that part works just fine, but I cannot seem to figure out how to install the zip file? Also, if I want to use this assembly in another artifact, how would I do that? I am intending on calling dependency:unpack, but I don't have an artifact in the repository to unpack. How can I get a zip file to be in my repository so that I may re-use it in another artifact? parent pom <build> <plugins> <plugin> <!--<groupId>org.apache.maven.plugins</groupId>--> <artifactId>maven-assembly-plugin</artifactId> <version>2.2-beta-5</version> <configuration> <filters> <filter></filter> </filters> <descriptors> <descriptor>../packaging.xml</descriptor> </descriptors> </configuration> </plugin> </plugins> </build> Child POM <parent> <groupId>com. ... .virtualHost</groupId> <artifactId>pom</artifactId> <version>0.0.1</version> <relativePath>../pom.xml</relativePath> </parent> <name>Virtual Host - ***</name> <groupId>com. ... .virtualHost</groupId> <artifactId>***</artifactId> <version>0.0.1</version> <packaging>pom</packaging> I filtered the name out. Is this POM correct? I just want to bundle files for a particular virtual host together. Thanks, Walter

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• Pass or Get a value from Parent ViewModel down to Sub-ViewModel?

  - by mkmurray

  I am using the MVVM Light framework as well as Unity for DI. I have some nested Views, each bound to a corresponding ViewModel. The ViewModels are bound to each View's root control DataContext via the ViewModelLocator idea that Laurent Bugnion has put into MVVM Light. This allows for finding ViewModels via a static resource and for controlling the lifetime of ViewModels via a Dependency Injection framework, in this case Unity. It also allows for Expression Blend to see everything in regard to ViewModels and how to bind them. As I stated the Views have a healthy dose of nesting, but the ViewModels don't really know anything about each other. A parent view binds to its corresponding ViewModel via the static resource ViewModelLocator (which uses Unity to control the construction and lifetime of the ViewModel object). That parent view contains a user control in it that is another sub-view, which then goes and gets its corresponding ViewModel via the ViewModelLocator as well. The ViewModels don't have references to each other or know any hierarchy in regard to each other. So here's an example of how the ViewModels do interact via messaging. I've got a parent View that has a ComboBox databound to an ObservableCollection in its ViewModel. The ComboBox's SelectedItem is also bound (two-way) to a property on the ViewModel. When the selection of the ComboBox changes, this is to trigger updates in other Views and sub-Views. Currently I am accomplishing this via the Messaging system that is found in MVVM Light. So I'm wondering what the best practice would be to get information from one ViewModel to another? In this case, what I need to pass down to sub-ViewModels is basically a user Guid representing the currently logged in user. The top-most parent View (well, ViewModel) will know this information, but I'm not sure how to get it down into the sub-ViewModels. Some possible approaches I can think of: Should the sub-ViewModel ask the static resource ViewModelLocator for a reference to the same object the parent View is using and access the property that way? It seems like ViewModels going through each other's properties is not very clean and couples them together unnecessarily. I'm already using messaging to notify the sub-Views that the user selected a new item in the ComboBox and to update accordingly. But the object type that is being selected in the ComboBox is not really directly related to this data value that the sub-Views need.

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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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• What do you expect from a package manager for Emacs

  - by tarsius

  Although several hundred Emacs Lisp libraries exist GNU Emacs does not have an (internal) package manager. I guess that most users would agree that it is currently rather inconvenient to find, install and especially keep up-to-date Emacs Lisp libraries. These pages make life a bit easier Emacs Lisp List - Problem: I see dead people (links). Emacswiki - Problem: May contain traces of nuts (malicious code). These are some package managers XEmacs package manager package.el - ELPA pases install.el install-elisp.el plugin.el use-package.el jem-pkg.el epkg/elm - the one I am working. And this are some packages that provide functionality that might be useful in a package manager ell.el - Browse the Emacs Lisp List genauto.el - helps generate autoloads for your elisp packages date-calc.el - date calculation and parsing routines strptime.el - partial implementation of POSIX date and time parsing wikirel.el - Visit relevant pages on the Emacs Wiki loadhist.el, lib-requires.el, elisp-depend.el - Commands to list Emacs Lisp library dependencies. project-root.el - Define a project root and take actions based upon it So I would like to know from you what you consider important/unimportant/supplementary... in a package manager for Emacs. Some ideas Many packages (incorporate the Emacs Lisp List and other lists of libraries). Only packages that have been tested. Support for more than one package archive (so people can choose between many/tested packages). Dependency calculated based on required features only. Dependencies take particular versions into account. Only use versions that have been released upstream. Use versions from version control systems if available. Packages are categorized. Packages can be uninstalled and updated not only installed. Support creating fork of upstream version of packages. Support publishing these forks. Support choosing a fork. After installation packages are activated. Generate autoloads. Integration with Emacswiki (see wikirel.el). Users can tag, comment ... packages and share that information. Only FSF-assigned/GPL/FOSS software or don't care about license. Package manager should be integrated in Emacs. Support contacting author. Lots of metadata. Suggest alternatives before installing a particular package. Some discussions about the subject at hand emacs-devel 20080801 comp.emacs 20021121 RationalElispPackaging I am hoping for these kinds of answers Pointers to more implementations, discussions etc. Lengthy descriptions of a set of features that make up your ideal package manager. Descriptions of one particular disired/undisired feature. This has the advantage that the regular voting mechanism allows us to see what features are most welcomed. Feel free to elaborate on my ideas from above. Surprise me.

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• Cannot install Apache Web Server on Ubuntu, Amazon WS

  - by Eugene Retunsky

  I enter command apt-get install apache2 --fix-missing (under the root user) and this is what I receive: Reading package lists... Done Building dependency tree Reading state information... Done The following extra packages will be installed: apache2-mpm-worker apache2-utils apache2.2-bin apache2.2-common libapr1 libaprutil1 libaprutil1-dbd-sqlite3 libaprutil1-ldap ssl-cert Suggested packages: apache2-doc apache2-suexec apache2-suexec-custom openssl-blacklist The following NEW packages will be installed: apache2 apache2-mpm-worker apache2-utils apache2.2-bin apache2.2-common libapr1 libaprutil1 libaprutil1-dbd-sqlite3 libaprutil1-ldap ssl-cert 0 upgraded, 10 newly installed, 0 to remove and 36 not upgraded. Need to get 2,945 kB/3,141 kB of archives. After this operation, 10.4 MB of additional disk space will be used. Do you want to continue [Y/n]? y Err http://us-west-1.ec2.archive.ubuntu.com/ubuntu/ oneiric-updates/main apache2.2-bin i386 2.2.20-1ubuntu1.1 404 Not Found [IP: 10.161.51.124 80] Err http://security.ubuntu.com/ubuntu/ oneiric-security/main apache2.2-bin i386 2.2.20-1ubuntu1.1 404 Not Found [IP: 91.189.92.167 80] Err http://security.ubuntu.com/ubuntu/ oneiric-security/main apache2-utils i386 2.2.20-1ubuntu1.1 404 Not Found [IP: 91.189.92.167 80] Err http://security.ubuntu.com/ubuntu/ oneiric-security/main apache2.2-common i386 2.2.20-1ubuntu1.1 404 Not Found [IP: 91.189.92.167 80] Err http://security.ubuntu.com/ubuntu/ oneiric-security/main apache2-mpm-worker i386 2.2.20-1ubuntu1.1 404 Not Found [IP: 91.189.92.167 80] Err http://security.ubuntu.com/ubuntu/ oneiric-security/main apache2 i386 2.2.20-1ubuntu1.1 404 Not Found [IP: 91.189.92.167 80] Failed to fetch http://security.ubuntu.com/ubuntu/pool/main/a/apache2/apache2.2-bin_2.2.20-1ubuntu1.1_i386.deb 404 Not Found [IP: 91.189.92.167 80] Failed to fetch http://security.ubuntu.com/ubuntu/pool/main/a/apache2/apache2-utils_2.2.20-1ubuntu1.1_i386.deb 404 Not Found [IP: 91.189.92.167 80] Failed to fetch http://security.ubuntu.com/ubuntu/pool/main/a/apache2/apache2.2-common_2.2.20-1ubuntu1.1_i386.deb 404 Not Found [IP: 91.189.92.167 80] Failed to fetch http://security.ubuntu.com/ubuntu/pool/main/a/apache2/apache2-mpm-worker_2.2.20-1ubuntu1.1_i386.deb 404 Not Found [IP: 91.189.92.167 80] Failed to fetch http://security.ubuntu.com/ubuntu/pool/main/a/apache2/apache2_2.2.20-1ubuntu1.1_i386.deb 404 Not Found [IP: 91.189.92.167 80] Unable to correct missing packages. E: Aborting install. Any help is appreciated.

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• Is the design notion of layers contrived?

  - by Bruce

  Hi all I'm reading through Eric Evans' awesome work, Domain-Driven Design. However, I can't help feeling that the 'layers' model is contrived. To expand on that statement, it seems as if it tries to shoe-horn various concepts into a specific, neat model, that of layers talking to each other. It seems to me that the layers model is too simplified to actually capture the way that (good) software works. To expand further: Evans says: "Partition a complex program into layers. Develop a design within each layer that is cohesive and that depends only on the layers below. Follow standard architectural patterns to provide loose coupling to the layers above." Maybe I'm misunderstanding what 'depends' means, but as far as I can see, it can either mean a) Class X (in the UI for example) has a reference to a concrete class Y (in the main application) or b) Class X has a reference to a class Y-ish object providing class Y-ish services (ie a reference held as an interface). If it means (a), then this is clearly a bad thing, since it defeats re-using the UI as a front-end to some other application that provides Y-ish functionality. But if it means (b), then how is the UI any more dependent on the application, than the application is dependent on the UI? Both are decoupled from each other as much as they can be while still talking to each other. Evans' layer model of dependencies going one way seems too neat. First, isn't it more accurate to say that each area of the design provides a module that is pretty much an island to itself, and that ideally all communication is through interfaces, in a contract-driven/responsibility-driven paradigm? (ie, the 'dependency only on lower layers' is contrived). Likewise with the domain layer talking to the database - the domain layer is as decoupled (through DAO etc) from the database as the database is from the domain layer. Neither is dependent on the other, both can be swapped out. Second, the idea of a conceptual straight line (as in from one layer to the next) is artificial - isn't there more a network of intercommunicating but separate modules, including external services, utility services and so on, branching off at different angles? Thanks all - hoping that your responses can clarify my understanding on this..

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• Maven best practice for generating multiple jars with different/filtered classes ?

  - by jaguard

  I developed a Java utility library (similarly to Apache Commons) that I use in various projects. Additionally to fat clients I also use it for mobile clients (PDA with J9 Foundation profile). In time the library that started as a single project spread over multiple packages. As a result I end up with a lot of functionality but not really needed in all the projects. Since this library is also used inside some mobile/PDA projects I need a way to collect just the used classes and generate the actual specialized jars Currently in the projects that area using this library, I have Ant jar tasks that generate (from the utility project) the specialized jar files (ex: my-util-1.0-pda.jar, my-util-1.0-rcp.jar) using include/exclude jar task features. This is mostly needed due to the generated jar size constraints for the mobile projects. Migrating now to Maven I just wonder if there are any best practices to arrive to something similar so I consider the following scenarios: [1] - additionally to the main jar artifact (my-lib-1.0.jar) also generating inside my-lib project the separate/specialized artifacts using classifiers (ex: my-lib-1.0-pda.jar) using Maven Jar Plugin or Maven Assembly Plugin filtering/includes ... I'm not very comfortable with this approach since it pollute the library with library consumers demands (filters) [2] - Create additional Maven projects for all the specialized clients/projects, that will "wrap" the "my-lib" and generate the filtered jar artifacts (ex: my-lib-wrapper-pda-1.0 ...etc). As a result, these wrapper projects will include the filtering (to generate the filtered artifact) and will depend just on the "my-lib" project and the client projects will depend on my-lib-wrapper-xxx-1.0 instead of my-lib-1.0. This approach my look problematic since even that will let "my-lib" project intact (with no additional classifiers & artifacts), basically will double the number of projects since for every client project I'll have one just to collect the needed classes from the "my-util" library ("my-pda-app" project will need a "my-lib-wrapper-for-my-pda-app" project/dependency) [3] - Into the every client project that use the library (ex: my-pda-app) add some specialized Maven plugins to trim - out (when generating the final artifact/package) the un-needed classes (ex: maven-assembly-plugin, maven-jar-plugin, proguard-maven-plugin) What is the best practice for solving this kind of problems in the "Maven way" ?!

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• Adding Parsekit To An Xcode Project

  - by Garry

  I am trying to add the Parsekit framework to my OSX Xcode project. I've never added a 3rd party framework before and I can't get it to work right. I dragged the included Xcode project into my 'Groups & Files' pane and chose to Add it to my project. I then dragged Parsekit.framework underneath the Link Binary With Libraries heading. Then I double-clicked my target app and added Parsekit as a Direct Dependency. I also added libicucore.dylib as a Linked Library (as it says to do this on their site). Finally, in the Build settings tab of my target info I set the Header Search Paths to /Users/path/to/include/directory and the Other Linker Flags to -ObjC -all_load. Running this as a debug build work fine with no errors. However, when I build my app to release and then try to run the executable created, the app fails to load with the following error message: MyApp cannot be opened because of a problem. Check with the developer to make sure myApp works with this version of Mac OS X. Here is the dump from the crash reporter: Process: MyApp [11658] Path: /Users/Garry/Programming/Xcode/Mac/MyApp/build/Release/MyApp.app/Contents/MacOS/MyApp Identifier: com.yourcompany.MyApp Version: ??? (???) Code Type: X86-64 (Native) Parent Process: launchd [135] Date/Time: 2010-05-24 17:08:08.475 +0100 OS Version: Mac OS X 10.6.3 (10D573) Report Version: 6Interval Since Last Report: 133300 sec Crashes Since Last Report: 3 Per-App Crashes Since Last Report: 3 Anonymous UUID: DF0265E4-B5A0-45E1-8B71-D52A27CFDDCA Exception Type: EXC_BREAKPOINT (SIGTRAP) Exception Codes: 0x0000000000000002, 0x0000000000000000 Crashed Thread: 0 Dyld Error Message: Library not loaded: @executable_path/../Frameworks/ParseKit.framework/Versions/A/ParseKit Referenced from: /Users/Garry/Programming/Xcode/Mac/MyApp/build/Release/MyApp.app/Contents/MacOS/MyApp Reason: image not found Model: MacBookPro5,5, BootROM MBP55.00AC.B03, 2 processors, Intel Core 2 Duo, 2.53 GHz, 4 GB, SMC 1.47f2 Graphics: NVIDIA GeForce 9400M, NVIDIA GeForce 9400M, PCI, 256 MB Memory Module: global_name AirPort: spairport_wireless_card_type_airport_extreme (0x14E4, 0x8D), Broadcom BCM43xx 1.0 (5.10.91.27) Bluetooth: Version 2.3.1f4, 2 service, 2 devices, 1 incoming serial ports Network Service: AirPort, AirPort, en1 Network Service: Ethernet Adaptor (en6), Ethernet, en6 Serial ATA Device: Hitachi HTS545025B9SA02, 232.89 GB Serial ATA Device: HL-DT-ST DVDRW GS23N USB Device: Built-in iSight, 0x05ac (Apple Inc.), 0x8507, 0x24400000 USB Device: Internal Memory Card Reader, 0x05ac (Apple Inc.), 0x8403, 0x26500000 USB Device: IR Receiver, 0x05ac (Apple Inc.), 0x8242, 0x04500000 USB Device: Apple Internal Keyboard / Trackpad, 0x05ac (Apple Inc.), 0x0237, 0x04600000 USB Device: BRCM2046 Hub, 0x0a5c (Broadcom Corp.), 0x4500, 0x06100000 USB Device: Bluetooth USB Host Controller, 0x05ac (Apple Inc.), 0x8213, 0x06110000 After building the app, in addition to the executable file, Xcode is also creating a file called MyApp.app.dSYM. Any idea what that is?? I am developing with Xcode 3.2.2 on an Intel MBP running 10.6.3. Many thanks for any help offered.

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• Silverlight 4 DataBinding: Binding to ObservableCollection<string> not working anymore

  - by Kurt

  Upgrading from SL3 - SL4. First problem: this throws a parser exception: <StackPanel Name={Binding} /> (same with x:Name) Collection is ObservableCollection<string>. Worked fine in SL3. So it seems that SL4 doen't allow binding to the Name property. Huh? So: changed to <StackPanel Tag={Binding} /> ... since I just need to ID the control in code behind. So here's the bug ('cuz this has got to be a bug!): In this frag, AllAvailableItems is an ObservableCollection<string>: <ItemsControl Name="lbItems" ItemsSource="{Binding AllAvailableItems}" Height="Auto" Width="Auto" BorderBrush="Transparent" BorderThickness="0" VerticalAlignment="Top" HorizontalAlignment="Left" Margin="12,6,0,0"> <ItemsControl.ItemTemplate> <DataTemplate> <Grid> <Grid.RowDefinitions> <RowDefinition /> <RowDefinition /> </Grid.RowDefinitions> <CheckBox Tag="{Binding}" Checked="ItemChecked_Click" Unchecked="ItemUnchecked_Click" Style="{StaticResource CheckBoxStyle}" Grid.Row="0"> <CheckBox.Content> <TextBlock Text="{Binding}" Style="{StaticResource FormLJustStyle}" /> </CheckBox.Content> </CheckBox> <StackPanel Tag="{Binding}" Orientation="Vertical" Grid.Row="1"> <configControls:ucLanguage /> <!-- simple user control --> </StackPanel> </Grid> </DataTemplate> </ItemsControl.ItemTemplate> </ItemsControl> In the code behind, I use a recursive function to find the Dependency object with either the Name or Tag property provided: public static T FindVisualChildByName<T>(DependencyObject parent, string name, DependencyProperty propToUse) where T : DependencyObject { for (int i = 0; i < VisualTreeHelper.GetChildrenCount(parent); i++) { var child = VisualTreeHelper.GetChild(parent, i); string controlName = child.GetValue(propToUse) as string; if (controlName == name) { return child as T; } else { T result = FindVisualChildByName<T>(child, name, propToUse); if (result != null) return result; } } return null; } OK, get this: in the code behind, I can get the control that is ORDERED FIRST in the XAML! In other words, if I put the CheckBox first, I can retrieve the CheckBox, but no StackPanel. And vice-versa. This all worked fine in SL3. Any help, ideas ... ? Thanks - Kurt

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• Hidden Features of PHP?

  - by George Mauer

  EDIT: This didn't really start as a hidden features of PHP topic, but thats what it ended up as, so go nuts. I know this sounds like a point-whoring question but let me explain where I'm coming from. Out of college I got a job at a PHP shop. I worked there for a year and a half and thought that I had learned all there was to learn about programming. Then I got a job as a one-man internal development shop at a sizable corporation where all the work was in C#. In my commitment to the position I started reading a ton of blogs and books and quickly realized how wrong I was to think I knew everything. I learned about unit testing, dependency injection and decorator patterns, the design principle of loose coupling, the composition over inheritance debate, and so on and on and on - I am still very much absorbing it all. Needless to say my programming style has changed entirely in the last year. Now I find myself picking up a php project doing some coding for a friend's start-up and I feel completely constrained as opposed to programming in C#. It really bothers me that all variables at a class scope have to be referred to by appending '$this-' . It annoys me that none of the IDEs that I've tried have very good intellisense and that my SimpleTest unit tests methods have to start with the word 'test'. It drives me crazy that dynamic typing keeps me from specifying implicitly which parameter type a method expects, and that you have to write a switch statement to do method overloads. I can't stand that you can't have nested namespaces and have to use the :: operator to call the base class's constructor. Now I have no intention of starting a PHP vs C# debate, rather what I mean to say is that I'm sure there are some PHP features that I either don't know about or know about yet fail to use properly. I am set in my C# universe and having trouble seeing outside the glass bowl. So I'm asking, what are your favorite features of PHP? What are things you can do in it that you can't or are more difficult in the .Net languages?

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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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• LINQ to SQL Could not find key member. Only fails on server.

  - by Adam Carr

  I have a scenario where I am inheriting from an abstract class in my partial linq to sql auto generated class implementation. My base abstract class has an abstract property called ID which I have flagged inside my LINQ to SQL model with the instance modifier override. This works fine locally without any issues. I have also done some development on another machine and it works fine there too (both in VS2008 and using Subversion). I am running CI with TeamCity and the build succeeds and deploys as desired. The problem is when the server tries to hit the database for the first time via the LINQ to SQL data context, it generates the following error. "Could not find key member 'Id' of key 'Id' on type 'CustomType'. The key may be wrong or the field or property on 'CustomType' has changed names." I have tried changing my configuration by not implementing the Id field in my base class but this still fails. Why does it work on both of my DEV machines but not on the server? I am using LINQ to SQL in another project that runs on this server just fine. FYI: LINQ to SQL, SQL 2008, .NET 3.5, SERVER 2008, IIS 7.0 UPDATE I have gone back and added the same table a second time in the same data model but without a base class and have then displayed the results from that table and got no errors. This tells me it has something to do with my base abstract class and the need to flag a property on one of my linq to sql model classes (that belongs to a key relationship) with the instance modifier of override. No answer to this yet but am getting closer. UPDATE I have fixed my issue by simply changing my approach to my problem but I am still interested in why this doesn't work. I created a new WinSrv2008 VPC and patched it, deployed a pre-built version of my site to it and still got the same error. I now assume the issue is like what the person said here, a dependency issue with VS2008. My question is what or what? Will install VS2008 on the VPC to see if it works after that.

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• Maven building for GoogleAppEngine, forced to include JDO libraries?

  - by James.Elsey

  Hi, I'm trying to build my application for GoogleAppEngine using maven. I've added the following to my pom which should "enhance" my classes after building, as suggested on the DataNucleus documentation <plugin> <groupId>org.datanucleus</groupId> <artifactId>maven-datanucleus-plugin</artifactId> <version>1.1.4</version> <configuration> <log4jConfiguration>${basedir}/log4j.properties</log4jConfiguration> <verbose>true</verbose> </configuration> <executions> <execution> <phase>process-classes</phase> <goals> <goal>enhance</goal> </goals> </execution> </executions> </plugin> According to the documentation on GoogleAppEngine, you have the choice to use JDO or JPA, I've chosen to use JPA since I have used it in the past. When I try to build my project (before I upload to GAE) using mvn clean package I get the following output [ERROR] BUILD ERROR [INFO] ------------------------------------------------------------------------ [INFO] Failed to resolve artifact. Missing: ---------- 1) javax.jdo:jdo2-api:jar:2.3-ec Try downloading the file manually from the project website. Then, install it using the command: mvn install:install-file -DgroupId=javax.jdo -DartifactId=jdo2-api -Dversion=2.3-ec -Dpackaging=jar -Dfile=/path/to/file Alternatively, if you host your own repository you can deploy the file there: mvn deploy:deploy-file -DgroupId=javax.jdo -DartifactId=jdo2-api -Dversion=2.3-ec -Dpackaging=jar -Dfile=/path/to/file -Durl=[url] -DrepositoryId=[id] Path to dependency: 1) org.datanucleus:maven-datanucleus-plugin:maven-plugin:1.1.4 2) javax.jdo:jdo2-api:jar:2.3-ec ---------- 1 required artifact is missing. for artifact: org.datanucleus:maven-datanucleus-plugin:maven-plugin:1.1.4 from the specified remote repositories: __jpp_repo__ (file:///usr/share/maven2/repository), DN_M2_Repo (http://www.datanucleus.org/downloads/maven2/), central (http://repo1.maven.org/maven2) [INFO] ------------------------------------------------------------------------ [INFO] For more information, run Maven with the -e switch [INFO] ------------------------------------------------------------------------ [INFO] Total time: 3 seconds [INFO] Finished at: Sat Apr 03 16:02:39 BST 2010 [INFO] Final Memory: 31M/258M [INFO] ------------------------------------------------------------------------ Any ideas why I should get such an error? I've searched through my entire source code and I'm not referencing JDO anywhere, so unless the app engine libraries require it, I'm not sure why I get this message.

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• How to get hibernate3-maven-plugin hbm2ddl to find JDBC driver?

  - by HDave

  I have a Java project I am building with Maven. I am now trying to get the hibernate3-maven-plugin to run the hbm2ddl tool to generate a schema.sql file I can use to create the database schema from my annotated domain classes. This is a JPA application that uses Hibernate as the provider. In my persistence.xml file I call out the mysql driver: <property name="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect"/> <property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver"/> When I run Maven, I see it processing all my classes, but when it goes to output the schema, I get the following error: ERROR org.hibernate.connection.DriverManagerConnectionProvider - JDBC Driver class not found: com.mysql.jdbc.Driver java.lang.ClassNotFoundException: com.mysql.jdbc.Driver I have the MySQL driver as a dependency of this module. However it seems like the hbm2ddl tool cannot find it. I would have guessed that the Maven plugin would have known to search the local Maven file repository for this driver. What gives? The relevant part of my pom.xml is this: <plugin> <groupId>org.codehaus.mojo</groupId> <artifactId>hibernate3-maven-plugin</artifactId> <executions> <execution> <phase>process-classes</phase> <goals> <goal>hbm2ddl</goal> </goals> </execution> </executions> <configuration> <components> <component> <name>hbm2ddl</name> <implementation>jpaconfiguration</implementation> </component> </components> <componentProperties> <persistenceunit>my-unit</persistenceunit> </componentProperties> </configuration> </plugin>

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• What was "The Next Big Thing" when you were just starting out in programming?

  - by Andrew

  I'm at the beginning of my career and there are lots of things which are being touted as "The Next Big Thing". For example: Dependency Injection (Spring, etc) MVC (Struts, ASP.NET MVC) ORMs (Linq To SQL, Hibernate) Agile Software Development These things have probably been around for some time, but I've only just started out. And don't get me wrong, I think these things are great! So, what was "The Next Big Thing" when you were starting out? When was it? Were people sceptical of it at first? Why? Did you think it would catch on? Did it pan out and become widely accepted/used? If not, why not? EDIT It's been nearly a week since I first posted this question and I can safely say that I did not expect such explosive interest. I asked the question so that I could gain a perspective of what kinds of innovations in programming people thought were most important when they were starting out. At the time of writing this I have read ~95% of all answers. To answer a few questions, the "Next Big Things" I listed are ones that I am currently really excited about and that I had not really been exposed to until I started working. I'm hoping to implement some or all of these in the near future at my current workplace. To many people they are probably old news. In regards to the "is this a real question" debate, I can see that obviously hasn't been settled yet. I feel bad whenever I read a comment saying that these kinds of questions take away from the real meaning of SO. I'm not wholly convinced that it doesn't. On the other hand, I have seen a lot of comments saying what a great question it is. Anyway, I have chosen "The Internet!" as my answer to this question. I don't think (in my very humble opinion, and, it seems many SOers opinions) that many things related to programming can compare. Nowadays every business and their dog has a website which can do anything from simply supplying information to purchasing goods halfway around the world to updating your blog. And of course, all these businesses need people like us. Thanks to everyone for all the great answers!

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• Can ASM method-visitors be used with interfaces?

  - by Olaf Mertens

  I need to write a tool that lists the classes that call methods of specified interfaces. It will be used as part of the build process of a large java application consisting of many modules. The goal is to automatically document the dependencies between certain java modules. I found several tools for dependency analysis, but they don't work on the method level, just for packages or jars. Finally I found ASM, that seems to do what I need. The following code prints the method dependencies of all class files in a given directory: import java.io.*; import java.util.*; import org.objectweb.asm.ClassReader; public class Test { public static void main(String[] args) throws Exception { File dir = new File(args[0]); List<File> classFiles = new LinkedList<File>(); findClassFiles(classFiles, dir); for (File classFile : classFiles) { InputStream input = new FileInputStream(classFile); new ClassReader(input).accept(new MyClassVisitor(), 0); input.close(); } } private static void findClassFiles(List<File> list, File dir) { for (File file : dir.listFiles()) { if (file.isDirectory()) { findClassFiles(list, file); } else if (file.getName().endsWith(".class")) { list.add(file); } } } } import org.objectweb.asm.MethodVisitor; import org.objectweb.asm.commons.EmptyVisitor; public class MyClassVisitor extends EmptyVisitor { private String className; @Override public void visit(int version, int access, String name, String signature, String superName, String[] interfaces) { this.className = name; } @Override public MethodVisitor visitMethod(int access, String name, String desc, String signature, String[] exceptions) { System.out.println(className + "." + name); return new MyMethodVisitor(); } } import org.objectweb.asm.commons.EmptyVisitor; public class MyMethodVisitor extends EmptyVisitor { @Override public void visitMethodInsn(int opcode, String owner, String name, String desc) { String key = owner + "." + name; System.out.println(" " + key); } } The Problem: The code works for regular classes only! If the class file contains an interface, visitMethod is called, but not visitMethodInsn. I don't get any info about the callers of interface methods. Any ideas?

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• Sunspot_Rails Rake Aborted When Running Reindex

  - by Walter Chen

  I'm getting the following output after running rake sunspot:reindex. I'm a novice at Rails. I want to add sunspot_rails to my project to add search functionality (with the hope of deploying the project with Heroku). I'm using Rails 3. I followed the instructions here: https://github.com/outoftime/sunspot/blob/master/sunspot_rails/README.rdoc. My various other attempts to diagnose the problem included: installing sunspot in addition to sunspot_rails. I ended up with sunspot_rails v. 1.2.0 and 1.2.1 so I uninstalled 1.2.1 because I have sunspot_rails 1.2.0. installed the nokogiri gem which I understand is a dependency for sunspot_rails. installed libxml2 separately following the instructions here to install nokogiri: http://www.engineyard.com/blog/2010/getting-started-with-nokogiri/ ** Invoke sunspot:reindex (first_time) ** Invoke environment (first_time) ** Execute environment ** Execute sunspot:reindex rake aborted! undefined local variable or method counter' for [removed pound]<Class:0x10359aef8> /Library/Ruby/Gems/1.8/gems/activerecord-3.0.3/lib/active_record/base.rb:1008:inmethod_missing' /Library/Ruby/Gems/1.8/gems/sunspot_rails-1.2.0/lib/sunspot/rails/searchable.rb:235:in solr_index' /Library/Ruby/Gems/1.8/gems/activerecord-3.0.3/lib/active_record/relation/batches.rb:71:infind_in_batches' /Library/Ruby/Gems/1.8/gems/activerecord-3.0.3/lib/active_record/base.rb:440:in __send__' /Library/Ruby/Gems/1.8/gems/activerecord-3.0.3/lib/active_record/base.rb:440:infind_in_batches' /Library/Ruby/Gems/1.8/gems/sunspot_rails-1.2.0/lib/sunspot/rails/searchable.rb:234:in solr_index' /Library/Ruby/Gems/1.8/gems/sunspot_rails-1.2.0/lib/sunspot/rails/searchable.rb:184:insolr_reindex' /Library/Ruby/Gems/1.8/gems/sunspot_rails-1.2.0/lib/sunspot/rails/tasks.rb:57 /Library/Ruby/Gems/1.8/gems/sunspot_rails-1.2.0/lib/sunspot/rails/tasks.rb:56:in each' /Library/Ruby/Gems/1.8/gems/sunspot_rails-1.2.0/lib/sunspot/rails/tasks.rb:56 /Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:636:incall' /Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:636:in execute' /Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:631:ineach' /Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:631:in execute' /Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:597:ininvoke_with_call_chain' /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/monitor.rb:242:in synchronize' /Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:590:ininvoke_with_call_chain' /Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:583:in invoke' /Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2051:ininvoke_task' /Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2029:in top_level' /Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2029:ineach' /Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2029:in top_level' /Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2068:instandard_exception_handling' /Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2023:in top_level' /Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2001:inrun' /Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2068:in standard_exception_handling' /Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:1998:inrun' /Library/Ruby/Gems/1.8/gems/rake-0.8.7/bin/rake:31 /usr/bin/rake:19:in `load' /usr/bin/rake:19 This is what I have in class I'd like to search: searchable do text :fname text :mname text :lname, :default_boost => 2 end Any help would be greatly appreciated!

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• hibernate3-maven-plugin: entiries in different maven projects, hbm2ddl fails

  - by Mike

  I'm trying to put an entity in a different maven project. In the current project I have: @Entity public class User { ... private FacebookUser facebookUser; ... public FacebookUser getFacebookUser() { return facebookUser; } ... public void setFacebookUser(FacebookUser facebookUser) { this.facebookUser = facebookUser; } Then FacebookUser (in a different maven project, that's a dependency of a current project) is defined as: @Entity public class FacebookUser { ... @Id @GeneratedValue(strategy = GenerationType.AUTO) public Long getId() { return id; } Here is my maven hibernate3-maven-plugin configuration: <plugin> <groupId>org.codehaus.mojo</groupId> <artifactId>hibernate3-maven-plugin</artifactId> <version>2.2</version> <executions> <execution> <phase>process-classes</phase> <goals> <goal>hbm2ddl</goal> </goals> </execution> </executions> <configuration> <components> <component> <name>hbm2ddl</name> <implementation>jpaconfiguration</implementation> </component> </components> <componentProperties> <ejb3>false</ejb3> <persistenceunit>Default</persistenceunit> <outputfilename>schema.ddl</outputfilename> <drop>false</drop> <create>true</create> <export>false</export> <format>true</format> </componentProperties> </configuration> </plugin> Here is the error I'm getting: org.hibernate.MappingException: Could not determine type for: com.xxx.facebook.model.FacebookUser, at table: user, for columns: [org.hibernate.mapping.Column(facebook_user)] I know that FacebookUser is on the classpath because if I make facebook user transient, project compiles fine: @Transient public FacebookUser getFacebookUser() { return facebookUser; }

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• How to force VS 2010 to skip "builds" of projects which haven't changed?

  - by Ladislav Mrnka

  Our product's solution has more than 100+ projects (500+ksloc of production code). Most of them are C# projects but we also have few using C++/CLI to bridge communication with native code. Rebuilding the whole solution takes several minutes. That's fine. If I want to rebuilt the solution I expect that it will really take some time. What is not fine is time needed to build solution after full rebuild. Imagine I used full rebuild and know without doing any changes to to the solution I press Build (F6 or Ctrl+Shift+B). Why it takes 35s if there was no change? In output I see that it started "building" of each project - it doesn't perform real build but it does something which consumes significant amount of time. That 35s delay is pain in the ass. Yes I can improve the time by not using build solution but only build project (Shift+F6). If I run build project on particular test project I'm currently working on it will take "only" 8+s. It requires me to run project build on correct project (the test project to ensure dependent tested code is build as well). At least ReSharper test runner correctly recognizes that only this single project must be build and rerunning test usually contains only 8+s compilation. My current coding Kata is: don't touch Ctrl+Shift+B. The test project build will take 8s even if I don't do any changes. The reason why it takes 8s is because it also "builds" dependencies = in my case it "builds" more than 20 projects but I made changes only to unit test or single dependency! I don't want it to touch other projects. Is there a way to simply tell VS to build only projects where some changes were done and projects which are dependent on changed ones (preferably this part as another build option)? I worry you will tell me that it is exactly what VS is doing but in MS way ... I want to improve my TDD experience and reduce the time of compilation (in TDD the compilation can happen twice per minute). To make this even more frustrated I'm working in a team where most of developers used to work on Java projects prior to joining this one. So you can imagine how they are pissed off when they must use VS in contrast to full incremental compilation in Java. I don't require incremental compilation of classes. I expect working incremental compilation of solutions. Especially in product like VS 2010 Ultimate which costs several thousands dollars. I really don't want to get answers like: Make a separate solution Unload projects you don't need etc. I can read those answers here. Those are not acceptable solutions. We're not paying for VS to do such compromises.

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• How to measure a canvas that has auto height and with

  - by Wymmeroo

  Hi Folks, I'm a beginner in silverlight so i hope i can get an answer that brings me some more light in the measure process of silverlight. I found an interessting flap out control from silverlight slide control and now I try to use it in my project. So that the slide out is working proper, I have to place the user control on a canvas. The user control then uses for itself the height of its content. I just wanna change that behavior so that the height is set to the available space from the parent canvas. You see the uxBorder where the height is set. How can I measure the actual height and set it to the border? I tried it with Height={Binding ElementName=notificationCanvas, Path=ActualHeight} but this dependency property has no callback, so the actualHeight is never set. What I want to achieve is a usercontrol like the tweetboard per example on Jesse Liberty's blog Sorry for my English writing, I hope you understand my question. <Canvas x:Name="notificationCanvas" Background="Red"> <SlideEffectEx:SimpleSlideControl GripWidth="20" GripTitle="Task" GripHeight="100"> <Border x:Name="uxBorder" BorderThickness="2" CornerRadius="5" BorderBrush="DarkGray" Background="DarkGray" Padding="5" Width="300" Height="700" > <StackPanel> <TextBlock Text="Tasks"></TextBlock> <Button x:Name="btn1" Margin="5" Content="{Binding ElementName=MainBorder, Path=Height}"></Button> <Button x:Name="btn2" Margin="5" Content="Second Button"></Button> <Button x:Name="btn3" Margin="5" Content="Third Button"></Button> <Button x:Name="btn1_Copy" Margin="5" Content="First Button"/> <Button x:Name="btn1_Copy1" Margin="5" Content="First Button"/> <Button x:Name="btn1_Copy2" Margin="5" Content="First Button"/> <Button x:Name="btn1_Copy3" Margin="5" Content="First Button"/> <Button x:Name="btn1_Copy4" Margin="5" Content="First Button"/> <Button x:Name="btn1_Copy5" Margin="5" Content="First Button"/> <Button x:Name="btn1_Copy6" Margin="5" Content="First Button"/> </StackPanel> </Border> </SlideEffectEx:SimpleSlideControl>

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• Why does my ko computed observable not update bound UI elements when its value changes?

  - by Allen

  I'm trying to wrap a cookie in a computed observable (which I'll later turn into a protectedObservable) and I'm having some problems with the computed observable. I was under the opinion that changes to the computed observable would be broadcast to any UI elements that have been bound to it. I've created the following fiddle JavaScript: var viewModel = {}; // simulating a cookie store, this part isnt as important var cookie = function () { // simulating a value stored in cookies var privateZipcode = "12345"; return { 'write' : function (val) { privateZipcode = val; }, 'read': function () { return privateZipcode; } } }(); viewModel.zipcode = ko.computed({ read: function () { return cookie.read(); }, write: function (value) { cookie.write(value); }, owner: viewModel }); ko.applyBindings(viewModel);? HTML: zipcode: <input type='text' data-bind="value: zipcode"> <br /> zipcode: <span data-bind="text: zipcode"></span>? I'm not using an observable to store privateZipcode since that's really just going to be in a cookie. I'm hoping that the ko.computed will provide the notifications and binding functionality that I need, though most of the examples I've seen with ko.computed end up using a ko.observable underneath the covers. Shouldn't the act of writing the value to my computed observable signal the UI elements that are bound to its value? Shouldn't these just update? Workaround I've got a simple workaround where I just use a ko.observable along side of my cookie store and using that will trigger the required updates to my DOM elements but this seems completely unnecessary, unless ko.computed lacks the signaling / dependency type functionality that ko.observable has. My workaround fiddle, you'll notice that the only thing that changes is that I added a seperateObservable that isn't used as a store, its only purpose is to signal to the UI that the underlying data has changed. // simulating a cookie store, this part isnt as important var cookie = function () { // simulating a value stored in cookies var privateZipcode = "12345"; // extra observable that isnt really used as a store, just to trigger updates to the UI var seperateObservable = ko.observable(privateZipcode); return { 'write' : function (val) { privateZipcode = val; seperateObservable(val); }, 'read': function () { seperateObservable(); return privateZipcode; } } }(); This makes sense and works as I'd expect because viewModel.zipcode depends on seperateObservable and updates to that should (and does) signal the UI to update. What I don't understand, is why doesn't a call to the write function on my ko.computed signal the UI to update, since that element is bound to that ko.computed? I suspected that I might have to use something in knockout to manually signal that my ko.computed has been updated, and I'm fine with that, that makes sense. I just haven't been able to find a way to accomplish that.

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• Rails. 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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• Isn't the C++ standard library backward-compatible?

  - by Chris Metzler

  Hi. I'm working on a 64-bit Linux system, trying to build some code that depends on third-party libraries for which I have binaries. During linking, I get a stream of undefined reference errors for one of the libraries, indicating that the linker couldn't resolve references to standard C++ functions/classes, e.g.: librxio.a(EphReader.o): In function `gpstk::EphReader::read_fic_data(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)': EphReader.cpp:(.text+0x27c): undefined reference to `std::basic_ostream<char, std::char_traits<char> >& std::__ostream_insert<char, std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*, long)' EphReader.cpp:(.text+0x4e8): undefined reference to `std::basic_ostream<char, std::char_traits<char> >& std::__ostream_insert<char, std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*, long)' I'm not really a C++ programmer, but this looks to me like it can't find the standard library. Doing some more research, I got the following when I looked at librxio's dependency for the standard library: $ ldd librxio.so.16.0 ./librxio.so.16.0: /usr/lib64/libstdc++.so.6: version `GLIBCXX_3.4.9' not found (required by ./librxio.so.16.0) libm.so.6 => /lib64/libm.so.6 (0x00002aaaaad45000) libstdc++.so.6 => /usr/lib64/libstdc++.so.6 (0x00002aaaaafc8000) libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x00002aaaab2c8000) libc.so.6 => /lib64/libc.so.6 (0x00002aaaab4d7000) /lib64/ld-linux-x86-64.so.2 (0x0000555555554000) So I read that as saying that librxio (one of the third-party libraries) requires at least v3.4.9 of the standard library. But the version I have installed is 4.1.2: $ rpm -qa | grep libstdc compat-libstdc++-33-3.2.3-61.x86_64 libstdc++-devel-4.1.2-14.el5.i386 libstdc++-devel-4.1.2-14.el5.x86_64 libstdc++-4.1.2-14.el5.x86_64 libstdc++-4.1.2-14.el5.i386 Shouldn't this work? The shared object major number is 6, same as for v3.4.9. At this level, shouldn't this be backward compatible? It seems like the third-party library is looking for an earlier version of the standard library than what I have installed; but isn't there backward compatibility between versions with the same major number for the shared library? Again, I'm not really a C++ programmer; but I don't see what the problem is. Any advice greatly appreciated. Thanks.

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• How can I structure and recode messy categorical data in R?

  - by briandk

  I'm struggling with how to best structure categorical data that's messy, and comes from a dataset I'll need to clean. The Coding Scheme I'm analyzing data from a university science course exam. We're looking at patterns in student responses, and we developed a coding scheme to represent the kinds of things students are doing in their answers. A subset of the coding scheme is shown below. Note that within each major code (1, 2, 3) are nested non-unique sub-codes (a, b, ...). What the Raw Data Looks Like I've created an anonymized, raw subset of my actual data which you can view here. Part of my problem is that those who coded the data noticed that some students displayed multiple patterns. The coders' solution was to create enough columns (reason1, reason2, ...) to hold students with multiple patterns. That becomes important because the order (reason1, reason2) is arbitrary--two students (like student 41 and student 42 in my dataset) who correctly applied "dependency" should both register in an analysis, regardless of whether 3a appears in the reason column or the reason2 column. How Can I Best Structure Student Data? Part of my problem is that in the raw data, not all students display the same patterns, or the same number of them, in the same order. Some students may do just one thing, others may do several. So, an abstracted representation of example students might look like this: Note in the example above that student002 and student003 both are coded as "1b", although I've deliberately shown the order as different to reflect the reality of my data. My (Practical) Questions Should I concatenate reason1, reason2, ... into one column? How can I (re)code the reasons in R to reflect the multiplicity for some students? Thanks I realize this question is as much about good data conceptualization as it is about specific features of R, but I thought it would be appropriate to ask it here. If you feel it's inappropriate for me to ask the question, please let me know in the comments, and stackoverflow will automatically flood my inbox with sadface emoticons. If I haven't been specific enough, please let me know and I'll do my best to be clearer.

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