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  • Accessing subclass members from a superclass pointer C++

    - by Dr. Monkey
    I have an array of custom class Student objects. CourseStudent and ResearchStudent both inherit from Student, and all the instances of Student are one or the other of these. I have a function to go through the array, determine the subtype of each Student, then call subtype-specific member functions on them. The problem is, because these functions are not overloaded, they are not found in Student, so the compiler kicks up a fuss. If I have a pointer to Student, is there a way to get a pointer to the subtype of that Student? Would I need to make some sort of fake cast here to get around the compile-time error?

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  • Using Mercurial in a Large Organization

    - by Kristopher Johnson
    I've been using Mercurial for my own personal projects for a while, and I love it. My employer is considering a switch from CVS to SVN, but I'm wondering whether I should push for Mercurial (or some other DVCS) instead. One wrinkle with Mercurial is that it seems to be designed around the idea of having a single repository per "project". In this organization, there are dozens of different executables, DLLs, and other components in the current CVS repository, hierarchically organized. There are a lot of generic reusable components, but also some customer-specific components, and customer-specific configurations. The current build procedures generally get some set of subtrees out of the CVS repository. If we move from CVS to Mercurial, what is the best way to organize the repository/repositories? Should we have one huge Mercurial repository containing everything? If not, how fine-grained should the smaller repositories be? I think people will find it very annoying if they have to pull and push updates from a lot of different places, but they will also find it annoying if they have to pull/push the entire company codebase. Anybody have experience with this, or advice?

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  • How can I validate two or more fields in combination?

    - by DR
    I'm using JPA 2.0/Hibernate validation to validate my models. I now have a situation where the combination of two fields has to be validated: public class MyModel { public Integer getValue1() { //... } public String getValue2() { //... } } The model is invalid if both getValue1() and getValue2() are null and valid otherwise. How can I perform this kind of validation with JPA 2.0/Hibernate? With a simple @NotNull annotation both getters must be non-null to pass validation.

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  • How can I change my JLabel to look like a table cell with Substance?

    - by DR
    I have a custom TableCellRenderer which returns a JLabel as the renderer component. Naturally the table cell now looks like a label and no longer like a table cell, which makes a difference especially when using Substance. Is it possible to modify the label so that the LaF renders it like an ordinary table cell? The best I could do was setting the background color of the label, but the borders and transition effets are missing.

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  • Finding City and Zip Code for a Location

    - by Kristopher Johnson
    Given a latitude and longitude, what is the easiest way to find the name of the city and the US zip code of that location. (This is similar to http://stackoverflow.com/questions/23572/latitude-longitude-database, except I want to convert in the opposite direction.) Related question: http://stackoverflow.com/questions/158557/get-street-address-at-latlong-pair

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  • Should frontend and backend be handled by different controllers?

    - by DR
    In my previous learning projects I always used a single controller, but now I wonder if that is good practice or even always possible. In all RESTful Rails tutorials the controllers have a show, an edit and an index view. If an authorized user is logged on, the edit view becomes available and the index view shows additional data manipulation controls, like a delete button or a link to the edit view. Now I have a Rails application which falls exactly into this pattern, but the index view is not reusable: The normal user sees a flashy index page with lots of pictures, complex layout, no Javascript requirement, ... The Admin user index has a completly different minimalistic design, jQuery table and lots of additional data, ... Now I'm not sure how to handle this case. I can think of the following: Single controller, single view: The view is split into two large blocks/partials using an if statement. Single controller, two views: index and index_admin. Two different controllers: BookController and BookAdminController None of these solutions seems perfect, but for now I'm inclined to use the 3rd option. What's the preferred way to do this?

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  • Cache an FTP connection via session variables for use via AJAX?

    - by Chad Johnson
    I'm working on a Ruby web Application that uses the Net::FTP library. One part of it allows users to interact with an FTP site via AJAX. When the user does something, and AJAX call is made, and then Ruby reconnects to the FTP server, performs an action, and outputs information. Every time the AJAX call is made, Ruby has to reconnect to the FTP server, and that's slow. Is there a way I could cache this FTP connection? I've tried caching in the session hash, but "We're sorry, but something went wrong" is displayed, and a TCP dump is outputted in my logs whenever I attempt to store it in the session hash. I haven't tried memcache yet. Any suggestions?

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  • Does SQL Server have any kind of magic undo feature?

    - by Andrew G. Johnson
    Long story short is I tried to quickly update a single row in SQL Server using the Management studio and just typed UPDATE table SET column='value' and forgot the WHERE other_column='other_value' portion. Went for lunch, came back and theres 15 unread emails waiting for me. Happened about an hour ago, waiting for the database guy to come back to see when the last backup was. There's no magic UNDO feature though is there?

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  • Dynamic Dispatch without Virtual Functions

    - by Kristopher Johnson
    I've got some legacy code that, instead of virtual functions, uses a kind field to do dynamic dispatch. It looks something like this: // Base struct shared by all subtypes // Plain-old data; can't use virtual functions struct POD { int kind; int GetFoo(); int GetBar(); int GetBaz(); int GetXyzzy(); }; enum Kind { Kind_Derived1, Kind_Derived2, Kind_Derived3 }; struct Derived1: POD { Derived1(): kind(Kind_Derived1) {} int GetFoo(); int GetBar(); int GetBaz(); int GetXyzzy(); // plus other type-specific data and function members }; struct Derived2: POD { Derived2(): kind(Kind_Derived2) {} int GetFoo(); int GetBar(); int GetBaz(); int GetXyzzy(); // plus other type-specific data and function members }; struct Derived3: POD { Derived3(): kind(Kind_Derived3) {} int GetFoo(); int GetBar(); int GetBaz(); int GetXyzzy(); // plus other type-specific data and function members }; and then the POD class's function members are implemented like this: int POD::GetFoo() { // Call kind-specific function switch (kind) { case Kind_Derived1: { Derived1 *pDerived1 = static_cast<Derived1*>(this); return pDerived1->GetFoo(); } case Kind_Derived2: { Derived2 *pDerived2 = static_cast<Derived2*>(this); return pDerived2->GetFoo(); } case Kind_Derived3: { Derived3 *pDerived3 = static_cast<Derived3*>(this); return pDerived3->GetFoo(); } default: throw UnknownKindException(kind, "GetFoo"); } } POD::GetBar(), POD::GetBaz(), POD::GetXyzzy(), and other members are implemented similarly. This example is simplified. The actual code has about a dozen different subtypes of POD, and a couple dozen methods. New subtypes of POD and new methods are added pretty frequently, and so every time we do that, we have to update all these switch statements. The typical way to handle this would be to declare the function members virtual in the POD class, but we can't do that because the objects reside in shared memory. There is a lot of code that depends on these structs being plain-old-data, so even if I could figure out some way to have virtual functions in shared-memory objects, I wouldn't want to do that. So, I'm looking for suggestions as to the best way to clean this up so that all the knowledge of how to call the subtype methods is centralized in one place, rather than scattered among a couple dozen switch statements in a couple dozen functions. What occurs to me is that I can create some sort of adapter class that wraps a POD and uses templates to minimize the redundancy. But before I start down that path, I'd like to know how others have dealt with this.

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  • Is it possible to "learn" a regular expression by user-provided examples?

    - by DR
    Is it possible to "learn" a regular expression by user-provided examples? To clarify: I do not want to learn regular expressions. I want to create a program which "learns" a regular expression from examples which are interactively provided by a user, perhaps by selecting parts from a text or selecting begin or end markers. Is it possible? Are there algorithms, keywords, etc. which I can Google for? EDIT: Thank you for the answers, but I'm not interested in tools which provide this feature. I'm looking for theoretical information, like papers, tutorials, source code, names of algorithms, so I can create something for myself.

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  • Using jQuery to make a group of images appear in order.

    - by Sean Johnson
    I have a page that shows a bunch of thumbnails (around 30), and the client is wanting them to appear one by one, in order, going from left to right on the page. This is what I've tried: var start_opacity = 500; $j('.grid-photo').each(function(i) { start_opacity = start_opacity + 500; setTimeout(function() { $j(i).animate({opacity: 1}, 4000); }, start_opacity); }); It doesn't seem to know what i is referencing. Any thoughts?

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  • Where do I place the launch image "Default.png" in my iPhone app's project directory?

    - by Dr Dork
    In the Apple documentation, it says... iPhone OS looks for a Default.png file, located in the top level of the application bundle. but I'm having a hard time figuring out how to get the image in that location in the bundle (I'm new to all this). I'm assuming my image will end up in the right place in the bundle when I compile it so long as I add it to the project correctly and place it in the right location in the project directory. My questions are... Where in my project directory should I place the "Default.png" image? Do I need add it to the project through Xcode? If so, how? Thanks so much in advance for all your help! I'm going to continue researching this question right now.

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  • Access of private field of another object in copy constructors - Really a problem?

    - by DR
    In my Java application I have some copy-constructors like this public MyClass(MyClass src) { this.field1 = src.field1; this.field2 = src.field2; this.field3 = src.field3; ... } Now Netbeans 6.9 warns about this and I wonder what is wrong with this code? My concerns: Using the getters might introduce unwanted side-effects. The new object might no longer be considered a copy of the original. If it is recommended using the getters, wouldn't it be more consistent if one would use setters for the new instance as well?

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  • collecting a "+" via CGI

    - by Dr.Dredel
    I'm collecting text through a web form and noticing that when it is collected by my PERL CGI all instances of "+" are transformed into " ". I run the text through a javascript escape before submission, but escape seems to leave + unaltered. There must be something really obvious that I'm missing... how do I send the string "2 + 2 = 4" through and not have it arrive as "2 2 = 4" ??

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  • What's the best way to skin my iPhone app (similar to how the Notes app is skinned)?

    - by Dr Dork
    If you look at the Notes app on the iPad, you can see it uses all native iPhone controls, but they're "skinned" to look like a pad of paper. What's the best way to implement something similar to that? Could I use interface builder and simply change the background image for each of the controls, including the TableViews? Thanks in advance for all your help! I'm going to continue researching this question right now.

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  • Is there a way to specify a per-host deploy_to path with Capistrano?

    - by Chad Johnson
    I have searched and searched and asked a question already and have not received a clear answer. I have the following deploy script (snippet): set :application, "testapplication" set :repository, "ssh://domain.com//srv/hg/#{application}" set :scm, :mercurial set :deploy_to, "/srv/www/#{application}" role :web, "domain1.com", "domain2.com" role :app, "domain1.com", "domain2.com" role :db, "domain1.com", :primary => true, :norelease => true role :db, "domain2.com", :norelease => true As you see, I have set deploy_to to a specific path. And, I also have specified multiple web servers. However, each web server should have a different deployment path. I want to be able to run "cap deploy" and deploy to all hosts in one shot. I am NOT trying to deploy to staging and then to production. This is all production. My question is: how exactly do I specify a path per server? I have read the "Roles" documentation for Capistrano, and this is unclear. Can someone please post a deploy file example? I have read the documentation, and it is unclear how to do this. Does anyone know? Am I crazy? Am I thinking of this wrong or something? No answers anywhere online. Nowhere. Nothing. Please, someone help.

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  • warning about data loss c++/c

    - by Dr Deo
    i am getting a benign warning about possible data loss warning C4244: 'argument' : conversion from 'const int' to 'float', possible loss of data question i remember as if float has a larger precision than int. So how can data be lost if i convert from a smaller data type (int) to a larger data type (float)

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  • Is there any conflict between NFS and calling getFD().sync()?

    - by Dr.Dredel
    My boss is worried that our NFS file system will not be happy with the jboss run java process calling getFD().sync on the files we are writing. We have noticed that frequently the time stamp on the created file is minutes (sometimes as many as 15 minutes) after the log claims the file was finished writing. My only guess is that the NFS is hanging on to the file in memory and not writing it till it feels like it. sync should solve that probelm, right? I also noticed that there is never a close() called on the file. Wondering if that could have been the cause as well? any thoughts appreciated.

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