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  • Multiple user roles in Ruby on Rails

    - by aguynamedloren
    I am building an inventory management application with four different user types: admin, employee, manufacturer, transporter. I haven't started coding yet, but this is what I'm thinking.. Manufacturers and transporters are related with has_many :through many-to-many association with products as follows: class Manufacturer < ActiveRecord::Base has_many :products has_many :transporters, :through => :products end class Product < ActiveRecord::Base belongs_to :manufacturer belongs_to :transporter end class Transporter < ActiveRecord::Base has_many :products has_many :manufacturers, :through => :products end All four user types will be able to login, but they will have different permissions and views, etc. I don't think I can put them in the same table (Users), however, because they will have different requirements, ie: vendors and manufacturers must have a billing address and contact info (through validations), but admins and employees should not have these fields. If possible, I would like to have a single login screen as opposed to 4 different screens. I'm not asking for the exact code to build this, but I'm having trouble determining the best way to make it happen. Any ideas would be greatly appreciated - thanks!

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  • Testing a wide variety of computers with a small company

    - by Tom the Junglist
    Hello everyone, I work for a small dotcom which will soon be launching a reasonably-complicated Windows program. We have uncovered a number of "WTF?" type scenarios that have turned up as the program has been passed around to the various not-technical-types that we've been unable to replicate. One of the biggest problems we're facing is that of testing: there are a total of three programmers -- only one working on this particular project, me -- no testers, and a handful of assorted other staff (sales, etc). We are also geographically isolated. The "testing lab" consists of a handful of VMWare and VPC images running sort-of fresh installs of Windows XP and Vista, which runs on my personal computer. The non-technical types try to be helpful when problems arise, we have trained them on how to most effectively report problems, and the software itself sports a wide array of diagnostic features, but since they aren't computer nerds like us their reporting is only so useful, and arranging remote control sessions to dig into the guts of their computers is time-consuming. I am looking for resources that allow us to amplify our testing abilities without having to put together an actual lab and hire beta testers. My boss mentioned rental VPS services and asked me to look in to them, however they are still largely very much self-service and I was wondering if there were any better ways. How have you, or any other companies in a similar situation handled this sort of thing? EDIT: According to the lingo, our goal here is to expand our systems testing capacity via an elastic computing platform such as Amazon EC2. At this point I am not sure suggestions of beefing up our unit/integration testing are going to help very much as we are consistently hitting walls at the systems testing phase. Has anyone attempted to do this kind of software testing on a cloud-type service like EC2? Tom

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  • Deserializing a FileStream on Client using WCF

    - by Grandpappy
    I'm very new to WCF, so I apologize in advance if I misstate something. This is using .NET 4.0 RC1. Using WCF, I am trying to deserialize a response from the server. The base response has a Stream as its only MessageBodyMember. public abstract class StreamedResponse { [MessageBodyMember] public Stream Stream { get; set; } public StreamedResponse() { this.Stream = Stream.Null; } } The derived versions of this class are actually what's serialized, but they don't have a MessageBodyMember attribute (they have other base types such as int, string, etc listed as MessageHeader values). [MessageContract] public class ChildResponse : StreamedResponse { [DataMember] [MessageHeader] public Guid ID { get; set; } [DataMember] [MessageHeader] public string FileName { get; set; } [DataMember] [MessageHeader] public long FileSize { get; set; } public ChildResponse() : base() { } } The Stream is always a FileStream, in my specific case (but may not always be). At first, WCF said FileStream was not a known type, so I added it to the list of known types and now it serializes. It also appears, at first glance, to deserialize it on the client's side (it's the FileStream type). The problem is that it doesn't seem to be usable. All the CanRead, CanWrite, etc are false, and the Length, Position, etc properties throw exceptions when being used. Same with ReadByte(). What am I missing that would keep me from getting a valid FileStream?

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  • Why is Collection<String>.class Illegal?

    - by Peter
    I am puzzled by generics. You can declare a field like: Class<Collection<String>> clazz = ... It seems logical that you could assign this field with: Class<Collection<String>> clazz = Collection<String>.class; However, this generates an error: Syntax error on token ">", void expected after this token So it looks like the .class operator does not work with generics. So I tried: class A<S> {} class B extends A<String> {} Class<A<String>> c = B.class; Also does not work, generates: Type mismatch: cannot convert from Class<Test.StringCollection> to Class<Collection<String>> Now, I really fail to see why this should not work. I know generic types are not reified but in both cases it seems to be fully type safe without having access to runtime generic types. Anybody an idea? Peter Kriens

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  • how to 'scale' these three tables?

    - by iddqd
    I have the following Tables: Players id playerName Weapons id type otherData Weapons2Player id playersID_reference weaponsID_reference That was nice and simple. Now I need to SELECT items from the Weapons table, according to some of their characteristics that i previously just packed into the otherData column (since it was only needed on the client side). The problem is, that the types have varying characteristics - but also a lot of similar data. So I'm trying to decide on the following possibilities, all of which have their pros and cons. Solution A Kill the Weapons table, and create a new table for each Weapon-Type: Weapons_Swords id bladeType damage otherData Weapons_Guns id accuracy damage ammoType otherData But how will i Link these to the Players ? create Weapons_Swords2Players, Weapons_Guns2Players for each weapon-type? (Will result in a lot more JOINS when loading the player with all his weapons...and it's also more complicated to insert a new player) or add another column to Weapons2Players called WeaponsTypeTable, then do sub-selects to the correct Weapons sub-table (seems easier, but not really right, slightly easier insert i guess) Solution B Keep the Weapons table, and add all the fields i need to it. The Problem is that then there will be NULL fields, since not all Weapon-Types use all fields (can't be right) Weapons id type accuracy damage ammoType bladeType otherData This seems to be pretty basic stuff, but i just can't decide what's best. Or is there a correct Solution C? many thanks.

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  • How can I sync files in two different git repositories (not clones) and maintain history?

    - by brian d foy
    I maintain two different git repos that need to share some files, and I'd like the commits in one repo to show up in the other. What's a good way to do that for ongoing maintenance? I've been one of the maintainers of the perlfaq (Github), and recently I fell into the role of maintaining the Perl core documentation, which is also in git. Long before I started maintaining the perlfaq, it lived in a separate source control repository. I recently converted that to git. Periodically, one of the perl5-porters would sync the shared files in the perlfaq repo and the perl repo. Since we've switched to git, we'e been a bit lazy converting the tools, and I'm now the one who does that. For the time being, the two repos are going to stay separate. Currently, to sync the FAQ for a new (monthly) release of perl, I'm almost ashamed to say that I merely copy the perlfaq*.pod files in the perlfaq repo and overlay them in the perl repo. That loses history, etc. Additionally, sometimes someone makes a change to those files in the perl repo and I end up overwriting it (yes, check git diff you idiot!). The files do not have the same paths in the repo, but that's something that I could change, I think. What I'd like to do, in the magical universe of rainbows and ponies, is pull the objects from the perlfaq repo and apply them in the perl repo, and vice-versa, so the history and commit ids correspond in each. Creating patches works, but it's also a lot work to manage it Git submodules seem to only work to pull in the entire external repo I haven't found something like svn's file externals, but that would work in both directions anyway I'd love to just fetch objects from one and cherry-pick them in the other What's a good way to manage this?

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  • C# style Action<T>, Func<T,T>, etc in C++0x

    - by Austin Hyde
    C# has generic function types such as Action<T> or Func<T,U,V,...> With the advent of C++0x and the ability to have template typedef's and variadic template parameters, it seems this should be possible. The obvious solution to me would be this: template <typename T> using Action<T> = void (*)(T); however, this does not accommodate for functors or C++0x lambdas, and beyond that, does not compile with the error "expected unqualified-id before 'using'" My next attempt was to perhaps use boost::function: template <typename T> using Action<T> = boost::function<void (T)>; This doesn't compile either, for the same reason. My only other idea would be STL style template arguments: template <typename T, typename Action> void foo(T value, Action f) { f(value); } But this doesn't provide a strongly typed solution, and is only relevant inside the templated function. Now, I will be the first to admit that I am not the C++ wiz I prefer to think I am, so it's very possible there is an obvious solution I'm not seeing. Is it possible to have C# style generic function types in C++?

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  • Multiple Table Inheritance vs. Single Table Inheritance in Ruby on Rails

    - by Tony
    I have been struggling for the past few hours thinking about which route I should go. I have a Notification model. Up until now I have used a notification_type column to manage the types but I think it will be better to create separate classes for the types of notifications as they behave differently. Right now, there are 3 ways notifications can get sent out: SMS, Twitter, Email Each notification would have: id subject message valediction sent_people_count deliver_by geotarget event_id list_id processed_at deleted_at created_at updated_at Seems like STI is a good candidate right? Of course Twitter/SMS won't have a subject and Twitter won't have a sent_people_count, valediction. I would say in this case they share most of their fields. However what if I add a "reply_to" field for twitter and a boolean for DM? My point here is that right now STI makes sense but is this a case where I may be kicking myself in the future for not just starting with MTI? To further complicate things, I want a Newsletter model which is sort of a notification but the difference is that it won't use event_id or deliver_by. I could see all subclasses of notification using about 2/3 of the notification base class fields. Is STI a no-brainer, or should I use MTI? Thanks!

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  • Possible to have multiple Profiles in ASP.NET for different users?

    - by asple
    My application has a few different user types with their own members. For example, I have the student user as well as the teacher user. I authenticate my users through active directory in my custom MembershipProvider's ValidateUser method. While querying AD, I pull out all their relevant information. I'd like to put that information into a Profile, but from what I've read and the examples I've sen, you can only define a single Profile (like so): <profile defaultProvider="CustomProfileProvider" enabled="true"> <properties> <add name="YearLevel" type="String" /> <add name="Name" type="String" /> <add name="Age" type="String" /> </properties> </profile> The above profile would work for a student, but not for a teacher, who does not have a value for "YearLevel" in AD. Is it possible to have multiple profiles to accomplish this? Or is it easier to add all properties from AD spanning all user types, then in my code, just check what user type they are and then access their specific properties?

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  • question/problem regarding assigning an array of char *

    - by Fantastic Fourier
    Hi I'm working with C and I have a question about assigning pointers. struct foo { int _bar; char * _car[MAXINT]; // this is meant to be an array of char * so that it can hold pointers to names of cars } int foofunc (void * arg) { int bar; char * car[MAXINT]; struct foo thing = (struct foo *) arg; bar = arg->_bar; // this works fine car = arg->_car; // this gives compiler errors of incompatible types in assignment } car and _car have same declaration so why am I getting an error about incompatible types? My guess is that it has something to do with them being pointers (because they are pointers to arrays of char *, right?) but I don't see why that is a problem. when i declared char * car; instead of char * car[MAXINT]; it compiles fine. but I don't see how that would be useful to me later when I need to access certain info using index, it would be very annoying to access that info later. in fact, I'm not even sure if I am going about the right way, maybe there is a better way to store a bunch of strings instead of using array of char *?

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  • strict aliasing and alignment

    - by cooky451
    I need a safe way to alias between arbitrary POD types, conforming to ISO-C++11 explicitly considering 3.10/10 and 3.11 of n3242 or later. There are a lot of questions about strict aliasing here, most of them regarding C and not C++. I found a "solution" for C which uses unions, probably using this section union type that includes one of the aforementioned types among its elements or nonstatic data members From that I built this. #include <iostream> template <typename T, typename U> T& access_as(U* p) { union dummy_union { U dummy; T destination; }; dummy_union* u = (dummy_union*)p; return u->destination; } struct test { short s; int i; }; int main() { int buf[2]; static_assert(sizeof(buf) >= sizeof(double), ""); static_assert(sizeof(buf) >= sizeof(test), ""); access_as<double>(buf) = 42.1337; std::cout << access_as<double>(buf) << '\n'; access_as<test>(buf).s = 42; access_as<test>(buf).i = 1234; std::cout << access_as<test>(buf).s << '\n'; std::cout << access_as<test>(buf).i << '\n'; } My question is, just to be sure, is this program legal according to the standard?* It doesn't give any warnings whatsoever and works fine when compiling with MinGW/GCC 4.6.2 using: g++ -std=c++0x -Wall -Wextra -O3 -fstrict-aliasing -o alias.exe alias.cpp * Edit: And if not, how could one modify this to be legal?

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  • Can a destructor be recursive?

    - by Cubbi
    Is this program well-defined, and if not, why exactly? #include <iostream> #include <new> struct X { int cnt; X (int i) : cnt(i) {} ~X() { std::cout << "destructor called, cnt=" << cnt << std::endl; if ( cnt-- > 0 ) this->X::~X(); // explicit recursive call to dtor } }; int main() { char* buf = new char[sizeof(X)]; X* p = new(buf) X(7); p->X::~X(); // explicit call to dtor delete[] buf; } My reasoning: although invoking a destructor twice is undefined behavior, per 12.4/14, what it says exactly is this: the behavior is undefined if the destructor is invoked for an object whose lifetime has ended Which does not seem to prohibit recursive calls. While the destructor for an object is executing, the object's lifetime has not yet ended, thus it's not UB to invoke the destructor again. On the other hand, 12.4/6 says: After executing the body [...] a destructor for class X calls the destructors for X's direct members, the destructors for X's direct base classes [...] which means that after the return from a recursive invocation of a destructor, all member and base class destructors will have been called, and calling them again when returning to the previous level of recursion would be UB. Therefore, a class with no base and only POD members can have a recursive destructor without UB. Am I right?

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  • Do the new NoPIA and Type Equivalence features in C#/.NET 4.0 mean Microsoft.mshtml.dll is no longer

    - by jpierson
    I'm maintaining a WPF based application which contains a WinForms based WebBrowser control that based on the IE web browser control. When we deploy, we have had to also supply Microsoft.mshtml.dll and do some custom configuration stuff for our ClickOnce publishing process as well in order to get things to work. I'm curious that with the new NoPIA and Type Equivalence features and dynamic type capabilities in C# 4.0 can we expect that if we upgrade that we can remove the dependencies on the Microsoft.mshtml.dll assembly? If so this will not only reduce the size of our deployment quite a bit but will also simplify our publishing process as well. It is my understanding that we should be able embed the types that normally get automatically generated into extra assemblies for COM types such as the MapPoint Control by Visual Studio. I don't know if this also applies to the Microsoft.mshtml.dll or even how it is done even in the most simple of cases. If somebody could provide an explanation about what the practical impact of these new features are on a project that relies on COM interop and especially the Microsoft.mshtml.dll assembly it would be of great help to me.

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  • A map and set which uses contiguous memory and has a reserve function

    - by edA-qa mort-ora-y
    I use several maps and sets. The lack of contiguous memory, and high number of (de)allocations, is a performance bottleneck. I need a mainly STL-compatbile map and set class which can use a contiguous block of memory for internal objects (or multiple blocks). It also needs to have a reserve function so that I can preallocate for expected sizes. Before I write my own I'd like to check what is available first. Is there something in Boost which does this? Does somebody know of an available implementation elsewhere? Intrusive collection types are not usable here as the same objects need to exist in several collections. As far as I know STL memory pools are per-type, not per instance. These global pools are not efficient with respect to memory locality in mutli-cpu/core processing. Object pools don't work as the types will be shared between instance but their pool should not. In many cases a hash map may be an option in some cases.

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  • Problems with reading into buffer using boost::asio::async_read

    - by Max
    Good day. I have a Types.hpp file in my project. And within it i have: .... namespace RC { ..... ..... struct ViewSettings { .... }; ..... } In the Server.cpp file I'm including this Types.hpp file, and i have there: class Session { ..... RC::ViewSettings tmp; boost::asio::async_read(socket_, boost::asio::buffer(&tmp, sizeof(RC::ViewSettings)), boost::bind(&Session::Finish_Reading_Data, shared_from_this(), boost::asio::placeholders::error)); ..... } And during the compilation i have an errors: error C2825: 'F': must be a class or namespace when followed by '::' : see reference to class template instantiation 'boost::_bi::result_traits<R,F>' being compiled with [ R=boost::_bi::unspecified, F=void (__thiscall Session::* )(void) ] : see reference to class template instantiation 'boost::_bi::bind_t<R,F,L>' being compiled with [ R=boost::_bi::unspecified, F=void (__thiscall Session::* )(void), L=boost::_bi::list2<boost::_bi::value<boost::shared_ptr<Session>>,boost::arg<1>> ] error C2039: 'result_type' : is not a member of '`global namespace'' And the code like this works in proper way: int w; boost::asio::async_read(socket_, boost::asio::buffer(&w, sizeof(int)), boost::bind(&Session::Handle_Read_Width, shared_from_this(), boost::asio::placeholders::error)); Please, help. What's the problem here? Thanks in advance.

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  • Perl cgi @INC different in shell and in http request

    - by pistacchio
    Hi to all, I have the follwing, simplest per cgi script: use strict; use warnings; use CGI(); use CGI::Carp qw(fatalsToBrowser); use Template; print CGI::header(); foreach(@INC) { print "$_\n"; } When called (http://[..]/cgi-bin/p.cgi) I am given the following error: Can't locate Template.pm in @INC (@INC contains: /usr/lib/perl5/site_perl/5.8.8/i386-linux-thread-multi /usr/lib/perl5/site_perl/5.8.8 /usr/lib/perl5/site_perl /usr/lib/perl5/vendor_perl/5.8.8/i386-linux-thread-multi /usr/lib/perl5/vendor_perl/5.8.8 /usr/lib/perl5/vendor_perl /usr/lib/perl5/5.8.8/i386-linux-thread-multi /usr/lib/perl5/5.8.8 .) at /home/pistacchio/webapps/htdocs/cgi-bin/p.cgi line 8. BEGIN failed--compilation aborted at /home/pistacchio/webapps/htdocs/cgi-bin/p.cgi line 8. I made sure that Template is installed and indeed when running this program from shell it works (loads Template) and outputs: Content-Type: text/html; charset=ISO-8859-1 /home/pistacchio/lib/perl5 /home/pistacchio/lib/perl5/lib/i386-linux-thread-multi /home/pistacchio/lib/perl5/lib /home/pistacchio/lib/perl5/lib/i386-linux-thread-multi /usr/lib/perl5/site_perl/5.8.8/i386-linux-thread-multi /usr/lib/perl5/site_perl/5.8.8 /usr/lib/perl5/site_perl /usr/lib/perl5/vendor_perl/5.8.8/i386-linux-thread-multi /usr/lib/perl5/vendor_perl/5.8.8 /usr/lib/perl5/vendor_perl /usr/lib/perl5/5.8.8/i386-linux-thread-multi /usr/lib/perl5/5.8.8 Template is installed in /home/pistacchio/lib/perl5/lib/i386-linux-thread-multi [pistacchio@web118 i386-linux-thread-multi]$ pwd /home/pistacchio/lib/perl5/lib/i386-linux-thread-multi [pistacchio@web118 i386-linux-thread-multi]$ ls auto perllocal.pod Template Template.pm This directory is correctly listed in env and, as previously posted, in @INC. In @INC it is shown twice, so I even tried to pop it out before calling use Template, but without result. From env: [pistacchio@web118 i386-linux-thread-multi]$ env [..] PERL5LIB=/home/pistacchio/lib/perl5:/home/pistacchio/lib/perl5/lib:/home/pistacchio/lib/perl5/lib/i386-linux-thread-multi [..] Removing use Template gets rid of the problem. Can anybody help?

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  • How to determine which source files are required for an Eclipse run configuration

    - by isme
    When writing code in an Eclipse project, I'm usually quite messy and undisciplined in how I create and organize my classes, at least in the early hacky and experimental stages. In particular, I create more than one class with a main method for testing different ideas that share most of the same classes. If I come up with something like a useful app, I can export it to a runnable jar so I can share it with friends. But this simply packs up the whole project, which can become several megabytes big if I'm relying on large library such as httpclient. Also, if I decide to refactor my lump of code into several projects once I work out what works, and I can't remember which source files are used in a particular run configuration, all I can do it copy the main class to a new project and then keep copying missing types till the new project compiles. Is there a way in Eclipse to determine which classes are actually used in a particular run configuration? EDIT: Here's an example. Say I'm experimenting with web scraping, and so far I've tried to scrape the search-result pages of both youtube.com and wrzuta.pl. I have a bunch of classes that implement scraping in general, a few that are specific to each of youtube and wrzuta. On top of this I have a basic gui common to both scrapers, but a few wrzuta- and youtube-specific buttons and options. The WrzutaGuiMain and YoutubeGuiMain classes each contain a main method to configure and show the gui for each respective website. Can Eclipse look at each of these to determine which types are referenced?

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  • Is their a definitive list for the differences between the current version of SQL Azure and SQL Serv

    - by Aim Kai
    I am a relative newbie when it comes to SQL Azure!! I was wondering if there was a definitive list somewhere regarding what is and is not supported by SQL Azure in regards to SQL Server 2008? I have had a look through google but I've noticed some of the blog posts are missing things which I have found through my own testing: For example, quite a lot is summarised in this blog entry http://www.keepitsimpleandfast.com/2009/12/main-differences-between-sql-azure-and.html Common Language Runtime (CLR) Database file placement Database mirroring Distributed queries Distributed transactions Filegroup management Global temporary tables Spatial data and indexes SQL Server configuration options SQL Server Service Broker System tables Trace Flags which is a repeat of the MSDN page http://msdn.microsoft.com/en-us/library/ff394115.aspx I've noticed from my own testing that the following seem to have issues when migrating from SQL Server 2008 to the Azure: XML Types (the msdn does mention large custom types - I guess it may include this?? even if the data schema is really small?) Multi-part views I've been using SQL Azure Migration Wizard v3.1.8 to migrate local databases into the cloud. I was wondering if anyone could point to a list or give me any information till when these features are likely to be included in SQL Azure.

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  • How does the last integer promotion rule ever get applied in C?

    - by SiegeX
    6.3.1.8p1: Otherwise, the integer promotions are performed on both operands. Then the following rules are applied to the promoted operands: If both operands have the same type, then no further conversion is needed. Otherwise, if both operands have signed integer types or both have unsigned integer types, the operand with the type of lesser integer conversion rank is converted to the type of the operand with greater rank. Otherwise, if the operand that has unsigned integer type has rank greater or equal to the rank of the type of the other operand, then the operand with signed integer type is converted to the type of the operand with unsigned integer type. Otherwise, if the type of the operand with signed integer type can represent all of the values of the type of the operand with unsigned integer type, then the operand with unsigned integer type is converted to the type of the operand with signed integer type. Otherwise, both operands are converted to the unsigned integer type corresponding to the type of the operand with signed integer type. For the bolded rule to be applied it would seem to imply you need to have have an unsigned interger type who's rank is less than the signed integer type and the signed integer type cannot hold all the values of the unsigned integer type. Is there a real world example of such a case or is this statement serving as a catch-all to cover all possible permutations?

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  • Error when calling SQL SP via LINQ

    - by PaulC
    Newbie problem: I have a SQL SP with ten parameters (eight input, two output) but when I attempt to call it via LINQ from code I get the following error message: "The best overloaded method match for 'DataClassesDataContext.ST_CR_CREATE_CASE_BASIS(string, string, string, string, System.DateTime?, string, string, string, ref int?, ref int?)' has some invalid arguments". The params with ? appear to be unrecognized, but I'm baffled: the data types match the SQL types, the number of parameters match, the other parmeters don't exhibit the same behaviour. Can anyone tell me what's going on? Thanks in advance. -- SQL SP: create procedure ST_CR_CREATE_CASE_BASIS @p_Pers_No nvarchar (50), @p_Subject nvarchar (255), @p_RQ_XML nvarchar(max), @p_RQ_XSL nvarchar(max), @p_Date_Submit smalldatetime, @p_User_ID_Submit nvarchar (255), @p_RQ_Status nvarchar (50), @p_User_ID_OnBehalf nvarchar (255), @p_Case_Number int output, @p_RQ_ID int output as begin -- ... etc.; the SP works fine when called from SSMS The code-behind proc from the aspx page looks like this: protected void cmdSubmit_Click(object sender, EventArgs e) { using (DataClassesDataContext vDataCont = new DataClassesDataContext()) { Int32 vNewCaseNr; Int32 vNewReqNr; DateTime vNow = System.DateTime.Now; vDataCont.ST_CR_CREATE_CASE_BASIS("101", "Test Subject Late Wed", null, null, vNow , "101", "1", "101", ref vNewCaseNr, vNewReqNr); } }

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  • How do I so a select input for a STI column in a Rails model?

    - by James A. Rosen
    I have a model with single-table inheritance on the type column: class Pet < ActiveRecord::Base TYPES = [Dog, Cat, Hamster] validates_presence_of :name end I want to offer a <select> dropdown on the new and edit pages: <% form_for @model do |f| %> <%= f.label :name %> <%= f.text_input :name %> <%= f.label :type %> <%= f.select :type, Pet::TYPES.map { |t| [t.human_name, t.to_s] } %> <% end %> That gives me the following error: ActionView::TemplateError (wrong argument type String (expected Module)) I read a suggestion to use an alias for the field #type since Ruby considers that a reserved word that's the same as #class. I tried both class Pet < ActiveRecord::Base ... alias_attribute :klass, :type end and class Pet < ActiveRecord::Base ... def klass self.type end def klass=(k) self.type = k end end Neither worked. Any suggestions? Oddly, it works fine on my machine (MRI 1.8.6 on RVM), but fails on the staging server (MRI 1.8.7 not on RVM).

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  • Thread safe lazy contruction of a singleton in C++

    - by pauldoo
    Is there a way to implement a singleton object in C++ that is: Lazily constructed in a thread safe manner (two threads might simultaneously be the first user of the singleton - it should still only be constructed once). Doesn't rely on static variables being constructed beforehand (so the singleton object is itself safe to use during the construction of static variables). (I don't know my C++ well enough, but is it the case that integral and constant static variables are initialized before any code is executed (ie, even before static constructors are executed - their values may already be "initialized" in the program image)? If so - perhaps this can be exploited to implement a singleton mutex - which can in turn be used to guard the creation of the real singleton..) Excellent, it seems that I have a couple of good answers now (shame I can't mark 2 or 3 as being the answer). There appears to be two broad solutions: Use static initialisation (as opposed to dynamic initialisation) of a POD static varible, and implementing my own mutex with that using the builtin atomic instructions. This was the type of solution I was hinting at in my question, and I believe I knew already. Use some other library function like pthread_once or boost::call_once. These I certainly didn't know about - and am very grateful for the answers posted.

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  • How to parse XML file to get specific data effectively

    - by Carlos_Liu
    I have an XML file looks like this: <?xml version="1.0" encoding="utf-8" ?> <PathMasks> <Mask desc="Masks_X1"> <config id="01" mask="88" /> <config id="03" mask="80" /> <config id="51" mask="85" /> </Mask> <Mask desc="Masks_X2"> <config id="70" mask="1" /> <config id="73" mask="6" /> </Mask> <Types> <path id="01" desc="TC->PP1" /> <path id="02" desc="TC->PP2" /> <path id="03" desc="TC->PPn" /> </Types> </PathMasks> How to parse the file and get all the data of Mask_X1 as following: id value ===== 01, 88 03, 80 51, 85

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  • Dynamically populated NSPopUpButtonCell menu in an NSOutlineView

    - by Mo
    I’m working with an NSOutlineView which has two columns. My dataSource supplies the outline view with a tree of items of a custom class which represents file types (that is, you initialise it with a UTI). The first column is the display name of the file type (e.g., “Source code”, “Interface Builder NIB document”, etc.). The second column is an NSPopUpButtonCell which is supposed to allow the user to pick a handler for the given document type (think of Xcode’s “File Types” preference pane, and you’re pretty much there). I can generate an NSMenu for a given item in the tree, populated with options based upon the Launch Services database entries for the UTI, complete with the relevant application icon and and so on. In fact, the menu itself works wonderfully, populated by way of NSPopUpButtonCellWillPopUpNotification. The problem is, try as I might, the cell when the menu isn’t popped up always contains precisely one of two things: either an empty string, or the default text for the cell, the former if the result of -handlerName on the item (the attribute assigned to the column) is non-nil, the latter otherwise. Moreover, I’m manually calling -selectItem: on the NSPopUpButtonCell instance, which just seems Wrong. In contrast, the left-hand column, which is just an NSTextFieldCell, everything just works (although granted, all it’s got to do is read the value from the item and present it). (Disclaimer: I’m fairly new at Cocoa UI stuff; I know Objective-C, and lots of other programming languages, but I’ve not a huge amount of experience of building Mac OS X UIs, so be gentle).

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  • Embedding Lua functions as member variables in Java

    - by Zarion
    Although the program I'm working on is in Java, answering this from a C perspective is also fine, considering that most of this is either language-agnostic, or happens on the Lua side of things. In the outline I have for the architecture of a game I'm programming, individual types of game objects within a particular class (eg: creatures, items, spells, etc.) are loaded from a data file. Most of their properties are simple data types, but I'd like a few of these members to actually contain simple scripts that define, for example, what an item does when it's used. The scripts will be extremely simple, since all fundamental game actions will be exposed through an API from Java. The Lua is simply responsible for stringing a couple of these basic functions together, and setting arguments. The question is largely about the best way to store a reference to a specific Lua function as a member of a Java class. I understand that if I store the Lua code as a string and call lua_dostring, Lua will compile the code fresh every time it's called. So the function needs to be defined somehow, and a reference to this specific function wrapped in a Java function object. One possibility that I've considered is, during the data loading process, when the loader encounters a script definition in a data file, it extracts this string, decorates the function name using the associated object's unique ID, calls lua_dostring on the string containing a full function definition, and then wraps the generated function name in a Java function object. A function declared in script run with lua_dostring should still be added to the global function table, correct? I'm just wondering if there's a better way of going about this. I admit that my knowledge of Lua at this point is rather superficial and theoretical, so it's possible that I'm overlooking something obvious.

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