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  • Using variables within Attributes in C#

    - by tehp
    We have some Well-Attributed DB code, like so: [Display(Name = "Phone Number")] public string Phone { get; set; } Since it is quite generic we'd like to use it again, but with a different string in the Name part of the attribute. Since it's an attribute it seems to want things to be const, so we tried: const string AddressType = "Student "; [Display(Name = AddressType + "Phone Number")] public string Phone { get; set; } This seems to work alright, except that having a const string means we can't overwrite it in any base classes, thereby removing the functionality that we originally were intending to add, and exposing my question: Is there a way to use some sort of variable inside of an attribute so that we can inherit and keep the attribute decorations?

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  • C++ Types Impossible to Name

    - by Kirakun
    While reading Wikipedia's page on decltype, I was curious about the statement, Its [decltype's] primary intended use is in generic programming, where it is often difficult, or even impossible, to name types that depend on template parameters. While I can understand the difficulty part of that statement, what is an example where there is a need to name a type that cannot be named under C++03? EDIT: My point is that since everything in C++ has a declaration of types. Why would there ever be a case where it is impossible to name a type? Furthermore, aren't trait classes designed to yield type informations? Could trait classes be an alternative to decltype?

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  • is there some lightweight tecnique for adding type safety to identifier properties?

    - by shoren
    After using C++ I got used to the concept of Identifier which can be used with a class for the type, provides type safety and has no runtime overhead (the actual size is the size of the primitive). I want to do something like that, so I will not make mistakes like: personDao.find(book.getId());//I want compilation to fail personDao.find(book.getOwnerId());//I want compilation to succeed Possible solutuions that I don't like: For every entity have an entity id class wrapping the id primitive. I don't like the code bloat. Create a generic Identifier class. Code like this will not compile: void foo(Identifier book); void foo(Identifier person); Does anyone know of a better way? Is there a library with a utility such as this? Is implementing this an overkill? And the best of all, can this be done in Java without the object overhead like in C++?

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  • When should one let an application crash because of an exception in Java (design issue)?

    - by JVerstry
    In most cases, it is possible to catch exceptions in Java, even unchecked ones. But, it is not necessarily possible to do something about it (for example out of memory). For other cases, the issue I am trying to solve is a design principle one. I am trying to set-up a design principle or a set of rules indicating when one should give up on an exceptional situation, even if it is detected in time. The objective is trying to not crash the application as much as possible. Has someone already brainstormed and communicated about this? I am looking for specific generic cases and possible solutions, or thumb-rules. UPDATE Suggestions so far: Stop running if data coherency can be compromised Stop running if data can be deleted Stop running if you can't do anything about it (Out of memory...) Stop running if key service is not available or becomes unavailable and cannot be restarted If application must be stopped, degrade as gracefully as possible Use rollbacks in db transactions Log as much relevant information as you can Notify the developers

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  • Avoid stuck calling callback

    - by andlomba
    Hello all, This is a question about generic c++ event driven applications design. Lets assume that we have two threads, a "Dispatcher" (or "Engine"...) and a "Listener" (or "Client"...). Let's assume that I write the Dispatcher code, and release it as a library. I also write the Listener interface, of course. When the Dispatcher executes (after Listener registration) listenerInstance.onSomeEvent(); the event handling code will actually be executed by the Dispatcher thread, so if the person that implements the Listener writes something like void Listener::onSomeEvent() { while(true) ; } The Dispatcher will stuck forever. Is there a "plain old c++" (I mean no boost or libsigc++) way to "decouple" the two classes, so I can be sure that my Dispatcher will work fine whatever the Listeners does in the callbacks? bye and thanks in advance, Andrea

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  • Linq to SQL - How to compare against a collection in the where clause?

    - by Sgraffite
    I'd like to compare against an IEnumerable collection in my where clause. Do I need to manually loop through the collection to pull out the column I want to compare against, or is there a generic way to handle this? I want something like this: public IEnumerable<Cookie> GetCookiesForUsers(IEnumerable<User> Users) { var cookies = from c in db.Cookies join uc in db.UserCookies on c.CookieID equals uc.CookieID join u in db.Users on uc.UserID equals u.UserID where u.UserID.Equals(Users.UserID) select c; return cookies.ToList(); } I'm used to using the lambda Linq to SQL syntax, but I decided to try the SQLesque syntax since I was using joins this time. What is a good way to do this?

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  • How to bind to foreach context ?

    - by Rebol Tutorial
    Currently I have this snippet of code: save-blocks: func[file /local f out][ foreach [field1 field2 field3 field4 field5 field6 field7 field8 field9] blocks [ out: copy "" repeat n 9 [ part: get bind to-word rejoin ["field" n] 'field1 out: rejoin [out part ";"] ] remove back tail out write/lines/append f out ] It's not generic enough, I'd like to pass this block: [field1 field2 field3 field4 field5 field6 field7 field8 field9] as parameter and write something like this: save-blocks: func[block file /local f out][ foreach block blocks [ out: copy "" repeat n 9 [ part: get bind to-word rejoin ["field" n] 'field1 out: rejoin [out part ";"] ] remove back tail out write/lines/append f out ] But I don't know how to bind in this case too hard for me :(

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  • Rails has_one vs belongs_to semantics

    - by Anurag
    I have a model representing a Content item that contains some images. The number of images are fixed as these image references are very specific to the content. For example, the Content model refers to the Image model twice (profile image, and background image). I am trying to avoid a generic has_many, and sticking to multiple has_one's. The current database structure looks like: contents - id:integer - integer:profile_image_id - integer:background_image_id images - integer:id - string:filename - integer:content_id I just can't figure out how to setup the associations correctly here. The Content model could contain two belongs_to references to an Image, but that doesn't seem semantically right cause ideally an image belongs to the content, or in other words, the content has two images. This is the best I could think of (by breaking the semantics): class Content belongs_to :profile_image, :class_name => 'Image', :foreign_key => 'profile_image_id' belongs_to :background_image, :class_name => 'Image', :foreign_key => 'background_image_id' end Am I way off, and there a better way to achieve this association?

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  • Are there any pitfalls to having two different Models from two different assemblies? (EF)

    - by Jonn
    I have two projects, both of them data access layers, and both using EF. I have another project calling services related to the two different assemblies. Are there any pitfalls on using two different models on two different databases linked to the same database? I'm asking this because I've been getting this generic "EntitySqlException" could not be resolved in the current scope or context. Make sure that all referenced variables are in scope, that required schemas are loaded, and that namespaces are referenced correctly., near escaped identifier. that does not appear when are run separately but appear when under the same project.

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  • Is there a way to inspect all controller variables at once in Rails?

    - by m.u.sheikh
    I am exploring an big controller method, with about 10 or so instance variables. Some of them are set in before_filter methods, and some others inside the method itself. I want to inspect them with puts, but dont want to write all of them out example: puts "var1: #{@var1.inspect}....var15: #{@var15.inspect}" Is there a generic method that will display all the instance variables with an @ sign set so far in the current method? If not, what is the next best way to inspect all of them at once without having to write all of them in a puts statement?

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  • How to setup Math program

    - by Miles
    I'm needing to write a program (C#) that will allow the user to create generic formulas with variables and numbers. For example: D = A + (A - C / X)(7.8 - 6.6) F = E + (E - C / X)(7.8 - 6.6) FinalResult = (A + D)(0.9) + (E + F)(0.32) + B(0.1) + .023 where all variables would mean for me to go to a database and look something up based on values and return a number in its place. So A would be 2.12 for example (and the same for C and E) Whats the best way to structure this program? How would I make my program read these formulas? I've seen a little bit of the MathML but not sure how to get that started (or an example of it)

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  • Using custom HTML attributes for JavaScript purposes?

    - by user1103990
    One of my colleagues doesn't like to use HTML classes and ids for javascript/jQuery purpose. Therefore I've seen that he had created custom html attribute such as <div id="myid" class="cssClasses ..." [some-purpose-id]="mycustomId">...</div> I asked him if it was really a good idea and he replied that he considers that classes and Ids should be reserved for styling. Personally, I would have used classes. Some classes would have been used for styling, and some other classes would have been used for programming (jQuery selectors). The idea is to keep things appart also. And of course jQuery could set styling classes but if possible not use them for selection. Of course I also use id when appropriate but since an id is unique on a page, I like to do generic stuff using classes. I would like to know you opinions on the better approach (if there is one). Thank you.

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  • Java generics conversion

    - by LittleGreenMan
    I have build a generic datacontainer and now I want to manipulate data depending on their type. However, I get an incompatable types warning. What am I doing wrong? Type _Value; public void set(Type t) throws Exception { if (_Value instanceof Integer && t instanceof Integer) { _Value = (((Integer) t - _MinValue + getRange()) % getRange()) + _MinValue; } else if (_Value instanceof Boolean && t instanceof Boolean) { _Value = t; } else throw new Exception("Invalid type"); }

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  • How to avoid "incomplete implementation" warning in partial base class

    - by garph0
    I have created a protocol that my classes need to implement, and then factored out some common functionality into a base class, so I did this: @protocol MyProtocol - (void) foo; - (void) bar; @end @interface Base <MyProtocol> @end @interface Derived_1 : Base @end @interface Derived_2 : Base @end @implementation Base - (void) foo{ //something foo } @end @implementation Derived_1 - (void) bar{ //something bar 1 } @end @implementation Derived_2 - (void) bar{ //something bar 2 } @end In this way in my code I use a generic id<MyProtocol>. The code works (as long as Base is not used directly) but the compiler chokes at the end of the implementation of Base with a warning: Incomplete implementation of class Base Is there a way to avoid this warning or, even better, a more proper way to obtain this partially implemented abstract base class behavior in Objc?

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  • How to create unique user key

    - by Grayson Mitchell
    Scenario: I have a fairly generic table (Data), that has an identity column. The data in this table is grouped (lets say by city). The users need an identifier in order for printing on paper forms, etc. The users can only access their cites data, so if they use the identity column for this purpose they will see odd numbers (e.g. a 'New York' user might see 1,37,2028... as the listed keys. Idealy they would see 1,2,3... (or something similar) The problem of course is concurrency, this being a web application you can't just have something like: UserId = Select Count(*)+1 from Data Where City='New York' Has anyone come up with any cunning ways around this problem?

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  • Accessing facebook sdk result Object using .NET 3.5 API?

    - by John K
    Consider the following in .NET 3.5 (using the Bin\Net35\Facebook*.dll assemblies): using Facebook; var app = new FacebookApp(); var result = app.Get("me"); // want to access result properties with no dynamic ... in the absence of the C# 4.0 dynamic keyword this provides only generic object members. How best should I access the facebook properties of this result object? Are there helper or utility methods or stronger types in the facebook C# SDK, or should I use standard .NET reflection techniques?

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  • Tiny C Compiler and Virus warnings...

    - by NoMoreZealots
    I wanted to try out the TCC and got the Win32 Binary zip file from the website. upon decompressing it I tried to compile the "hello_win.c" source from the example directory. As soon as the compiler tried to write to the disk McAfee Popped up a dialog box and identified a Trojan named "Generic.dx." Has anyone else experience this? Dropping a virus into a compiler would be a sneaky, but brilliant, delivery mechanizism. I just want to know if this is a legit threat.

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  • I want to be able to derive from a class internally, but disallow class in other assemblies to derive from the class

    - by Rokke
    Hej I have the following setup: Assembly 1 public abstract class XX<T> : XX where T: YY { } public abstract class XX {} Assembly 2 public class ZZ : YY {} public class ZZFriend : XX<ZZ> {} I use this feature in reflection when in YY: public class YY { public Type FindFriend { return GetType().Assembly.GetTypes().FirstOrDefault( t => t.BaseType != null && t.BaseType.IsGenericType && typeof(XX).IsAssignableFrom(t) && t.BaseType.GetGenericArguments().FirstOrDefault() == GetType()); } } I would like do disallow inheritance of the non generic class XX like: public class ZZFriend: XX {} Alternatively, I need a method like (that can be used in the reflection in YY.FindFrind()): public Type F(Type t) { return GetTypeThatIsGeneric(XX, Type genericTypeParameter); } That can be used in YY as: Typeof(XX<ZZ) == F(typeof(GetType()) Hope that makes sense... Thanks in advance Søren Rokkedal

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  • Rscript does not recognize setGeneric function

    - by Branko K.
    I am trying to convert an R script into something that a client can run in batch mode. My code uses generic functions and one snippet which is near the beginning goes like: setGeneric("testInput", function(inputData, params = list()) standardGeneric("testInput")) I've been using R CMD BATCH and it works fine. However I couldn't find an easy way to make my script print the output on the console, so based on that (and suggestion that Rscript.exe is the "proper" way to run R batch files) I decided to switch to Rscript. However when running the very same .R file with Rscript I get the following: Error: could not find function "setGeneric" Execution halted I know there is probably a trivial reason behind this but I just cannot figure it out. Can someone please point me to where the mistake is? Thanks so much in advance. Cheers!

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  • Container<ImplementerOfIInterface> is not Container<IInterface>. Why not?

    - by Chris Simmons
    Why wouldn't DoesntWork() work below? The error is: Cannot implicitly convert type 'List' to 'IEnumerable'. An explicit conversion exists (are you missing a cast?). I know this is something about generic/templates I'm not getting, but List is IEnumerable and Implementer is an IInterface. I don't see why this needs to be casted (or if it really can be). public interface IInterface { // ... } public class Implementer : IInterface { // ... } IEnumerable<IInterface> DoesntWork() { List<Implementer> result = new List<Implementer>(); return result; }

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  • How to use pointers and pointer aritmetic

    - by booby
    : error C2064: term does not evaluate to a function taking 1 arguments : error C2227: left of '-name' must point to class/struct/union/generic type how do i fix this so this error doesn't happen for(int index = 0; index < (numStudents); index++) { if (student(index + 1)->score >= 90 ) student(index + 1)->grade = 'A'; else if (student(index + 1)->score >= 80 ) student(index + 1)->grade = 'B'; else if (student(index + 1)->score >= 70 ) student(index + 1)->grade = 'C'; else if (student(index + 1)->score >= 60 ) student(index + 1)->grade = 'D'; else student(index + 1)->grade = 'F'; }

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  • SQL compare entire rows

    - by zmaster
    In SQL server 2008 I have some huge tables (200-300+ cols). Every day we run a batch job generating a new table with timestamp appended to the name of the table. The the tables have no PK. I would like a generic way to compare 2 rows from two tables. Showing which cols having different values is sufficient, but showing the values would be perfect. Thanks a lot Thanks for the answers. I ended up writing my own C# tool to do the job - as Im not allowed to install 3rd party software in my company.

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  • How to use a class as the base, but hide the class type publically?

    - by James
    I am currently just exposing the properties through a generic interface e.g. public interface IBaseClass { int ID { get; set; } } internal class MyBaseClass : IBaseClass { public MyBaseClass() { } public int ID { get; set; } } public class MyExposedClass : IBaseClass { private MyBaseClass _base = new MyBaseClass(); public int ID { get { return _base.ID; } set { _base.ID = value; } } } Then in my main application I can do: IBaseClass c = new MyExposedClass(); c.ID = 12345; But can't do: MyBaseClass b = new MyBaseClass(); This is my desired behaviour. However, I was just wondering if this is the correct approach? Or if there was a better way?

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  • Using xsl:character-map on text nodes only

    - by jramos95
    I am trying to create a generic stylesheet that can convert all Latin characters in Unicode to uppercase ASCII characters. Using <xsl:character-map> works well except for one thing: namespaces. The character map converts all of my namespaces to upper case, which I do not want. Is there a way to utilize a character map to do what I want to all the other nodes while leaving the namespaces untouched? I see the disable-output-escaping attribute might be an option, but I haven't been able to make it work.

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  • Understanding reflection

    - by sdmiller
    I recently started work at a new company and a .net web application we have is built using reflection. I have only been out of school for a year and haven't worked with this concept. After studying the code... it looks like there is a single backend interface of type object that has about 20 classes that inherit from it. lots of generic gets and sets On the surface it looks like standard inheritance to me. I guess my question is, what makes this reflection? Is it because the interface is not strongly typed? Thanks

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