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• Warning: XXX may not respond to YYY

  - by Aurel300

  Hey, I am making some stuff in Objective-C++... And I must say that I am a total newbie when it comes to the Objective-C part... I don't really want to learn it, I kinda just need it for accessing a few Mac APIs (ObjC is such a dumb language). So - compiling with g++ -x objective-c++ - and I somehow keep getting this warning: XXX may not respond to YYY First it was with a NSScreen, now it is with a NSWindow: NSWindow may not respond to +initWithContentRect:styleMask:backing:defer: I saw somewhere that I should cast it to id, but didn't work, throwing absolutely cryptic errors... So - WHAT does this warning actually mean and HOW am I supposed to make it stop?

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• Type result with Ternary operator in C#

  - by Vaccano

  I am trying to use the ternary operator, but I am getting hung up on the type it thinks the result should be. Below is an example that I have contrived to show the issue I am having: class Program { public static void OutputDateTime(DateTime? datetime) { Console.WriteLine(datetime); } public static bool IsDateTimeHappy(DateTime datetime) { if (DateTime.Compare(datetime, DateTime.Parse("1/1")) == 0) return true; return false; } static void Main(string[] args) { DateTime myDateTime = DateTime.Now; OutputDateTime(IsDateTimeHappy(myDateTime) ? null : myDateTime); Console.ReadLine(); ^ } | } | // This line has the compile issue ---------------+ On the line indicated above, I get the following compile error: Type of conditional expression cannot be determined because there is no implicit conversion between '< null ' and 'System.DateTime' I am confused because the parameter is a nullable type (DateTime?). Why does it need to convert at all? If it is null then use that, if it is a date time then use that. I was under the impression that: condition ? first_expression : second_expression; was the same as: if (condition) first_expression; else second_expression; Clearly this is not the case. What is the reasoning behind this? (NOTE: I know that if I make "myDateTime" a nullable DateTime then it will work. But why does it need it? As I stated earlier this is a contrived example. In my real example "myDateTime" is a data mapped value that cannot be made nullable.)

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• Does the JPQL avg aggregate function work with Integers?

  - by Kyle Renfro

  I have a JPA 2 Entity named Surgery. It has a member named transfusionUnits that is an Integer. There are two entries in the database. Executing this JPQL statement: Select s.transfusionUnits from Surgery s produces the expected result: 2 3 The following statement produces the expected answer of 5: Select sum(s.transfusionUnits) from Surgery s I expect the answer of the following statement to be 2.5, but it returns 2.0 instead. Select avg(s.transfusionUnits) from Surgery s If I execute the statement on a different (Float) member, the result is correct. Any ideas on why this is happening? Do I need to do some sort of cast in JPQL? Is this even possible? Surely I am missing something trivial here.

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• Getting error in MVC Proj while writing Lambda Expression

  - by Shrewd Demon

  hi, i am creating a sample movie (MVC) application. I was getting fine with Viewing and Creating a new record, but when i wrote the code to get the details of a particular record i met with the following error: Unable to cast objec`t of type 'System.Data.Objects.ObjectQuery`1[MovieApp.Models.Movie]' to type 'MovieApp.Model`s.Movie'. here is the code i wrote for getting the details public ActionResult Details(int id) { var moviedetail = (Movie)_entities.MovieSet.Where(mvid => mvid.Id == id); return View(moviedetail); } can any body tell me whats going wrong and where ?? thank you.

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• Typecast to a type from just the string representation of the type name

  - by Water Cooler v2

  sTypeName = ... //do some string stuff here to get the name of the type /* The Assembly.CreateInstance function returns a type of System.object. I want to type cast it to the type whose name is sTypeName. assembly.CreateInstance(sTypeName) So, in effect I want to do something like: */ assembly.CreateInstance(sTypeName) as Type.GetType(sTypeName); How do I do that? And, what do I take on the left side of the assignment expression, assuming this is C# 2.0. I don't have the var keyword.

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• What adapter to use for ExpandableListView with non-TextView views?

  - by David

  I have an ExpandableListView in which I'd like to have controls other than TextView. Apparently, SimpleExandableListViewAdapter assumes all the controls are TextViews. A cast exception is generated if they are not. What is the recommended solution? Options I can think of include: - Use some other included adapter. But I can't tell if they all have the same assumption. - Create my own adapter. Is there a doc which describes the contract, ie the sequence of method calls an adapter will encounter? I expected the existing adapters to require the views to conform to some interface to allow any conforming view to be used, rather than hardcode to textview and limit where they can be used.

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• How can we order a column as int using hibernate criteria API?

  - by Satya

  Hi I want to fetch the data form data base using hibernate Criteria API. That data should be ordered by some column as number. This column is defined as varchar in DB. But I have to fetch as numberic. I am facing problem using criteria API as it is ordering like string onyly. Ex: I am getting data like 9, 8, 7, 6, 5, 4, 3, 2, 1,10 but i want data as 10,9,8,7,6,5,4,3,2,1 Is there any Hibernate methods to covert varchar to number like convert("some column",int ) or cast("some column",int) ?

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• Does all SPWeb or SPSite instances automatically disposed when console app process has ended?

  - by Janis Veinbergs

  We have Best practices on using disposable object in SharePoint. But i`m thinking - can I skip these when using Console Application? That's some code I want to execute once and after that process has finished. Do or don't SPSite and SPWeb's remain opened somwhere? Why i`m asking this? I just don't want to stress when using something like var lists = from web in site.AllWebs.Cast<SPWeb>() where web is meeting workspace && list is task list select list then do some stuff on lists etc. Some serious resource leak there because webs get opened, filtered and NOT closed. So should I worry in console app?

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• Quickly retrieve the subset of properties used in a huge collection in C#

  - by ccornet

  I have a huge Collection (which I can cast as an enumerable using OfType<()) of objects. Each of these objects has a Category property, which is drawn from a list somewhere else in the application. This Collection can reach sizes of hundreds of items, but it is possible that only, say, 6/30 of the possible Categories are actually used. What is the fastest method to find these 6 Categories? The size of the huge Collection discourages me from just iterating across the entire thing and returning all unique values, so is there a faster method of accomplishing this? Ideally I'd collect the categories into a List.

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• C Nested Structure Pointer Problem

  - by Halo

  I have a shared structure, and inside it a request structure: struct shared_data { pthread_mutex_t th_mutex_queue; struct request_queue { int min; int max; char d_name[DIR_SIZE]; pid_t pid; int t_index; } request_queue[BUFSIZE]; int count; int data_buffer_allocation[BUFSIZE]; int data_buffers[BUFSIZE][100]; }; Then I prepare a request; struct shared_data *sdata_ptr; ... ... sdata_ptr->request_queue[index].pid = pid; strcpy(sdata_ptr->request_queue[index].d_name, dir_path_name); sdata_ptr->request_queue[index].min = min; sdata_ptr->request_queue[index].max = max; And the compiler warns me that I'm doing an incompatible implicit declaration in the strcpy function. I guess that's a problem with the pointers, but isn't what I wrote above supposed to be true?

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• Thread-safe data structure design

  - by Inso Reiges

  Hello, I have to design a data structure that is to be used in a multi-threaded environment. The basic API is simple: insert element, remove element, retrieve element, check that element exists. The structure's implementation uses implicit locking to guarantee the atomicity of a single API call. After i implemented this it became apparent, that what i really need is atomicity across several API calls. For example if a caller needs to check the existence of an element before trying to insert it he can't do that atomically even if each single API call is atomic: if(!data_structure.exists(element)) { data_structure.insert(element); } The example is somewhat awkward, but the basic point is that we can't trust the result of "exists" call anymore after we return from atomic context (the generated assembly clearly shows a minor chance of context switch between the two calls). What i currently have in mind to solve this is exposing the lock through the data structure's public API. This way clients will have to explicitly lock things, but at least they won't have to create their own locks. Is there a better commonly-known solution to these kinds of problems? And as long as we're at it, can you advise some good literature on thread-safe design? EDIT: I have a better example. Suppose that element retrieval returns either a reference or a pointer to the stored element and not it's copy. How can a caller be protected to safely use this pointer\reference after the call returns? If you think that not returning copies is a problem, then think about deep copies, i.e. objects that should also copy another objects they point to internally. Thank you.

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• [C#] How to consume web service adheres to the Event-based Asynchronous Pattern?

  - by codemonkie

  I am following the example from http://msdn.microsoft.com/en-us/library/8wy069k1.aspx to consume a web service implemented (by 3rd party) using the Event-based Asynchronous Pattern. However, my program needs to do multiple calls to the DoStuffAsync() hence will get back as many DoStuffCompleted. I chose the overload which takes an extra parameter - Object userState to distinguish them. My first question is: Is it valid to cast a GUID to Object as below, where GUID is used to generate unique taskID? Object userState = Guid.NewGuid(); Secondly, do I need to spawn off a new thread for each DoStuffAsync() call, since I am calling it multiple times? Also, would be nice to have some online examples or tutorials on this subject. (I've been googling for it the whole day and didn't get much back) Many thanks

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• C++0x rvalue references and temporaries

  - by Doug

  (I asked a variation of this question on comp.std.c++ but didn't get an answer.) Why does the call to f(arg) in this code call the const ref overload of f? void f(const std::string &); //less efficient void f(std::string &&); //more efficient void g(const char * arg) { f(arg); } My intuition says that the f(string &&) overload should be chosen, because arg needs to be converted to a temporary no matter what, and the temporary matches the rvalue reference better than the lvalue reference. This is not what happens in GCC and MSVC. In at least G++ and MSVC, any lvalue does not bind to an rvalue reference argument, even if there is an intermediate temporary created. Indeed, if the const ref overload isn't present, the compilers diagnose an error. However, writing f(arg + 0) or f(std::string(arg)) does choose the rvalue reference overload as you would expect. From my reading of the C++0x standard, it seems like the implicit conversion of a const char * to a string should be considered when considering if f(string &&) is viable, just as when passing a const lvalue ref arguments. Section 13.3 (overload resolution) doesn't differentiate between rvalue refs and const references in too many places. Also, it seems that the rule that prevents lvalues from binding to rvalue references (13.3.3.1.4/3) shouldn't apply if there's an intermediate temporary - after all, it's perfectly safe to move from the temporary. Is this: Me misreading/misunderstand the standard, where the implemented behavior is the intended behavior, and there's some good reason why my example should behave the way it does? A mistake that the compiler vendors have somehow all made? Or a mistake based on common implementation strategies? Or a mistake in e.g. GCC (where this lvalue/rvalue reference binding rule was first implemented), that was copied by other vendors? A defect in the standard, or an unintended consequence, or something that should be clarified?

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• How to make that the LanguageBinder take precedence over the DynamicBinder

  - by rudimenter

  Hi I Have a class which implement IDynamicMetaObjectProvider I implement the BindGetMember Method from DynamicMetaObject. Now when i Generate a dynamic Object and Access a property every call gets implicit passed through the BindGetMember Method. I want that at first the language Binder get his chance before my code comes in. It is somehow doable with "binder.FallbackGetMember" but i am not sure how the expression has to look like. I call here dynamic com=CommandFactory.GetCommand(); com.testprop; //expected: "test"; but "test2" comes back public class Command : System.Dynamic.IDynamicMetaObjectProvider { public string testprop { get { return "test"; } } public object GetValue(string name) { return "test2"; } System.Dynamic.DynamicMetaObject System.Dynamic.IDynamicMetaObjectProvider.GetMetaObject(System.Linq.Expressions.Expression parameter) { return new MetaCommand(parameter, this); } private class MetaCommand : System.Dynamic.DynamicMetaObject { public MetaCommand(Expression expression, Command value) : base(expression, System.Dynamic.BindingRestrictions.Empty, value) { } public override System.Dynamic.DynamicMetaObject BindGetMember(System.Dynamic.GetMemberBinder binder) { var self = this.Expression; var bag = (Command)base.Value; Expression target; target = Expression.Call( Expression.Convert(self, typeof(Command)), typeof(Command).GetMethod("GetValue"), Expression.Constant(binder.Name) ); var restrictions = BindingRestrictions .GetInstanceRestriction(self, bag); return new DynamicMetaObject(target, restrictions); } #endregion } }

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• Dynamic classloading fails on runtime

  - by Henrik Paul

  I have the following snippet of java code: final Class<?> junitCoreClass = AccessController.doPrivileged( new PrivilegedAction<URLClassLoader>() { @Override public URLClassLoader run() { return new URLClassLoader(new URL[] { junitJarUrl }); } }).loadClass("org.junit.runner.JUnitCore"); System.out.println(junitCoreClass.getName()); final JUnitCore junitCore = (JUnitCore) junitCoreClass.newInstance(); This compiles fine. But when I try to run it, something weird happens; a java.lang.NoClassDefFoundError is thrown on that last line, referring to the class just loaded. The weird part is, the println prints the exact class name. I checked that if I keep the reference as an Object and manipulate it only through reflection, everything's fine, so the offending piece of code must be the explicit cast. Can someone explain to me why this happens, and also tell me how I can achieve what I'm trying to do?

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• C++ fixed point library?

  - by uj2

  I am looking for a free C++ fixed point library (Mainly for use with embedded devices, not for arbitrary precision math). Basically, the requirements are: No unnecessary runtime overhead: whatever can be done at compile time, should be done at compile time. Ability to transparently switch code between fixed and floating point, with no inherent overhead. Fixed point math functions. There's no much point using fixed point if you need to cast back and forth in order to take a square root. Small footprint. Any suggestions?

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• Display field from another table in SQL

  - by Roland Bengtsson

  I'm a newbie with SQL... Now I want to do display some instances of AddrDistances from DevExpress CxGrid with SQL. Select Cast((DistanceAsMeters * 0.001) as Decimal(8,1)) DistanceAsKm, bold_id, created, fromAddress, toAddress From AddrDistance Where DistanceAsMeters = 0 and PseudoDistanceAsCostKm = 0 and not AddrDistance.bold_id in (select bold_id from DistanceQueryTask) Order By Created Desc This SQL is working and the result is: DistanceAsKM Bold_ID Created FromAddress ToAddress 0 134808 16.02.2010 121795 134570 0 121701 10.03.2010 120850 122991 The result I want is this: DistanceAsKM Bold_ID Created FromAddress ToAddress 0 134808 16.02.2010 Kalmar Stockholm 0 121701 10.03.2010 Falkenberg Oslo So the amount of rows is right but I want to replace the numbers in FromAddress and ToAddress with strings from another table. The numbers shows here is just the boldid. Every object in the database have an unique boldid. The addresses above is stored in table Address and it have a City field with the column and a boldid as a key. What should I write in SQL to get this right ? Is there something in the CxGrid that could help here ? Regards

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• Worst side effects from chars signedness. (Explanation of signedness effects on chars and casts)

  - by JustSmith

  I frequently work with libraries that use char when working with bytes in C++. The alternative is to define a "Byte" as unsigned char but that not the standard they decided to use. I frequently pass bytes from C# into the C++ dlls and cast them to char to work with the library. When casting ints to chars or chars to other simple types what are some of the side effects that can occur. Specifically, when has this broken code that you have worked on and how did you find out it was because of the char signedness? Lucky i haven't run into this in my code, used a char signed casting trick back in an embedded systems class in school. I'm looking to better understand the issue since I feel it is relevant to the work I am doing.

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• Changing a datatype solely for the purpose of Excel Export in Crystal Reports

  - by yeahumok

  I have a report that has several numerical fields. To fill a project requirement, i had to use the following formula: if {DataTable1.No of Investments}>9999 then '*****' else toText({DataTable1.No of Investments},0) Basically, if the number fed in is bigger than 9999 it turns into * on the report. Now, when i try to export into excel, not only is the data type for all fields, strings...but the * show up versus numbers. I was wondering if there was a way to re-cast this back into a numerical value SOLELY for the purpose of excel exportation so that i'd be able to use excel formulas as well as see numbers instead of asterisks. I'd only be doing data-only excel exports. Any ideas?

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• Why are symbols not frozen strings?

  - by Alex Chaffee

  I understand the theoretical difference between Strings and Symbols. I understand that Symbols are meant to represent a concept or a name or an identifier or a label or a key, and Strings are a bag of characters. I understand that Strings are mutable and transient, where Symbols are immutable and permanent. I even like how Symbols look different from Strings in my text editor. What bothers me is that practically speaking, Symbols are so similar to Strings that the fact that they're not implemented as Strings causes a lot of headaches. They don't even support duck-typing or implicit coercion, unlike the other famous "the same but different" couple, Float and Fixnum. The mere existence of HashWithIndifferentAccess, and its rampant use in Rails and other frameworks, demonstrates that there's a problem here, an itch that needs to be scratched. Can anyone tell me a practical reason why Symbols should not be frozen Strings? Other than "because that's how it's always been done" (historical) or "because symbols are not strings" (begging the question). Consider the following astonishing behavior: :apple == "apple" #=> false, should be true :apple.hash == "apple".hash #=> false, should be true {apples: 10}["apples"] #=> nil, should be 10 {"apples" => 10}[:apples] #=> nil, should be 10 :apple.object_id == "apple".object_id #=> false, but that's actually fine All it would take to make the next generation of Rubyists less confused is this: class Symbol < String def initialize *args super self.freeze end (and a lot of other library-level hacking, but still, not too complicated) See also: http://onestepback.org/index.cgi/Tech/Ruby/SymbolsAreNotImmutableStrings.red http://www.randomhacks.net/articles/2007/01/20/13-ways-of-looking-at-a-ruby-symbol Why does my code break when using a hash symbol, instead of a hash string? Why use symbols as hash keys in Ruby? What are symbols and how do we use them? Ruby Symbols vs Strings in Hashes Can't get the hang of symbols in Ruby

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• Reading a Delphi binary file in Python

  - by Brendan

  I have a file that was written with the following Delphi declaration ... Type Tfulldata = Record dpoints, dloops : integer; dtime, bT, sT, hI, LI : real; tm : real; data : array[1..armax] Of Real; End; ... Var: fh: File Of Tfulldata; I want to analyse the data in the files (many MB in size) using Python if possible - is there an easy way to read in the data and cast the data into Python objects similar in form to the Delphi records? Does anyone know of a library perhaps that does this?

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• Play 2.0 RESTful request post-processing

  - by virtualeyes

  In regard to this question I am curious how one can do post-request REST processing a la (crude): def postProcessor[T](content: T) = { request match { case Accepts.Json() => asJson(content) case Accepts.Xml() => asXml(content) case _ => content } } overriding onRouteRequest in Global config does not appear to provide access to body of the response, so it would seem that Action composition is the way to go to intercept the response and do post-processing task(s). Question: is this a good idea, or is it better to do content-type casting directly within a controller (or other class) method where the type to cast is known? Currently I'm doing this kind of thing everywhere: toJson( i18n("account not found") ) toJson( Map('orderNum-> orderNum) ) while I'd like the toJson/toXml conversion to happen based on accepts header post-request.

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• Trying to put a generic MyObj<T, U> into an IList where U can be different between objects

  - by Sergio Romero

  I have the following class definition: public interface IItem{} public class FirstObject<T, U> : IItem { public U SomeProperty { get; private set; } } IList<IItem> myList = new List<IItem>(); I did it like this because U can be of different types. Now I want to iterate the list and get my items back, the problem is that I do not know how to cast them back to their original type so I can read the value of SomeProperty. Thanks for your help.

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• What is the problem with this Java code dealing with Generics?

  - by devoured elysium

  interface Addable<E> { public E add(E x); public E sub(E y); public E zero(); } class SumSet<E extends Addable> implements Set<E> { private E element; public SumSet(E element) { this.element = element; } public E getSum() { return element.add(element.zero()); } } It seems that element.add() doesn't return an E extends Addable but rather an Object. Why is that? Has it anything to do with Java not knowing at run-time what the object types really are, so it just assumes them to be Objects(thus requiring a cast)? Thanks

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• Doing a join across two databases with different collations on SQL Server and getting an error.

  - by Andrew G. Johnson

  I know, I know with what I wrote in the question I shouldn't be surprised. But my situation is slowly working on an inherited POS system and my predecessor apparently wasn't aware of JOINs so when I looked into one of the internal pages that loads for 60 seconds I see that it's a fairly quick, rewrite these 8 queries as one query with JOINs situation. Problem is that besides not knowing about JOINs he also seems to have had a fetish for multiple databases and surprise, surprise they use different collations. Fact of the matter is we use all "normal" latin characters that English speaking people would consider the entire alphabet and this whole thing will be out of use in a few months so a bandaid is all I need. Long story short is I need some kind of method to cast to a single collation so I can compare two fields from two databases. Exact error is: Cannot resolve the collation conflict between "SQL_Latin1_General_CP850_CI_AI" and "SQL_Latin1_General_CP1_CI_AS" in the equal to operation.

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