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• AIR File.resolvePath won't work anymore

  - by Palleas

  Hi all, I'm having a very strange issue, it looks like my application can't create file anymore. It works w/ directories, but the so-many-times-used resolvePath() methods doesn't. Here is what I do : var databaseFileContent : File = new File(File.desktopDirectory.nativePath + "/testing"); databaseFileContent.createDirectory(); databaseFileContent.resolvePath("test"); (Here I'm trying on desktop but that's the same w/ applicationStorageDirectory) When I execute this, it works only for the "testing" folder which is actually created, but my file isn't. I tried to create another application, doing this : trace(File.desktopDirectory.resolvePath("maiswtf.db").exists); trace(File.applicationStorageDirectory.resolvePath("wtf.db").exists); Both are displaying "false". Am I missing something here? I have another application with this code : var databaseFileContent : File = File.applicationStorageDirectory.resolvePath(File.separator + "sitra.db"); When I run this one, it works perfectly! My file is created at /sitra.db! Any hints? I thinks I'm going mad :/ Thanks!

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• PyGTK: Manually render an existing widget at a given Rectangle? (TextView in a custom CellRenderer)

  - by NicDumZ

  Hello! I am trying to draw a TextView into the cell of a TreeView. (Why? I would like to have custom tags on text, so they can be clickable and trigger different actions/popup menus depending on where user clicks). I have been trying to write a customized CellRenderer for this purpose, but so far I failed because I find it extremely difficult to find generic documentation on rendering design in gtk. More than an answer at the specific question (that might be hard/not doable, and I'm not expecting you to do everything for me), I am first looking for documentation on how a widget is rendered, to understand how one is supposed to implement a CellRenderer. Can you share any link that explains, either for gtk or for pygtk, the rendering mechanism? More specifically: size allocation mechanism (should I say protocol?). I understand that a window has a defined size, and then queries its children, saying "my size is w x h, what would be your ideal size, buddy?", and then sometimes shrinks children when all children cant fit together at their ideal sizes. Any specific documentation on that, and on particular on when this happens during rendering? How are rendered "builtin" widgets? What kind of methods do they call on Widget base class? On the parent Window? When? Do they use pango.Layout? can you manually draw a TextView onto a pango.Layout object? This link gives an interesting example showing how you can draw content in a pango.Layout object and use it in a CellRenderer. I guess that I could adapt it if only I understood how TextView widget are rendered. Or perhaps, to put it more simply: given an existing widget instance, how does one render it at a specific gdk.Rectangle? Thanks a lot.

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• How do you pass a generic delegate argument to a method in .NET 2.0

  - by Seth Spearman

  Hello, I have a class with a delegate declaration as follows... Public Class MyClass Public Delegate Function Getter(Of TResult)() As TResult 'the following code works. Public Shared Sub MyMethod(ByVal g As Getter(Of Boolean)) 'do stuff End Sub End Class However, I do not want to explicitly type the Getter delegate in the Method call. Why can I not declare the parameter as follows... ... (ByVal g As Getter(Of TResult)) Is there a way to do it? My end goal was to be able to set a delegate for property setters and getters in the called class. But my reading indicates you can't do that. So I put setter and getter methods in that class and then I want the calling class to set the delegate argument and then invoke. Is there a best practice for doing this. I realize in the above example that I can set set the delegate variable from the calling class...but I am trying to create a singleton with tight encapsulation. For the record, I can't use any of the new delegate types declared in .net35. Answers in C# are welcome. Any thoughts? Seth

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• Link compatibility between C++ and D

  - by Caspin

  D easily interfaces with C. D just as easily interfaces with C++, but (and it's a big but) the C++ needs to be extremely trivial. The code cannot use: namespaces templates multiple inheritance mix virtual with non-virtual methods more? I completely understand the inheritance restriction. The rest however, feel like artificial limitations. Now I don't want to be able to use std::vector<T> directly, but I would really like to be able to link with std::vector<int> as an externed template. The C++ interfacing page has this particularly depressing comment. D templates have little in common with C++ templates, and it is very unlikely that any sort of reasonable method could be found to express C++ templates in a link-compatible way with D. This means that the C++ STL, and C++ Boost, likely will never be accessible from D. Admittedly I'll probably never need std::vector while coding in D, but I'd love to use QT or boost. So what's the deal. Why is it so hard to express non-trivial C++ classes in D? Would it not be worth it to add some special annotations or something to express at least namespaces?

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• Inline function v. Macro in C -- What's the Overhead (Memory/Speed)?

  - by Jason R. Mick

  I searched Stack Overflow for the pros/cons of function-like macros v. inline functions. I found the following discussion: Pros and Cons of Different macro function / inline methods in C ...but it didn't answer my primary burning question. Namely, what is the overhead in c of using a macro function (with variables, possibly other function calls) v. an inline function, in terms of memory usage and execution speed? Are there any compiler-dependent differences in overhead? I have both icc and gcc at my disposal. My code snippet I'm modularizing is: double AttractiveTerm = pow(SigmaSquared/RadialDistanceSquared,3); double RepulsiveTerm = AttractiveTerm * AttractiveTerm; EnergyContribution += 4 * Epsilon * (RepulsiveTerm - AttractiveTerm); My reason for turning it into an inline function/macro is so I can drop it into a c file and then conditionally compile other similar, but slightly different functions/macros. e.g.: double AttractiveTerm = pow(SigmaSquared/RadialDistanceSquared,3); double RepulsiveTerm = pow(SigmaSquared/RadialDistanceSquared,9); EnergyContribution += 4 * Epsilon * (RepulsiveTerm - AttractiveTerm); (note the difference in the second line...) This function is a central one to my code and gets called thousands of times per step in my program and my program performs millions of steps. Thus I want to have the LEAST overhead possible, hence why I'm wasting time worrying about the overhead of inlining v. transforming the code into a macro. Based on the prior discussion I already realize other pros/cons (type independence and resulting errors from that) of macros... but what I want to know most, and don't currently know is the PERFORMANCE. I know some of you C veterans will have some great insight for me!!

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• How should I handle expected errors? eg. "username already exists"

  - by Pheter

  I am struggling to understand how I should design the error handling parts of my code. I recently asked a similar question about how I should go about returning server error codes to the user, eg. 404 errors. I learnt that I should handle the error from within the current part of the application; seem's simple enough. However, what should I do when I can't handle the error from the current link in the chain? For example, I may have a class that is used to manage authentication. One of it's methods could be createUser($username, $password). Within that function, I need to determine if the username already exists. If this is true, how should I alert the calling code about this? Returning null instead of a user object is one way. But how do I then know what caused the error? How should I handle errors in such a way that calling code can easily find out what caused the error? Is there a design pattern commonly used for this kind of situation?

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• How to check at runtime if a class implements certain interface?

  - by mare

  Let's say I have some content classes like Page, TabGroup, Tab, etc. Certain of those will be implementing my IWidgetContainer interface - it means they will geet an additional field named ContainedItems from the interface and some methods for manipulating this field. Now I need to reflect the fact that some class implements this interface by rendering out some special custom controls in my ASP.NET MVC Views (like jQuery Add/Remove/Move/Reorder buttons). For instance, TabGroup will implement IWidgetContainer because it will contain tabs but a tab will not implement it because it won't have the ability to contain anything. So I have to somehow check in my view, when I render my content objects (The problem is, I use my base class as strong type in my view not concrete classes), whether it implements IWidgetContainer. How is that possible or have I completely missed something? To rephrase the question, how do you reflect some special properties of a class (like interface implementation) in the UI in general (not necessarily ASP.NET MVC)? Here's my code so far: [DataContract] public class ContentClass { [DataMember] public string Slug; [DataMember] public string Title; [DataMember] protected ContentType Type; } [DataContract] public class Group : ContentClass, IWidgetContainer { public Group() { Type = ContentType.TabGroup; } public ContentList ContainedItems { get; set; } public void AddContent(ContentListItem toAdd) { throw new NotImplementedException(); } public void RemoveContent(ContentListItem toRemove) { throw new NotImplementedException(); } } [DataContract] public class GroupElement : ContentClass { public GroupElement() { Type = ContentType.Tab; } } Interface: interface IWidgetContainer { [DataMember] ContentList ContainedItems { get; set; } void AddContent(ContentListItem toAdd); void RemoveContent(ContentListItem toRemove); }

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• Compiler turning a string& into a basic_string<>&

  - by Shtong

  Hello I'm coming back to C++ after long years spent on other technologies and i'm stuck on some weird behavior when calling some methods taking std::string as parameters : An example of call : LocalNodeConfiguration *LocalNodeConfiguration::ReadFromFile(std::string & path) { // ... throw configuration_file_error(string("Configuration file empty"), path); // ... } When I compile I get this (I cropped file names for readability) : /usr/bin/g++ -g -I/home/shtong/Dev/OmegaNoc/build -I/usr/share/include/boost-1.41.0 -o CMakeFiles/OmegaNocInternals.dir/configuration/localNodeConfiguration.cxx.o -c /home/shtong/Dev/OmegaNoc/source/configuration/localNodeConfiguration.cxx .../localNodeConfiguration.cxx: In static member function ‘static OmegaNoc::LocalNodeConfiguration* OmegaNoc::LocalNodeConfiguration::ReadFromFile(std::string&)’: .../localNodeConfiguration.cxx:72: error: no matching function for call to ‘OmegaNoc::configuration_file_error::configuration_file_error(std::string, std::basic_string<char, std::char_traits<char>, std::allocator<char> >&)’ .../configurationManager.hxx:25: note: candidates are: OmegaNoc::configuration_file_error::configuration_file_error(std::string&, std::string&) .../configurationManager.hxx:22: note: OmegaNoc::configuration_file_error::configuration_file_error(const OmegaNoc::configuration_file_error&) So as I understand it, the compiler is considering that my path parameter turned into a basic_string at some point, thus not finding the constructor overload I want to use. But I don't really get why this transformation happened. Some search on the net suggested me to use g++ but I was already using it. So any other advice would be appreciated :) Thanks

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• Internal Java code best practice for dealing with invalid REST API parameters

  - by user326389

  My colleague wrote the following stackoverflow question: other stack overflow question on this topic The question seems to have been misinterpreted and I want to find out the answer, so I'm starting this new question... hopefully a little more clear. Basically, we have a REST API. Users of our API call our methods with parameters. But sometimes users call them with the wrong parameters!! Maybe a mistake in their code, maybe they're just trying to play with us, maybe they're trying to see how we respond, who knows! We respond with HTTP status error codes and maybe a detailed description of the invalid parameter in the XML response. All is well. But internally we deal with these invalid parameters by throwing exceptions. For example, if someone looks up a Person object by giving us their profile id, but the profile id doesn't exist... we throw a PersonInvalidException when looking them up. Then we catch this exception in our API controller and send back an HTTP 400 status error code. Our question is... is this the best practice, throwing exceptions internally for this kind of user error? These exceptions never get propogated back to the user, this is a REST API. They only make our code cleaner. Otherwise we could have a validation method in each of our API controllers to make sure the parameters all make sense, but that seems inefficient. We have to look up things in our database potentially twice. Or we could return nulls and check for them, but that sucks... What are your thoughts?

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• Contrary to Python 3.1 Docs, hash(obj) != id(obj). So which is correct?

  - by Don O'Donnell

  The following is from the Python v3.1.2 documentation: From The Python Language Reference Section 3.3.1 Basic Customization: object.__hash__(self) ... User-defined classes have __eq__() and __hash__() methods by default; with them, all objects compare unequal (except with themselves) and x.__hash__() returns id(x). From The Glossary: hashable ... Objects which are instances of user-defined classes are hashable by default; they all compare unequal, and their hash value is their id(). This is true up through version 2.6.5: Python 2.6.5 (r265:79096, Mar 19 2010 21:48:26) ... ... >>> class C(object): pass ... >>> c = C() >>> id(c) 11335856 >>> hash(c) 11335856 But in version 3.1.2: Python 3.1.2 (r312:79149, Mar 21 2010, 00:41:52) ... ... >>> class C: pass ... >>> c = C() >>> id(c) 11893680 >>> hash(c) 743355 So which is it? Should I report a documentation bug or a program bug? And if it's a documentation bug, and the default hash() value for a user class instance is no longer the same as the id() value, then it would be interesting to know what it is or how it is calculated, and why it was changed in version 3.

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• How do I implement Hibernate Pagination using a cursor (so the results stay consistent, despite new

  - by hunterae

  Hey all, Is there any way to maintain a database cursor using Hibernate between web requests? Basically, I'm trying to implement pagination, but the data that is being paged is consistently changing (i.e. new records are added into the database). We are trying to set it up such that when you do your initial search (returning a maximum of 5000 results), and you page through the results, those same records always appear on the same page (i.e. we're not continuously running the query each time next and previous page buttons are clicked). The way we're currently implementing this is by merely selecting 5000 (at most) primary keys from the table we're paging, storing those keys in memory, and then just using 20 primary keys at a time to fetch their details from the database. However, we want to get away from having to store these keys in memory and would much prefer a database cursor that we just keep going back to and moving backwards and forwards over the cursor to generate pages. I tried doing this with Hibernate's ScrollableResults but found that I could not call methods like next() and previous() would cause an exception if you within a different web request / Hibernate session (no surprise there). Is there any way to reattach a ScrollableResults object to a Session, much the same way you would reattach a detached database object to make it persistent? Are there any other approaches to implement this data paging with consistent paging results without caching the primary keys?

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• How to use interfaces in exception handling

  - by vikp

  Hi, I'm working on the exception handling layer for my application. I have read few articles on interfaces and generics. I have used inheritance before quite a lot and I'm comfortable with in that area. I have a very brief design that I'm going to implement: public interface IMyExceptionLogger { public void LogException(); // Helper methods for writing into files,db, xml } I'm slightly confused what I should be doing next. public class FooClass: IMyExceptionLogger { // Fields // Constructors } Should I implement LogException() method within FooClass? If yes, than I'm struggling to see how I'm better of using an interface instead of the concrete class... I have a variety of classes that will make a use of that interface, but I don't want to write an implementation of that interface within each class. In the same time If I implement an interface in one class, and then use that class in different layers of the application I will be still using concrete classes instead of interfaces, which is a bad OO design... I hope this makes sense. Any feedback and suggestions are welcome. Please notice that I'm not interested in using net4log or its competitors because I'm doing this to learn. Thank you Edit: Wrote some more code. So I will implement variety of loggers with this interface, i.e. DBExceptionLogger, CSVExceptionLogger, XMLExceptionLogger etc. Than I will still end up with concrete classes that I will have to use in different layers of my application.

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• How might a C# programmer approach writing a solution in javascript?

  - by Ben McCormack

  UPDATE: Perhaps this wasn't clear from my original post, but I'm mainly interested in knowing a best practice for how to structure javascript code while building a solution, not simply learning how to use APIs (though that is certainly important). I need to add functionality to a web site and our team has decided to approach the solution using a web service that receives a call from a JSON-formatted AJAX request from within the web site. The web service has been created and works great. Now I have been tasked with writing the javascript/html side of the solution. If I were solving this problem in C#, I would create separate classes for formatting the request, handling the AJAX request/response, parsing the response, and finally inserting the response somehow into the DOM. I would build properties and methods appropriately into each class, doing my best to separate functionality and structure where appropriate. However, I have to solve this problem in javascript. Firstly, how could I approach my solution in javascript in the way I would approach it from C# as described above? Or more importantly, what's a better way to approach structuring code in javascript? Any advice or links to helpful material on the web would be greatly appreciated. NOTE: Though perhaps not immediately relevant to this question, it may be worth noting that we will be using jQuery in our solution.

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• unexpected behaviour of object stored in web service Session

  - by draconis

  Hi. I'm using Session variables inside a web service to maintain state between successive method calls by an external application called QBWC. I set this up by decorating my web service methods with this attribute: [WebMethod(EnableSession = true)] I'm using the Session variable to store an instance of a custom object called QueueManager. The QueueManager has a property called ChangeQueue which looks like this: [Serializable] public class QueueManager { ... public Queue<QBChange> ChangeQueue { get; set; } ... where QBChange is a custom business object belonging to my web service. Now, every time I get a call to a method in my web service, I use this code to retrieve my QueueManager object and access my queue: QueueManager qm = (QueueManager)Session[ticket]; then I remove an object from the queue, using qm.dequeue() and then I save the modified query manager object (modified because it contains one less object in the queue) back to the Session variable, like so: Session[ticket] = qm; ready for the next web service method call using the same ticket. Now here's the thing: if I comment out this last line //Session[ticket] = qm; , then the web service behaves exactly the same way, reducing the size of the queue between method calls. Now why is that? The web service seems to be updating a class contained in serialized form in a Session variable without being asked to. Why would it do that? When I deserialize my Queuemanager object, does the qm variable hold a reference to the serialized object inside the Session[ticket] variable?? This seems very unlikely.

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• Breaking dependencies when you can't make changes to other files?

  - by codemuncher

  I'm doing some stealth agile development on a project. The lead programmer sees unit testing, refactoring, etc as a waste of resources and there is no way to convince him otherwise. His philosophy is "If it ain't broke don't fix it" and I understand his point of view. He's been working on the project for over a decade and knows the code inside and out. I'm not looking to debate development practices. I'm new to the project and I've been tasked with adding a new feature. I've worked on legacy projects before and used agile development practices with good result but those teams were more receptive to the idea and weren't afraid of making changes to code. I've been told I can use whatever development methodology I want but I have to limit my changes to only those necessary to add the feature. I'm using tdd for the new classes I'm writing but I keep running into road blocks caused by the liberal use of global variables and the high coupling in the classes I need to interact with. Normally I'd start extracting interfaces for these classes and make their dependence on the global variables explicit by injecting them as constructor arguments or public properties. I could argue that the changes are necessary but considering the lead never had to make them I doubt he would see it my way. What techniques can I use to break these dependencies without ruffling the lead developer's feathers? I've made some headway using: Extract Interface (for the new classes I'm creating) Extend and override the wayward classes with test stubs. (luckily most methods are public virtual) But these two can only get me so far.

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• Implicit conversion between Scala collection types

  - by ebruchez

  I would like to implicitly convert between the Scala XML Elem object and another representation of an XML element, in my case dom4j Element. I wrote the following implicit conversions: implicit def elemToElement(e: Elem): Element = ... do conversion here ... implicit def elementToElem(e: Element): Elem = ... do conversion here ... So far so good, this works. Now I also need collections of said elements to convert both ways. First, do I absolutely need to write additional conversion methods? Things didn't seem to work if I didn't. I tried to write the following: implicit def elemTToElementT(t: Traversable[Elem]) = t map (elemToElement(_)) implicit def elementTToElemT(t: Traversable[Element]) = t map (elementToElem(_)) This doesn't look too ideal because if the conversion method takes a Traversable, then it also returns a Traversable. If I pass a List, I also get a Traversable out. So I assume the conversion should be parametrized somehow. So what's the standard way of writing these conversions in order to be as generic as possible?

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• asp.net, wcf authentication and caching

  - by andrew

  I need to place my app business logic into a WCF service. The service shouldn't be dependent on ASP.NET and there is a lot of data regarding the authenticated user which is frequently used in the business logic hence it's supposed to be cached (probably using a distributed cache). As for authentication - I'm going to use two level authentication: Front-End - forms authentication back-end (WCF Service) - message username authentication. For both authentications the same custom membership provider is supposed to be used. To cache the authenticated user data, I'm going to implement two service methods: 1) Authenticate - will retrieve the needed data and place it into the cache(where username will be used as a key) 2) SignOut - will remove the data from the cache Question 1. Is correct to perform authentication that way (in two places) ? Question 2. Is this caching strategy worth using or should I look at using aspnet compatible service and asp.net session ? Maybe, these questions are too general. But, anyway I'd like to get any suggestions or recommendations. Any Idea

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• avoiding code duplication in Rails 3 models

  - by Dustin Frazier

  I'm working on a Rails 3.1 application where there are a number of different enum-like models that are stored in the database. There is a lot of identical code in these models, as well as in the associated controllers and views. I've solved the code duplication for the controllers and views via a shared parent controller class and the new view/layout inheritance that's part of Rails 3. Now I'm trying to solve the code duplication in the models, and I'm stuck. An example of one of my enum models is as follows: class Format < ActiveRecord::Base has_and_belongs_to_many :videos attr_accessible :name validates :name, presence: true, length: { maximum: 20 } before_destroy :verify_no_linked_videos def verify_no_linked_videos unless self.videos.empty? self.errors[:base] << "Couldn't delete format with associated videos." raise ActiveRecord::RecordInvalid.new self end end end I have four or five other classes with nearly identical code (the association declaration being the only difference). I've tried creating a module with the shared code that they all include (which seems like the Ruby Way), but much of the duplicate code relies on ActiveRecord, so the methods I'm trying to use in the module (validate, attr_accessible, etc.) aren't available. I know about ActiveModel, but that doesn't get me all the way there. I've also tried creating a common, non-persistent parent class that subclasses ActiveRecord::Base, but all of the code I've seen to accomplish this assumes that you won't have subclasses of your non-persistent class that do persist. Any suggestions for how best to avoid duplicating these identical lines of code across many different enum models?

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• Request header field x-user-session is not allowed by Access-Control-Allow-Headers

  - by Saurabh Bhandari

  I am trying to do a CORS call to a WCF service endpoint hosted on IIS7.5. I have configured custom headers in IIS. My configuration looks like below <customHeaders> <add name="Access-Control-Allow-Methods" value="GET,PUT,POST,DELETE,OPTIONS" /> <add name="Access-Control-Allow-Headers" value="x-user-session,origin, content-type, accept" /> <add name="Access-Control-Allow-Credentials" value="true" /> </customHeaders> When I do a POST request I get following error message "Request header field x-user-session is not allowed by Access-Control-Allow-Headers" If I remove my custom header from the call and run it, everything works fine. Also if I do a GET call with custom header then also API works correctly. $.ajax({ type:"POST", success: function(d) { console.log(d) }, timeout: 9000, url: "http://api.myserver.com/Services/v2/CreditCard.svc/update_cc_detail", data: JSON.stringify({"card_id": 1234,"expire_month":"11","expire_year":"2020","full_name":"Demo Account", "number":"4111111111111111","is_primary":true}), xhrFields: { withCredentials: true}, headers: { x-user-session': "B23680D0B8CB5AFED9F624271F1DFAE5052085755AEDDEFDA3834EF16115BCDDC6319BD79FDCCB1E199BB6CC4D0C6FBC9F30242A723BA9C0DFB8BCA3F31F4C7302B1A37EE0A20C42E8AFD45FAB85282FCB62C0B4EC62329BD8573FEBAEBC6E8269FFBF57C7D57E6EF880E396F266E7AD841797792619AD3F1C27A5AE" }, crossDomain: true, contentType: 'application/json' });

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• OOP/MVC advice on where to place a global helper function

  - by franko75

  Hi, I have a couple of controllers on my site which are handling form data. The forms use AJAX and I have quite a few methods across different controllers which are having to do some specific processing to return errors in a JSON encoded format - see code below. Obviously this isn't DRY and I need to move this code into a single helper function which I can use globally, but I'm wondering where this should actually go! Should I create a static helper class which contains this function (e.g Validation::build_ajax_errors()), or as this code is producing a format which is application specific and tied into the jQuery validation plugin I'm using, should it be a static method stored in, for example, my main Website controller which the form handling controllers extend from? //if ajax request, output errors if (request::is_ajax()) { //need to build errors into array form for javascript validation - move this into a helper method accessible globally $errors = $post->errors('form_data/form_error_messages'); $i = 0; $new_errors = array(); foreach ($errors as $key => $value) { $new_errors[$i][0] = '#' . $key; $new_errors[$i][1] = $value; $new_errors[$i][2] = "error"; $i++; } echo '{"jsonValidateReturn":' . json_encode($new_errors) . '}'; return; }

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• Entity framework with Linq to Entities performance

  - by mare

  If I have a static method like this public static string GetTicClassificationTitle(string classI, string classII, string classIII) { using (TicDatabaseEntities ticdb = new TicDatabaseEntities()) { var result = from classes in ticdb.Classifications where classes.ClassI == classI where classes.ClassII == classII where classes.ClassIII == classIII select classes.Description; return result.FirstOrDefault(); } } and use this method in various places in foreach loops or just plain calling it numerous times, does it create and open new connection every time? If so, how can I tackle this? Should I cache the results somewhere, like in this case, I would cache the entire Classifications table in Memory Cache? And then do queries vs this cached object? Or should I make TicDatabaseEntities variable static and initialize it at class level? Should my class be static if it contains only static methods? Because right now it is not.. Also I've noticed that if I return result.First() instead of FirstOrDefault() and the query does not find a match, it will issue an exception (with FirstOrDefault() there is no exception, it returns null). Thank you for clarification.

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• Advice on Linq to SQL mapping object design

  - by fearofawhackplanet

  I hope the title and following text are clear, I'm not very familiar with the correct terms so please correct me if I get anything wrong. I'm using Linq ORM for the first time and am wondering how to address the following. Say I have two DB tables: User ---- Id Name Phone ----- Id UserId Model The Linq code generator produces a bunch of entity classes. I then write my own classes and interfaces which wrap these Linq classes: class DatabaseUser : IUser { public DatabaseUser(User user) { _user = user; } public Guid Id { get { return _user.Id; } } ... etc } so far so good. Now it's easy enough to find a users phones from Phones.Where(p => p.User = user) but surely comsumers of the API shouldn't need to be writing their own Linq queries to get at data, so I should wrap this query in a function or property somewhere. So the question is, in this example, would you add a Phones property to IUser or not? In other words, should my interface specifically be modelling my database objects (in which case Phones doesn't belong in IUser), or are they actually simply providing a set of functions and properties which are conceptually associated with a User (in which case it does)? There seems drawbacks to both views, but I'm wondering if there is a standard approach to the problem. Or just any general words of wisdom you could share. My first thought was to use extension methods but in fact that doesn't work in this case.

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• Why does VS2005 skip execution of lines when debugging managed C++ without optimizations?

  - by Sakin

  I ran into a rather odd behavior that I don't even know how to start describing. I wrote a piece of managed C++ code that makes calls to native methods. A (very) simplified version of the code would look like this (I know it looks like a full native function, just assume there is managed stuff being done all over the place): int somefunction(ptrHolder x) { // the accessptr method returns a native pointer if (x.accessptr() != nullptr) // I tried this with nullptr, NULL, 0) { try { x->doSomeNativeVeryImportantStuff(); // or whatever, doesn't matter } catch (SomeCustomExceptionClass &) { return 0; } } SomeOtherNativeClass::doStaticMagic(); return 1; } I compiled this code without optimizations using the /clr flag (VS.NET 2005, SP2) and when running it in the debugger I get to the if statement, since the pointer is actually null, I don't enter the if, but surprisingly, the cursor jumps directly to the return 1 statement, ignoring the doStaticMagic() method completely!!! When looking at the assembly code, I see that it really jumps directly to that line. If I force the debugger to enter the if block, I also jump to the return 1 statement after I press F10. Any ideas why this is happening? Thanks, Ariel

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• How to compensate the flipped coordinate system of core graphics for easy drawing?

  - by mystify

  It's really a pain, but always when I draw an UIImage in -drawRect:, it's upside-down. When I flip the coordinates, the image draws correctly, but at the cost of all other CG functions drawing "wrong" (flipped). What's your strategy when you have to draw images and other things? Is there any rule of thumb how to not get stuck in this problem over and over again? Also, one nasty thing when I flip the y-axis is, that my CGRect from the UIImageView frame is wrong. Instead of the origin appearing at 10,10 upper left as expected, it appears at the bottom. But at the same time, all those normal line drawing functions of CGContext take correct coordinates. drawing a line in -drawRect with origin 10,10 upper left, will really start at upper left. But at the same time that's strange, because core graphics actually has a flipped coordinate system with y 0 at the bottom. So it seems like something is really inconsistent there. Drawing with CGContext functions takes coordinates as "expected" (cmon, nobody thinks in coordinates starting from bottom left, that's silly), while drawing any kind of image still works the "wrong" way. Do you use helper methods to draw images? Or is there anything useful that makes image drawing not a pain in the butt?

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• C++ destructor problem with boost::scoped_ptr

  - by bb-generation

  I have a question about the following code: #include <iostream> #include <boost/scoped_ptr.hpp> class Interface { }; class A : public Interface { public: A() { std::cout << "A()" << std::endl; } virtual ~A() { std::cout << "~A()" << std::endl; } }; Interface* get_a() { A* a = new A; return a; } int main() { { std::cout << "1" << std::endl; boost::scoped_ptr<Interface> x(get_a()); std::cout << "2" << std::endl; } std::cout << "3" << std::endl; } It creates the following output: 1 A() 2 3 As you can see, it doesn't call the destructor of A. The only way I see to get the destructor of A being called, is to add a destructor for the Interface class like this: virtual ~Interface() { } But I really want to avoid any Implementation in my Interface class and virtual ~Interface() = 0; doesn't work (produces some linker errors complaining about a non existing implementation of ~Interface(). So my question is: What do I have to change in order to make the destructor being called, but (if possible) leave the Interface as an Interface (only abstract methods).

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