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  • Simplest way to mix sequences of types with iostreams?

    - by Kylotan
    I have a function void write<typename T>(const T&) which is implemented in terms of writing the T object to an ostream, and a matching function T read<typename T>() that reads a T from an istream. I am basically using iostreams as a plain text serialisation format, which obviously works fine for most built-in types, although I'm not sure how to effectively handle std::strings just yet. I'd like to be able to write out a sequence of objects too, eg void write<typename T>(const std::vector<T>&) or an iterator based equivalent (although in practice, it would always be used with a vector). However, while writing an overload that iterates over the elements and writes them out is easy enough to do, this doesn't add enough information to allow the matching read operation to know how each element is delimited, which is essentially the same problem that I have with a single std::string. Is there a single approach that can work for all basic types and std::string? Or perhaps I can get away with 2 overloads, one for numerical types, and one for strings? (Either using different delimiters or the string using a delimiter escaping mechanism, perhaps.)

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  • MVC and jQuery data retrieval.

    - by user337542
    Hello, I am using mvc and jQuery and I am trying to display someone's profile with some additional institutions that the person belongs to. I am new to this but I've done something like this in ProfileControler: public ActionResult Institutions(int id) { var inst = fr.getInstitutions(id); return Json(inst); } getInstitutions(id) returns Institution objects(with Name, City, Post Code etc.) Then in a certain View I am trying to get the data with jQuery and display them as follows: $(document).ready(function () { $.post("/Profile/Institutions", { id: <%= Model.Profile.userProfileID %> }, function (data) { $.each(data, function () { var new_div = $("<div>"); var new_label = $("<label>"); new_label.html(this.City); var new_input_b = $("<input>"); new_input_b.attr("type", "button"); new_div.append(new_label); new_div.append(new_input_b); $("#institutions").append(new_div); }); }); }); $("#institutions") is a div where i want to display all of the results. .post works correct for sure because certain institutions are retrieved from database, and passed to the view as Json result. But then I am affraid it wont itterate with .each. Any help, coments or pointing in some direction would be much appriciated

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  • C++: Reference and Pointer question (example regarding OpenGL)

    - by Jay
    I would like to load textures, and then have them be used by multiple objects. Would this work? class Sprite { GLuint* mTextures; // do I need this to also be a reference? Sprite( GLuint* textures ) // do I need this to also be a reference? { mTextures = textures; } void Draw( textureNumber ) { glBindTexture( GL_TEXTURE_2D, mTextures[ textureNumber ] ); // drawing code } }; // normally these variables would be inputed, but I did this for simplicity. const int NUMBER_OF_TEXTURES = 40; const int WHICH_TEXTURE = 10; void main() { std::vector<GLuint> the_textures; the_textures.resize( NUMBER_OF_TEXTURES ); glGenTextures( NUMBER_OF_TEXTURES, &the_textures[0] ); // texture loading code Sprite the_sprite( &the_textures[0] ); the_sprite.Draw( WHICH_TEXTURE ); } And is there a different way I should do this, even if it would work? Thanks.

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  • Does it exist: smart pointer, owned by one object allowing access.

    - by Noah Roberts
    I'm wondering if anyone's run across anything that exists which would fill this need. Object A contains an object B. It wants to provide access to that B to clients through a pointer (maybe there's the option it could be 0, or maybe the clients need to be copiable and yet hold references...whatever). Clients, lets call them object C, would normally, if we're perfect developers, be written carefully so as to not violate the lifetime semantics of any pointer to B they might have...but we're not perfect, in fact we're pretty dumb half the time. So what we want is for object C to have a pointer to object B that is not "shared" ownership but that is smart enough to recognize a situation in which the pointer is no longer valid, such as when object A is destroyed or it destroys object B. Accessing this pointer when it's no longer valid would cause an assertion/exception/whatever. In other words, I wish to share access to data in a safe, clear way but retain the original ownership semantics. Currently, because I've not been able to find any shared pointer in which one of the objects owns it, I've been using shared_ptr in place of having such a thing. But I want clear owneship and shared/weak pointer doesn't really provide that. Would be nice further if this smart pointer could be attached to member variables and not just hold pointers to dynamically allocated memory regions. If it doesn't exist I'm going to make it, so I first want to know if someone's already released something out there that does it. And, BTW, I do realize that things like references and pointers do provide this sort of thing...I'm looking for something smarter.

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  • ADO.NET DataTable/DataRow Thread Safety

    - by Allen E. Scharfenberg
    Introduction A user reported to me this morning that he was having an issue with inconsistent results (namely, column values sometimes coming out null when they should not be) of some parallel execution code that we provide as part of an internal framework. This code has worked fine in the past and has not been tampered with lately, but it got me to thinking about the following snippet: Code Sample lock (ResultTable) { newRow = ResultTable.NewRow(); } newRow["Key"] = currentKey; foreach (KeyValuePair<string, object> output in outputs) { object resultValue = output.Value; newRow[output.Name] = resultValue != null ? resultValue : DBNull.Value; } lock (ResultTable) { ResultTable.Rows.Add(newRow); } (No guarantees that that compiles, hand-edited to mask proprietery information.) Explanation We have this cascading type of locking code other places in our system, and it works fine, but this is the first instance of cascading locking code that I have come across that interacts with ADO .NET. As we all know, members of framework objects are usually not thread safe (which is the case in this situation), but the cascading locking should ensure that we are not reading and writing to ResultTable.Rows concurrently. We are safe, right? Hypothesis Well, the cascading lock code does not ensure that we are not reading from or writing to ResultTable.Rows at the same time that we are assigning values to columns in the new row. What if ADO .NET uses some kind of buffer for assigning column values that is not thread safe--even when different object types are involved (DataTable vs. DataRow)? Has anyone run into anything like this before? I thought I would ask here at StackOverflow before beating my head against this for hours on end :) Conclusion Well, the consensus appears to be that changing the cascading lock to a full lock has resolved the issue. That is not the result that I expected, but the full lock version has not produced the issue after many, many, many tests. The lesson: be wary of cascading locks used on APIs that you do not control. Who knows what may be going on under the covers!

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  • java: libraries for immutable functional-style data structures

    - by Jason S
    This is very similar to another question (Functional Data Structures in Java) but the answers there are not particularly useful. I need to use immutable versions of the standard Java collections (e.g. HashMap / TreeMap / ArrayList / LinkedList / HashSet / TreeSet). By "immutable" I mean immutable in the functional sense (e.g. purely functional data structures), where updating operations on the data structure do not change the original data, but instead return a new instance of the same kind of data structure. Also typically new and old instances of the data structure will share immutable data to be efficient in time and space. From what I can tell my options include: Functional Java Scala Clojure but I'm not sure whether any of these are particularly appealing to me. I have a few requirements/desirements: the collections in question should be usable directly in Java (with the appropriate libraries in the classpath). FJ would work for me; I'm not sure if I can use Scala's or Clojure's data structures in Java w/o having to use the compilers/interpreters from those languages and w/o having to write Scala or Clojure code. Core operations on lists/maps/sets should be possible w/o having to create function objects with confusing syntaxes (FJ looks slightly iffy) They should be efficient in time and space. I'm looking for a library which ideally has done some performance testing. FJ's TreeMap is based on a red-black tree, not sure how that rates. Documentation / tutorials should be good enough so someone can get started quickly using the data structures. FJ fails on that front. Any suggestions?

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  • What's the best way of accessing a DRb object (e.g. Ruby Queue) from Scala (and Java)?

    - by Tom Morris
    I have built a variety of little scripts using Ruby's very simple Queue class, and share the Queue between Ruby and JRuby processes using DRb. It would be nice to be able to access these from Scala (and maybe Java) using JRuby. I've put together something Scala and the JSR-223 interface to access jruby-complete.jar. import javax.script._ class DRbQueue(host: String, port: Int) { private var engine = DRbQueue.factory.getEngineByName("jruby") private var invoker = engine.asInstanceOf[Invocable] engine.eval("require \"drb\" ") private var queue = engine.eval("DRbObject.new(nil, \"druby://" + host + ":" + port.toString + "\")") def isEmpty(): Boolean = invoker.invokeMethod(this.queue, "empty?").asInstanceOf[Boolean] def size(): Long = invoker.invokeMethod(this.queue, "length").asInstanceOf[Long] def threadsWaiting: Long = invoker.invokeMethod(this.queue, "num_waiting").asInstanceOf[Long] def offer(obj: Any) = invoker.invokeMethod(this.queue, "push", obj.asInstanceOf[java.lang.Object]) def poll(): Any = invoker.invokeMethod(this.queue, "pop") def clear(): Unit = { invoker.invokeMethod(this.queue, "clear") } } object DRbQueue { var factory = new ScriptEngineManager() } (It conforms roughly to java.util.Queue interface, but I haven't declared the interface because it doesn't implement the element and peek methods because the Ruby class doesn't offer them.) The problem with this is the type conversion. JRuby is fine with Scala's Strings - because they are Java strings. But if I give it a Scala Int or Long, or one of the other Scala types (List, Set, RichString, Array, Symbol) or some other custom type. This seems unnecessarily hacky: surely there has got to be a better way of doing RMI/DRb interop without having to use JSR-223 API. I could either make it so that the offer method serializes the object to, say, a JSON string and takes a structural type of only objects that have a toJson method. I could then write a Ruby wrapper class (or just monkeypatch Queue) to would parse the JSON. Is there any point in carrying on with trying to access DRb from Java/Scala? Might it just be easier to install a real message queue? (If so, any suggestions for a lightweight JVM-based MQ?)

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  • Async task ASP.net HttpContext.Current.Items is empty - How do handle this?

    - by GuruC
    We are running a very large web application in asp.net MVC .NET 4.0. Recently we had an audit done and the performance team says that there were a lot of null reference exceptions. So I started investigating it from the dumps and event viewer. My understanding was as follows: We are using Asyn Tasks in our controllers. We rely on HttpContext.Current.Items hashtable to store a lot of Application level values. Task<Articles>.Factory.StartNew(() => { System.Web.HttpContext.Current = ControllerContext.HttpContext.ApplicationInstance.Context; var service = new ArticlesService(page); return service.GetArticles(); }).ContinueWith(t => SetResult(t, "articles")); So we are copying the context object onto the new thread that is spawned from Task factory. This context.Items is used again in the thread wherever necessary. Say for ex: public class SomeClass { internal static int StreamID { get { if (HttpContext.Current != null) { return (int)HttpContext.Current.Items["StreamID"]; } else { return DEFAULT_STREAM_ID; } } } This runs fine as long as number of parallel requests are optimal. My questions are as follows: 1. When the load is more and there are too many parallel requests, I notice that HttpContext.Current.Items is empty. I am not able to figure out a reason for this and this causes all the null reference exceptions. 2. How do we make sure it is not null ? Any workaround if present ? NOTE: I read through in StackOverflow and people have questions like HttpContext.Current is null - but in my case it is not null and its empty. I was reading one more article where the author says that sometimes request object is terminated and it may cause problems since dispose is already called on objects. I am doing a copy of Context object - its just a shallow copy and not a deep copy.

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  • ios UITableView reloadData don't increase content height

    - by Zoltan Varadi
    I'm facing a strange error in my iOS app and haven't been able to figure out the reason why. In my UITableView i can add new cells, so i refresh the array that is the datasource and call reloadData. Everything works without error. The numberOfRowsInSection is called again, and it's value is one more than it's previous value was. The new cell even gets inserted at the bottom of the tableview, but i cant scroll down to it. I only know that it's there because the tableview bounces and i can see it. I'm guessing the tableview's content height is not getting increased for some reason, but i have no idea why. I'm using iOS 6 btw. Any help is very much appreciated! Thanks, Zoli EDIT, answers for Srikanth's questions: How is data getting added. There's an NSArray containing objects of a specific type. The array.count is the number of the number of cells. This NSArray gets its values from a database query. When you say, you are refreshing the array, what do you mean. By refreshing the array i mean i execute a new query in the database and put the results of this query into an NSArray. this will be the tableview's datasource array. Like this: dataSourceArray = [dbManager executeQuery]; [tableView reloadData]; Are you adding the data within the same view controller Yes. Can you show some code as to what you are doing See above. Is the table view at the root of the view controllers view or is it within another view The tableview is the main view's first child. Can you try adding data to the array at the beginning, so that you can view the cell being added at the top. I don't understand what you mean.

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  • Flex vs GWT again

    - by CK Lee
    Hi all, I am working on a customized web ontology editor (something like http://webprotege.stanford.edu/ which is built by GWT). My backend will be Java+Spring+Hibernate and domain models are in Java. My frontend will be something like WebProtege which requires extensive RPC call. It is quite clear that I should use GWT as I can refer to the open source code. However, due to company policy, I shall consider Flex as well. I understand Flex can remotely invoke Java backend methods via BlazeDS using AMF (Is there a Flex equivalent of GWT-RPC?). I have read discussion on GWT vs Flex vs ?. If I can make full decision sure I will go with GWT. GWT strengths like support right to left characters, support iPhone/iPad, smaller size, support JSON out of the box, support printing are not important considerations for my project. Besides GWT supports Java generic, enum; domain objects can be shared with both GWT client and server; coding are more seamlessly... anyone can suggest other strong reasons that I should only go with GWT? FYI, I have plenty of Java experience but both GWT and Flex are new to me. Thanks.

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  • iPhone Development - calling external JSON API (will Apple reject?)

    - by RPM1984
    Ok guys, so im new to iPhone development, so apologies if this is a silly question, but before i actually create my app i want to know if this is possible, and if Apple will reject this. (Note this is all theoretical) So i'd have a API (.NET) that runs on a cloud server somewhere and can return HTML/JSON/XML. I'll have a website that can access this API and allow customers to do some stuff (but this is not important for this question). I would then like my iPhone app to make a call to this API which would return JSON data. So my iPhone app might make a call to http://myapp/Foos which would return a JSON string of Foo objects. The iPhone app would then parse this JSON and do some funky stuff with it. So, that's the background, now the questions: Is this possible? (that is, call an external cloud API over HTTP, parse JSON response?) What are the chances of Apple rejecting this application (because it would be calling a non-Apple API) Are there any limitations (security, libraries, etc) on the iPhone/Objective-C/Cocoa that might hinder this solution? On this website, they seem to be doing exactly what im asking. Thoughts, suggestions, links would be greatly appreciated...

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  • For business people to manage, keep binary images in MySQL or just the urls?

    - by Michael Mao
    Hello everyone: I am working on a task to enable image uploading and auto-scaling(from full sized to thumbnail) by jQuery & PHP. I can naturally come up with two approaches : First, store both images as binary objects directly into MySQL; Second, store only urls to the images and keep the images somewhere on server. The images are for everyone to view, so there are no security restrictions, as far as I know. Personally I don't have any preference, however, at the end of the day, it is the business people that are going to manage the images as part of the system(CRUD). So I am wondering which seems to be a bit better for them? Of course I am building a easy-to-use, visualize web interface for the staff to control the process, but I am not sure if that is enough. Lessons told me that if I don't think for the future and seek the most flexible approach, the I will probably screw myself sooner or later. PS. The following link is what I've found so far, which is pretty cool, no flash involved :) Andrew Valum's ajax image upload jQuery plugin

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  • Some questions about the .NET Entity Framework and Stored Procedures

    - by Bara
    Hey everyone, I had a couple of questions relating to the .NET Entity Framework and using stored procedures. Here goes: I know that we can right click a stored procedure and choose Function Import to be able to use with code. Is there a way to do this for many stored procedures at once? When doing a Function Import, I can create a new Complex type or use an existing Complex type. Well, how can I access Complex types/objects that are outside of the edmx file? That is, if I have a class in my project, is it possible to access it while doing a Function Import? When calling the stored procedure from code, it returns an IEnumerable of the Complex type I set it as. However, sometimes these complex types do not have all of the properties that I need, so I create a new class in my project that inherits from the complex type used in the stored procedure. Problem is, I can't seem to cast the complex type returned from the stored procedure to the new class I created. Any reason why I can't do this? What I ended up doing is looping through the IEnumerable and adding each item to a new list of the class that I created. But this feels and looks messy. Bara

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  • Need an advice for unit testing using mock object

    - by Andree
    Hi there, I just recently read about "Mocking objects" for unit testing and currently I'm having a difficulties implementing this approach in my application. Please let me explain my problem. I have a User model class, which is dependent on 2 data sources (database and facebook web service). The controller class simply use this User model as an interface to access data and it doesn't care about where the data came from. Currently I never done any unit test to this User model because it is dependent on an external web service. But just a while ago, I read about object mocking and now I know that it is a common approach to unit test a class that depends on external resources (like in my case). Now I want to create a unit test for the User model, but then I encountered a design issue: In order for the User model to use a mocked Facebook SDK, I have to inject this mocked Facebook SDK to the User object (probably using a setter). Therefore I can't construct the Facebook SDK inside the User object. I have to construct it outside the User object, and inject the SDK into the User object. The real client of my User model is the application's controller. Therefore I have to construct the Facebook SDK inside the controller and inject it to the user object. Well, this is a problem because I want my controller to be as clean as possible. I want my controller to be ignorant about the application's data source. I'm not good at explaining something systematically, so you'll probably sleeping before reading this last paragraph. But anyway, I want to ask if anyone here ever encountered the same problem as mine? How do you solve this problem? Regards, Andree

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  • Passing list of values to django view via jQuery ajax call

    - by finspin
    I'm trying to pass a list of numeric values (ids) from one web page to another with jQuery ajax call. I can't figure out how to pass and read all the values in the list. I can successfully post and read 1 value but not multiple values. Here is what I have so far: jQuery: var postUrl = "http://localhost:8000/ingredients/"; $('li').click(function(){ values = [1, 2]; $.ajax({ url: postUrl, type: 'POST', data: {'terid': values}, traditional: true, dataType: 'html', success: function(result){ $('#ingredients').append(result); } }); }); /ingredients/ view: def ingredients(request): if request.is_ajax(): ourid = request.POST.get('terid', False) ingredients = Ingredience.objects.filter(food__id__in=ourid) t = get_template('ingredients.html') html = t.render(Context({'ingredients': ingredients,})) return HttpResponse(html) else: html = '<p>This is not ajax</p>' return HttpResponse(html) With Firebug I can see that POST contains both ids but probably in the wrong format (terid=1&terid=2). So my ingredients view picks up only terid=2. What am I doing wrong? EDIT: To clarify, I need the ourid variable pass values [1, 2] to the filter in the ingredients view.

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  • OpenCV. cvFnName() works, but cv::FunName() doesn't work

    - by Innuendo
    I'm using OpenCV to write a plugin for a simulator. I've made an OpenCV project (single - not a plugin) and it works fine. When I added OpenCV libs to the plugin project, I added all libs required. Visual Studio 2010 doesn't highlight any code line with red. All looks fine and compiles fine. But in execution, the program halts with a Runtime Error on any cv::function. For example: cv::imread, or cv::imwrite. But if I replace them with cvLoadImage() and cvSaveImage(), it works fine. Why does this happen? I don't want to rewrite the whole script in old-api-style (cvFnName). It means I should change all Mat objects to IplImages, and so on. UPDATE: // preparing template ifstream ifile(tmplfilename); if ( !FILE_LOADED && ifile ) { // loading template file Mat tmpl = cv::imread(tmplfilename, 1); // << here occurs error FILE_LOADED = true; } Mat src; Bmp2Mat(hDC, hBitmap, src); TargetDetector detector(src, tmpl); detector.detectTarget(); If I change to: if ( !FILE_LOADED && ifile ) { IplImage* tmpl = 0; tmpl = cvLoadImage(tmplfilename, 1); // no error occurs } And then no error occurs. Early it displayed some Runtime Error. Now, I wanted to copy exact message and it just crashes the application (simulator, what I am pluginning). It displays window error - to kill process or no. (I can't show exact message, because I'm using russian windows now)

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  • nhibernate mapping: delete collection, insert new collection with old IDs

    - by npeBeg
    my issue lokks similar to this one: (link) but i have one-to-many association: <set name="Fields" cascade="all-delete-orphan" lazy="false" inverse="true"> <key column="[TEMPLATE_ID]"></key> <one-to-many class="MyNamespace.Field, MyLibrary"/> </set> (i also tried to use ) this mapping is for Template object. this one and the Field object has their ID generators set to identity. so when i call session.Update for the Template object it works fine, well, almost: if the Field object has an Id number, UPDATE sql request is called, if the Id is 0, the INSERT is performed. But if i delete a Field object from the collection it has no effect for the Database. I found that if i also call session.Delete for this Field object, everything will be ok, but due to client-server architecture i don't know what to delete. so i decided to delete all the collection elements from the DB and call session.Update with a new collection. and i've got an issue: nhibernate performs the UPDATE operation for the Field objects that has non-zero Id, but they are removed from DB! maybe i should use some other Id generator or smth.. what is the best way to make nhibernate perform "delete all"/"insert all" routine for the collection?

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  • Analyzing an IronPython Scope

    - by Vercinegetorix
    I'm trying to write C# code with an embedded IronPython script. Then want to analyze the contents of the script, i.e. list all variables, functions, class and their members/methods. There's an easy way to start, assuming I've got a scope defined and code executed in it already: dynamic variables=pyScope.GetVariables(); foreach (string v in variables) { dynamic dynamicV=pyScope.GetVariable(); /*seems to return everything. variables, functions, classes, instances of classes*/ } But how do I figure out what the type of a variable is? For the following python 'objects', dynamicV.GetType() will return different values: x=5 --system.Int32 y="asdf" --system.String def func():... --IronPython.Runtime.PythonFunction z=class() -- IronPython.Runtime.Types.OldInstance, how can I identify what the actual python class is? class NewClass -- throws an error, GetType() is unavailable. This is almost what I'm looking for. I could capture the exception thrown when unavailable and assume it's a class declaration, but that seems unclean. Is there a better approach? To discover the members/methods of a class it looks like I can use: ObjectOperations op = pyEngine.Operations; object instance = op.Call("className"); foreach (string j in op.GetMemberNames("className")) { object member=op.GetMember(instance, j); Console.WriteLine(member.GetType()); /*once again, GetType() provides some info about the type of the member, but returns null sometimes*/ } Also, how do I get the parameters to a method? Thanks!

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  • Elegant Disjunctive Normal Form in Django

    - by Mike
    Let's say I've defined this model: class Identifier(models.Model): user = models.ForeignKey(User) key = models.CharField(max_length=64) value = models.CharField(max_length=255) Each user will have multiple identifiers, each with a key and a value. I am 100% sure I want to keep the design like this, there are external reasons why I'm doing it that I won't go through here, so I'm not interested in changing this. I'd like to develop a function of this sort: def get_users_by_identifiers(**kwargs): # something goes here return users The function will return all users that have one of the key=value pairs specified in **kwargs. Here's an example usage: get_users_by_identifiers(a=1, b=2) This should return all users for whom a=1 or b=2. I've noticed that the way I've set this up, this amounts to a disjunctive normal form...the SQL query would be something like: SELECT DISTINCT(user_id) FROM app_identifier WHERE (key = "a" AND value = "1") OR (key = "b" AND value = "2") ... I feel like there's got to be some elegant way to take the **kwargs input and do a Django filter on it, in just 1-2 lines, to produce this result. I'm new to Django though, so I'm just not sure how to do it. Here's my function now, and I'm completely sure it's not the best way to do it :) def get_users_by_identifiers(**identifiers): users = [] for key, value in identifiers.items(): for identifier in Identifier.objects.filter(key=key, value=value): if not identifier.user in users: users.append(identifier.user) return users Any ideas? :) Thanks!

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  • Is it possible, in a django template, to check if an object is contained in a list

    - by AlexH
    I'm very new to django, about a week into it. I'm making a site where users enter stuff, then other users can vote on whether they like the stuff or not. I know it's not so novel, but it's a good project to learn a bunch of tools. I have a many-to-many table for storing who likes or dislikes what. Before I render the page, I pull out all the likes and dislikes for the current user, along with the stuff I'm going to show on the page. When I render the page, I go through the list of stuff I'm going to show and print them out one at a time. I want to show the user which stuff they liked, and which they didn't. So in my django template, I have an object called entry. I also have two lists of objects called likes and dislikes. Is there any way to determine if entry is a member of either list, inside my django template. I think what I'm looking for is a filter where I can say something like {% if entry|in:likes %} or {% if likes|contains:entry %} I know I could add a method to my model and check for each entry individually, but that seems like it would be database intensive. Is there a better way to think about this problem?

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  • How can i mock or test my deferred execution functionality?

    - by cottsak
    I have what could be seen as a bizarre hybrid of IQueryable<T> and IList<T> collections of domain objects passed up my application stack. I'm trying to maintain as much of the 'late querying' or 'lazy loading' as possible. I do this in two ways: By using a LinqToSql data layer and passing IQueryable<T>s through by repositories and to my app layer. Then after my app layer passing IList<T>s but where certain elements in the object/aggregate graph are 'chained' with delegates so as to defer their loading. Sometimes even the delegate contents rely on IQueryable<T> sources and the DataContext are injected. This works for me so far. What is blindingly difficult is proving that this design actually works. Ie. If i defeat the 'lazy' part somewhere and my execution happens early then the whole thing is a waste of time. I'd like to be able to TDD this somehow. I don't know a lot about delegates or thread safety as it applies to delegates acting on the same source. I'd like to be able to mock the DataContext and somehow trace both methods of deferring (IQueryable<T>'s SQL and the delegates) the loading so that i can have tests that prove that both functions are working at different levels/layers of the app/stack. As it's crucial that the deferring works for the design to be of any value, i'd like to see tests fail when i break the design at a given level (separate from the live implementation). Is this possible?

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  • Are there equivalents to Ruby's method_missing in other languages?

    - by Justin Ethier
    In Ruby, objects have a handy method called method_missing which allows one to handle method calls for methods that have not even been (explicitly) defined: Invoked by Ruby when obj is sent a message it cannot handle. symbol is the symbol for the method called, and args are any arguments that were passed to it. By default, the interpreter raises an error when this method is called. However, it is possible to override the method to provide more dynamic behavior. The example below creates a class Roman, which responds to methods with names consisting of roman numerals, returning the corresponding integer values. class Roman def romanToInt(str) # ... end def method_missing(methId) str = methId.id2name romanToInt(str) end end r = Roman.new r.iv #=> 4 r.xxiii #=> 23 r.mm #=> 2000 For example, Ruby on Rails uses this to allow calls to methods such as find_by_my_column_name. My question is, what other languages support an equivalent to method_missing, and how do you implement the equivalent in your code?

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  • Whose fault is a NullReferenceException?

    - by stefan.at.wpf
    I'm currently working on a class which exposes an internal List through a property. The List shall and can be modified. The problem is, entries in the internal list could be set to null from outside the class. My code actually looks like this: class ClassWithList { List<object> _list = new List<object>(); // get accessor, which however returns the reference to the list, // therefore the list can be modified (this is intended) public List<object> Data { get { return _list; } } private void doSomeWorkWithTheList() { foreach(object obj in _list) // do some work with the objects in the list without checking for null. } } So now in the doSomeWorkWithTheList() I could always check whether the current list entry is null or I could just asume that the person using this class doesn't have the great idea to set entries to null. So finally the questions end up in: Whose fault is a NullReferenceException in this case? Is it the fault of the class developer not checking everything for null (which would make code generally - not only in this class - more complex) or is it the fault of the user of this class, as setting a List entry to null doesn't really make sense? I'd tend to generally not check values for null except in some really special cases. Is this a bad style or de facto standard / standard in praxis? I know there's probably no ultimate answer for this, I'm just missing enough experience for such thing and therefore wondering what other developers think about such cases and want to hear what's done in reality about checking null (or not).

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  • How to play simultaneous multiply audio sources in Silverlight

    - by Shurup
    I want to play simultaneous multiply audio sources in Silverlight. So I've created a prototype in Silverlight 4 that should play a two mp3 files containing the same ticks sound with an intervall 1 second. So these files must be sounded as one sound if they will be played together with any whole second offsets (0 and 1, 0 and 2, 1 and 1 seconds, etc.) I my prototype I use two MediaElement (me and me2) objects. DateTime startTime; private void Play_Clicked(object sender, RoutedEventArgs e) { me.SetSource(new FileStream(file1), FileMode.Open))); me2.SetSource(new FileStream(file2), FileMode.Open))); var timer = new DispatcherTimer { Interval = TimeSpan.FromMilliseconds(1) }; timer.Tick += RefreshData; timer.Start(); } First file should be played at 00:00 sec. and the second in 00:02 second. void RefreshData(object sender, EventArgs e) { if(me.CurrentState != MediaElementState.Playing) { startTime = DateTime.Now; me.Play(); return; } var elapsed = DateTime.Now - startTime; if(me2.CurrentState != MediaElementState.Playing && elapsed >= TimeSpan.FromSeconds(2)) { me2.Play(); ((DispatcherTimer)sender).Stop(); } } The tracks played every time different and not simultaneous as they should (as one sound).

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  • rails xml to active record object

    - by Brian D.
    I've been googling for a while to try and convert and incoming XML request into an active record object. I've tried using the ActiveRecordObject.new.from_xml method but it doesn't seem to handle relationships. For example, say I have the following xml: <blog> <title></title> <blog-pages> <blog-page> <page-number></page-number> <content></content> </blog-page> </blog-pages> </blog> And I have the following model objects: class Blog < ActiveRecord::Base has_many :blog_pages end class BlogPage < ActiveRecord::Base belongs_to :blog end Is there a way to convert the xml into a blog object WITH relationships? Or do I need to manually parse the XML? Thanks in advance.

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