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  • sqlite3-ruby can't make on rvm 1.8.7

    - by Josh Crews
    Upgrading to Rails 3 by starting with RVM 1.8.7. OSX 10.5.8 Output: josh-crewss-macbook:~ joshcrews$ gem install sqlite3-rubyBuilding native extensions. This could take a while...ERROR: Error installing sqlite3-ruby: ERROR: Failed to build gem native extension. /Users/joshcrews/.rvm/rubies/ruby-1.8.7-p174/bin/ruby extconf.rb checking for sqlite3.h... yes checking for sqlite3_libversion_number() in -lsqlite3... yes checking for rb_proc_arity()... no checking for sqlite3_column_database_name()... no checking for sqlite3_enable_load_extension()... no checking for sqlite3_load_extension()... no creating Makefile make gcc -I. -I. -I/Users/joshcrews/.rvm/rubies/ruby-1.8.7-p174/lib/ruby/1.8/i686-darwin9.8.0 -I. -I/usr/local/include -I/opt/local/include -I/usr/include -D_XOPEN_SOURCE -D_DARWIN_C_SOURCE -fno-common -g -O2 -fno-common -pipe -fno-common -O3 -Wall -Wcast-qual -Wwrite-strings -Wconversion -Wmissing-noreturn -Winline -c database.c database.c: In function ‘deallocate’: database.c:17: warning: implicit declaration of function ‘sqlite3_next_stmt’ database.c:17: warning: assignment makes pointer from integer without a cast database.c: In function ‘initialize’: database.c:76: warning: implicit declaration of function ‘sqlite3_open_v2’ database.c:79: error: ‘SQLITE_OPEN_READWRITE’ undeclared (first use in this function) database.c:79: error: (Each undeclared identifier is reported only once database.c:79: error: for each function it appears in.) database.c:79: error: ‘SQLITE_OPEN_CREATE’ undeclared (first use in this function) database.c: In function ‘set_sqlite3_func_result’: database.c:277: error: ‘sqlite3_int64’ undeclared (first use in this function) database.c: In function ‘rb_sqlite3_func’: database.c:311: warning: passing argument 1 of ‘ruby_xcalloc’ as signed due to prototype database.c: In function ‘rb_sqlite3_step’: database.c:378: warning: passing argument 1 of ‘ruby_xcalloc’ as signed due to prototype make: *** [database.o] Error 1 Gem list (these are under RVM, under system I've got lot more gems included the sqlite3-ruby that's worked for 1.5 years) josh-crewss-macbook:~ joshcrews$ gem list *** LOCAL GEMS *** abstract (1.0.0) actionmailer (3.0.0.beta3) actionpack (3.0.0.beta3) activemodel (3.0.0.beta3) activerecord (3.0.0.beta3) activeresource (3.0.0.beta3) activesupport (3.0.0.beta3, 2.3.8) arel (0.3.3) builder (2.1.2) bundler (0.9.25) capybara (0.3.8) configuration (1.1.0) cucumber (0.7.2) cucumber-rails (0.3.1) culerity (0.2.10) database_cleaner (0.5.2) diff-lcs (1.1.2) erubis (2.6.5) ffi (0.6.3) gherkin (1.0.30) i18n (0.4.0, 0.3.7) json_pure (1.4.3) launchy (0.3.5) mail (2.2.1) memcache-client (1.8.3) mime-types (1.16) nokogiri (1.4.2) polyglot (0.3.1) rack (1.1.0) rack-mount (0.6.3) rack-test (0.5.4) rails (3.0.0.beta3) railties (3.0.0.beta3) rake (0.8.7) rdoc (2.5.8) rspec (2.0.0.beta.10, 2.0.0.beta.8) rspec-core (2.0.0.beta.10, 2.0.0.beta.8) rspec-expectations (2.0.0.beta.10, 2.0.0.beta.8) rspec-mocks (2.0.0.beta.10, 2.0.0.beta.8) rspec-rails (2.0.0.beta.10, 2.0.0.beta.8) rubygems-update (1.3.7) selenium-webdriver (0.0.20) spork (0.8.3) term-ansicolor (1.0.5) text-format (1.0.0) text-hyphen (1.0.0) thor (0.13.6) treetop (1.4.8) trollop (1.16.2) tzinfo (0.3.22) webrat (0.7.1) Version of XCode: 3.1.1 My suspicion is it has to do with "-I/Users/joshcrews/.rvm/rubies/ruby-1.8.7-p174/lib/ruby/1.8/i686-darwin9.8.0", because i686-darwin9.8.0 doesnt exist in that file

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  • QueryInterface fails at casting inside COM-interface implementation

    - by brecht
    I am creating a tool in c# to retrieve messages of a CAN-network (network in a car) using an Dll written in C/C++. This dll is usable as a COM-interface. My c#-formclass implements one of these COM-interfaces. And other variables are instantiated using these COM-interfaces (everything works perfect). The problem: The interface my C#-form implements has 3 abstract functions. One of these functions is called -by the dll- and i need to implement it myself. In this function i wish to retrieve a property of a form-wide variable that is of a COM-type. The COM library is CANSUPPORTLib The form-wide variable: private CANSUPPORTLib.ICanIOEx devices = new CANSUPPORTLib.CanIO(); This variable is also form-wide and is retrieved via the devices-variable: canreceiver = (CANSUPPORTLib.IDirectCAN2)devices.get_DirectDispatch(receiverLogicalChannel); The function that is called by the dll and implemented in c# public void Message(double dTimeStamp) { Console.WriteLine("!!! message ontvangen !!!" + Environment.NewLine); try { CANSUPPORTLib.can_msg_tag message = new CANSUPPORTLib.can_msg_tag(); message = (CANSUPPORTLib.can_msg_tag) System.Runtime.InteropServices.Marshal.PtrToStructure(canreceiver.RawMessage, message.GetType()); for (int i = 0; i < message.data.Length; i++) { Console.WriteLine("byte " + i + ": " + message.data[i]); } } catch (Exception e) { Console.WriteLine(e.Message); } } The error rises at this line: message = (CANSUPPORTLib.can_msg_tag)System.Runtime.InteropServices.Marshal.PtrToStructure(canreceiver.RawMessage, message.GetType()); Error: Unable to cast COM object of type 'System.__ComObject' to interface type 'CANSUPPORTLib.IDirectCAN2'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{33373EFC-DB42-48C4-A719-3730B7F228B5}' failed due to the following error: No such interface supported (Exception from HRESULT: 0x80004002 (E_NOINTERFACE)). Notes: It is possible to have a timer-clock that checks every 100ms for the message i need. The message is then retrieved in the exact same way as i do now. This timer is started when the form starts. The checking is only done when Message(double) has put a variable to true (a message arrived). When the timer-clock is started in the Message function, i have the same error as above Starting another thread when the form starts, is also not possible. Is there someone with experience with COM-interop ? When this timer

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  • Shawn Wildermuth violating MVVM in MSDN article?

    - by rasx
    This may be old news but back in March 2009, Shawn Wildermuth, his article, “Model-View-ViewModel In Silverlight 2 Apps,” has a code sample that includes DataServiceEntityBase: // COPIED FROM SILVERLIGHTCONTRIB Project for simplicity /// <summary> /// Base class for DataService Data Contract classes to implement /// base functionality that is needed like INotifyPropertyChanged. /// Add the base class in the partial class to add the implementation. /// </summary> public abstract class DataServiceEntityBase : INotifyPropertyChanged { /// <summary> /// The handler for the registrants of the interface's event /// </summary> PropertyChangedEventHandler _propertyChangedHandler; /// <summary> /// Allow inheritors to fire the event more simply. /// </summary> /// <param name="propertyName"></param> protected void FirePropertyChanged(string propertyName) { if (_propertyChangedHandler != null) { _propertyChangedHandler(this, new PropertyChangedEventArgs(propertyName)); } } #region INotifyPropertyChanged Members /// <summary> /// The interface used to notify changes on the entity. /// </summary> event PropertyChangedEventHandler INotifyPropertyChanged.PropertyChanged { add { _propertyChangedHandler += value; } remove { _propertyChangedHandler -= value; } } #endregion What this class implies is that the developer intends to bind visuals directly to data (yes, a ViewModel is used but it defines an ObservableCollection of data objects). Is this design diverging too far from the guidance of MVVM? Now I can see some of the reasons why Shawn would go this way: what Shawn can do with DataServiceEntityBase is this sort of thing (which is intimate with the Entity Framework): // Partial Method to support the INotifyPropertyChanged interface public partial class Game : DataServiceEntityBase { #region Partial Method INotifyPropertyChanged Implementation // Override the Changed partial methods to implement the // INotifyPropertyChanged interface // This helps with the Model implementation to be a mostly // DataBound implementation partial void OnDeveloperChanged() { base.FirePropertyChanged("Developer"); } partial void OnGenreChanged() { base.FirePropertyChanged("Genre"); } partial void OnListPriceChanged() { base.FirePropertyChanged("ListPrice"); } partial void OnListPriceCurrencyChanged() { base.FirePropertyChanged("ListPriceCurrency"); } partial void OnPlayerInfoChanged() { base.FirePropertyChanged("PlayerInfo"); } partial void OnProductDescriptionChanged() { base.FirePropertyChanged("ProductDescription"); } partial void OnProductIDChanged() { base.FirePropertyChanged("ProductID"); } partial void OnProductImageUrlChanged() { base.FirePropertyChanged("ProductImageUrl"); } partial void OnProductNameChanged() { base.FirePropertyChanged("ProductName"); } partial void OnProductTypeIDChanged() { base.FirePropertyChanged("ProductTypeID"); } partial void OnPublisherChanged() { base.FirePropertyChanged("Publisher"); } partial void OnRatingChanged() { base.FirePropertyChanged("Rating"); } partial void OnRatingUrlChanged() { base.FirePropertyChanged("RatingUrl"); } partial void OnReleaseDateChanged() { base.FirePropertyChanged("ReleaseDate"); } partial void OnSystemNameChanged() { base.FirePropertyChanged("SystemName"); } #endregion } Of course MSDN code can seen as “toy code” for educational purposes but is anyone doing anything like this in the real world of Silverlight development?

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  • Ruby on Rails has_one Model Not Supplying ID Column

    - by Metric Scantlings
    I have a legacy rails (version 1.2.3) app which runs without issue on a number of servers (not to mention my local environment). Deployed to its newest server, though, and I now get ActiveRecord::StatementInvalid: Mysql::Error: #23000Column 'video_id' cannot be null errors. Below are the models/relationships, simplified: class Video < ActiveRecord::Base has_one(:user, :dependent => :destroy) end class User < ActiveRecord::Base belongs_to(:video) end And below is a rails console transcript of the relationships failing: >> video = Video.create(:title => 'New Video') => #<Video:0xb6d5e31c>... >> video.id => 5 >> video.user = User.create(:name => 'Tester') ActiveRecord::StatementInvalid: Mysql::Error: #23000Column 'video_id' cannot be null: INSERT INTO users (`name`, `video_id`) VALUES('Tester', NULL) from /usr/lib/ruby/gems/1.8/gems/activerecord-1.15.3/lib/active_record/connection_adapters/abstract_adapter.rb:128:in `log' from /usr/lib/ruby/gems/1.8/gems/activerecord-1.15.3/lib/active_record/connection_adapters/mysql_adapter.rb:243:in `execute' from /usr/lib/ruby/gems/1.8/gems/activerecord-1.15.3/lib/active_record/connection_adapters/mysql_adapter.rb:253:in `insert' from /usr/lib/ruby/gems/1.8/gems/activerecord-1.15.3/lib/active_record/base.rb:1811:in `create_without_callbacks' from /usr/lib/ruby/gems/1.8/gems/activerecord-1.15.3/lib/active_record/callbacks.rb:254:in `create_without_timestamps' from /usr/lib/ruby/gems/1.8/gems/activerecord-1.15.3/lib/active_record/timestamp.rb:39:in `create' from /usr/lib/ruby/gems/1.8/gems/activerecord-1.15.3/lib/active_record/base.rb:1789:in `create_or_update_without_callbacks' from /usr/lib/ruby/gems/1.8/gems/activerecord-1.15.3/lib/active_record/callbacks.rb:242:in `create_or_update' from /usr/lib/ruby/gems/1.8/gems/activerecord-1.15.3/lib/active_record/base.rb:1545:in `save_without_validation' from /usr/lib/ruby/gems/1.8/gems/activerecord-1.15.3/lib/active_record/validations.rb:752:in `save_without_transactions' from /usr/lib/ruby/gems/1.8/gems/activerecord-1.15.3/lib/active_record/transactions.rb:129:in `save' from /usr/lib/ruby/gems/1.8/gems/activerecord-1.15.3/lib/active_record/connection_adapters/abstract/database_statements.rb:59:in `transaction' from /usr/lib/ruby/gems/1.8/gems/activerecord-1.15.3/lib/active_record/transactions.rb:95:in `transaction' from /usr/lib/ruby/gems/1.8/gems/activerecord-1.15.3/lib/active_record/transactions.rb:121:in `transaction' from /usr/lib/ruby/gems/1.8/gems/activerecord-1.15.3/lib/active_record/transactions.rb:129:in `save' from /usr/lib/ruby/gems/1.8/gems/activerecord-1.15.3/lib/active_record/base.rb:451:in `create' from (irb):3 from :0 Has anyone else come across ActiveRecord not sending an ID when it clearly knows it?

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  • "type not defined" exception with WF4 RC

    - by avi1234
    Hi, I`m gettin the following exception while invoking my workflow (dynamically): The following errors were encountered while processing the workflow tree: 'DynamicActivity': The private implementation of activity '1: DynamicActivity' has the following validation error: Compiler error(s) encountered processing expression "TryCast(simplerule_out,OutputBase2)". Type 'OutputBase2' is not defined. 'DynamicActivity': The private implementation of activity '1: DynamicActivity' has the following validation error: Compiler error(s) encountered processing expression "Res". Type 'OutputBase2' is not defined. 'DynamicActivity': The private implementation of activity '1: DynamicActivity' has the following validation error: Compiler error(s) encountered processing expression "Res". Type 'OutputBase2' is not defined. 'DynamicActivity': The private implementation of activity '1: DynamicActivity' has the following validation error: Compiler error(s) encountered processing expression "New List(Of OutputBase2)". Type 'OutputBase2' is not defined. The workflow is very simple and worked fine on VS 2010 beta 2! All I`m trying to do is to create new list of my abstract custom type "OutputBase2". public class OutputBase2 { public OutputBase2() { } public bool Succeeded { get; set; } } class Example { public void Exec() { ActivityBuilder builder = new ActivityBuilder(); builder.Name = "act1"; var res = new DynamicActivityProperty { Name = "Res", Type = typeof(OutArgument<List<OutputBase2>>), Value = new OutArgument<List<OutputBase2>>() }; builder.Properties.Add(res); builder.Implementation = new Sequence(); ((Sequence)builder.Implementation).Activities.Add(new Assign<List<OutputBase2>> { To = new VisualBasicReference<List<OutputBase2>> { ExpressionText = res.Name }, Value = new VisualBasicValue<List<OutputBase2>>("New List(Of OutputBase2)") }); Activity act = getActivity(builder); var res2 = WorkflowInvoker.Invoke(act); } string getXamlStringFromActivityBuilder(ActivityBuilder activityBuilder) { string xamlString; StringBuilder stringBuilder = new StringBuilder(); System.IO.StringWriter stringWriter = new System.IO.StringWriter(stringBuilder); System.Xaml.XamlSchemaContext xamlSchemaContext = new System.Xaml.XamlSchemaContext(); System.Xaml.XamlXmlWriter xamlXmlWriter = new System.Xaml.XamlXmlWriter(stringWriter, xamlSchemaContext); System.Xaml.XamlWriter xamlWriter = System.Activities.XamlIntegration.ActivityXamlServices.CreateBuilderWriter(xamlXmlWriter); System.Xaml.XamlServices.Save(xamlWriter, activityBuilder); xamlString = stringBuilder.ToString(); return xamlString; } public Activity getActivity(ActivityBuilder t) { string xamlString = getXamlStringFromActivityBuilder(t); System.IO.StringReader stringReader = new System.IO.StringReader(xamlString); Activity activity = System.Activities.XamlIntegration.ActivityXamlServices.Load(stringReader); return activity; } } Thanks!

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  • Keeping the DI-container usage in the composition root in Silverlight and MVVM

    - by adrian hara
    It's not quite clear to me how I can design so I keep the reference to the DI-container in the composition root for a Silverlight + MVVM application. I have the following simple usage scenario: there's a main view (perhaps a list of items) and an action to open an edit view for one single item. So the main view has to create and show the edit view when the user takes the action (e.g. clicks some button). For this I have the following code: public interface IView { IViewModel ViewModel {get; set;} } Then, for each view that I need to be able to create I have an abstract factory, like so public interface ISomeViewFactory { IView CreateView(); } This factory is then declared a dependency of the "parent" view model, like so: public class SomeParentViewModel { public SomeParentViewModel(ISomeViewFactory viewFactory) { // store it } private void OnSomeUserAction() { IView view = viewFactory.CreateView(); dialogService.ShowDialog(view); } } So all is well until here, no DI-container in sight :). Now comes the implementation of ISomeViewFactory: public class SomeViewFactory : ISomeViewFactory { public IView CreateView() { IView view = new SomeView(); view.ViewModel = ???? } } The "????" part is my problem, because the view model for the view needs to be resolved from the DI-container so it gets its dependencies injected. What I don't know is how I can do this without having a dependency to the DI-container anywhere except the composition root. One possible solution would be to have either a dependency on the view model that gets injected into the factory, like so: public class SomeViewFactory : ISomeViewFactory { public SomeViewFactory(ISomeViewModel viewModel) { // store it } public IView CreateView() { IView view = new SomeView(); view.ViewModel = viewModel; } } While this works, it has the problem that since the whole object graph is wired up "statically" (i.e. the "parent" view model will get an instance of SomeViewFactory, which will get an instance of SomeViewModel, and these will live as long as the "parent" view model lives), the injected view model implementation is stateful and if the user opens the child view twice, the second time the view model will be the same instance and have the state from before. I guess I could work around this with an "Initialize" method or something similar, but it doesn't smell quite right. Another solution might be to wrap the DI-container and have the factories depend on the wrapper, but it'd still be a DI-container "in disguise" there :) Any thoughts on this are greatly appreciated. Also, please forgive any mistakes or rule-breaking, since this is my first post on stackoverflow :) Thanks! ps: my current solution is that the factories know about the DI-container, and it's only them and the composition root that have this dependency.

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  • Best way to handle multiple tables to replace one big table in Rails? (e.g. 'Books1', 'Books2', etc.

    - by mikep
    Hello, I've decided to use multiple tables for an entity (e.g. Books1, Books2, Books3, etc.), instead of just one main table which could end up having a lot of rows (e.g. just Books). I'm doing this to try and to avoid a potential future performance drop that could come with having too many rows in one table. With that, I'm looking for a good way to handle this in Rails, mainly by trying to avoid loading a bunch of unused associations. (I know that I could use a partition for this, but, for now, I've decided to go the 'multiple tables' route.) Each user has their books placed into a specific table. The actual book table is chosen when the user is created, and all of their books go into the same table. I'm going to split the adds across the tables. The goal is to try and keep each table pretty much even -- but that's a different issue. One thing I don't particularly want to have is a bunch of unused associations in the User class. Right now, it looks like I'd have to do the following: class User < ActiveRecord::Base has_many :books1, :books2, :books3, :books4, :books5 end class Books1 < ActiveRecord::Base belongs_to :user end class Books2 < ActiveRecord::Base belongs_to :user end class Books3 < ActiveRecord::Base belongs_to :user end I'm assuming that the main performance hit would come in terms of memory and possibly some method call overhead for each User object, since it has to load all of those associations, which in turn creates all of those nice, dynamic model accessor methods like User.find_by_. But for each specific user, only one of the book tables would be usable/applicable, since all of a user's books are stored in the same table. So, only one of the associations would be in use at any time and any other has_many :bookX association that was loaded would be a waste. For example, with a user.id of 2, I'd only need books3.find_by_author('Author'), but the way I'm thinking of setting this up, I'd still have access to Books1..n. I don't really know Ruby/Rails does internally with all of those has_many associations though, so maybe it's not so bad. But right now I'm thinking that it's really wasteful, and that there may just be a better, more efficient way of doing this. So, a few questions: 1) Is there's some sort of special Ruby/Rails methodology that could be applied to this 'multiple tables to represent one entity' scheme? Are there any 'best practices' for this? 2) Is it really bad to have so many unused has_many associations for each object? Is there a better way to do this? 3) Does anyone have any advice on how to abstract the fact that there's multiple book tables behind a single books model/class? For example, so I can call books.find_by_author('Author') instead of books3.find_by_author('Author'). Thank you!

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  • .NET asmx web services: serialize object property as string property to support versioning

    - by mcliedtk
    I am in the process of upgrading our web services to support versioning. We will be publishing our versioned web services like so: http://localhost/project/services/1.0/service.asmx http://localhost/project/services/1.1/service.asmx One requirement of this versioning is that I am not allowed to break the original wsdl (the 1.0 wsdl). The challenge lies in how to shepherd the newly versioned classes through the logic that lies behind the web services (this logic includes a number of command and adapter classes). Note that upgrading to WCF is not an option at the moment. To illustrate this, let's consider an example with Blogs and Posts. Prior to the introduction of versions, we were passing concrete objects around instead of interfaces. So an AddPostToBlog command would take in a Post object instead of an IPost. // Old AddPostToBlog constructor. public AddPostToBlog(Blog blog, Post post) { // constructor body } With the introduction of versioning, I would like to maintain the original Post while adding a PostOnePointOne. Both Post and PostOnePointOne will implement the IPost interface (they are not extending an abstract class because that inheritance breaks the wsdl, though I suppose there may be a way around that via some fancy xml serialization tricks). // New AddPostToBlog constructor. public AddPostToBlog(Blog blog, IPost post) { // constructor body } This brings us to my question regarding serialization. The original Post class has an enum property named Type. For various cross-platform compatibility issues, we are changing our enums in our web services to strings. So I would like to do the following: // New IPost interface. public interface IPost { object Type { get; set; } } // Original Post object. public Post { // The purpose of this attribute would be to maintain how // the enum currently is serialized even though now the // type is an object instead of an enum (internally the // object actually is an enum here, but it is exposed as // an object to implement the interface). [XmlMagic(SerializeAsEnum)] object Type { get; set; } } // New version of Post object public PostOnePointOne { // The purpose of this attribute would be to force // serialization as a string even though it is an object. [XmlMagic(SerializeAsString)] object Type { get; set; } } The XmlMagic refers to an XmlAttribute or some other part of the System.Xml namespace that would allow me to control the type of the object property being serialized (depending on which version of the object I am serializaing). Does anyone know how to accomplish this?

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  • Mock static method Activator.CreateInstance to return a mock of another class

    - by Jeep87c
    I have this factory class and I want to test it correctly. Let's say I have an abstract class which have many child (inheritance). As you can see in my Factory class the method BuildChild, I want to be able to create an instance of a child class at Runtime. I must be able to create this instance during Runtime because the type won't be know before runtime. And, I can NOT use Unity for this project (if so, I would not ask how to achieve this). Here's my Factory class that I want to test: public class Factory { public AnAbstractClass BuildChild(Type childType, object parameter) { AnAbstractClass child = (AnAbstractClass) Activator.CreateInstance(childType); child.Initialize(parameter); return child; } } To test this, I want to find a way to Mock Activator.CreateInstance to return my own mocked object of a child class. How can I achieve this? Or maybe if you have a better way to do this without using Activator.CreateInstance (and Unity), I'm opened to it if it's easier to test and mock! I'm currently using Moq to create my mocks but since Activator.CreateInstance is a static method from a static class, I can't figure out how to do this (I already know that Moq can only create mock instances of objects). I took a look at Fakes from Microsoft but without success (I had some difficulties to understand how it works and to find some well explained examples). Please help me! EDIT: I need to mock Activator.CreateInstance because I want to force this method to return another mocked object. The correct thing I want is only to stub this method (not to mock it). So when I test BuildChild like this: [TestMethod] public void TestBuildChild() { var mockChildClass = new Mock(AChildClass); // TODO: Stub/Mock Activator.CreateInstance to return mockChildClass when called with "type" and "parameter" as follow. var type = typeof(AChildClass); var parameter = "A parameter"; var child = this._factory.BuildChild(type, parameters); } Activator.CreateInstance called with type and parameter will return my mocked object instead of creating a new instance of the real child class (not yet implemented).

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  • Any software for pattern-matching and -rewriting source code?

    - by Steven A. Lowe
    I have some old software (in a language that's not dead but is dead to me ;-)) that implements a basic pattern-matching and -rewriting system for source code. I am considering resurrecting this code, translating it into a modern language, and open-sourcing the project as a refactoring power-tool. Before I go much further, I want to know if anything like this exists already (my google-fu is fanning air on this tonight). Here's how it works: the pattern-matching part matches source-code patterns spanning multiple lines of code using a template with binding variables, the pattern-rewriting part uses a template to rewrite the matched code, inserting the contents of the bound variables from the matching template matching and rewriting templates are associated (1:1) by a simple (unconditional) rewrite rule the software operates on the abstract syntax tree (AST) of the input application, and outputs a modified AST which can then be regenerated into new source code for example, suppose we find a bunch of while-loops that really should be for-loops. The following template will match the while-loop pattern: Template oldLoopPtrn int @cnt@ = 0; while (@cnt@ < @max@) { … @body@ ++@cnt@; } End_Template while the following template will specify the output rewrite pattern: Template newLoopPtrn for(int @cnt@ = 0; @cnt@ < @max@; @cnt@++) { @body@ } End_Template and a simple rule to associate them Rule oldLoopPtrn --> newLoopPtrn so code that looks like this int i=0; while(i<arrlen) { printf("element %d: %f\n",i,arr[i]); ++i; } gets automatically rewritten to look like this for(int i = 0; i < arrlen; i++) { printf("element %d: %f\n",i,arr[i]); } The closest thing I've seen like this is some of the code-refactoring tools, but they seem to be geared towards interactive rewriting of selected snippets, not wholesale automated changes. I believe that this kind of tool could supercharge refactoring, and would work on multiple languages (even HTML/CSS). I also believe that converting and polishing the code base would be a huge project that I simply cannot do alone in any reasonable amount of time. So, anything like this out there already? If not, any obvious features (besides rewrite-rule conditions) to consider? EDIT: The one feature of this system that I like very much is that the template patterns are fairly obvious and easy to read because they're written in the same language as the target source code, not in some esoteric mutated regex/BNF format.

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  • Where to put a glossary of important terms and patterns in documentation?

    - by Tetha
    Greetings. I want to document certain patterns in the code in order to build up a consistent terminology (in order to easen communication about the software). I am, however, unsure, where to define the terms given. In order to get on the same level, an example: I have a code generator. This code generator receives a certain InputStructure from the Parser (yes, the name InputStructure might be less than ideal). This InputStructure is then transformed into various subsequent datastructures (like an abstract description of the validation process). Each of these datastructures can be either transformed into another value of the same datastructure or it can be transformed into the next datastructure. This should sound like Pipes and Filters to some degree. Given this, I call an operation which takes a datastructures and constructs a value of the same datastructure a transformation, while I call an operation which takes a datastructure and produces a different follow-up datastructure a derivation. The final step of deriving a string containing code is called emitting. (So, overall, the codegenerator takes the input-structure and transforms, transforms, derives, transforms, derives and finally emits). I think emphasizing these terms will be benefitial in communications, because then it is easy to talk about things. If you hear "transformation", you know "Ok, I only need to think about these two datastructures", if you hear "emitting", you know "Ok, I only need to know this datastructure and the target language.". However, where do I document these patterns? The current code base uses visitors and offers classes called like ValidatorTransformationBase<ResultType> (or InputStructureTransformationBase<ResultType>, and so one and so on). I do not really want to add the definition of such terms to the interfaces, because in that case, I'd have to repeat myself on each and every interface, which clearly violates DRY. I am considering to emphasize the distinction between Transformations and Derivations by adding further interfaces (I would have to think about a better name for the TransformationBase-classes, but then I could do thinks like ValidatorTransformation extends ValidatorTransformationBase<Validator>, or ValidatorDerivationFromInputStructure extends InputStructureTransformation<Validator>). I also think I should add a custom page to the doxygen documentation already existing, as in "Glossary" or "Architecture Principles", which contains such principles. The only disadvantage of this would be that a contributor will need to find this page in order to actually learn about this. Am I missing possibilities or am I judging something wrong here in your opinion? -- Regards, Tetha

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  • Does this MSDN article violate MVVM?

    - by rasx
    This may be old news but back in March 2009, this article, “Model-View-ViewModel In Silverlight 2 Apps,” has a code sample that includes DataServiceEntityBase: // COPIED FROM SILVERLIGHTCONTRIB Project for simplicity /// <summary> /// Base class for DataService Data Contract classes to implement /// base functionality that is needed like INotifyPropertyChanged. /// Add the base class in the partial class to add the implementation. /// </summary> public abstract class DataServiceEntityBase : INotifyPropertyChanged { /// <summary> /// The handler for the registrants of the interface's event /// </summary> PropertyChangedEventHandler _propertyChangedHandler; /// <summary> /// Allow inheritors to fire the event more simply. /// </summary> /// <param name="propertyName"></param> protected void FirePropertyChanged(string propertyName) { if (_propertyChangedHandler != null) { _propertyChangedHandler(this, new PropertyChangedEventArgs(propertyName)); } } #region INotifyPropertyChanged Members /// <summary> /// The interface used to notify changes on the entity. /// </summary> event PropertyChangedEventHandler INotifyPropertyChanged.PropertyChanged { add { _propertyChangedHandler += value; } remove { _propertyChangedHandler -= value; } } #endregion What this class implies is that the developer intends to bind visuals directly to data (yes, a ViewModel is used but it defines an ObservableCollection of data objects). Is this design diverging too far from the guidance of MVVM? Now I can see some of the reasons Why would we go this way: what we can do with DataServiceEntityBase is this sort of thing (which is intimate with the Entity Framework): // Partial Method to support the INotifyPropertyChanged interface public partial class Game : DataServiceEntityBase { #region Partial Method INotifyPropertyChanged Implementation // Override the Changed partial methods to implement the // INotifyPropertyChanged interface // This helps with the Model implementation to be a mostly // DataBound implementation partial void OnDeveloperChanged() { base.FirePropertyChanged("Developer"); } partial void OnGenreChanged() { base.FirePropertyChanged("Genre"); } partial void OnListPriceChanged() { base.FirePropertyChanged("ListPrice"); } partial void OnListPriceCurrencyChanged() { base.FirePropertyChanged("ListPriceCurrency"); } partial void OnPlayerInfoChanged() { base.FirePropertyChanged("PlayerInfo"); } partial void OnProductDescriptionChanged() { base.FirePropertyChanged("ProductDescription"); } partial void OnProductIDChanged() { base.FirePropertyChanged("ProductID"); } partial void OnProductImageUrlChanged() { base.FirePropertyChanged("ProductImageUrl"); } partial void OnProductNameChanged() { base.FirePropertyChanged("ProductName"); } partial void OnProductTypeIDChanged() { base.FirePropertyChanged("ProductTypeID"); } partial void OnPublisherChanged() { base.FirePropertyChanged("Publisher"); } partial void OnRatingChanged() { base.FirePropertyChanged("Rating"); } partial void OnRatingUrlChanged() { base.FirePropertyChanged("RatingUrl"); } partial void OnReleaseDateChanged() { base.FirePropertyChanged("ReleaseDate"); } partial void OnSystemNameChanged() { base.FirePropertyChanged("SystemName"); } #endregion } Of course MSDN code can seen as “toy code” for educational purposes but is anyone doing anything like this in the real world of Silverlight development?

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  • Multiple views and source list in a Core Data app

    - by Ellie P.
    I'm working on my first major Cocoa app for an undergraduate research project. The application is document-based and uses Core Data. One of the entities is an abstract entity, Page. Page is parent of several types of pages: ie PageWithHeaderAndFooter, PageWithTwoColumns, BasicPage etc. Page has attributes, such as title and author, that all pages have in common. Each specific type of page has a certain number of layout blocks (PageWithHeaderAndFooter has three: header, footer, body. BasicPage has one: body. etc.) Additionally, all Page subclasses define layout-specific implementations of certain methods. The other relevant entity is Style, which defines the visual look of a Page. (Think of Pages as HTML and Style as CSS.) I would like my app to have an iTunes/Mail-like source list with sections. (One section would be Pages, the other would be Styles.) I have a pretty good idea how to do the sectioned source list (this was a great help). However, after hours of headbanging and fruitless googling, here's what I can't figure out: Pages and Styles listed in the source list, and when you select one of them, all of the relevant fields for that object appear at the right (mostly NSTextViews, pop up menus, etc). I laid that out and did all of the bindings in Interface Builder. The problem is, if my source list contains different types of pages, how do I get a different view to display at the right depending on the type of page selected? For example, if a BasicPage is selected, I want just what you see above: the general page stuff and one NSTextView that corresponds to the one field body of BasicPage. But if I select a PageWithHeaderAndFooter, I want to display the general page stuff plus three NSTextViews (one for header, body, and footer.) If I have a Style selected, I want to display various pop up menus, color wells, etc. For the pages at least, we're only talking about one or more NSTextViews, each of which corresponds to a String attribute of the respective entity. How would you do this? Thank you for your help!

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  • Dynamic Linq help, different errors depending on object passed as parameter?

    - by sah302
    I have an entityDao that is inherbited by everyone of my objectDaos. I am using Dynamic Linq and trying to get some generic queries to work. I have the following code in my generic method in my EntityDao : public abstract class EntityDao<ImplementationType> where ImplementationType : Entity { public ImplementationType getOneByValueOfProperty(string getProperty, object getValue){ ImplementationType entity = null; if (getProperty != null && getValue != null) { LCFDataContext lcfdatacontext = new LCFDataContext(); //Generic LINQ Query Here entity = lcfdatacontext.GetTable<ImplementationType>().Where(getProperty + " =@0", getValue).FirstOrDefault(); //.Where(getProperty & "==" & CStr(getValue)) } //lcfdatacontext.SubmitChanges() //lcfdatacontext.Dispose() return entity; } }         Then I do the following method call in a unit test (all my objectDaos inherit entityDao): [Test] public void getOneByValueOfProperty() { Accomplishment result = accomplishmentDao.getOneByValueOfProperty("AccomplishmentType.Name", "Publication"); Assert.IsNotNull(result); } The above passes (AccomplishmentType has a relationship to accomplishment) Accomplishment result = accomplishmentDao.getOneByValueOfProperty("Description", "Can you hear me now?"); Accomplishment result = accomplishmentDao.getOneByValueOfProperty("LocalId", 4); Both of the above work Accomplishment result = accomplishmentDao.getOneByValueOfProperty("Id", New Guid("95457751-97d9-44b5-8f80-59fc2d170a4c"))       Does not work and says the following: Operator '=' incompatible with operand types 'Guid' and 'Guid Why is this happening? Guid's can't be compared? I tried == as well but same error. What's even moreso confusing is that every example of Dynamic Linq I have seen simply usings strings whether using the parameterized where predicate or this one I have commented out: //.Where(getProperty & "==" & CStr(getValue)) With or without the Cstr, many datatypes don't work with this format. I tried setting the getValue to a string instead of an object as well, but then I just get different errors (such as a multiword string would stop comparison after the first word). What am I missing to make this work with GUIDs and/or any data type? Ideally I would like to be able to just pass in a string for getValue (as I have seen for every other dynamic LINQ example) instead of the object and have it work regardless of the data Type of the column.

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  • How do I refactor these two C# functions to abstrtact their logic from the specific class properties

    - by ObligatoryMoniker
    I have two functions whose underlying logic is the same but in one case it sets one property value on a class and in another case it sets a different one. How can I rewrite the following two functions to abstract away as much of the algorithm as possible so that I can make changes in logic in a single place? SetBillingAddress private void SetBillingAddress(OrderAddress newBillingAddress) { BasketHelper basketHelper = new BasketHelper(SiteConstants.BasketName); OrderAddress oldBillingAddress = basketHelper.Basket.Addresses[basketHelper.BillingAddressID]; bool NewBillingAddressIsNotOldBillingAddress = ((oldBillingAddress == null) || (newBillingAddress.OrderAddressId != oldBillingAddress.OrderAddressId)); bool BillingAddressHasBeenPreviouslySet = (oldBillingAddress != null); bool BillingAddressIsNotSameAsShippingAddress = (basketHelper.ShippingAddressID != basketHelper.BillingAddressID); bool NewBillingAddressIsNotShippingAddress = (newBillingAddress.OrderAddressId != basketHelper.ShippingAddressID); if (NewBillingAddressIsNotOldBillingAddress && BillingAddressHasBeenPreviouslySet && BillingAddressIsNotSameAsShippingAddress) { basketHelper.Basket.Addresses.Remove(oldBillingAddress); } if (NewBillingAddressIsNotOldBillingAddress && NewBillingAddressIsNotShippingAddress) { basketHelper.Basket.Addresses.Add(newBillingAddress); } basketHelper.BillingAddressID = newBillingAddress.OrderAddressId; basketHelper.Basket.Save(); } And here is the second one: SetShippingAddress private void SetBillingAddress(OrderAddress newShippingAddress) { BasketHelper basketHelper = new BasketHelper(SiteConstants.BasketName); OrderAddress oldShippingAddress = basketHelper.Basket.Addresses[basketHelper.ShippingAddressID]; bool NewShippingAddressIsNotOldShippingAddress = ((oldShippingAddress == null) || (newShippingAddress.OrderAddressId != oldShippingAddress.OrderAddressId)); bool ShippingAddressHasBeenPreviouslySet = (oldShippingAddress != null); bool ShippingAddressIsNotSameAsBillingAddress = (basketHelper.ShippingAddressID != basketHelper.BillingAddressID); bool NewShippingAddressIsNotBillingAddress = (newShippingAddress.OrderAddressId != basketHelper.BillingAddressID); if (NewShippingAddressIsNotOldShippingAddress && ShippingAddressHasBeenPreviouslySet && ShippingAddressIsNotSameAsBillingAddress) { basketHelper.Basket.Addresses.Remove(oldShippingAddress); } if (NewShippingAddressIsNotOldShippingAddress && NewShippingAddressIsNotBillingAddress) { basketHelper.Basket.Addresses.Add(newShippingAddress); } basketHelper.ShippingAddressID = newShippingAddress.OrderAddressId; basketHelper.Basket.Save(); } My initial thought was that if I could pass a class's property by refernce then I could rewrite the previous functions into something like private void SetPurchaseOrderAddress(OrderAddress newAddress, ref String CurrentChangingAddressIDProperty) and then call this function and pass in either basketHelper.BillingAddressID or basketHelper.ShippingAddressID as CurrentChangingAddressIDProperty but since I can't pass C# properties by reference I am not sure what to do with this code to be able to reuse the logic in both places. Thanks for any insight you can give me.

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  • How can I import one Gradle script into another?

    - by Ant
    Hi all, I have a complex gradle script that wraps up a load of functionality around building and deploying a number of netbeans projects to a number of environments. The script works very well, but in essence it is all configured through half a dozen maps holding project and environment information. I want to abstract the tasks away into another file, so that I can simply define my maps in a simple build file, and import the tasks from the other file. In this way, I can use the same core tasks for a number of projects and configure those projects with a simple set of maps. Can anyone tell me how I can import one gradle file into another, in a similar manner to Ant's task? I've trawled Gradle's docs to no avail so far. Additional Info After Tom's response below, I thought I'd try and clarify exactly what I mean. Basically I have a gradle script which runs a number of subprojects. However, the subprojects are all Netbeans projects, and come with their own ant build scripts, so I have tasks in gradle to call each of these. My problem is that I have some configuration at the top of the file, such as: projects = [ [name:"MySubproject1", shortname: "sub1", env:"mainEnv", cvs_module="mod1"], [name:"MySubproject2", shortname: "sub2", env:"altEnv", cvs_module="mod2"] ] I then generate tasks such as: projects.each({ task "checkout_$it.shortname" << { // Code to for example check module out from cvs using config from 'it'. } }) I have many of these sort of task generation snippets, and all of them are generic - they entirely depend on the config in the projects list. So what I want is a way to put this in a separate script and import it in the following sort of way: projects = [ [name:"MySubproject1", shortname: "sub1", env:"mainEnv", cvs_module="mod1"], [name:"MySubproject2", shortname: "sub2", env:"altEnv", cvs_module="mod2"] ] import("tasks.gradle") // This will import and run the script so that all tasks are generated for the projects given above. So in this example, tasks.gradle will have all the generic task generation code in, and will get run for the projects defined in the main build.gradle file. In this way, tasks.gradle is a file that can be used by all large projects that consist of a number of sub-projects with Netbeans ant build files.

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  • Paperclip: delete attachment and "can't convert nil into String" error

    - by snitko
    I'm using Paperclip and here's what I do in the model to delete attachments: def before_save self.avatar = nil if @delete_avatar == 1.to_s end Works fine unless @delete_avatar flag is set when the user is actually uploading the image (so the model receives both params[:user][:avatar] and params[:user][:delete_avatar]. This results in the following error: TypeError: can't convert nil into String from /Work/project/src/vendor/plugins/paperclip/lib/paperclip/storage.rb:40:in `dirname' from /Work/project/src/vendor/plugins/paperclip/lib/paperclip/storage.rb:40:in `flush_writes' from /Work/project/src/vendor/plugins/paperclip/lib/paperclip/storage.rb:38:in `each' from /Work/project/src/vendor/plugins/paperclip/lib/paperclip/storage.rb:38:in `flush_writes' from /Work/project/src/vendor/plugins/paperclip/lib/paperclip/attachment.rb:144:in `save' from /Work/project/src/vendor/plugins/paperclip/lib/paperclip/attachment.rb:162:in `destroy' from /Work/project/src/app/models/user.rb:72:in `before_save' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/callbacks.rb:347:in `send' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/callbacks.rb:347:in `callback' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/callbacks.rb:249:in `create_or_update' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/base.rb:2538:in `save_without_validation' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/validations.rb:1078:in `save_without_dirty' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/dirty.rb:79:in `save_without_transactions' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/transactions.rb:229:in `send' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/transactions.rb:229:in `with_transaction_returning_status' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/connection_adapters/abstract/database_statements.rb:136:in `transaction' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/transactions.rb:182:in `transaction' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/transactions.rb:228:in `with_transaction_returning_status' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/transactions.rb:196:in `save' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/transactions.rb:208:in `rollback_active_record_state!' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/transactions.rb:196:in `save' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/base.rb:723:in `create' I assume it has something to do with the avatar.dirty? value because when it certainly is true when this happens. The question is, how do I totally reset the thing if there are changes to be saved and abort avatar upload when the flag is set?

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  • Why can't I use __getattr__ with Django models?

    - by Joshmaker
    I've seen examples online of people using __getattr__ with Django models, but whenever I try I get errors. (Django 1.2.3) I don't have any problems when I am using __getattr__ on normal objects. For example: class Post(object): def __getattr__(self, name): return 42 Works just fine... >>> from blog.models import Post >>> p = Post() >>> p.random 42 Now when I try it with a Django model: from django.db import models class Post(models.Model): def __getattr__(self, name): return 42 And test it on on the interpreter: >>> from blog.models import Post >>> p = Post() ERROR: An unexpected error occurred while tokenizing input The following traceback may be corrupted or invalid The error message is: ('EOF in multi-line statement', (6, 0)) --------------------------------------------------------------------------- TypeError Traceback (most recent call last) /Users/josh/project/ in () /Users/josh/project/lib/python2.6/site-packages/django/db/models/base.pyc in init(self, *args, **kwargs) 338 if kwargs: 339 raise TypeError("'%s' is an invalid keyword argument for this function" % kwargs.keys()[0]) -- 340 signals.post_init.send(sender=self.class, instance=self) 341 342 def repr(self): /Users/josh/project/lib/python2.6/site-packages/django/dispatch/dispatcher.pyc in send(self, sender, **named) 160 161 for receiver in self._live_receivers(_make_id(sender)): -- 162 response = receiver(signal=self, sender=sender, **named) 163 responses.append((receiver, response)) 164 return responses /Users/josh/project/python2.6/site-packages/photologue/models.pyc in add_methods(sender, instance, signal, *args, **kwargs) 728 """ 729 if hasattr(instance, 'add_accessor_methods'): -- 730 instance.add_accessor_methods() 731 732 # connect the add_accessor_methods function to the post_init signal TypeError: 'int' object is not callable Can someone explain what is going on? EDIT: I may have been too abstract in the examples, here is some code that is closer to what I actually would use on the website: class Post(models.Model): title = models.CharField(max_length=255) slug = models.SlugField() date_published = models.DateTimeField() content = RichTextField('Content', blank=True, null=True) # Etc... Class CuratedPost(models.Model): post = models.ForeignKey('Post') position = models.PositiveSmallIntegerField() def __getattr__(self, name): ''' If the user tries to access a property of the CuratedPost, return the property of the Post instead... ''' return self.post.name # Etc... While I could create a property for each attribute of the Post class, that would lead to a lot of code duplication. Further more, that would mean anytime I add or edit a attribute of the Post class I would have to remember to make the same change to the CuratedPost class, which seems like a recipe for code rot.

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  • Coming Up with a Good Algorithm for a Simple Idea

    - by mkoryak
    I need to come up with an algorithm that does the following: Lets say you have an array of positive numbers (e.g. [1,3,7,0,0,9]) and you know beforehand their sum is 20. You want to abstract some average amount from each number such that the new sum would be less by 7. To do so, you must follow these rules: you can only subtract integers the resulting array must not have any negative values you can not make any changes to the indices of the buckets. The more uniformly the subtraction is distributed over the array the better. Here is my attempt at an algorithm in JavaScript + underscore (which will probably make it n^2): function distributeSubtraction(array, goal){ var sum = _.reduce(arr, function(x, y) { return x + y; }, 0); if(goal < sum){ while(goal < sum && goal > 0){ var less = ~~(goal / _.filter(arr, _.identity).length); //length of array without 0s arr = _.map(arr, function(val){ if(less > 0){ return (less < val) ? val - less : val; //not ideal, im skipping some! } else { if(goal > 0){ //again not ideal. giving preference to start of array if(val > 0) { goal--; return val - 1; } } else { return val; } } }); if(goal > 0){ var newSum = _.reduce(arr, function(x, y) { return x + y; }, 0); goal -= sum - newSum; sum = newSum; } else { return arr; } } } else if(goal == sum) { return _.map(arr, function(){ return 0; }); } else { return arr; } } var goal = 7; var arr = [1,3,7,0,0,9]; var newArray = distributeSubtraction(arr, goal); //returned: [0, 1, 5, 0, 0, 7]; Well, that works but there must be a better way! I imagine the run time of this thing will be terrible with bigger arrays and bigger numbers. edit: I want to clarify that this question is purely academic. Think of it like an interview question where you whiteboard something and the interviewer asks you how your algorithm would behave on a different type of a dataset.

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  • Partial overriding in Java (or dynamic overriding while overloading)

    - by Lie Ryan
    If I have a parent-child that defines some method .foo() like this: class Parent { public void foo(Parent arg) { System.out.println("foo in Function"); } } class Child extends Parent { public void foo(Child arg) { System.out.println("foo in ChildFunction"); } } When I called them like this: Child f = new Child(); Parent g = f; f.foo(new Parent()); f.foo(new Child()); g.foo(new Parent()); g.foo(new Child()); the output is: foo in Parent foo in Child foo in Parent foo in Parent But, I want this output: foo in Parent foo in Child foo in Parent foo in Child I have a Child class that extends Parent class. In the Child class, I want to "partially override" the Parent's foo(), that is, if the argument arg's type is Child then Child's foo() is called instead of Parent's foo(). That works Ok when I called f.foo(...) as a Child; but if I refer to it from its Parent alias like in g.foo(...) then the Parent's foo(..) get called irrespective of the type of arg. As I understand it, what I'm expecting doesn't happen because method overloading in Java is early binding (i.e. resolved statically at compile time) while method overriding is late binding (i.e. resolved dynamically at compile time) and since I defined a function with a technically different argument type, I'm technically overloading the Parent's class definition with a distinct definition, not overriding it. But what I want to do is conceptually "partially overriding" when .foo()'s argument is a subclass of the parent's foo()'s argument. I know I can define a bucket override foo(Parent arg) in Child that checks whether arg's actual type is Parent or Child and pass it properly, but if I have twenty Child, that would be lots of duplication of type-unsafe code. In my actual code, Parent is an abstract class named "Function" that simply throws NotImplementedException(). The children includes "Polynomial", "Logarithmic", etc and .foo() includes things like Child.add(Child), Child.intersectionsWith(Child), etc. Not all combination of Child.foo(OtherChild) are solvable and in fact not even all Child.foo(Child) is solvable. So I'm best left with defining everything undefined (i.e. throwing NotImplementedException) then defines only those that can be defined. So the question is: Is there any way to override only part the parent's foo()? Or is there a better way to do what I want to do?

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  • How to best integrate generated code

    - by Arne
    I am evaluating the use of code generation for my flight simulation project. More specifically there is a requirement to allow "the average engineer" (no offense I am one myself) to define the differential equations that describe the dynamic system in a more natural syntax than C++ provides. The idea is to devise a abstract descriptor language that can be easily understood and edited to generate C++ code from. This descriptor is supplied by the modeling engineer and used by the ones implementing and maintaining the simulation evironment to generate code. I've got something like this in mind: model Aircraft has state x1, x2; state x3; input double : u; input bool : flag1, flag2; algebraic double : x1x2; model Engine : tw1, tw2; model Gear : gear; model ISA : isa; trim routine HorizontalFight; trim routine OnGround, General; constant double : c1, c2; constant int : ci1; begin differential equations x1' = x1 + 2.*x2; x2' = x2 + x1x2; begin algebraic equations x1x2 = x1*x2 + x1'; end model It is important to retain the flexibility of the C language thus the descriptor language is meant to only define certain parts of the definition and implementation of the model class. This way one enigneer provides the model in from of the descriptor language as examplified above and the maintenance enigneer will add all the code to read parameters from files, start/stop/pause the execution of the simulation and how a concrete object gets instatiated. My first though is to either generate two files from the descriptor file: one .h file containing declarations and one .cpp file containing the implementation of certain functions. These then need to be #included at appropriate places [File Aircarft.h] class Aircraft { public: void Aircraft(..); // hand-written constructor void ReadParameters(string &file_name); // hand-written private: /* more hand wirtten boiler-plate code */ /* generate declarations follow */ #include "Aircraft.generated.decl" }; [File Aircraft.cpp] Aircarft::Aircraft(..) { /* hand-written constructer implementation */ } /* more hand-written implementation code */ /* generated implementation code follows */ #include "Aircraft.generated.impl" Any thoughts or suggestions?

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  • Observer pattern used with decorator pattern

    - by icelated
    I want to make a program that does an order entry system for beverages. ( i will probably do description, cost) I want to use the Decorator pattern and the observer pattern. I made a UML drawing and saved it as a pic for easy viewing. This site wont let me upload as a word doc so i have to upload a pic - i hope its easily viewable.... I need to know if i am doing the UML / design patterns correctly before moving on to the coding part. Beverage is my abstract component class. Espresso, houseblend, darkroast are my concrete subject classes.. I also have a condiment decorator class milk,mocha,soy,whip. would be my observer? because they would be interested in data changes to cost? Now, would the espresso,houseblend etc, be my SUBJECT and the condiments be my observer? My theory is that Cost is a changes and that the condiments need to know the changes? So, subject = esspresso,houseblend,darkroast,etc.. // they hold cost() Observer = milk,mocha,soy,whip? // they hold cost() would be the concrete components and the milk,mocha,soy,whip? would be the decorator! So, following good software engineering practices "design to an interface and not implementation" or "identify things that change from those that dont" would i need a costbehavior interface? If you look at the UML you will see where i am going with this and see if i am implementing observer + Decorator pattern correctly? I think the decorator is correct. since, the pic is not very viewable i will detail the classes here: Beverage class(register observer, remove observer, notify observer, description) these classes are the concrete beverage classes espresso, houseblend,darkroast, decaf(cost,getdescription,setcost,costchanged) interface observer class(update) // cost? interface costbehavior class(cost) // since this changes? condiment decorator class( getdescription) concrete classes that are linked to the 2 interface s and decorator are: milk,mocha,soy,whip(cost,getdescription,update) these are my decorator/ wrapper classes. Thank you.. Is there a way to make this picture bigger?

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  • How hard programming is? Really. [closed]

    - by Bubba88
    Hi! The question is about your perception of programming activity. How hard/exacting this task is? There is much buzz about programming nowadays, people say that programmers are smart, very technical and abstract at a time, know much about world, psychology etc.. They say, that programmers got really powerful brain thing, cause there is much to keep in consideration simultaneously again with much information folded into each other associatively (up 10 levels of folding they say))) Still, there are some terms to specify at our own.. So that is the question: What do you think about programming in general? Is it hard? Is it 'for everyone' or for the particular kind of people only? How much non-CS background do you need to program (just to program, really; enterprise applications for example)? How long is the learning curve? (again, for programming in general) And another bunch of random questions: - If you were not to like/love programming, would that be a serious trouble bothering your current employment? - If you were to start from the beginning, would you chose that direction this time? - What other areas (jobs or maybe hobbies) are comparable to programming in the way they can explode someone's lovely brain? - Is 'non turing-complete programming' (SQL, XML, etc.) comparable to what we do or is it really way easier, less requiring, cheap and akin to cooking :)? Well, the essence is: How would you describe programming activity WRT to its difficulty? Or, on the other hand: Did you ever catch yourself thinking at some point: OMG, it's sooo hard! I don't know how would I ever program, even carried away this way and doing programming just for fun? It's very interesting to know your opinion, your'e the programmers after all. I mean much people must be exaggerating/speculating about the thing they do not really know about. But that musn't be the case here on SO :) P.S.: I'll try my best to update this post later, and you please edit it too. At least I'll get decent English in my question text :)

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  • Paperclip: delete attachments and "can't convert nil into String" error

    - by snitko
    I'm using Paperclip and here's what I do in the model to delete attachments: def before_save self.avatar = nil if @delete_avatar == 1.to_s end Works fine unless @delete_avatar flag is set when the user is actually uploading the image (so the model receives both params[:user][:avatar] and params[:user][:delete_avatar]. This results in the following error: TypeError: can't convert nil into String from /Work/project/src/vendor/plugins/paperclip/lib/paperclip/storage.rb:40:in `dirname' from /Work/project/src/vendor/plugins/paperclip/lib/paperclip/storage.rb:40:in `flush_writes' from /Work/project/src/vendor/plugins/paperclip/lib/paperclip/storage.rb:38:in `each' from /Work/project/src/vendor/plugins/paperclip/lib/paperclip/storage.rb:38:in `flush_writes' from /Work/project/src/vendor/plugins/paperclip/lib/paperclip/attachment.rb:144:in `save' from /Work/project/src/vendor/plugins/paperclip/lib/paperclip/attachment.rb:162:in `destroy' from /Work/project/src/app/models/user.rb:72:in `before_save' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/callbacks.rb:347:in `send' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/callbacks.rb:347:in `callback' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/callbacks.rb:249:in `create_or_update' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/base.rb:2538:in `save_without_validation' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/validations.rb:1078:in `save_without_dirty' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/dirty.rb:79:in `save_without_transactions' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/transactions.rb:229:in `send' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/transactions.rb:229:in `with_transaction_returning_status' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/connection_adapters/abstract/database_statements.rb:136:in `transaction' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/transactions.rb:182:in `transaction' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/transactions.rb:228:in `with_transaction_returning_status' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/transactions.rb:196:in `save' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/transactions.rb:208:in `rollback_active_record_state!' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/transactions.rb:196:in `save' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/base.rb:723:in `create' I assume it has something to do with the avatar.dirty? value because when it certainly is true when this happens. The question is, how do I totally reset the thing if there are changes to be saved and abort avatar upload when the flag is set?

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  • Silverlight with MVVM Inheritance: ModelView and View matching the Model

    - by moonground.de
    Hello Stackoverflowers! :) Today I have a special question on Silverlight (4 RC) MVVM and inheritance concepts and looking for a best practice solution... I think that i understand the basic idea and concepts behind MVVM. My Model doesn't know anything about the ViewModel as the ViewModel itself doesn't know about the View. The ViewModel knows the Model and the Views know the ViewModels. Imagine the following basic (example) scenario (I'm trying to keep anything short and simple): My Model contains a ProductBase class with a few basic properties, a SimpleProduct : ProductBase adding a few more Properties and ExtendedProduct : ProductBase adding another properties. According to this Model I have several ViewModels, most essential SimpleProductViewModel : ViewModelBase and ExtendedProductViewModel : ViewModelBase. Last but not least, according Views SimpleProductView and ExtendedProductView. In future, I might add many product types (and matching Views + VMs). 1. How do i know which ViewModel to create when receiving a Model collection? After calling my data provider method, it will finally end up having a List<ProductBase>. It containts, for example, one SimpleProduct and two ExtendedProducts. How can I transform the results to an ObservableCollection<ViewModelBase> having the proper ViewModel types (one SimpleProductViewModel and two ExtendedProductViewModels) in it? I might check for Model type and construct the ViewModel accordingly, i.e. foreach(ProductBase currentProductBase in resultList) if (currentProductBase is SimpleProduct) viewModels.Add( new SimpleProductViewModel((SimpleProduct)currentProductBase)); else if (currentProductBase is ExtendedProduct) viewModels.Add( new ExtendedProductViewModels((ExtendedProduct)currentProductBase)); ... } ...but I consider this very bad practice as this code doesn't follow the object oriented design. The other way round, providing abstract Factory methods would reduce the code to: foreach(ProductBase currentProductBase in resultList) viewModels.Add(currentProductBase.CreateViewModel()) and would be perfectly extensible but since the Model doesn't know the ViewModels, that's not possible. I might bring interfaces into game here, but I haven't seen such approach proven yet. 2. How do i know which View to display when selecting a ViewModel? This is pretty the same problem, but on a higher level. Ended up finally having the desired ObservableCollection<ViewModelBase> collection would require the main view to choose a matching View for the ViewModel. In WPF, there is a DataTemplate concept which can supply a View upon a defined DataType. Unfortunately, this doesn't work in Silverlight and the only replacement I've found was the ResourceSelector of the SLExtensions toolkit which is buggy and not satisfying. Beside that, all problems from Question 1 apply as well. Do you have some hints or even a solution for the problems I describe, which you hopefully can understand from my explanation? Thank you in advance! Thomas

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