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• Why is there no service-oriented language?

  - by Wolfgang

  Edit: To avoid further confusion: I am not talking about web services and such. I am talking about structuring applications internally, it's not about how computers communicate. It's about programming languages, compilers and how the imperative programming paradigm is extended. Original: In the imperative programming field, we saw two paradigms in the past 20 years (or more): object-oriented (OO), and service-oriented (SO) aka. component-based (CB). Both paradigms extend the imperative programming paradigm by introducing their own notion of modules. OO calls them objects (and classes) and lets them encapsulates both data (fields) and procedures (methods) together. SO, in contrast, separates data (records, beans, ...) from code (components, services). However, only OO has programming languages which natively support its paradigm: Smalltalk, C++, Java and all other JVM-compatibles, C# and all other .NET-compatibles, Python etc. SO has no such native language. It only comes into existence on top of procedural languages or OO languages: COM/DCOM (binary, C, C++), CORBA, EJB, Spring, Guice (all Java), ... These SO frameworks clearly suffer from the missing native language support of their concepts. They start using OO classes to represent services and records. This leads to designs where there is a clear distinction between classes that have methods only (services) and those that have fields only (records). Inheritance between services or records is then simulated by inheritance of classes. Technically, its not kept so strictly but in general programmers are adviced to make classes to play only one of the two roles. They use additional, external languages to represent the missing parts: IDL's, XML configurations, Annotations in Java code, or even embedded DSL like in Guice. This is especially needed, but not limited to, since the composition of services is not part of the service code itself. In OO, objects create other objects so there is no need for such facilities but for SO there is because services don't instantiate or configure other services. They establish an inner-platform effect on top of OO (early EJB, CORBA) where the programmer has to write all the code that is needed to "drive" SO. Classes represent only a part of the nature of a service and lots of classes have to be written to form a service together. All that boiler plate is necessary because there is no SO compiler which would do it for the programmer. This is just like some people did it in C for OO when there was no C++. You just pass the record which holds the data of the object as a first parameter to the procedure which is the method. In a OO language this parameter is implicit and the compiler produces all the code that we need for virtual functions etc. For SO, this is clearly missing. Especially the newer frameworks extensively use AOP or introspection to add the missing parts to a OO language. This doesn't bring the necessary language expressiveness but avoids the boiler platform code described in the previous point. Some frameworks use code generation to produce the boiler plate code. Configuration files in XML or annotations in OO code is the source of information for this. Not all of the phenomena that I mentioned above can be attributed to SO but I hope it clearly shows that there is a need for a SO language. Since this paradigm is so popular: why isn't there one? Or maybe there are some academic ones but at least the industry doesn't use one.

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• What are the disadvantages of self-encapsulation?

  - by Dave Jarvis

  Background Tony Hoare's billion dollar mistake was the invention of null. Subsequently, a lot of code has become riddled with null pointer exceptions (segfaults) when software developers try to use (dereference) uninitialized variables. In 1989, Wirfs-Brock and Wikerson wrote: Direct references to variables severely limit the ability of programmers to re?ne existing classes. The programming conventions described here structure the use of variables to promote reusable designs. We encourage users of all object-oriented languages to follow these conventions. Additionally, we strongly urge designers of object-oriented languages to consider the effects of unrestricted variable references on reusability. Problem A lot of software, especially in Java, but likely in C# and C++, often uses the following pattern: public class SomeClass { private String someAttribute; public SomeClass() { this.someAttribute = "Some Value"; } public void someMethod() { if( this.someAttribute.equals( "Some Value" ) ) { // do something... } } public void setAttribute( String s ) { this.someAttribute = s; } public String getAttribute() { return this.someAttribute; } } Sometimes a band-aid solution is used by checking for null throughout the code base: public void someMethod() { assert this.someAttribute != null; if( this.someAttribute.equals( "Some Value" ) ) { // do something... } } public void anotherMethod() { assert this.someAttribute != null; if( this.someAttribute.equals( "Some Default Value" ) ) { // do something... } } The band-aid does not always avoid the null pointer problem: a race condition exists. The race condition is mitigated using: public void anotherMethod() { String someAttribute = this.someAttribute; assert someAttribute != null; if( someAttribute.equals( "Some Default Value" ) ) { // do something... } } Yet that requires two statements (assignment to local copy and check for null) every time a class-scoped variable is used to ensure it is valid. Self-Encapsulation Ken Auer's Reusability Through Self-Encapsulation (Pattern Languages of Program Design, Addison Wesley, New York, pp. 505-516, 1994) advocated self-encapsulation combined with lazy initialization. The result, in Java, would resemble: public class SomeClass { private String someAttribute; public SomeClass() { setAttribute( "Some Value" ); } public void someMethod() { if( getAttribute().equals( "Some Value" ) ) { // do something... } } public void setAttribute( String s ) { this.someAttribute = s; } public String getAttribute() { String someAttribute = this.someAttribute; if( someAttribute == null ) { setAttribute( createDefaultValue() ); } return someAttribute; } protected String createDefaultValue() { return "Some Default Value"; } } All duplicate checks for null are superfluous: getAttribute() ensures the value is never null at a single location within the containing class. Efficiency arguments should be fairly moot -- modern compilers and virtual machines can inline the code when possible. As long as variables are never referenced directly, this also allows for proper application of the Open-Closed Principle. Question What are the disadvantages of self-encapsulation, if any? (Ideally, I would like to see references to studies that contrast the robustness of similarly complex systems that use and don't use self-encapsulation, as this strikes me as a fairly straightforward testable hypothesis.)

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• Is my class structure good enough?

  - by Rivten

  So I wanted to try out this challenge on reddit which is mostly about how you structure your data the best you can. I decided to challenge my C++ skills. Here's how I planned this. First, there's the Game class. It deals with time and is the only class main has access to. A game has a Forest. For now, this class does not have a lot of things, only a size and a Factory. Will be put in better use when it will come to SDL-stuff I guess A Factory is the thing that deals with the Game Objects (a.k.a. Trees, Lumberjack and Bears). It has a vector of all GameObjects and a queue of Events which will be managed at the end of one month. A GameObject is an abstract class which can be updated and which can notify the Event Listener The EventListener is a class which handles all the Events of a simulation. It can recieve events from a Game Object and notify the Factory if needed, the latter will manage correctly the event. So, the Tree, Lumberjack and Bear classes all inherits from GameObject. And Sapling and Elder Tree inherits from Tree. Finally, an Event is defined by an event_type enumeration (LUMBERJACK_MAWED, SAPPLING_EVOLUTION, ...) and an event_protagonists union (a GameObject or a pair of GameObject (who killed who ?)). I was quite happy at first with this because it seems quite logic and flexible. But I ended up questionning this structure. Here's why : I dislike the fact that a GameObject need to know about the Factory. Indeed, when a Bear moves somewhere, it needs to know if there's a Lumberjack ! Or it is the Factory which handles places and objects. It would be great if a GameObject could only interact with the EventListener... or maybe it's not that much of a big deal. Wouldn't it be better if I separate the Factory in three vectors ? One for each kind of GameObject. The idea would be to optimize research. If I'm looking do delete a dead lumberjack, I would only have to look in one shorter vector rather than a very long vector. Another problem arises when I want to know if there is any particular object in a given case because I have to look for all the gameObjects and see if they are at the given case. I would tend to think that the other idea would be to use a matrix but then the issue would be that I would have empty cases (and therefore unused space). I don't really know if Sapling and Elder Tree should inherit from Tree. Indeed, a Sapling is a Tree but what about its evolution ? Should I just delete the sapling and say to the factory to create a new Tree at the exact same place ? It doesn't seem natural to me to do so. How could I improve this ? Is the design of an Event quite good ? I've never used unions before in C++ but I didn't have any other ideas about what to use. Well, I hope I have been clear enough. Thank you for taking the time to help me !

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• Html.hiddenfor does not return value

  - by jackma1210

  Hi I have a template partial view, which used to render a model named VerificationCode, this model has a element 'CaptchaGeneratedText' which is hidden in the view and set value by Html.HiddenFor(m=m.CaptchaGeneratedText, captchaText), the problem is when view post, in the model validation the value of element 'CaptchaGeneratedText' is null, but it should not be as varant 'captchaText' has some value. meanwhile, the other element 'CaptchaUserInput' of this model does have value. Anybody have experienced similiar problem? Sorry I was unable to submit script file.

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• Problem with core data migration mapping model

  - by dpratt

  I have an iphone app that uses Core Data to do storage. I have successfully deployed it, and now I'm working on the second version. I've run into a problem with the data model that will require a few very simple data transformations at the time that the persistent store gets upgraded, so I can't just use the default inferred mapping model. My object model is stored in an .xcdatamodeld bundle, with versions 1.0 and 1.1 next to each other. Version 1.1 is set as the active version. Everything works fine when I use the default migration behavior and set NSInferMappingModelAutomaticallyOption to YES. My sqlite storage gets upgraded from the 1.0 version of the model, and everything is good except for, of course, the few transformations I need done. As an additional experimental step, I added a new Mapping Model to the core data model bundle, and have made no changes to what xcode generated. When I run my app (with an older version of the data store), I get the following * Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Object's persistent store is not reachable from this NSManagedObjectContext's coordinator' What am I doing wrong? Here's my code for to get the managed object model and the persistent store coordinator. - (NSPersistentStoreCoordinator *)persistentStoreCoordinator { if (_persistentStoreCoordinator != nil) { return _persistentStoreCoordinator; } _persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]]; NSURL *storeUrl = [NSURL fileURLWithPath: [[self applicationDocumentsDirectory] stringByAppendingPathComponent: @"gti_store.sqlite"]]; NSError *error; NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption, [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil]; if (![_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeUrl options:options error:&error]) { NSLog(@"Eror creating persistent store coodinator - %@", [error localizedDescription]); } return _persistentStoreCoordinator; } - (NSManagedObjectModel *)managedObjectModel { if(_managedObjectModel == nil) { _managedObjectModel = [[NSManagedObjectModel mergedModelFromBundles:nil] retain]; NSDictionary *entities = [_managedObjectModel entitiesByName]; //add a sort descriptor to the 'Foo' fetched property so that it can have an ordering - you can't add these from the graphical core data modeler NSEntityDescription *entity = [entities objectForKey:@"Foo"]; NSFetchedPropertyDescription *fetchedProp = [[entity propertiesByName] objectForKey:@"orderedBar"]; NSSortDescriptor* sortDescriptor = [[[NSSortDescriptor alloc] initWithKey:@"index" ascending:YES] autorelease]; NSArray* sortDescriptors = [NSArray arrayWithObjects:sortDescriptor, nil]; [[fetchedProp fetchRequest] setSortDescriptors:sortDescriptors]; } return _managedObjectModel; }

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• PHP MVC Principles

  - by George

  I'm not using an off-the-shelf framework and don't particularly want to (nor d I want to go into the reasons why...). Anyway, onto my question(s), I hope it make sense.... I'm trying to get my head around what should go in the model and what should go in the controller. Originally I had the impression that a model class should represent an actual object (eg - a car from the cars table of a database) and model properties should mirror the database fields. However I'm now getting the feeling that I've got the wrong idea - should an instance of a model class represent an actual item, or should it contain a number of methods for doing stuff - sometimes to one car or sometimes to multiple cars based on my example earlier. For example I want to get all the cars from a the database and show them in the view. Am I right in think it should be along the lines of this? Controller File function list() { $cars = $this->model->get_all(); $this->view->add($cars); $this->view->render('cars-list'); } Model File function get_all() { // Use a database interaction class that I've written $cars = Database::select(); return $cars; } Now, if the car had a "status" field that was stored as an integer in the database and I wanted to change that to a string, where should that be done? By looping the SQL results array in the get_all() method in the model? Also, where should form validation live? I have written a validation class that works a little like this: $validator = new Validator(); $validator->check('field_name', 'required'); If the check fails, it adds an error message to the array in the Validator. This array of error messages would then get passed to the view. Should the use of my validator class go in model or the controller? Thanks in advance for for any help anyone can offer. If you know of any links to a simple MVC example / open source application that deals with basic CRUD, they would be much appreciated.

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• Can I set a property on an object that is only declared on the instance type, when I don't know the

  - by WilberBeast

  Let me explain. I have a List into which I am adding various ASP.NET controls. I then wish to loop through the list and set a CssClass, however not every Control supports the property CssClass. What I would like to do is test if the underlying instance type supports the CssClass property and set it, but I'm not sure how to do the conversion prior to setting the property since I don't know the type of each Control object. I know that I can use typeof or x.GetType(), but I'm not sure how to use these to convert the controls back to the instance type in order to test for and then set the property. Actually I seem to have solved this, so I thought that I would post the code here for others. foreach (Control c in controlList) { PropertyInfo pi = c.GetType().GetProperty("CssClass"); if (pi != null) pi.SetValue(c, "desired_css_class", null); } I hope that this helps someone else as I has taken me hours to research these 2 lines of code. Cheers Steve

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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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• Model Binding using ASP.NET MVC, getting datainput to the controller.

  - by Calibre2010

  Pretty Basic one here guys. I have a View which holds 2 textfields for input and a submit button <%using (Html.BeginForm("DateRetrival", "Home", FormMethod.Post)){ %> <%=Html.TextBox("sday")%> <%=Html.TextBox("eday")%> <input type="submit" value="ok" id="run"/> <% }%> the following controller action which I want to bind the data input is as follows [AcceptVerbs(HttpVerbs.Get)] public ActionResult DateRetrival() { return View(); } [AcceptVerbs(HttpVerbs.Post)] public ActionResult DateRetrival(string submit) { return null; } When I debug this and look in the action methods parameter, the value is null. When I've entered values in both textboxes and and clicked the submit method.

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• How to get elements from an object in C#?

  - by Drew

  I am using the AutoCompleteBox in WPF, I populate the suggestions with a List that consists of four fields. When the user selects an item and I reach my eventHandler, i can see that MyAutoCompleteBox.SelectedItem is an object that has my four values, if i hover this text in the debugger i can see the four values listed, however i don't know how to access these values in the code. I tried List<Codes> selected = MyAutoCompleteBox.SelectedItem as List<Codes>; where Codes is my List. selected returns as null and empty every time. Is there a way to get to these values? Thanks!

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• Why ruby object has two to_s and inspect methods that (looks like) do the same thing?

  - by prosseek

  The p calls inspect, and puts/print calls to_s for representing its object. If I run class Graph def initialize @nodeArray = Array.new @wireArray = Array.new end def to_s # called with print / puts "Graph : #{@nodeArray.size}" end def inspect # called with p "G" end end if __FILE__ == $0 gr = Graph.new p gr print gr puts gr end I get G Graph : 0Graph : 0 Then, why does ruby has two functions do the same thing? What makes the difference between to_s and inspect? And what's the difference between puts/print/p? If I comment out the to_s or inspect function, I get as follows. #<Graph:0x100124b88>#<Graph:0x100124b88>

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• Java: How do you access a sub-object of an object with no "getXXX" method to that sub-object

  - by Daxon

  I'll explain with pictures from Eclipse Debugger I have an Class called "FieldContext", (I can't edit it, it's compiled in the Java OVal API) Within "FieldContext" on the eclipse variable tab are "CompileTimeType" and "field" Q1 Is there a legend for the icons in the variables tab? like what the red box with the "F" means + yellow diamond boxes? Now I want to access the fields inside the "field" object (RedBox) .. preferably "name" But the "FieldContext" does not have a "getField()" method, yet it has a "getCompileTimeType()" method. Q2 So is there anyway to get that field object being a "SerializableField" Class from the "FieldContext"? If eclipse debugger can see/get/edit them then I hope I can do the same in Java.

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• How should I implement items that are normalized in the Database, in Object Oriented Design?

  - by Jonas

  How should I implement items that are normalized in the Database, in Object Oriented classes? In the database I have a big table of items and a smaller of groups. Each item belong to one group. This is how my database design look like: +----------------------------------------+ | Inventory | +----+------+-------+----------+---------+ | Id | Name | Price | Quantity | GroupId | +----+------+-------+----------+---------+ | 43 | Box | 34.00 | 456 | 4 | | 56 | Ball | 56.50 | 3 | 6 | | 66 | Tin | 23.00 | 14 | 4 | +----+------+-------+----------+---------+ Totally 3000 lines +----------------------+ | Groups | +---------+------+-----+ | GroupId | Name | VAT | +---------+------+-----+ | 4 | Mini | 0.2 | | 6 | Big | 0.3 | +---------+------+-----+ Totally 10 lines I will use the OOP classes in a GUI, where the user can edit Items and Groups in the inventory. It should also be easy to do calculations with a bunch of items. The group information like VAT are needed for the calculations. I will write an Item class, but do I need a Group class? and if I need it, should I keep them in a global location or how do I access it when I need it for Item-calculations? Is there any design pattern for this case?

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• How extensive is an Object in CakePHP model linkage?

  - by Andre

  I was hoping someone with an understanding on CakePHP could shed some light on a question I've been having. Here's my scenario, I have a User this User has a Company which in turn has many Department and many Address. If I were to get a User could I expect to have access to the Company and all models associated with that Company? So would $user['Company']['Department'][0] or $user['Company']['Address'][0] be possible? Which brings me back to the original question, how extensive is the linkage between models?

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• What comes first in Ruby's object model?

  - by Timothy

  I've been reading Metaprogramming Ruby and the object model like the chicken or egg dilemma. In Ruby 1.8, the Object class is an instance of Class. Module's superclass is Object and is an instance of Class. Class' superclass is Module, and it is an instance of Class (self-referential). Say class SomeClass; end is defined somewhere; SomeClass is an instance of Class, however its superclass is Object. Why does an instance of Class have Object as the superclass instead of nil? Also, if Object is to exist, then Class has to exist, but then Module has to exist, but for Module to exist Object has to exist. How are these classes created?

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• What's The Best Object-Relational Mapping Tool For .NET?

  - by Icono123

  I've worked on a few Java web projects and we've always used Hibernate for our data object layer. I haven't worked on a large scale ASP.NET site and I'm unsure which solution to choose. I'm tempted to try NHibernate, but I don't like the fact that they use so many third party libraries. I found this list on Wikipedia of available ORM software: http://en.wikipedia.org/wiki/List_of_object-relational_mapping_software#.NET What ORM have you used? Was it easy to use? Would you recommend using it again? Was it used on a small, medium, or large project? Would you write your own? Thanks.

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• How can I access this nested array within my JSON object?

  - by Charles

  I'm using PHP to return a json_encode()'d array for use in my Javascript code. It's being returned as: {"parent1[]":["child1","child2","child2"],"parent2[]":["child1"]} By using the following code, I am able to access parent2 > child1 $.getJSON('myfile.php', function(data) { for (var key in data) { alert(data[key]); } } However, this doesn't give me access to child1, child2, child, of parent1. Alerting the key by itself shows 'parent1' but when I try to alert it's contents, I get undefined. I figured it would give me an object/array? How do I access the children of parent1? data[key][0] ?

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• What could possibly cause this error when declaring an object inside a class?

  - by M4design

  I'm battling with this assignment :) I've got two classes: Ocean and Grid. When I declare an object of the Grid inside the Ocean: unsigned int sharkCount; Grid grid; The compiler/complainer says: error C2146: syntax error : missing ';' before identifier 'grid' Can you possibly predict what produces this error with the limited info I provided? It seems that as if the Ocean doesn't like the Grid class. Could this be because of the poor implementation of the grid class. BTW the Grid has a default constructor. Yet the error happens in compiling time!. EDIT: They're each in separate header file, and I've included the Grid.h in the Ocean.h.

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• What could possibly cause this error(when declaring an object inside a class) ? //noobie question

  - by M4design

  I'm battling with this assignment :) I've got two classes: Ocean and Grid. When I declare an object of the Grid inside the Ocean: unsigned int sharkCount; Grid grid; The compiler/complainer says: error C2146: syntax error : missing ';' before identifier 'grid' Can you possibly predict what produces this error with the limited info' I provided? It seems that as if the Ocean doesn't like the Grid class. Could this be because of the poor implementation of the grid class. BTW the Grid has a default constructor. Yet the error happens in compiling time!. Thanks. EDIT: They're each in separate header file, and I've included the Grid.h in the Ocean.h.

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• How to get search results in grails if you have the domain (model) name stored in a string

  - by Shekhar

  I have a method which has domain name as a String parameter. def modelName="Equity" I want to use it like def results=modelName.findAll() Please guide me!

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• Rails object inheritence with belongs_to

  - by Rabbott

  I have a simple has_many/belongs_to relationship between Report and Chart. The issue I'm having is that my Chart model is a parent that has children. So in my Report model I have class Report < ActiveRecord::Base has_many :charts end And my Chart model is a parent, where Pie, Line, Bar all inherit from Chart. I'm not sure where the belongs_to :report belongs within the chart model, or children of chart model. I get errors when I attempt to access chart.report because the object is of type "Class" undefined local variable or method `report' for #< Class:0x104974b90 The Chart model uses STI so its pulling say.. 'Pie' from the chart_type column in the charts table.. what am I missing?

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• How do I setup model associations in an RSpec test?

  - by Eric M.

  I've pastied the specs I've written for the posts/show.html.erb view in an application I'm writing as a means to learn RSpec. I am still learning about mocks and stubbing. This question is specific to the "should list all related comments" spec. What I want is to test that the show view displays a post's comments. But what I'm not sure about is how to setup this test and then have the test iterate through with should contain('xyz') statements. Any hints? Other suggestions are also appreciated! Thanks. ---Edit Some more information. I have a named_scope applied to comments in my view (I know, I did this a bit backwards in this case), so @post.comments.approved_is(true). The code pastied responds with the error "undefined method `approved_is' for #", which makes sense since I told it stub comments and return a comment. I'm still not sure, however, how to chain the stubs so that @post.comments.approved_is(true) will return an array of comments.

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• What's wrong with the architecture of a game object drawing and updating itself?

  - by Ricket

  What are the reasons for and against a game object drawing and updating itself? For example, if you have a game where the player has a position on screen, why not have an all-encompassing class: public class Player { private int x, y, xVelocity, yVelocity; private Sprite s; //... public Player() { // load the sprite here, somehow? } public void draw(CustomGraphicsClass g) { g.draw(s, x, y); } public void update(long timeElapsed) { x += (xVelocity * timeElapsed); y += (yVelocity * timeElapsed); } } What is wrong with this design? What are the downfalls or concerns? How would you better write something like this, or better architect this type of thing in a game? Also, somewhat connected, how would you implement loading that Sprite image? And furthermore, how would you then implement collision between two Players? (I should probably separate these extra two questions into new questions, huh?)

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• TypeError: Result of expression 'printWindow' [undefined] is not an object.

  - by orangebrainer

  I'm trying to create hidden iframes in my page dynamically to load 3 other pages so that i can grab all the HTML and combine them into 1 in a new window. However i'm stuck at this. tHe frames are created fine. But whenever the javascript runs to the part of function openNewWindow() { var printWindow = window.open("",""); printWindow.document.open(); printWindow.document.write(HTMLfromFrames); printWindow.document.close(); } i get this error: TypeError: Result of expression 'printWindow' [undefined] is not an object. but if i generate a button to call this function seperately, it works fine. however i need it to run all in one click event Anybody has any idea what's wrong? Thanks!

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• No such file to load, Model/Lib naming conflict?

  - by Tom

  I'm working on a Rails application. I have a Module called Animals. Inside this Module is a Class with the same name as one of my Models (Dog). show_animal action: def show_animal require 'Animals/Bear.rb' #Works require 'Animals/Dog.rb' #Fails end So the first require definitely works, the seconds fails. MissingSourceFile (no such file to load -- Animals/Dog.rb): I noticed that Dog.rb is the same file name as one of my models, is that what's causing this? I'm using Webrick.

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