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• For a Javascript library, what is the best or standard way to support extensibility

  - by Michael Best

  Specifically, I want to support "plugins" that modify the behavior of parts of the library. I couldn't find much information on the web about this subject. But here are my ideas for how a library could be extensible. The library exports an object with both public and "protected" functions. A plugin can replace any of those functions, thus modifying the library's behavior. Advantages of this method are that it's simple and that the plugin's functions can have full access to the library's "protected" functions. Disadvantages are that the library may be harder to maintain with a larger set of exposed functions and it could be hard to debug if multiple plugins are involved (how to know which plugin modified which function?). The library provides an "add plugin" function that accepts an object with a specific interface. Internally, the library will use the plugin instead of it's own code if appropriate. With this method, the internals of the library can be rearranged more freely as long as it still supports the same plugin interface. This could also support having different plugin interfaces to modify different parts of the library. A disadvantage of this method is that the plugins may have to re-implement code that is already part of the library since the library's internal functions are not exported. The library provides a "set implementation" function that accepts an object inherited from a specific base object. The library's public API calls functions in the implementation object for any functionality that can be modified and the base implementation object includes the core functionality, with both external (to the API) and internal functions. A plugin creates a new implementation object, which inherits from the base object and replaces any functions it wants to modify. This combines advantages and disadvantages of both the other methods.

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• Rails: Law of Demeter Confusion

  - by user2158382

  I am reading a book called Rails AntiPatterns and they talk about using delegation to to avoid breaking the Law of Demeter. Here is their prime example: They believe that calling something like this in the controller is bad (and I agree) @street = @invoice.customer.address.street Their proposed solution is to do the following: class Customer has_one :address belongs_to :invoice def street address.street end end class Invoice has_one :customer def customer_street customer.street end end @street = @invoice.customer_street They are stating that since you only use one dot, you are not breaking the Law of Demeter here. I think this is incorrect, because you are still going through customer to go through address to get the invoice's street. I primarily got this idea from a blog post I read: http://www.dan-manges.com/blog/37 In the blog post the prime example is class Wallet attr_accessor :cash end class Customer has_one :wallet # attribute delegation def cash @wallet.cash end end class Paperboy def collect_money(customer, due_amount) if customer.cash < due_ammount raise InsufficientFundsError else customer.cash -= due_amount @collected_amount += due_amount end end end The blog post states that although there is only one dot customer.cash instead of customer.wallet.cash, this code still violates the Law of Demeter. Now in the Paperboy collect_money method, we don't have two dots, we just have one in "customer.cash". Has this delegation solved our problem? Not at all. If we look at the behavior, a paperboy is still reaching directly into a customer's wallet to get cash out. EDIT I completely understand and agree that this is still a violation and I need to create a method in Wallet called withdraw that handles the payment for me and that I should call that method inside the Customer class. What I don't get is that according to this process, my first example still violates the Law of Demeter because Invoice is still reaching directly into Customer to get the street. Can somebody help me clear the confusion. I have been searching for the past 2 days trying to let this topic sink in, but it is still confusing.

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• Explicitly pass context object versus injecting with IoC

  - by SonOfPirate

  I have a layered service application where the service layer delegates operations into the domain layer for execution. Many of these operations need to know the context under which they are operation. (The context included the identity of the current user, culture information, etc. received from the caller.) For example, I have an API method that returns a list of announcements. The list is based on the current user's role and each announcement is localized to their culture. The API is a thin-facade that delegates to an Application Service in my domain layer. The Application Service method obviously needs to know the context of the current request/operation as another call to the same API from another user should result in a different list. Within this method, we also have logging that uses some of the context information so we a clear understanding of the context when the operation was performed (this is especially useful if something goes wrong.) While this is a contrived example, in the real world, my Application Services will coordinate operations with many collaborative components, any number of them also needing the context information. My choice is to pass the context to the Application Service which would then pass it with any calls to collaborators or have the IoC container satisfy the dependency the Application Service and any collaborators have on the context. I am wondering if it is considered good/bad, best practices/code smell, etc. if I pass the context object as a parameter to the domain methods or if injecting the context via an IoC container is preferred. (EDIT: I should mention that the context object is instantiated per-request.)

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• Initializing entities vs having a constructor parameter

  - by Vee

  I'm working on a turn-based tile-based puzzle game, and to create new entities, I use this code: Field.CreateEntity(10, 5, Factory.Player()); This creates a new Player at [10; 5]. I'm using a factory-like class to create entities via composition. This is what the CreateEntity method looks like: public void CreateEntity(int mX, int mY, Entity mEntity) { mEntity.Field = this; TileManager.AddEntity(mEntity, true); GetTile(mX, mY).AddEntity(mEntity); mEntity.Initialize(); InvokeOnEntityCreated(mEntity); } Since many of the components (and also logic) of the entities require to know what the tile they're in is, or what the field they belong to is, I need to have mEntity.Initialize(); to know when the entity knows its own field and tile. The Initialize(); method contains a call to an event handler, so that I can do stuff like this in the factory class: result.OnInitialize += () => result.AddTags(TDLibConstants.GroundWalkableTag, TDLibConstants.TrapdoorTag); result.OnInitialize += () => result.AddComponents(new RenderComponent(), new ElementComponent(), new DirectionComponent()); This works so far, but it is not elegant and it's very open to bugs. I'm also using the same idea with components: they have a parameterless constructor, and when you call the AddComponent(mComponent); method in an entity, it is the entity's job to set the component's entity to itself. The alternative would be having a Field, int, int parameters in the factory class, to do stuff like: new Entity(Field, 10, 5); But I also don't like the fact that I have to create new entities like this. I would prefer creating entities via the Field object itself. How can I make entity/component creation more elegant and less prone to bugs?

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• Reaching Intermediate Programming Status

  - by George Stocker

  I am a software engineer that's had positions programming in VBA (though I dare not consider that 'real' experience, as it was trial and error!), Perl w/ CGI, C#, and ASP.NET. The latter two are post-undergraduate, with my entrance into the 'real world'. I'm 2 years out of college, and have had 5 years of experience (total) across the languages I've mentioned. However, when it comes to my resume, I can only put 2 years down for C#, and less than a year down for ASP.NET. I feel like I know C#, but I still have to spend time going 'What does this method do?', whereas some of the more senior level engineers can immediately say, "Oh, Method X does this, without ever having looked at that method before." So I know empirically that there's a gulf there, but I'm not exactly sure how to bridge it. I've started programming in Project Euler, and I picked up a book on design patterns, but I still feel like I spend each day treading water, instead of moving forward. That isn't to say that I don't feel like I've made progress, it just means that as far as I come each day, I still see the mountain top way off in the distance. My question is this: How did you overcome this plateau? How long did it take you? What methods can you suggest to assist me in this? I've read through Code Complete, The Mythical Man Month, and CLR via C#, 2nd edition -- my question is: What do I do now? Edit: I just found this question on projects for an intermediate level programmer. I think it adds to the discussion (though it does not supplant my question). As such, I'm adding it to the question as a "For More Information".

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• Should I modify an entity with many parameters or with the entity itself?

  - by Saeed Neamati

  We have a SOA-based system. The service methods are like: UpdateEntity(Entity entity) For small entities, it's all fine. However, when entities get bigger and bigger, to update one property we should follow this pattern in UI: Get parameters from UI (user) Create an instance of the Entity, using those parameters Get the entity from service Write code to fill the unchanged properties Give the result entity to the service Another option that I've experienced in previous experiences is to create semantic update methods for each update scenario. In other words instead of having one global all-encompasing update method, we had many ad-hoc parametric methods. For example, for the User entity, instead of having UpdateUser (User user) method, we had these methods: ChangeUserPassword(int userId, string newPassword) AddEmailToUserAccount(int userId, string email) ChangeProfilePicture(int userId, Image image) ... Now, I don't know which method is truly better, and for each approach, we encounter problems. I mean, I'm going to design the infrastructure for a new system, and I don't have enough reasons to pick any of these approaches. I couldn't find good resources on the Internet, because of the lack of keywords I could provide. What approach is better? What pitfalls each has? What benefits can we get from each one?

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• How to implment the database for event conditions and item bonuses for a browser based game

  - by Saifis

  I am currently creating a browser based game, and was wondering what was the standard approach in making diverse conditions and status bonuses database wise. Currently considering two cases. Event Conditions Needs min 1000 gold Needs min Lv 10 Needs certain item. Needs fulfillment of another event Status Bonus Reduces damage by 20% +100 attack points Deflects certain type of attack I wish to be able to continually change these parameters during the process of production and operation, so having them hard-coded isn't the best way. All I could come up with are the following two methods. Method 1 Create a table that contains each conditions with needed attributes Have a model named conditions with all the attributes it would need to set them conditions condition_type (level, money_min, money_max item, event_aquired) condition_amount prerequisite_condition_id prerequisite_item_id Method 2 write it in a DSL form that could be interpreted later in the code Perhaps something like yaml, have a text area in the setting form and have the code interpret it. condition_foo: condition_type :level min_level: 10 condition_type :item item_id: 2 At current Method 2 looks to be more practical and flexible for future changes, trade off being that all the flex must be done on the code side. Not to sure how this is supposed to be done, is it supposed to be hard coded? separate config file? Any help would be appreciated. Added For additional info, it will be implemented with Ruby on Rails

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• How to write PowerShell code part 2 (Using function)

  - by ybbest

  In the last post, I have showed you how to use external configuration file in your PowerShell script. In this post, I will show you how to create PowerShell function and call external PowerShell script.You can download the script here. 1. In the original script, I create the site directly using New-SPSite command. I will refactor it so that I will create a new function to create the site using New-SPSite. The PowerShell function is quite similar to a C# method. You put your function parameters in () and separate each parameter by a comma (,). Then you put your method body in {}. function add ([int] $num1 , [int] $num2){ $total=$num1+$num2 #Return $total $total } 2. The difference is you do not need semi-colon (;) at the end of each statement and when calling the method you do not need comma (,) to separate each parameter. function add ([int] $num1 , [int] $num2){ $total=$num1+$num2 #Return $total $total } #Calling the function [int] $num1=3 [int] $num2=4 $d= add $num1 $num2 Write-Host $d 3. If you like to return anything from the function, you just need to type in the object you like to return, not need to type return .e.g. $ObjectToReturn not return $ObjectToReturn

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• Adding tolerance to a point in polygon test

  - by David Gouveia

  I've been using this method which was taken from Game Coding Complete to detect whether a point is inside of a polygon. It works in almost every case, but is failing on a few edge cases, and I can't figure out the reason. For example, given a polygon with vertices at (0,0) (0,100) and (100,100), the algorithm is returning: True for any point strictly inside the polygon False for any of the vertices False for (0, 50) which lies on one of the edges of the polygon True (?) for (50,50) which is also on one of the edges of the polygon I'd actually like to relax the algorithm so that it returns true in all of these cases. In other words, it should return true for points that are strictly inside, for the vertices themselves, and for points on the edges of the polygon. If possible I'd also like to give it enough tolerance so that it always tend towards "true" in face of floating point fluctuations. For example, I have another method, that given a line segment and a point, returns the closest location on the line segment to the given point. Currently, given any point outside the polygon and one of its edges, there are cases where the result is categorized as being inside by the method above, while other points are considered outside. I'd like to give it enough tolerance so that it always returns true in this situation. The way I've currently solved the problem is an hack, which consists of using an external library to inflate the polygon by a few pixels, and performing the tests on the inflated polygon, but I'd really like to replace this with a proper solution.

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• Is it necessary to add an HP printer to CUPS using the hplip URI?

  - by JPbuntu

  I recently setup a CUPS print server (Ubuntu server 12.04) and I having trouble with performance of a HP Color LaserJet Printer CP3505n. The printer pauses for about a second between printing each page, which is annoying when there is a lot of printing to be done. This doesn't happen when the printer is installed directly to a Windows client. In an attempt to fix this I have setup the printer a couple different ways. I decided not to do a Samba share since this wiki said IPP is preferred. First Method Added to HP LaserJet to CUPS as a Discovered Network Printer, and selected HP Color LaserJet cp3505 hpijs pcl3, 3.12.2 (en) driver. I did not use a hplip URI. Second Method (hplip URI) I thought adding hplip to the mix might improve the performance, so I added the printer like this: Ran hp-setup -m 192.168.2.60, prompted to select driver Selected HP Color LaserJet cp3505 hpijs pcl3, 3.12.2 (en) Used hplip to generate a URI: hp-makeuri 192.168.2.60 Then added the printer to CUPS as a Local Printer: HP Printer (HPLIP), and entered: hp:/net/HP_Color_LaserJet_CP3505?ip=192.168.2.60. Either method I use I am able to share the printer on the network by adding a printer as http://192.168.2.2:631/printers/HP_LASER-TERRAC. Does it make a difference which way the printer is added cups? If so, and I install the printer with the hp URI, can I still change the driver using the CUPS web interface? I have been trying out different drivers to try and improve performance, and the cups interface is the easiest way to change them. Thanks in advance.

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• Kinect Click counter function

  - by Sweta Dwivedi

  So i have the following kinect click function which will check if the hand is within the bounds then it will click with a counter . . however there is a slight problem . .the first few button clicks work fine.. but after it clicks one of the buttons it changes the game state and immediately clicks the other button without the counter reaching 200. . . Kinect click is a method in the button class. . .and each button inside a list can access the Kinect click method. . . public bool KinectClick(int x,int y) { if ((x >= position.X && x <= position.X + position.Width) && (y >= position.Y && y <= position.Y + position.Height)) { counter++; if (counter > 200) { counter = 0; return true; } } else { counter = 0; } return false; } I call to check if this property is true in the Game update method to act as a button click. . foreach(Button g_t in Game_theme) { if ((g_t.KinectClick(x_c, y_c) == true || g_t.ButtonClicked() == true) && g_t.name == "animoe") { Selected_anim = true; currentGameState = GameState.InGame; } if ((g_t.KinectClick(x_c, y_c) == true || g_t.ButtonClicked() == true) && g_t.name == "planet") { Selected_planet = true; currentGameState = GameState.InGame; }

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• Ninject/DI: How to correctly pass initialisation data to injected type at runtime

  - by MrLane

  I have the following two classes: public class StoreService : IStoreService { private IEmailService _emailService; public StoreService(IEmailService emailService) { _emailService = emailService; } } public class EmailService : IEmailService { } Using Ninject I can set up bindings no problem to get it to inject a concrete implementation of IEmailService into the StoreService constructor. StoreService is actually injected into the code behind of an ASP.NET WebForm as so: [Ninject.Inject] public IStoreService StoreService { get; set; } But now I need to change EmailService to accept an object that contains SMTP related settings (that are pulled from the ApplicationSettings of the Web.config). So I changed EmailService to now look like this: public class EmailService : IEmailService { private SMTPSettings _smtpSettings; public void SetSMTPSettings(SMTPSettings smtpSettings) { _smtpSettings = smtpSettings; } } Setting SMTPSettings in this way also requires it to be passed into StoreService (via another public method). This has to be done in the Page_Load method in the WebForms code behind (I only have access to the Settings class in the UI layer). With manual/poor mans DI I could pass SMTPSettings directly into the constructor of EmailService and then inject EmailService into the StoreService constructor. With Ninject I don't have access to the instances of injected types outside of the objects they are injected to, so I have to set their data AFTER Ninject has already injected them via a separate public setter method. This to me seems wrong. How should I really be solving this scenario?

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• Basic 3D Collision detection in XNA 4.0

  - by NDraskovic

  I have a problem with detecting collision between 2 models using BoundingSpheres in XNA 4.0. The code I'm using i very simple: private bool IsCollision(Model model1, Matrix world1, Model model2, Matrix world2) { for (int meshIndex1 = 0; meshIndex1 < model1.Meshes.Count; meshIndex1++) { BoundingSphere sphere1 = model1.Meshes[meshIndex1].BoundingSphere; sphere1 = sphere1.Transform(world1); for (int meshIndex2 = 0; meshIndex2 < model2.Meshes.Count; meshIndex2++) { BoundingSphere sphere2 = model2.Meshes[meshIndex2].BoundingSphere; sphere2 = sphere2.Transform(world2); if (sphere1.Intersects(sphere2)) return true; } } return false; } The problem I'm getting is that when I call this method from the Update method, the program behaves as if this method always returns true value (which of course is not correct). The code for calling is very simple (although this is only the test code): if (IsCollision(model1, worldModel1, model2, worldModel2)) { Window.Title = "Intersects"; } What is causing this?

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• What is the value to checking in broken unit tests?

  - by Adam W.

  While there are ways of keeping unit tests from being executed, what is the value of checking in broken unit tests? I will use a simple example. Case sensitivity. The current code is Case Sensitive. A valid input into the method is "Cat" and it would return an enum of Animal.Cat. However, the desired functionality of the method should not be case sensitive. So if the method described was passed "cat" it could possibly return something like Animal.Null instead of Animal.Cat and the unit test would fail. Though a simple code change would make this work, a more complex issue may take weeks to fix, but identifying the bug with a unit test could be a less complex task. The application currently being analyzed has 4 years of code that "works". However, recent discussions regarding unit tests has found flaws in the code. Some just need explicit implementation documentation (ex. case sensitive or not), or code that does not execute the bug based on how it is currently called. But unit tests can be created executing specific scenarios that will cause the bug to be seen and are valid inputs. What is the value of checking in unit tests that exercise the bug until someone can get around to fixing the code? Should this unit test be flagged with ignore, priority, category etc, to determine whether a build was successful based on tests executed? Eventually the unit test should be created to execute the code once someone fixes it. On one hand it shows that identified bugs have not been fixed. On the other, there could be hundreds of failed unit tests showing up in the logs and weeding through the ones that should fail vs. failures due to a code check-in would be difficult to find.

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• How to write PowerShell code part 2 (Using function)

  - by ybbest

  In the last post, I have showed you how to use external configuration file in your PowerShell script. In this post, I will show you how to create PowerShell function and call external PowerShell script.You can download the script here. 1. In the original script, I create the site directly using New-SPSite command. I will refactor it so that I will create a new function to create the site using New-SPSite. The PowerShell function is quite similar to a C# method. You put your function parameters in () and separate each parameter by a comma (,). Then you put your method body in {}. function add ([int] $num1 , [int] $num2){ $total=$num1+$num2 #Return $total $total } 2. The difference is you do not need semi-colon (;) at the end of each statement and when calling the method you do not need comma (,) to separate each parameter. function add ([int] $num1 , [int] $num2){ $total=$num1+$num2 #Return $total $total } #Calling the function [int] $num1=3 [int] $num2=4 $d= add $num1 $num2 Write-Host $d 3. If you like to return anything from the function, you just need to type in the object you like to return, not need to type return .e.g. $ObjectToReturn not return $ObjectToReturn

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• Versioning APIs

  - by Sharon

  Suppose that you have a large project supported by an API base. The project also ships a public API that end(ish) users can use. Sometimes you need to make changes to the API base that supports your project. For example, you need to add a feature that needs an API change, a new method, or requires altering of one of the objects, or the format of one of those objects, passed to or from the API. Assuming that you are also using these objects in your public API, the public objects will also change any time you do this, which is undesirable as your clients may rely on the API objects remaining identical for their parsing code to work. (cough C++ WSDL clients...) So one potential solution is to version the API. But when we say "version" the API, it sounds like this also must mean to version the API objects as well as well as providing duplicate method calls for each changed method signature. So I would then have a plain old clr object for each version of my api, which again seems undesirable. And even if I do this, I surely won't be building each object from scratch as that would end up with vast amounts of duplicated code. Rather, the API is likely to extend the private objects we are using for our base API, but then we run into the same problem because added properties would also be available in the public API when they are not supposed to be. So what is some sanity that is usually applied to this situation? I know many public services such as Git for Windows maintains a versioned API, but I'm having trouble imagining an architecture that supports this without vast amounts of duplicate code covering the various versioned methods and input/output objects. I'm aware that processes such as semantic versioning attempt to put some sanity on when public API breaks should occur. The problem is more that it seems like many or most changes require breaking the public API if the objects aren't more separated, but I don't see a good way to do that without duplicating code.

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• How to help FGLRX detect a device

  - by user113416

  I have HD 4850 card, Ubuntu 12.10 and installed legacy drivers using makson96 ppa. The issue is, that FGLRX can not detect my device and loads vesa bios. I had the same problem on ubuntu 11.10, 12.04 versions. I want to manually help fglrx find a matching device to load as it shoudld do. It is interesting, why does fglrx search for a device in a PCI:0@1:0:1 Bus? in xorg.cof different bus is indicated: Section "Device" Identifier "aticonfig-Device[0]-0" Driver "fglrx" BusID "PCI:1:0:0" EndSection fglrxinfo display: :0.0 screen: 0 OpenGL vendor string: Advanced Micro Devices, Inc. OpenGL renderer string: ATI Radeon HD 4800 Series OpenGL version string: 3.3.11653 Compatibility Profile Context Here is a part of my xorg log: [ 3.846] (II) VESA: driver for VESA chipsets: vesa [ 3.846] (II) FBDEV: driver for framebuffer: fbdev [ 3.846] (++) using VT number 7 [ 3.846] (WW) Falling back to old probe method for fglrx [ 3.883] (II) Loading PCS database from /etc/ati/amdpcsdb [ 3.883] (--) Assigning device section with no busID to primary device [ 3.883] (--) Chipset Supported AMD Graphics Processor (0x9442) found [ 3.884] (WW) fglrx: No matching Device section for instance (BusID PCI:0@1:0:1) found [ 3.884] (II) AMD Video driver is running on a device belonging to a group targeted for this release [ 3.884] (II) AMD Video driver is signed [ 3.884] (II) fglrx(0): pEnt->device->identifier=0xb7791d8f [ 3.884] (WW) Falling back to old probe method for vesa [ 3.884] (WW) Falling back to old probe method for fbdev Thanks in advance.

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• Avoid overwriting all the methods in the child class

  - by Heckel

  The context I am making a game in C++ using SFML. I have a class that controls what is displayed on the screen (manager on the image below). It has a list of all the things to draw like images, text, etc. To be able to store them in one list I created a Drawable class from which all the other drawable class inherit. The image below represents how I would organize each class. Drawable has a virtual method Draw that will be called by the manager. Image and Text overwrite this method. My problem is that I would like Image::draw method to work for Circle, Polygon, etc. since sf::CircleShape and sf::ConvexShape inherit from sf::Shape. I thought of two ways to do that. My first idea would be for Image to have a pointer on sf::Shape, and the subclasses would make it point onto their sf::CircleShape or sf::ConvexShape classes (Like on the image below). In the Polygon constructor I would write something like ptr_shape = &polygon_shape; This doesn't look very elegant because I have two variables that are, in fact, just one. My second idea is to store the sf::CircleShape and sf::ConvexShape inside the ptr_shape like ptr_shape = new sf::ConvexShape(...); and to use a function that is only in ConvexShape I would cast it like so ((sf::ConvexShape*)ptr_shape)->convex_method(); But that doesn't look very elegant either. I am not even sure I am allowed to do that. My question I added details about the whole thing because I thought that maybe my whole architecture was wrong. I would like to know how I could design my program to be safe without overwriting all the Image methods. I apologize if this question has already been asked; I have no idea what to google.

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• backlight doesn't work on acer 5732z tried everything I can find

  - by Dude Random21

  Ok if you can solve my problem you're really really good. I want to run ubuntu 12.04 on my acer aspire 5732z I know (from research) that these computer's have issues with the backlight on ubuntu. So I tried a couple of solutions: The "sudo lightdm restart" method. I get no change at all. The "sudo setpci -s 00:02.0 F4.B=30" method. This so far has been the most effective, I first tried it in the F1 console right away I get the screen back, problem is going back to the desktop it goes back to being black. So I tried it from a terminal window and it works as well but as soon as I unplug my external monitor the screen turns black again and doesn't come back. If I plug the monitor back in the screen stays black and the only thing I see is the mouse pointer. From here I go back into console (which I am able to see) and reboot from there. The "sudo sed -i 's/GRUB_CMDLINE_LINUX=""/GRUB_CMDLINE_LINUX="acpi_osi=Linux"/g' /etc/default/grub" method. This one I got no instant change and after reboot still no change. I'm open to pretty much any suggestions you may have.

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• What level of detail to use in an interface members descriptions?

  - by famousgarkin

  I am extracting interfaces from some classes in .NET, and I am not completely sure about what level of detail of description to use for some of the interface members (properties, methods). An example: interface ISomeInterface { /// <summary> /// Checks if the object is checked out. /// </summary> /// <returns> /// Returns true if the object is checked out, or if the object locking is not enabled, /// otherwise returns false. /// </returns> bool IsObjectCheckedOut(); } class SomeImplementation : ISomeInterface { public bool IsObjectCheckedOut() { // An implementation of the method that returns true if the object is checked out, // or if the object locking is not enabled } } The part in question is the <returns>...</returns> section of the IsObjectCheckedOut description in the interface. Is it ok to include such a detail about return value in the interface itself, as the code that will work with the interface should know exactly what that method will do? All the current implementations of the method will do just that. But is it ok to limit the possible other/future implementations by description this way? Or should this not be included in the interface description, as there is no way to actually ensure that other/future implementations will do exactly this? Is it better to be as general as possible regarding the interface in such circumstances? I am currently inclined to the latter option.

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• Finding Buried Controls

  - by Bunch

  This post is pretty specific to an issue I had but still has some ideas that could be applied in other scenarios. The problem I had was updating a few buttons so their Text values could be set in the code behind which had a method to grab the proper value from an external source. This was so that if the application needed to be installed by a customer using a language other than English or needed a different notation for the button's Text they could simply update the database. Most of the time this was no big deal. However I had one instance where the button was part of a control, the button had no set ID and that control was only found in a dll. So there was no markup to edit for the Button. Also updating the dll was not an option so I had to make the best of what I had to work with. In the cs file for the aspx file with the control on it I added the Page_LoadComplete. The problem button was within a GridView so I added a foreach to go through each GridViewRow and find the button I needed. Since I did not have an ID to work with besides a random ctl00$main$DllControl$gvStuff$ctl03$ctl05 using the GridView's FindControl was out. I ended up looping through each GridViewRow, then if a RowState equaled Edit loop through the Cells, each control in the Cell and check each control to see if it held a Panel that contained the button. If the control was a Panel I could then loop through the controls in the Panel, find the Button that had text of "Update" (that was the hard coded part) and change it using the method to return the proper value from the database. if (rowState.Contains("Edit")){  foreach (DataControlFieldCell rowCell in gvr.Cells)  {   foreach (Control ctrl in rowCell.Controls)   {    if (ctrl.GetType() == typeof(Panel))     {     foreach (Control childCtrl in ctrl.Controls)     {      if (childCtrl.GetType() == typeof(Button))      {       Button update = (Button)childCtrl;       if (update.Text == "Update")       {        update.Text = method to return the external value for the button's text;       }      }     }    }   }  }} Tags: ASP.Net, CSharp

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• Should all public methods in an abstract class be marked virtual?

  - by Justin Pihony

  I recently had to update an abstract base class on some OSS that I was using so that it was more testable by making them virtual (I could not use an interface as it combined two). This got me thinking whether I should mark all of the methods that I needed virtual, or if I should mark every public method/property virtual. I generally agree with Roy Osherove that every method should be made virtual, but I came across this article that got me thinking about whether this was necessary or not. I am going to limit this down to abstract classes for simplicity, however (whether all concrete public methods should be virtual is especially debatable, I am sure). I could see where you might want to allow a sub-class to use a method, but not want it overriding the implementation. However, as long as you trust that Liskov's Substitution Principle will be followed, then why would you not allow it to be overriden? By marking it abstract, you are forcing a certain override anyway, so, it seems to me that all public methods inside of an abstract class should indeed be marked virtual. However, I wanted to ask in case there was something I might not be thinking. Should all public methods within an abstract class be made virtual?

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• Rails: The Law of Demeter [duplicate]

  - by user2158382

  This question already has an answer here: Rails: Law of Demeter Confusion 4 answers I am reading a book called Rails AntiPatterns and they talk about using delegation to to avoid breaking the Law of Demeter. Here is their prime example: They believe that calling something like this in the controller is bad (and I agree) @street = @invoice.customer.address.street Their proposed solution is to do the following: class Customer has_one :address belongs_to :invoice def street address.street end end class Invoice has_one :customer def customer_street customer.street end end @street = @invoice.customer_street They are stating that since you only use one dot, you are not breaking the Law of Demeter here. I think this is incorrect, because you are still going through customer to go through address to get the invoice's street. I primarily got this idea from a blog post I read: http://www.dan-manges.com/blog/37 In the blog post the prime example is class Wallet attr_accessor :cash end class Customer has_one :wallet # attribute delegation def cash @wallet.cash end end class Paperboy def collect_money(customer, due_amount) if customer.cash < due_ammount raise InsufficientFundsError else customer.cash -= due_amount @collected_amount += due_amount end end end The blog post states that although there is only one dot customer.cash instead of customer.wallet.cash, this code still violates the Law of Demeter. Now in the Paperboy collect_money method, we don't have two dots, we just have one in "customer.cash". Has this delegation solved our problem? Not at all. If we look at the behavior, a paperboy is still reaching directly into a customer's wallet to get cash out. EDIT I completely understand and agree that this is still a violation and I need to create a method in Wallet called withdraw that handles the payment for me and that I should call that method inside the Customer class. What I don't get is that according to this process, my first example still violates the Law of Demeter because Invoice is still reaching directly into Customer to get the street. Can somebody help me clear the confusion. I have been searching for the past 2 days trying to let this topic sink in, but it is still confusing.

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• What is the value of checking in failing unit tests?

  - by Adam W.

  While there are ways of keeping unit tests from being executed, what is the value of checking in failing unit tests? I will use a simple example: Case Sensitivity. The current code is case sensitive. A valid input into the method is "Cat" and it would return an enum of Animal.Cat. However, the desired functionality of the method should not be case sensitive. So if the method described was passed "cat" it could possibly return something like Animal.Null instead of Animal.Cat and the unit test would fail. Though a simple code change would make this work, a more complex issue may take weeks to fix, but identifying the bug with a unit test could be a less complex task. The application currently being analyzed has 4 years of code that "works". However, recent discussions regarding unit tests have found flaws in the code. Some just need explicit implementation documentation (ex. case sensitive or not), or code that does not execute the bug based on how it is currently called. But unit tests can be created executing specific scenarios that will cause the bug to be seen and are valid inputs. What is the value of checking in unit tests that exercise the bug until someone can get around to fixing the code? Should this unit test be flagged with ignore, priority, category etc, to determine whether a build was successful based on tests executed? Eventually the unit test should be created to execute the code once someone fixes it. On one hand it shows that identified bugs have not been fixed. On the other, there could be hundreds of failed unit tests showing up in the logs and weeding through the ones that should fail vs. failures due to a code check-in would be difficult to find.

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• Strategies for managing use of types in Python

  - by dave

  I'm a long time programmer in C# but have been coding in Python for the past year. One of the big hurdles for me was the lack of type definitions for variables and parameters. Whereas I totally get the idea of duck typing, I do find it frustrating that I can't tell the type of a variable just by looking at it. This is an issue when you look at someone else's code where they've used ambiguous names for method parameters (see edit below). In a few cases, I've added asserts to ensure parameters comply with an expected type but this goes against the whole duck typing thing. On some methods, I'll document the expected type of parameters (eg: list of user objects), but even this seems to go against the idea of just using an object and let the runtime deal with exceptions. What strategies do you use to avoid typing problems in Python? Edit: Example of the parameter naming issues: If our code base we have a task object (ORM object) and a task_obj object (higher level object that embeds a task). Needless to say, many methods accept a parameter named 'task'. The method might expect a task or a task_obj or some other construct such as a dictionary of task properties - it is not clear. It is them up to be to look at how that parameter is used in order to work out what the method expects.

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