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• Go/Obj-C style interfaces with ability to extend compiled objects after initial release

  - by Skrylar

  I have a conceptual model for an object system which involves combining Go/Obj-C interfaces/protocols with being able to add virtual methods from any unit, not just the one which defines a class. The idea of this is to allow Ruby-ish open classes so you can take a minimalist approach to library development, and attach on small pieces of functionality as is actually needed by the whole program. Implementation of this involves a table of methods marked virtual in an RTTI table, which system functions are allowed to add to during module initialization. Upon typecasting an object to an interface, a Go-style lookup is done to create a vtable for that particular mapping and pass it off so you can have comparable performance to C/C++. In this case, methods may be added /afterwards/ which were not previously known and these new methods allow newer interfaces to be satisfied; while I like this idea because it seems like it would be very flexible (disregarding the potential for spaghetti code, which can happen with just about any model you use regardless). By wrapping the system calls for binding methods up in a set of clean C-compatible calls, one would also be able to integrate code with shared libraries and retain a decent amount of performance (Go does not do shared linking, and Objective-C does a dynamic lookup on each call.) Is there a valid use-case for this model that would make it worth the extra background plumbing? As much as this Dylan-style extensibility would be nice to have access to, I can't quite bring myself to a use case that would justify the overhead other than "it could make some kinds of code more extensible in future scenarios."

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• Confused about javascript module pattern implementation

  - by Damon

  I have a class written on a project I'm working on that I've been told is using the module pattern, but it's doing things a little differently than the examples I've seen. It basically takes this form: (function ($, document, window, undefined) { var module = { foo : bar, aMethod : function (arg) { className.bMethod(arg); }, bMethod : function (arg) { console.log('spoons'); } }; window.ajaxTable = ajaxTable; })(jQuery, document, window); I get what's going on here. But I'm not sure how this relates to most of the definitions I've seen of the module (or revealing?) module pattern. like this one from briancray var module = (function () { // private variables and functions var foo = 'bar'; // constructor var module = function () { }; // prototype module.prototype = { constructor: module, something: function () { } }; // return module return module; })(); var my_module = new module(); Is the first example basically like the second except everything is in the constructor? I'm just wrapping my head around patterns and the little things at the beginnings and endings always make me not sure what I should be doing.

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• Objected oriented approach to structure inside structure

  - by RishiD

  This is for C++ but should apply to any OO language. Trying to figure out the correct object oriented apporach to do the following (this is what I do in C). struct Container { enum type; union { TypeA a; TypeB b; }; } The type field determines if it TypeA or TypeB object. I am using this to handle responses coming back from a connection, they get parsed and get put into this structure and then based on the message type the appropriate fields get filled in. e.g. struct Container parseResponse(bufferIn, bufferLength); Is there an OO approach for doing this?

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• Distinguishing between UI command & domain commands

  - by SonOfPirate

  I am building a WPF client application using the MVVM pattern that provides an interface on top of an existing set of business logic residing in a library which is shared with other applications. The business library followed a domain-driven architecture using CQRS to separate the read and write models (no event sourcing). The combination of technologies and patterns has brought up an interesting conundrum: The MVVM pattern uses the command pattern for handling user-interaction with the view models. .NET provides an ICommand interface which is implemented by most MVVM frameworks, like MVVM Light's RelayCommand and Prism's DelegateCommand. For example, the view model would expose a number of command objects as properties that are bound to the UI and respond when the user performs actions like clicking buttons. Many implementations of the CQRS use the command pattern to isolate and encapsulate individual behaviors. In my business library, we have implemented the write model as command / command-handler pairs. As such, when we want to do some work, such as create a new order, we 'issue' a command (CreateOrderCommand) which is routed to the command-handler responsible for executing the command. This is great, clearly explained in many sources and I am good with it. However, take this scenario: I have a ToolbarViewModel which exposes a CreateNewOrderCommand property. This ICommand object is bound to a button in the UI. When clicked, the UI command creates and issues a new CreateOrderCommand object to the domain which is handled by the CreateOrderCommandHandler. This is difficult to explain to other developers and I am finding myself getting tongue-tied because everything is a command. I'm sure I'm not the first developer to have patterns overlap like this where the naming/terminology also overlap. How have you approached distinguishing your commands used in the UI from those used in the domain? (Edit: I should mention that the business library is UI-agnostic, i.e. no UI technology-specific code exists, or will exists, in this library.)

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• What is the best website width? [on hold]

  - by Salvis Dišlers

  What is the best website width? I can't decide between 1200px max-width and 1236px....with 300px sidebar as enough or 320px? I personally like wide website, my current website is 1236px; but I hear it's considered very wide for eyesight and all those gadgets keeping in mind... The website is for reading - I mean, mostly articles with around 3000 words on average per page, so no matter - whether they look wide, whether they love to scroll down :) Also - what to decide about Banner size / sidebar? Probably the 300px I can put a 300px banner, but on 320px sidebar I could put 336px banner, if necessary...

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• Do ORMs enable the creation of rich domain models?

  - by Augusto

  After using Hibernate on most of my projects for about 8 years, I've landed on a company that discourages its use and wants applications to only interact with the DB through stored procedures. After doing this for a couple of weeks, I haven't been able to create a rich domain model of the application I'm starting to build, and the application just looks like a (horrible) transactional script. Some of the issues I've found are: Cannot navigate object graph as the stored procedures just load the minimum amount of data, which means that sometimes we have similar objects with different fields. One example is: we have a stored procedure to retrieve all the data from a customer, and another to retrieve account information plus a few fields from the customer. Lots of the logic ends up in helper classes, so the code becomes more structured (with entities used as old C structs). More boring scaffolding code, as there's no framework that extracts result sets from a stored procedure and puts it in an entity. My questions are: has anyone been in a similar situation and didn't agree with the store procedure approch? what did you do? Is there an actual benefit of using stored procedures? appart from the silly point of "no one can issue a drop table". Is there a way to create a rich domain using stored procedures? I know that there's the posibility of using AOP to inject DAOs/Repositories into entities to be able to navigate the object graph. I don't like this option as it's very close to voodoo.

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• Write own messaging system vs. utilize existing ones

  - by A.Rashad

  We are trying to have our own startup, with a middleware application to glue small applications with enterprise legacy systems. for such middle-ware to function properly, we will need some sort of messaging system to make different components talk to each other in a reliable way. the alternatives are: use an existing messaging system, such as 0MQ, jBOSS, WebSphere MQ, etc. build our own messaging system the way we see the problem I am more biased towards the later option for the following reasons: to have more control over our final product to avoid any licensing problems later on to learn about messaging while writing the code to invent something new, that might cost us lots of $$$ if reused an existing system What would you do if in my shoes?

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• DDD and validation of aggregate root

  - by Mik378

  Suppose an aggregate root : MailConfiguration (wrapping an AddressPart object). The AddressPart object is a simple immutable value object with some fields like senderAdress, recipentAddress (to make example simple). As being an invariant object, AddressPart should logically wrap its own Validator (by the way of external a kind of AddressValidator for respecting Single Responsibility Principle) I read some articles that claimed an aggregateRoot must validate its 'children'. However, if we follow this principle, one could create an AddressPart with an uncohesive/invalid state. What are your opinion? Should I move the collaborator AddressValidator(used in constructor so in order to validate immediately the cohesion of an AddressPart) from AddressPart and assign it to aggregateRoot (MailConfiguration) ?

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• Client-Server connection response timeout issues

  - by Srikar

  User creates a folder in client and in the client-side code I hit an API to the server to make this persistent for that user. But in some cases, my server is so busy that the request timesout. The server has executed my request but timedout before sending a response back to client. The timeout set is 10 seconds in client. At this point the client thinks that server has not executed its request (of creating a folder) and ends up sending it again. Now I have 2 folders on the server but the user has created only 1 folder in the client. How to prevent this? One of the ways to solve this is to use a unique ID with each new request. So the ID acts as a distinguisher between old and new requests from client. But this leads to storing these IDs on my server and do a lookup for each API call which I want to avoid. Other way is to increase the timeout duration. But I dont want to change this from 10 seconds. Something tells me that there are better solutions. I have posted this question in stackoverflow but I think its better suited here. UPDATE: I will make my problem even more explicit. The client is a webbrowser and the server is running nginx+django+mysql (standard stack). The user creates a folder in webbrowser. As a result I need to hit a server API. The API call responds back, thereby client knows API call was success. This is normal scenario. Sometimes though, server successfully completes the API request but the client-side (webbrowser) connection timesout before server can respond back. The client has no clue at this point. The user thinks the request was a fail & clicks again. This time it was a success but when the UI refreshes he sees 2 folders. I want to remedy this situation.

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• Designing an API on top with Java RMI and Rest APIs

  - by user1303881

  I'm working on the backend of a java web application. We have a document repository (Fedora Commons specifically) where we house xml files. I want to abstract the API of the repository internally so that we aren't tightly coupled to one product. I'd also like to give the flexibility of connecting to to a repository via Java RMI or REST APIs. I was hoping to get advice or resources on how to implement something like this. My thought it that I'd have some abstract repository class that had methods like getRecord, updateRecord, and deleteRecord. In the constructor I would pass the URI for the repository and the API method and port. This would allow some flexibility in the future so that if the REST api became more practical, but allow the flexibility or using RMI which could (should?) have better performance. Am I over thinking this or am I on the right path?

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• My Last "Catch-Up" Post for 2010 Content

  - by KKline

  I did a lot of writing in 2010. Unfortunately, I didn't do a good job of keeping all of that writing equally distributed throughout all of the channels where I'm active. So here are a few more posts from my blog, put on-line during the months of November and December 2010, that I didn't get posted here on SQLBlog.com: 1. It's Time to Upgrade! So many of my customers and many of you, dear readers, are still on SQL Server 2005. Join Kevin Kline , SQL Server MVP and SQL Server Technology Strategist...(read more)

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• Share Mulitple Classes as one dll or a lib with Mulitple Projects

  - by JNL

  Currently I have some shared class files(.cpp and .h) which I include them in around 20 Projects. Currently I have to include them in all of the projects. So if I get some business requirments and I change some of the shared(.cpp or .h) files I have to include them in all the 20 Projects which is kind of tedious. Is there a way where I can create a shared dll or library and include it all of my Projects. So if I have to change it, I just have to change it once and then just Add Reference to include that dll or library which contains all the shared(.cpp, .h) files. Any help/recommendations regarding the same, will be highly appreciated. I am using VS2012 for VC++.

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• designing classes with similar goal but widely different decisional core

  - by Stefano Borini

  I am puzzled on how to model this situation. Suppose you have an algorithm operating in a loop. At every loop, a procedure P must take place, whose role is to modify an input data I into an output data O, such that O = P(I). In reality, there are different flavors of P, say P1, P2, P3 and so on. The choice of which P to run is user dependent, but all P have the same finality, produce O from I. This called well for a base class PBase with a method PBase::apply, with specific reimplementations of P1::apply(I), P2::apply(I), and P3::apply(I). The actual P class gets instantiated in a factory method, and the loop stays simple. Now, I have a case of P4 which follows the same principle, but this time needs additional data from the loop (such as the current iteration, and the average value of O during the previous iterations). How would you redesign for this case?

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• Speaking this week at Richmond SQL Server User Group

  - by drsql

  Thursday night, at 6:00 (or so) I will be speaking in Richmond ( http://richmondsql.org/cs2007/ ), talking about How to Implement a Hierarchy using SQL Server. The abstract is: One of the most common structures you will come across in the real world is a hierarchy (either a single parent "tree" or a multi-parent "graph"). Many systems will implement the obvious examples, such as a corporate managerial structure or a bill of materials. It turns out that almost any many-to-many relationship can be...(read more)

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• Disqus integration in website.. what is wrong??

  - by Thieme Hennis

  hi, I try to embed a disqus forum in a website I created. I used the exact code and instructions they give on the installation instructions. I just don't get it. Not much on Google either. Is something wrong in the code? Should I change anything? <!DOCTYPE HTML> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <link rel="shortcut icon" href="../favicon.ico"> <title>Little Louie | Hennis &amp; Blaisse Lovers Productions</title> <META NAME="keywords" CONTENT="some,tags"> <link href="../style2.css" rel="stylesheet" type="text/css"> </head> <body> <p><b>Some text</p> <p> <div id="disqus_thread"></div> <script type="text/javascript"> (function() { var dsq = document.createElement('script'); dsq.type = 'text/javascript'; dsq.async = true; dsq.src = 'http://littelouie.disqus.com/embed.js'; (document.getElementsByTagName('head')[0] || document.getElementsByTagName('body')[0]).appendChild(dsq); })(); </script> <noscript>Please enable JavaScript to view the <a href="http://disqus.com/?ref_noscript=littelouie">comments powered by Disqus.</a></noscript> <a href="http://disqus.com" class="dsq-brlink">blog comments powered by <span class="logo-disqus">Disqus</span></a> </p> <p> <script type="text/javascript"> var disqus_shortname = 'littelouie'; (function () { var s = document.createElement('script'); s.async = true; s.src = 'http://disqus.com/forums/littelouie/count.js'; (document.getElementsByTagName('HEAD')[0] || document.getElementsByTagName('BODY')[0]).appendChild(s); }()); </script> </p> </body> </html>

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• constructor should not call methods

  - by Stefano Borini

  I described to a colleague why a constructor calling a method is an antipattern. example (in my rusty C++) class C { public : C(int foo); void setFoo(int foo); private: int foo; } C::C(int foo) { setFoo(foo); } void C::setFoo(int foo) { this->foo = foo } I would like to motivate better this fact through your additional contribute. If you have examples, book references, blog pages, or names of principles, they would be very welcome. Edit: I'm talking in general, but we are coding in python.

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• Changelog Management

  - by Gnial0id

  I'm currently developing a WinForm application. In order to inform the client about the improvements and corrections made during the last version, I would like to manage and display a changelog. I mostly found existing changelog on website (the term changelog is pretty used) or explanation on how to manage the release numbers, which I don't care. So, these are my questions: How do I manage a changelog (using XML, pure text in the app, etc.) in a desktop application? How do I present it to the user (external website, inside the winform application)?

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• Who should control navigation in an MVVM application?

  - by SonOfPirate

  Example #1: I have a view displayed in my MVVM application (let's use Silverlight for the purposes of the discussion) and I click on a button that should take me to a new page. Example #2: That same view has another button that, when clicked, should open up a details view in a child window (dialog). We know that there will be Command objects exposed by our ViewModel bound to the buttons with methods that respond to the user's click. But, what then? How do we complete the action? Even if we use a so-called NavigationService, what are we telling it? To be more specific, in a traditional View-first model (like URL-based navigation schemes such as on the web or the SL built-in navigation framework) the Command objects would have to know what View to display next. That seems to cross the line when it comes to the separation of concerns promoted by the pattern. On the other hand, if the button wasn't wired to a Command object and behaved like a hyperlink, the navigation rules could be defined in the markup. But do we want the Views to control application flow and isn't navigation just another type of business logic? (I can say yes in some cases and no in others.) To me, the utopian implementation of the MVVM pattern (and I've heard others profess this) would be to have the ViewModel wired in such a way that the application can run headless (i.e. no Views). This provides the most surface area for code-based testing and makes the Views a true skin on the application. And my ViewModel shouldn't care if it displayed in the main window, a floating panel or a child window, should it? According to this apprach, it is up to some other mechanism at runtime to 'bind' what View should be displayed for each ViewModel. But what if we want to share a View with multiple ViewModels or vice versa? So given the need to manage the View-ViewModel relationship so we know what to display when along with the need to navigate between views, including displaying child windows / dialogs, how do we truly accomplish this in the MVVM pattern?

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• What is wrong with Unix/linux

  - by John Smith

  This is a genuine question motivated by Ideal Operating System When I moved from DOS to Linux in the late 90s it was an eye opener for me. Long file names, arbitrarily many extensions etc... Now I look at Linux and Unix and see all sorts of issues. Here are things I see which could be fixed. Too much depends on root, and rootly powers cannot be voluntarily delegated over several users. (I would love to give up my power to manager printers and delegate the job to another account) File permissions are very limited, and there is not much metadata to go with files. The "everything is a file" metaphor is not true, Plan 9 gets it right(er).

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• Code Smell: Inheritance Abuse

  - by dsimcha

  It's been generally accepted in the OO community that one should "favor composition over inheritance". On the other hand, inheritance does provide both polymorphism and a straightforward, terse way of delegating everything to a base class unless explicitly overridden and is therefore extremely convenient and useful. Delegation can often (though not always) be verbose and brittle. The most obvious and IMHO surest sign of inheritance abuse is violation of the Liskov Substitution Principle. What are some other signs that inheritance is The Wrong Tool for the Job even if it seems convenient?

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• Use Case Diagrams - should I create a diagram just for a view business rule?

  - by Periback

  I'm modeling a UCD where I have two actors ( a content producer and a developer).. the content producer is going to create and specify details of a storyboard functionality, and the other actor (developer) will only be able to view this storyboard ( he'll log in the application and read the storyboard to start developing what it says, outside the application..) I'm working on the specification of this storyboard functionality and I'd like to know it would be like a best-practice if I describe something like " actor- developer", "UCD - read scenes of storyboard" . This is the specification of an application I developed for my thesis and they asked me to add some specification...

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• Where to start learning OpenGL with C++?

  - by NERDcustard

  I'm 16 years old and my name is Norbert. I have learnt C++ and made some cool text based games and such but I would love to start graphic's programming. I'm a decent artiest (I will have some of my work bellow) I know the base of C++ but I really would like to get into OpenGL. I need someone to show me some good tutorials for OpenGl with C++ so I can really get into game dev. My goal is to be able to program a simple 2d game by the end of the year and I have lots of time to do so. I'm en-rolled in a game dev next year and really need some help with starting off. http://imgur.com/QZjKX http://imgur.com/3CZy7

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• How to safely copy an object?

  - by Prog

  This question is going to be a little long. Please bear with me. Something that happened in a project of mine made me think about how to safely copy objects. I'll present the situation I had and then ask a question. There was a class SomeClass: class SomeClass{ Thing[] things; public SomeClass(Thing[] things){ this.things = things; } // irrelevant stuff omitted public SomeClass copy(){ return new SomeClass(things); } } There was another class Processor that takes SomeClass objects, copies them (via someClassInstance.copy()), manipulates the copy's state, and returns the copy. Here it is: class Processor{ public SomeClass processObject(SomeClass object){ SomeClass copy = object.copy(); manipulateTheCopy(copy); return copy; } // irrelevant stuff omitted } I ran this, and it had bugs. I looked into these bugs, and it turned out that the manipulations Processor does on copy actually affect not only the copy, but also the original SomeClass object that was passed into processObject. I found out that it was because the original and the copy shared state - because the original passed it's field things into the copy when creating it. This made me realize that copying objects is harder than simply instantiating them with the same fields as the original. For the two objects to be completely disconnected, without any shared state, each of the fields passed to the copy also has to be copied. And if that object contains other objects - they have to be copied too. And so on. So basically, in order to be able to actually copy an object, each class in the system must have a copy() method, that also invokes copy() on all of it's fields, and so on. So for example, for copy() in SomeClass to work, it needs to look like this: public SomeClass copy(){ Thing[] copyThings = new Thing[things.length]; for(int i=0; i<things.length; i++) copyThings[i] = things[i].copy(); return new SomeClass(copyThings); } And if Thing has object fields of it's own, than it's own copy() method must be appropriate: class Thing{ Apple apple; Pencil pencil; int number; public Thing(Apple apple, Pencil pencil, int number){ this.apple = apple; this.pencil = pencil; this.number = number; } public Thing copy(){ // 'number' is a primitve. return new Thing(apple.getCopy(), pencil.getCopy(), number); } } And so on. Of course, instead of all classes having a copy() method, the copying mechanism can happen in all of the getters and the constructors of classes (unless places where it isn't suitable, for example when the field points to an external object, not to an object that 'is part' of this object). Still, that means that in order to be able to safely copy an object - most classes would have to have copying mechanisms in their getters. My question is divided into two parts: How frequently do you need to get a copy of an object? Is this a regular issue? Is the technique described common and/or reasonable? Or is there a better way to make safe copies of objects? Or is there an easier way to safely copy objects, without them sharing any state?

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• Is it evil to model JSON responses to classes when they are mostly smilar?

  - by Aybe

  Here's the problem : While implementing a C# wrapper for an online API (Discogs) I've been faced to a dilemma : quite often the responses returned have mostly similar members and while modeling these responses to classes, some questions surfaces on which way to go would be the best. Example : Querying for a 'release' or a 'master' will return an object that contains an array of 'artist', however these 'artists' do not exactly have the same members. Currently I decided to represent these 'artists' as a single 'Artist' class, against having respective 'ReleaseArtist' and 'MasterArtist' classes which soon becomes very confusing even though another problem arises : when a category (master or release) does not return these members, they will be null. Though it might sound confusing as well I find it less confusing than the former situation as I've tackled the problem by simply not showing null members when visualizing these objects. Is this the right approach to follow ? An example of these differences : public class Artist { public List<Alias> Aliases { get; set; } public string DataQuality { get; set; } public List<Image> Images { get; set; } public string Name { get; set; } public List<string> NameVariations { get; set; } public string Profile { get; set; } public string Realname { get; set; } public string ReleasesUrl { get; set; } public string ResourceUrl { get; set; } public string Uri { get; set; } public List<string> Urls { get; set; } } public class ReleaseArtist { public string Join { get; set; } public string Name { get; set; } public string Anv { get; set; } public string Tracks { get; set; } public string Role { get; set; } public string ResourceUrl { get; set; } public int Id { get; set; } }

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• Comparison of languages by usage type? [closed]

  - by Tom

  Does anyone know of a good place to go find comparisons of programming languages by the intended platform/usage? Basically, what I want to know, is of the more popular languages, which ones are meant for high level application development, low level system development, mobile development, web, etc. If there's a good listing out there already, I'm not finding it so far. Does anyone know of a place that would have this? Thanks.

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