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  • Which design pattern should I be using?

    - by Gabriel
    Here's briefly what I'm trying to do. The user supplies me with a link to a photo from one of several photo-sharing websites (such as Flickr, Zooomr, et. al). I then do some processing on the photo using their respective APIs. Right now, I'm only implementing one service, but I will most likely add more in the near future. I don't want to have a bunch of if/else or switch statements to define the logic for the different websites (but maybe that's necessary?) I'd rather just call GetImage(url) and have it get me the image from whatever service the url's domain is from. I'm confused how the GetImage function and classes should be designed. Maybe I need the strategy pattern? I'm still reading and trying to understand the various design patterns and how I could make one fit in this case. I'm doing this in C#, but this question is language-agnostic.

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  • Parent child class relationship design pattern

    - by Jeremy
    I have a class which has a list of child items. Is there a design pattern I can copy that I can apply to these classes so that I can access the parent instance from the child, and it enforces rules such as not being able to add the child to multiple parents, etc?

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  • Initialization of components with interdependencies - possible antipattern?

    - by Rosarch
    I'm writing a game that has many components. Many of these are dependent upon one another. When creating them, I often get into catch-22 situations like "WorldState's constructor requires a PathPlanner, but PathPlanner's constructor requires WorldState." Originally, this was less of a problem, because references to everything needed were kept around in GameEngine, and GameEngine was passed around to everything. But I didn't like the feel of that, because it felt like we were giving too much access to different components, making it harder to enforce boundaries. Here is the problematic code: /// <summary> /// Constructor to create a new instance of our game. /// </summary> public GameEngine() { graphics = new GraphicsDeviceManager(this); Components.Add(new GamerServicesComponent(this)); //Sets dimensions of the game window graphics.PreferredBackBufferWidth = 800; graphics.PreferredBackBufferHeight = 600; graphics.ApplyChanges(); IsMouseVisible = true; screenManager = new ScreenManager(this); //Adds ScreenManager as a component, making all of its calls done automatically Components.Add(screenManager); // Tell the program to load all files relative to the "Content" directory. Assets = new CachedContentLoader(this, "Content"); inputReader = new UserInputReader(Constants.DEFAULT_KEY_MAPPING); collisionRecorder = new CollisionRecorder(); WorldState = new WorldState(new ReadWriteXML(), Constants.CONFIG_URI, this, contactReporter); worldQueryUtils = new WorldQueryUtils(worldQuery, WorldState.PhysicsWorld); ContactReporter contactReporter = new ContactReporter(collisionRecorder, worldQuery, worldQueryUtils); gameObjectManager = new GameObjectManager(WorldState, assets, inputReader, pathPlanner); worldQuery = new DefaultWorldQueryEngine(collisionRecorder, gameObjectManager.Controllers); gameObjectManager.WorldQueryEngine = worldQuery; pathPlanner = new PathPlanner(this, worldQueryUtils, WorldQuery); gameObjectManager.PathPlanner = pathPlanner; combatEngine = new CombatEngine(worldQuery, new Random()); } Here is an excerpt of the above that's problematic: gameObjectManager = new GameObjectManager(WorldState, assets, inputReader, pathPlanner); worldQuery = new DefaultWorldQueryEngine(collisionRecorder, gameObjectManager.Controllers); gameObjectManager.WorldQueryEngine = worldQuery; I hope that no one ever forgets that setting of gameObjectManager.WorldQueryEngine, or else it will fail. Here is the problem: gameObjectManager needs a WorldQuery, and WorldQuery needs a property of gameObjectManager. What can I do about this? Have I found an anti-pattern?

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  • C# unusual inheritance syntax w/ generics

    - by anon
    I happened upon this in an NHibernate class definition: public class SQLiteConfiguration : PersistenceConfiguration<SQLiteConfiguration> So this class inherits from a base class that is parameterized by... the derived class?   My head just exploded. Can someone explain what this means and how this pattern is useful? (This is NOT an NHibernate-specific question, by the way.)

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  • Looking for design help

    - by jess
    I have this scenario in most of the WindowsForms having grids I have a sequence of code which is similar - AddNewRow(in grid),CreateNewEntity,notifyUser,few other steps Now, I want to use a template kind of pattern.But,my issue is with CreateEntity method since sometimes it is passed a parameter which is different depending on the type of object being created.Should I make createentity accept an "object" type,and cast when the parameter is to be used.What other way can I tackle this design issue? Also,CreateEntity returns the object being created.

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  • How to use a 3rd party control inside the viewmodel?

    - by Sander
    I have a 3rd party control which among other things performs loading of some data. I want my viewmodel to keep track of this load operation and adjust its own state accordingly. If it were up to me, I'd do the data loading far away from the view, but it is not. So, I seem to be in the situation where my viewmodel depends on my view. How do I best handle this? I feel rather dirty making the view publish events to the viewmodel but I don't see any other reasonable way to get this info into the viewmodel. A similar situation might crop up with standard controls, too - imagine if your viewmodel depends on the events coming from a MediaElement - how do you properly model this? Do you put the MediaElement into the viewmodel? That doesn't sound right. If publishing the events to the viewmodel is indeed the most reasonable way, is there some common pattern used for this? How do you do it?

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  • Design pattern to encapsulate common funtionality among UI controls

    - by Dan
    I'm brainstorming some ideas around a pattern to use for the following scenario. I have some 3rd party controls that I want to add common functionality to. Functionality is added by handling several of the the events and doing certain things when the events fire along with adding some private variables to hold some state info between events. I want to reuse the code and functionality so this is what I'd typically do. Create a class for this functionality and pass in the instance of the control that I want to add the functionality to in the constructor. Then I can add event handlers to the control in the instance of the class. Can anyone think of alternative patterns to use in order to create this kind of reusable functionality.

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  • Design pattern to separate messages from actual process.

    - by Manish Gupta
    I am having a C# application to sync data between PC and palm devices. There are codes written like below: showMessage("synchronizing Table1"); Sync(destTable1,sourceTable1); Sync(destTable2,sourceTable2); showMessage("synchronizing Table2"); // more code How do I separate the actual process of synchronizing from displaying message? Which design pattern to follow? Thanks in advance...

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  • Design pattern for data entry forms with LINQ2SQL

    - by petebob796
    I am about to start a new winforms data entry application, it already has the database designed which I am comfortable with. I was going to use LINQ2SQL to access the tables to keep things type safe but am now wondering about design patterns, something I am just getting into. Since LINQ is giving me objects to use should I still create classes in between to hold the validation code and helper methods or should these just go in with the UI? It just seems I will end up with classes sat in between with little code which will cause the UI classes to have code just getting and setting values in the intermediate class and returning from validation to flag errors... Any good reading on this? Should I consider the entity framework (or similar) instead?

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  • How to see "anti if" movement and its gaol?

    - by Vijay Shanker
    I have a developer for last 3 years, have been using if-else or if-else if statements a lot in my programing habit. And today, I found This link. One obvious sample i put here public void doSomthing(String target, String object){ //validate requests if(target != null && target.trim().length() < 1){ //invalid request; } //further logic } Now, I have seen this sort of check all over the places, libraries. So, I wanted to have a discussion about the worthiness of such a movement. Please let me know your views.

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  • I'd want a method to be called only by objects of a specific class

    - by mp
    Suppose you have this class: public class A { private int number; public setNumber(int n){ number = n; } } I'd like the method setNumber could be called only by objects of a specific class. Does it make sense? I know it is not possible, is it? Which are the design alternatives? Some well known design pattern? Sorry for the silly question, but I'm a bit rusty in OO design.

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  • How to make 2 incompatible types, but with the same members, interchangeable?

    - by Quigrim
    Yesterday 2 of the guys on our team came to me with an uncommon problem. We are using a third-party component in one of our winforms applications. All the code has already been written against it. They then wanted to incorporate another third-party component, by the same vender, into our application. To their delight they found that the second component had the exact same public members as the first. But to their dismay, the 2 components have completely separate inheritance hierarchies, and implement no common interfaces. Makes you wonder... Well, makes me wonder. An example of the problem: public class ThirdPartyClass1 { public string Name { get { return "ThirdPartyClass1"; } } public void DoThirdPartyStuff () { Console.WriteLine ("ThirdPartyClass1 is doing its thing."); } } public class ThirdPartyClass2 { public string Name { get { return "ThirdPartyClass2"; } } public void DoThirdPartyStuff () { Console.WriteLine ("ThirdPartyClass2 is doing its thing."); } } Gladly they felt copying and pasting the code they wrote for the first component was not the correct answer. So they were thinking of assigning the component instant into an object reference and then modifying the code to do conditional casts after checking what type it was. But that is arguably even uglier than the copy and paste approach. So they then asked me if I can write some reflection code to access the properties and call the methods off the two different object types since we know what they are, and they are exactly the same. But my first thought was that there goes the elegance. I figure there has to be a better, graceful solution to this problem.

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  • My User control belonging to which Design Pattern??

    - by prashant
    Hello, I am creating a reusable component in C#.net. For that i have started a Control Library project and added a Control. Class MyControl : Control{} My user control just displays some images which will be used in many Windows Applications. Can you please tell me which design pattern i am using here. I am unable to decide which pattern they belongs. Thanks

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  • Does this pattern have a name?

    - by LK7jb
    Disclaimer: I'm trying to learn proper OO programming/design, so I'm pretty new to this stuff. I guess this is a general design patterns question, but I'll base my example on a game engine or something that renders objects to the display. Consider the following: How can this sort of separation between physical objects (e.g., cubes, spheres, etc.) and the rendering mechanism be achieved in an extensible manner? This design is not set in stone, and perhaps I've got something wrong from the start. I'm just curious as to how a problem like this is solved in real world code.

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  • Quick and Good: ( Requirement -> Validation -> Design ) for self use?

    - by Yugal Jindle
    How to casually do the required Software Engineering and designing? I am an inexperienced developer and face the following problem: My company is a start up and has no fix Software engineering systems. I am assigned tasks with not very clear and conflicting requirements. I don't have to follow any designs or verify requirements officially. Problem: I code all day and finally get stuck where requirement conflicts and I have to start over again. I can-not spend a lot of time doing proper SRS or SDD. How should I: List out Requirements for myself. (Not an official document) How to verify and validate the requirements? How to visualize them? How to design them with minimum effort? (As its going to be with me only) I don't want to waste my time coding something that's gonna collapse according to requirement conflict or something! I don't want to compromise with quality but don't want to re-write everything on some change that I didn't expected. I imagine making a diagram for my thought process that will show me conflict in the diagram itself, then finally correcting the diagram - I decide my design and structure my code in terms of interfaces or something. And then finally start implementing my design. I am able to sense the lack of systematic approach, but don't know how to proceed! Update: Please suggest me some tools that can ask me the questions and help me aggregate important details. How can I have diagram that I talked about for requirement verification?

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  • Windows Phone 7 Design using Expression Blend - Resources

    - by Nikita Polyakov
    I’ve been doing a series of talks across Florida regarding Windows Phone 7 Design using Microsoft Expression Blend 4. I discuss the WP7 phone and application experience; show how to use Expression Blend toolset to effectively design such apps. Next presentation is on 5/4/2010 at 6:30PM EST will be a webcast format over LiveMeeting at Ft. Lauderdale Online group. Registration and the LiveMeeting link are both here: http://www.fladotnet.com/Reg.aspx?EventID=459 [I will post a link if it’s recorded]   Here are the resources from my presentations: The Biggest source is the Windows Phone UI and Design Language video from MIX10 Windows Phone 7 Design Guide as it’s found on the WP7 Dev Home Page Study The Silverlight Mobile Tutorials on official Silverlight website I will be blogging a separate entry for a new demo app that will showcase the elements I presented. I suggest you actually watch all of the MIX videos about SL and Design as great primer to get you thinking the WP7 way.   A lot happening with WP7Dev and it’s just the beginning! So watch these Twitter accounts and blogs: @Ckindel - Charlie Kindel - WP7 Dev Head http://blogs.msdn.com/ckindel @WP7Dev - Official Dev Twitter @WP7 - Official WP7 Twitter Peter Torr - http://blogs.msdn.com/ptorr Mike Harsh - http://blogs.msdn.com/mharsh Shawn Oster - http://www.shawnoster.com   Other worthwhile mention my local friends speaking and blogging about Windows Phone 7: Bill Reiss is doing great presentations on Building games with XNA for Windows Phone 7. Be on the lookout for those around Florida. Bill is a Silverlight MVP and has a legacy of XNA and Silverlight games, see his site. Kevin Wolf aka ByteMaster he is a Device Application Developer MVP with tremendous experience building mobile applications. He has developed WinMo-GF a multi-platform gaming framework. Get these tools and get creating! You will need the following components installed in this order: Expression Blend 4 Beta Windows Phone Developer Tools Microsoft Expression Blend Add-in Preview for Windows Phone Microsoft Expression Blend SDK Preview for Windows Phone Want more training? Don’t forget that Channel 9 has complete walkthroughs of their WP7 Training Kit posted online. PS: To continue with all this design talk check out Microsoft .toolbox “Learn to create Silverlight applications using Expression Studio and to apply fundamental design principles.” A great website with a lot of design tutorials set up as a wonderful full course on design all for free, including a great forum community and neat little avatars you can build yourself.

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  • JavaScript Class Patterns

    - by Liam McLennan
    To write object-oriented programs we need objects, and likely lots of them. JavaScript makes it easy to create objects: var liam = { name: "Liam", age: Number.MAX_VALUE }; But JavaScript does not provide an easy way to create similar objects. Most object-oriented languages include the idea of a class, which is a template for creating objects of the same type. From one class many similar objects can be instantiated. Many patterns have been proposed to address the absence of a class concept in JavaScript. This post will compare and contrast the most significant of them. Simple Constructor Functions Classes may be missing but JavaScript does support special constructor functions. By prefixing a call to a constructor function with the ‘new’ keyword we can tell the JavaScript runtime that we want the function to behave like a constructor and instantiate a new object containing the members defined by that function. Within a constructor function the ‘this’ keyword references the new object being created -  so a basic constructor function might be: function Person(name, age) { this.name = name; this.age = age; this.toString = function() { return this.name + " is " + age + " years old."; }; } var john = new Person("John Galt", 50); console.log(john.toString()); Note that by convention the name of a constructor function is always written in Pascal Case (the first letter of each word is capital). This is to distinguish between constructor functions and other functions. It is important that constructor functions be called with the ‘new’ keyword and that not constructor functions are not. There are two problems with the pattern constructor function pattern shown above: It makes inheritance difficult The toString() function is redefined for each new object created by the Person constructor. This is sub-optimal because the function should be shared between all of the instances of the Person type. Constructor Functions with a Prototype JavaScript functions have a special property called prototype. When an object is created by calling a JavaScript constructor all of the properties of the constructor’s prototype become available to the new object. In this way many Person objects can be created that can access the same prototype. An improved version of the above example can be written: function Person(name, age) { this.name = name; this.age = age; } Person.prototype = { toString: function() { return this.name + " is " + this.age + " years old."; } }; var john = new Person("John Galt", 50); console.log(john.toString()); In this version a single instance of the toString() function will now be shared between all Person objects. Private Members The short version is: there aren’t any. If a variable is defined, with the var keyword, within the constructor function then its scope is that function. Other functions defined within the constructor function will be able to access the private variable, but anything defined outside the constructor (such as functions on the prototype property) won’t have access to the private variable. Any variables defined on the constructor are automatically public. Some people solve this problem by prefixing properties with an underscore and then not calling those properties by convention. function Person(name, age) { this.name = name; this.age = age; } Person.prototype = { _getName: function() { return this.name; }, toString: function() { return this._getName() + " is " + this.age + " years old."; } }; var john = new Person("John Galt", 50); console.log(john.toString()); Note that the _getName() function is only private by convention – it is in fact a public function. Functional Object Construction Because of the weirdness involved in using constructor functions some JavaScript developers prefer to eschew them completely. They theorize that it is better to work with JavaScript’s functional nature than to try and force it to behave like a traditional class-oriented language. When using the functional approach objects are created by returning them from a factory function. An excellent side effect of this pattern is that variables defined with the factory function are accessible to the new object (due to closure) but are inaccessible from anywhere else. The Person example implemented using the functional object construction pattern is: var personFactory = function(name, age) { var privateVar = 7; return { toString: function() { return name + " is " + age * privateVar / privateVar + " years old."; } }; }; var john2 = personFactory("John Lennon", 40); console.log(john2.toString()); Note that the ‘new’ keyword is not used for this pattern, and that the toString() function has access to the name, age and privateVar variables because of closure. This pattern can be extended to provide inheritance and, unlike the constructor function pattern, it supports private variables. However, when working with JavaScript code bases you will find that the constructor function is more common – probably because it is a better approximation of mainstream class oriented languages like C# and Java. Inheritance Both of the above patterns can support inheritance but for now, favour composition over inheritance. Summary When JavaScript code exceeds simple browser automation object orientation can provide a powerful paradigm for controlling complexity. Both of the patterns presented in this article work – the choice is a matter of style. Only one question still remains; who is John Galt?

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  • JavaScript Class Patterns

    - by Liam McLennan
    To write object-oriented programs we need objects, and likely lots of them. JavaScript makes it easy to create objects: var liam = { name: "Liam", age: Number.MAX_VALUE }; But JavaScript does not provide an easy way to create similar objects. Most object-oriented languages include the idea of a class, which is a template for creating objects of the same type. From one class many similar objects can be instantiated. Many patterns have been proposed to address the absence of a class concept in JavaScript. This post will compare and contrast the most significant of them. Simple Constructor Functions Classes may be missing but JavaScript does support special constructor functions. By prefixing a call to a constructor function with the ‘new’ keyword we can tell the JavaScript runtime that we want the function to behave like a constructor and instantiate a new object containing the members defined by that function. Within a constructor function the ‘this’ keyword references the new object being created -  so a basic constructor function might be: function Person(name, age) { this.name = name; this.age = age; this.toString = function() { return this.name + " is " + age + " years old."; }; } var john = new Person("John Galt", 50); console.log(john.toString()); Note that by convention the name of a constructor function is always written in Pascal Case (the first letter of each word is capital). This is to distinguish between constructor functions and other functions. It is important that constructor functions be called with the ‘new’ keyword and that not constructor functions are not. There are two problems with the pattern constructor function pattern shown above: It makes inheritance difficult The toString() function is redefined for each new object created by the Person constructor. This is sub-optimal because the function should be shared between all of the instances of the Person type. Constructor Functions with a Prototype JavaScript functions have a special property called prototype. When an object is created by calling a JavaScript constructor all of the properties of the constructor’s prototype become available to the new object. In this way many Person objects can be created that can access the same prototype. An improved version of the above example can be written: function Person(name, age) { this.name = name; this.age = age; } Person.prototype = { toString: function() { return this.name + " is " + this.age + " years old."; } }; var john = new Person("John Galt", 50); console.log(john.toString()); In this version a single instance of the toString() function will now be shared between all Person objects. Private Members The short version is: there aren’t any. If a variable is defined, with the var keyword, within the constructor function then its scope is that function. Other functions defined within the constructor function will be able to access the private variable, but anything defined outside the constructor (such as functions on the prototype property) won’t have access to the private variable. Any variables defined on the constructor are automatically public. Some people solve this problem by prefixing properties with an underscore and then not calling those properties by convention. function Person(name, age) { this.name = name; this.age = age; } Person.prototype = { _getName: function() { return this.name; }, toString: function() { return this._getName() + " is " + this.age + " years old."; } }; var john = new Person("John Galt", 50); console.log(john.toString()); Note that the _getName() function is only private by convention – it is in fact a public function. Functional Object Construction Because of the weirdness involved in using constructor functions some JavaScript developers prefer to eschew them completely. They theorize that it is better to work with JavaScript’s functional nature than to try and force it to behave like a traditional class-oriented language. When using the functional approach objects are created by returning them from a factory function. An excellent side effect of this pattern is that variables defined with the factory function are accessible to the new object (due to closure) but are inaccessible from anywhere else. The Person example implemented using the functional object construction pattern is: var john = new Person("John Galt", 50); console.log(john.toString()); var personFactory = function(name, age) { var privateVar = 7; return { toString: function() { return name + " is " + age * privateVar / privateVar + " years old."; } }; }; var john2 = personFactory("John Lennon", 40); console.log(john2.toString()); Note that the ‘new’ keyword is not used for this pattern, and that the toString() function has access to the name, age and privateVar variables because of closure. This pattern can be extended to provide inheritance and, unlike the constructor function pattern, it supports private variables. However, when working with JavaScript code bases you will find that the constructor function is more common – probably because it is a better approximation of mainstream class oriented languages like C# and Java. Inheritance Both of the above patterns can support inheritance but for now, favour composition over inheritance. Summary When JavaScript code exceeds simple browser automation object orientation can provide a powerful paradigm for controlling complexity. Both of the patterns presented in this article work – the choice is a matter of style. Only one question still remains; who is John Galt?

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  • Design a T-shirt for .NET Reflector Pro

    - by Laila
    Win a .NET Reflector Pro license, a box of Red Gate goodies, and a t-shirt printed with your design! Red Gate likes t-shirts. Each of our teams has one. In fact, each individual person has one, numbered according to when they joined the company: Red Gate's 1st, 2nd, and so on right up to Red Gate's 170th, with the slogan "More than just a number". Those t-shirts are important, chiefly because they remind the people wearing them that they are important. But that isn't enough. What really makes us great are the people who choose to use our tools. So we'd like to extend our tradition of t-shirts to include you and put the design of our next shirt entirely in your hands. We'd like you to come up with a witty slogan or create an inventive or simply beautiful t-shirt design for .NET Reflector Pro, our add-in for Visual Studio, which allows you to step into decompiled assemblies whilst debugging in Visual Studio. When you're done, post your masterpiece to Twitter with the hash tag #reflectortees, and @redgate will take a look! We'll pick the best design, and the winner will get a licensed copy of .NET Reflector Pro and a box of Red Gate goodies - not to mention a copy of their t-shirt. The winning design will go into production and be worn and given out at tradeshows, conferences, and user group events across the world, proudly bearing the name of their designer. We'll also pick three runners-up who will receive licenses for .NET Reflector Pro. Red Gate goodie box Interested? If you're up for the challenge, then we've got some resources to get you started. Inside the .zip file you'll find high-quality versions of the following: T-shirt templates: don't forget to design the front and the back! Different versions of the .NET Reflector Pro logo and Red Gate logo. Colour sheets to give you an easy reference to the Red Gate colours, including hex and RGB values. You can create and send us as many designs as you like, and each of them will be considered for the prize. To submit your designs, simply tweet including the competition hash tag, #reflectortees, and a link to somewhere we can see your design: either an image hosting site such as Twitpic, Flickr or Picasa, or a personal blog. You will need to create a Twitter account (which is free), if you don't already have one. You only have three limits: The background colour of the t-shirt should be one of our brand colours (red, light/dark grey or black), though you're welcome to use other colours in the rest of the design. You need to make use of either the .NET Reflector Pro logo OR the Red Gate logo (please keep them as they are) If you include any text or slogan, stick with just one or two colors for it. Apart from that, go wild. Go and do whatever it is you do when you get creative: whether you walk barefoot on the grass with a pencil and paper, sit cross-legged on a pile of cushions with a laptop, or simply close your eyes and float through a mist of ideas, now is your chance. Make sure you enjoy it. We're looking forward to seeing your creations. Terms and conditions 1. The closing date for entries is June 11th, 2010 (4 p.m. UK time). Red Gate Software Ltd reserves the right to extend the competition deadline at its discretion. If there is a revision, the revised date will be published on this blog and the date for announcing the results will be postponed accordingly. 2. The winning designer will be notified on June 14th, 2010 through Twitter. The winner must claim his/her prize by sending us a high-resolution image of their design via email (i.e. Illustrator EPS files or appropriate format, ideally at 300dpi). If the winner does not come forward within 3 days of the announcement, they will forfeit their prize and another winner will be selected from the runners-up. The names of the winner and runners-up will be posted on this blog by June 18th.  3. Entry is completed on the designer posting a link to their entry in a tweet with the correct hash tag, #reflectortees. 4. Red Gate Software needs to hold the rights to using the winning design in order to put the t-shirt into production. We will make sure that this is fine with the winner before we do so, but if you do not want us holding the rights to your design, please do not submit your designs. We reserve the right to slightly alter or adjust any artwork we decide to use (mainly to make it easier to print), but we will make sure we contact the winner for approval first. The winner will also need to allow us the use of his/her name for purposes of promoting your design. 5. Entries must be entirely your own original work and must not breach any copyright or third party rights. Red Gate Software Ltd will not be made partially or fully liable for any non-original work submitted by you. 6. This competition is free: you do not need to buy anything or be an existing customer to enter. 7. This competition is not open to employees of Red Gate Software Ltd, their families, or any other company directly connected with the administration of this promotion.

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  • Appropriate programming design questions.

    - by Edward
    I have a few questions on good programming design. I'm going to first describe the project I'm building so you are better equipped to help me out. I am coding a Remote Assistance Tool similar to TeamViewer, Microsoft Remote Desktop, CrossLoop. It will incorporate concepts like UDP networking (using Lidgren networking library), NAT traversal (since many computers are invisible behind routers nowadays), Mirror Drivers (using DFMirage's Mirror Driver (http://www.demoforge.com/dfmirage.htm) for realtime screen grabbing on the remote computer). That being said, this program has a concept of being a client-server architecture, but I made only one program with both the functionality of client and server. That way, when the user runs my program, they can switch between giving assistance and receiving assistance without having to download a separate client or server module. I have a Windows Form that allows the user to choose between giving assistance and receiving assistance. I have another Windows Form for a file explorer module. I have another Windows Form for a chat module. I have another Windows Form form for a registry editor module. I have another Windows Form for the live control module. So I've got a Form for each module, which raises the first question: 1. Should I process module-specific commands inside the code of the respective Windows Form? Meaning, let's say I get a command with some data that enumerates the remote user's files for a specific directory. Obviously, I would have to update this on the File Explorer Windows Form and add the entries to the ListView. Should I be processing this code inside the Windows Form though? Or should I be handling this in another class (although I have to eventually pass the data to the Form to draw, of course). Or is it like a hybrid in which I process most of the data in another class and pass the final result to the Form to draw? So I've got like 5-6 forms, one for each module. The user starts up my program, enters the remote machine's ID (not IP, ID, because we are registering with an intermediary server to enable NAT traversal), their password, and connects. Now let's suppose the connection is successful. Then the user is presented with a form with all the different modules. So he can open up a File Explorer, or he can mess with the Registry Editor, or he can choose to Chat with his buddy. So now the program is sort of idle, just waiting for the user to do something. If the user opens up Live Control, then the program will be spending most of it's time receiving packets from the remote machine and drawing them to the form to provide a 'live' view. 2. Second design question. A spin off question #1. How would I pass module-specific commands to their respective Windows Forms? What I mean is, I have a class like "NetworkHandler.cs" that checks for messages from the remote machine. NetworkHandler.cs is a static class globally accessible. So let's say I get a command that enumerates the remote user's files for a specific directory. How would I "give" that command to the File Explorer Form. I was thinking of making an OnCommandReceivedEvent inside NetworkHandler, and having each form register to that event. When the NetworkHandler received a command, it would raise the event, all forms would check it to see if it was relevant, and the appropriate form would take action. Is this an appropriate/the best solution available? 3. The networking library I'm using, Lidgren, provides two options for checking networking messages. One can either poll ReadMessage() to return null or a message, or one can use an AutoResetEvent OnMessageReceived (I'm guessing this is like an event). Which one is more appropriate?

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  • Magento Onepage Success Conversion Tracking Design Pattern

    - by user1734954
    My intent is to track conversions through multiple channels by inserting third party javascript (for example google analytics, optimizely, pricegrabber etc.) into the footer of onepage success . I've accomplished this by adding a block to the footer reference inside of the checkout success node within local.xml and everything works appropriately. My questions are more about efficiency and extensibility. It occurred to me that it would be better to combine all of the blocks into a single block reference and then use a various methods acting on a single call to the various related models to provide the data needed for insertion into the javascript for each of the conversion tracking scripts. Some examples of the common data that conversion tracking may rely on(pseudo): Order ID , Order Total, Order.LineItem.Name(foreach) and so on Currently for each of the scripts I've made a call to the appropriate model passing the customers last order id as the load value and the calling a get() assigning the return value to a variable and then iterating through the data to match the values with the expectations of the given third party service. All of the data should be pulled once when checkout is complete each third party services may expect different data in different formats Here is an example of one of the conversion tracking template files which loads at the footer of checkout success. $order = Mage::getModel('sales/order')->loadByIncrementId(Mage::getSingleton('checkout/session')->getLastRealOrderId()); $amount = number_format($order->getGrandTotal(),2); $customer = Mage::helper('customer')->getCustomer()->getData(); ?> <script type="text/javascript"> popup_email = '<?php echo($customer['email']);?>'; popup_order_number = '<?php echo $this->getOrderId() ?>'; </script> <!-- PriceGrabber Merchant Evaluation Code --> <script type="text/javascript" charset="UTF-8" src="https://www.pricegrabber.com/rating_merchrevpopjs.php?retid=<something>"></script> <noscript><a href="http://www.pricegrabber.com/rating_merchrev.php?retid=<something>" target=_blank> <img src="https://images.pricegrabber.com/images/mr_noprize.jpg" border="0" width="272" height="238" alt="Merchant Evaluation"></a></noscript> <!-- End PriceGrabber Code --> Having just a single piece of code like this is not that big of a deal, but we are doing similar things with a number of different third party services. Pricegrabber is one of the simpler examples. A more sophisticated tracking service expects a comma separated list of all of the product names, ids, prices, categories , order id etc. I would like to make it all more manageable so my idea to do the following: combine all of the template files into a single file Develop a helper class or library to deliver the data to the conversion template Goals Include Extensibility Minimal Model Calls Minimal Method Calls The Questions 1. Is a Mage helper the best route to take? 2. Is there any design pattern you may recommend for the "helper" class? 3. Why would this the design pattern you've chosen be best for this instance?

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  • C# Static constructors design problem - need to specify parameter

    - by Neil Dobson
    I have a re-occurring design problem with certain classes which require one-off initialization with a parameter such as the name of an external resource such as a config file. For example, I have a corelib project which provides application-wide logging, configuration and general helper methods. This object could use a static constructor to initialize itself but it need access to a config file which it can't find itself. I can see a couple of solutions, but both of these don't seem quite right: 1) Use a constructor with a parameter. But then each object which requires corelib functionality should also know the name of the config file, so this has to be passed around the application. Also if I implemented corelib as a singleton I would also have to pass the config file as a parameter to the GetInstance method, which I believe is also not right. 2) Create a static property or method to pass through the config file or other external parameter. I have sort of used the latter method and created a Load method which initializes an inner class which it passes through the config file in the constructor. Then this inner class is exposed through a public property MyCoreLib. public static class CoreLib { private static MyCoreLib myCoreLib; public static void Load(string configFile) { myCoreLib = new MyCoreLib(configFile); } public static MyCoreLib MyCoreLib { get { return myCoreLib; } } public class MyCoreLib { private string configFile; public MyCoreLib(string configFile) { this.configFile = configFile; } public void DoSomething() { } } } I'm still not happy though. The inner class is not initialized until you call the load method, so that needs to be considered anywhere the MyCoreLib is accessed. Also there is nothing to stop someone calling the load method again. Any other patterns or ideas how to accomplish this?

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  • Design pattern to use instead of multiple inheritance

    - by mizipzor
    Coming from a C++ background, Im used to multiple inheritance. I like the feeling of a shotgun squarely aimed at my foot. Nowadays, I work more in C# and Java, where you can only inherit one baseclass but implement any number of interfaces (did I get the terminology right?). For example, lets consider two classes that implement a common interface but different (yet required) baseclasses: public class TypeA : CustomButtonUserControl, IMagician { public void DoMagic() { // ... } } public class TypeB : CustomTextUserControl, IMagician { public void DoMagic() { // ... } } Both classes are UserControls so I cant substitute the base class. Both needs to implement the DoMagic function. My problem now is that both implementations of the function are identical. And I hate copy-and-paste code. The (possible) solutions: I naturally want TypeA and TypeB to share a common baseclass, where I can write that identical function definition just once. However, due to having the limit of just one baseclass, I cant find a place along the hierarchy where it fits. One could also try to implement a sort of composite pattern. Putting the DoMagic function in a separate helper class, but the function here needs (and modifies) quite a lot of internal variables/fields. Sending them all as (reference) parameters would just look bad. My gut tells me that the adapter pattern could have a place here, some class to convert between the two when necessery. But it also feels hacky. I tagged this with language-agnostic since it applies to all languages that use this one-baseclass-many-interfaces approach. Also, please point out if I seem to have misunderstood any of the patterns I named. In C++ I would just make a class with the private fields, that function implementation and put it in the inheritance list. Whats the proper approach in C#/Java and the like?

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