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  • abstract method signature, inheritance, and "Do" naming convention

    - by T. Webster
    I'm learning about design patterns and in examples of code I've seen a convention where the abstract class declares a method, for example: public abstract class ServiceBase { ... public virtual object GetSomething(); and then protected abstract object DoGetSomething(); My question is on why these two methods exist, since they appear to serve the same purpose. Is this so that the base class GetSomething() method logic cannot be overridden by inherited classes? But then again, the method is marked virtual, so it can be overridden anyway. What is the usefulness here in requiring derived class implementers to implement the abstract method when the virtual method can be called anyway?

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  • How useful are design patterns when it comes to web programming?

    - by Raja
    Background: My organization uses Microsoft .Net (3.5) with SQL Server 2005 as back end. With RAD being the norm and Agile being the widely used process. I have always found using design patterns difficult since it involves a bit more understanding and bit more training. Can you give me some examples where design patterns have solved real time problems in Web programming? What is the criteria for using any design pattern? What is the benefit reaped from it. I know it is a general question but this would help me a bunch.

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  • Free GUI-like web design tool for Java?

    - by Peter C.
    Our company needs to build web solution and we're somewhat short on time. We use Java and do not have a design yet. We're looking for some tools/plugins for: GUI-like web design (drag and drop components) WYSIWYG The tools must be *free We like GWT but any other UI framework is fine. Plugins for NetBeans or Eclipse would be great. Any ideas?

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  • How to program a connection pool?

    - by the_drow
    Is there a known algorithm for implementing a connection pool? If not what are the known algorithms and what are their trade-offs? What design patterns are common when designing and programming a connection pool? Are there any code examples implement a connection pool using boost.asio? Is it a good idea to use a connection pool for presisting connections (not http)? How is threading related to connection pooling? When do you need a new thread?

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  • Maker/ Checker Design Module

    - by user288198
    i want to design maker/ checker module in my project like if user A add new user so the another User B will approve or reject this adding. i want to know the best practices of design for this module in the database ....... any help

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  • What do you call the concept of dynamic data definition?

    - by DJTripleThreat
    Maybe this is simpler and more straightforward then what I'm thinking but I can't seem to find this concept on google anywhere. The concept is this: You have a table in a database and the table has a specified number of columns. However, it has been asked of me by previous clients that there also be a set of dynamic user defined columns that can be added on the fly. What is this concept called and is it considered a design pattern?

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  • Database design 1 to 1 relationship

    - by Khou
    I design my database incorrectly, should I fix this while its in development? "user" table is suppose to have a 1.1 relationship with "userprofile" table however the actual design the "user" table has a 1.* relationship with "userprofile" table. Everything works! but should it be fixed anyways?

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  • JavaScript Class Patterns &ndash; In CoffeeScript

    - by Liam McLennan
    Recently I wrote about JavaScript class patterns, and in particular, my favourite class pattern that uses closure to provide encapsulation. A class to represent a person, with a name and an age, looks like this: var Person = (function() { // private variables go here var name,age; function constructor(n, a) { name = n; age = a; } constructor.prototype = { toString: function() { return name + " is " + age + " years old."; } }; return constructor; })(); var john = new Person("John Galt", 50); console.log(john.toString()); Today I have been experimenting with coding for node.js in CoffeeScript. One of the first things I wanted to do was to try and implement my class pattern in CoffeeScript and then see how it compared to CoffeeScript’s built-in class keyword. The above Person class, implemented in CoffeeScript, looks like this: # JavaScript style class using closure to provide private methods Person = (() -> [name,age] = [{},{}] constructor = (n, a) -> [name,age] = [n,a] null constructor.prototype = toString: () -> "name is #{name} age is #{age} years old" constructor )() I am satisfied with how this came out, but there are a few nasty bits. To declare the two private variables in javascript is as simple as var name,age; but in CoffeeScript I have to assign a value, hence [name,age] = [{},{}]. The other major issue occurred because of CoffeeScript’s implicit function returns. The last statement in any function is returned, so I had to add null to the end of the constructor to get it to work. The great thing about the technique just presented is that it provides encapsulation ie the name and age variables are not visible outside of the Person class. CoffeeScript classes do not provide encapsulation, but they do provide nicer syntax. The Person class using native CoffeeScript classes is: # CoffeeScript style class using the class keyword class CoffeePerson constructor: (@name, @age) -> toString: () -> "name is #{@name} age is #{@age} years old" felix = new CoffeePerson "Felix Hoenikker", 63 console.log felix.toString() So now I have a trade-off: nice syntax against encapsulation. I think I will experiment with both strategies in my project and see which works out better.

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  • Object oriented n-tier design. Am I abstracting too much? Or not enough?

    - by max
    Hi guys, I'm building my first enterprise grade solution (at least I'm attempting to make it enterprise grade). I'm trying to follow best practice design patterns but am starting to worry that I might be going too far with abstraction. I'm trying to build my asp.net webforms (in C#) app as an n-tier application. I've created a Data Access Layer using an XSD strongly-typed dataset that interfaces with a SQL server backend. I access the DAL through some Business Layer Objects that I've created on a 1:1 basis to the datatables in the dataset (eg, a UsersBLL class for the Users datatable in the dataset). I'm doing checks inside the BLL to make sure that data passed to DAL is following the business rules of the application. That's all well and good. Where I'm getting stuck though is the point at which I connect the BLL to the presentation layer. For example, my UsersBLL class deals mostly with whole datatables, as it's interfacing with the DAL. Should I now create a separate "User" (Singular) class that maps out the properties of a single user, rather than multiple users? This way I don't have to do any searching through datatables in the presentation layer, as I could use the properties created in the User class. Or would it be better to somehow try to handle this inside the UsersBLL? Sorry if this sounds a little complicated... Below is the code from the UsersBLL: using System; using System.Data; using PedChallenge.DAL.PedDataSetTableAdapters; [System.ComponentModel.DataObject] public class UsersBLL { private UsersTableAdapter _UsersAdapter = null; protected UsersTableAdapter Adapter { get { if (_UsersAdapter == null) _UsersAdapter = new UsersTableAdapter(); return _UsersAdapter; } } [System.ComponentModel.DataObjectMethodAttribute (System.ComponentModel.DataObjectMethodType.Select, true)] public PedChallenge.DAL.PedDataSet.UsersDataTable GetUsers() { return Adapter.GetUsers(); } [System.ComponentModel.DataObjectMethodAttribute (System.ComponentModel.DataObjectMethodType.Select, false)] public PedChallenge.DAL.PedDataSet.UsersDataTable GetUserByUserID(int userID) { return Adapter.GetUserByUserID(userID); } [System.ComponentModel.DataObjectMethodAttribute (System.ComponentModel.DataObjectMethodType.Select, false)] public PedChallenge.DAL.PedDataSet.UsersDataTable GetUsersByTeamID(int teamID) { return Adapter.GetUsersByTeamID(teamID); } [System.ComponentModel.DataObjectMethodAttribute (System.ComponentModel.DataObjectMethodType.Select, false)] public PedChallenge.DAL.PedDataSet.UsersDataTable GetUsersByEmail(string Email) { return Adapter.GetUserByEmail(Email); } [System.ComponentModel.DataObjectMethodAttribute (System.ComponentModel.DataObjectMethodType.Insert, true)] public bool AddUser(int? teamID, string FirstName, string LastName, string Email, string Role, int LocationID) { // Create a new UsersRow instance PedChallenge.DAL.PedDataSet.UsersDataTable Users = new PedChallenge.DAL.PedDataSet.UsersDataTable(); PedChallenge.DAL.PedDataSet.UsersRow user = Users.NewUsersRow(); if (UserExists(Users, Email) == true) return false; if (teamID == null) user.SetTeamIDNull(); else user.TeamID = teamID.Value; user.FirstName = FirstName; user.LastName = LastName; user.Email = Email; user.Role = Role; user.LocationID = LocationID; // Add the new user Users.AddUsersRow(user); int rowsAffected = Adapter.Update(Users); // Return true if precisely one row was inserted, // otherwise false return rowsAffected == 1; } [System.ComponentModel.DataObjectMethodAttribute (System.ComponentModel.DataObjectMethodType.Update, true)] public bool UpdateUser(int userID, int? teamID, string FirstName, string LastName, string Email, string Role, int LocationID) { PedChallenge.DAL.PedDataSet.UsersDataTable Users = Adapter.GetUserByUserID(userID); if (Users.Count == 0) // no matching record found, return false return false; PedChallenge.DAL.PedDataSet.UsersRow user = Users[0]; if (teamID == null) user.SetTeamIDNull(); else user.TeamID = teamID.Value; user.FirstName = FirstName; user.LastName = LastName; user.Email = Email; user.Role = Role; user.LocationID = LocationID; // Update the product record int rowsAffected = Adapter.Update(user); // Return true if precisely one row was updated, // otherwise false return rowsAffected == 1; } [System.ComponentModel.DataObjectMethodAttribute (System.ComponentModel.DataObjectMethodType.Delete, true)] public bool DeleteUser(int userID) { int rowsAffected = Adapter.Delete(userID); // Return true if precisely one row was deleted, // otherwise false return rowsAffected == 1; } private bool UserExists(PedChallenge.DAL.PedDataSet.UsersDataTable users, string email) { // Check if user email already exists foreach (PedChallenge.DAL.PedDataSet.UsersRow userRow in users) { if (userRow.Email == email) return true; } return false; } } Some guidance in the right direction would be greatly appreciated!! Thanks all! Max

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  • Software to draw IT-infrastructure

    - by ICTdesk.net
    Hi everybody, I have to design and present the ICT-infrastructure for a startup. Does anybody know a good piece of software for making a good looking layout of the ICT-infrastructure? Until now I have been doing this by hand, but this time I need to present it in a very nice way. What do you use? I prefer software that will run on Ubuntu Linux, but Windows is also fine. Thanks... Marcel

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  • Software Architecture and Design vs Psychology of HCI class

    - by Joey Green
    I have two classes to choose from and I'm wanting to get an opinion from the more experienced game devs which might be better for someone who wants to be an indie game dev. The first is a Software Architecture and Design course and the second is a course titled Psychology of HCI. I've previously have taken a Software Design course that was focused only on design patterns. I've also taken an Introduction to HCI course. Software Architecture and Design Description Topics include software architectures, methodologies, model representations, component-based design ,patterns,frameworks, CASE-based desgins, and case studies. Psychology of HCI Description Exploration of psychological factors that interact with computer interface usablilty. Interface design techniques and usability evaluation methods are emphasized. I know I would find both interesting, but my concern is really which one might be easier to pick up on my own. I know HCI is relevant to game dev, but am un-sure if the topics in the Software Architecture class would be more for big software projects that go beyond the scope of games. Also, I'm not able to take both because the overlap.

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  • Design mode in Visual studio 2010 sp1 beta

    - by anirudha
    in MVC3 razor we found that their is no way to watch the design in Visual studio as well we can see aspx file by going to design mode. their is a little trick to solve this issue first is that if you have Expression web or Vs 2008 then open the file on them how see here in expression web 4 you need to add the extension .cshtml and open them as html as we open other. in Visual studio 2008 you need to add the extension .cshtml and set them open as html. well their is no big trouble if design not worked. but in some case when you need to get this issue solved this need to be work for configuration do this: Expression Web 4 > tools > application options > configure editor > click on new extension icon show in exact left put the cshtml in the window they show you and choose expression web [open as html] after that you can see the design in expression web. by default Expression web not have cshtml as known extension so you need to do that to add them because without it they never handle cshtml file and refer them to Visual studio. after setting this you  EW4 open the cshtml file as html and show you design in design mode. in Visual studio 2008 you can use same trick to solve this issue just follow this step > options > text editors > file extension put cshtml in textbox and set the option html editor from dropdown and click on add and ok this will open your cshtml file as html.

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  • I don't understand how TDD helps me get a good design if I need a design to start testing it

    - by Michael Stum
    I'm trying to wrap my head around TDD, specifically the development part. I've looked at some books, but the ones I found mainly tackle the testing part - the History of NUnit, why testing is good, Red/Green/Refactor and how to create a String Calculator. Good stuff, but that's "just" Unit Testing, not TDD. Specifically, I don't understand how TDD helps me get a good design if I need a Design to start testing it. To illustrate, imagine these 3 requirements: A catalog needs to have a list of products The catalog should remember which products a user viewed Users should be able to search for a product At this points, many books pull a magic rabbit out of a hat and just dive into "Testing the ProductService", but they don't explain how they came to the conclusion that there is a ProductService in the first place. That is the "Development" part in TDD that I'm trying to understand. There needs to be an existing design, but stuff outside of entity-services (that is: There is a Product, so there should be a ProductService) is nowhere to be found (e.g., the second requirement requires me to have some concept of a User, but where would I put the functionality to remind? And is Search a feature of the ProductService or a separate SearchService? How would I know which I should choose?) According to SOLID, I would need a UserService, but if I design a system without TDD, I might end up with a whole bunch of Single-Method Services. Isn't TDD intended to make me discover my design in the first place? I'm a .net developer, but Java resources would also work. I feel that there doesn't seem to be a real sample application or book that deals with a real line of business application. Can someone provide a clear example that illustrates the process of creating a design using TDD?

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  • What are the design principles that promote testable code? (designing testable code vs driving design through tests)

    - by bot
    Most of the projects that I work on consider development and unit testing in isolation which makes writing unit tests at a later instance a nightmare. My objective is to keep testing in mind during the high level and low level design phases itself. I want to know if there are any well defined design principles that promote testable code. One such principle that I have come to understand recently is Dependency Inversion through Dependency injection and Inversion of Control. I have read that there is something known as SOLID. I want to understand if following the SOLID principles indirectly results in code that is easily testable? If not, are there any well-defined design principles that promote testable code? I am aware that there is something known as Test Driven Development. Although, I am more interested in designing code with testing in mind during the design phase itself rather than driving design through tests. I hope this makes sense. One more question related to this topic is whether it's alright to re-factor an existing product/project and make changes to code and design for the purpose of being able to write a unit test case for each module?

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  • Accommodating hierarchical data in SQL Server 2005 database design

    - by Remnant
    Context I am fairly new to database design (=know the basics) and am grappling with how best to design my database for a project I am currently working on. In short, my database will keep a log of which employees have attended certain health and safety courses throughout the year. There are multiple types of course e.g. moving objects, fire safety, hygiene etc. In terms of my database design I need to accommodate the following: Each location can have multiple divisions Each division can have multiple departments Each department can have multiple functions Each function can have multiple job roles Each job role can have different course requirements Also note that the structure at each location may not be the same e.g. the departments within divisions are not the same across locations and the functions within departments may also differ. Edit - updated to better articulate problem Let's assume I am just looking at Location, Division and Department and I have my database as follows: LocationTable DivisionTable DepartmentTable LocationID(PK) DivisionID(PK) DepartmentID(PK) LocationName DivisionName DepartmentName There is a many-to-many relationship between Locations and Divisions and also between Departments and Divisions. Suppose I set up a 'Junction Table' as follows: Location_Division LocationID(FK) DivisionID(FK) Using Location_Division I could easily pull back the Divisions for any Location. However, suppose I want to pull back all departments for a given Division in a given Location. If I set up another 'Junction Table' for Division and Department then I can't see how I would differentiate Division by Location? Division_Department DivisionID(FK) DepartmentID(FK) Location_Division Division_Department LocationID DivisionID DivisionID DepartmentID 1 1 1 1 1 2 1 2 2 1 2 1 2 2 2 2 Do I need to expand the number of columns in my 'Junction Table' e.g. Location_Division_Department LocationID(FK) DivisionID(FK) DepartmentID(FK) Location_Division_Department LocationID DivisionID DepartmentID 1 1 1 1 1 2 1 1 3 2 1 1 2 1 2 2 1 3

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  • Help me with DB design

    - by eugeneK
    Hi, i'm developing text ads system. Some small clone of Google Ads. Here is diagram with common tables. Basically make it short, advertiser can have up to 10 variant of same campaign with different text variations, can geo-target his ads and unique impressions count only for IP that haven't been on certain site for more than 24 hours. Pretty simple but the question is what i lack in here from your experience because later it would much harder to fix design flaws and some of you probably done something alike also many SQL gurus in here so maybe i did over normalized DB or did not normalized as needed ? Second question is. My end goal is to get ads for user from ie. Germany that haven't seen same ad on same site for 24 hours as long as ads fit country of user. Each impression is count same as each click if there is one. I need to get 5 "random" ads based on IP, Country and higher CPC (pay per click). How can i achieve this with current design or maybe to design database the way it would be easy to get ads and show stats for advirtisers... thanks for any help...

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  • When is factory method better than simple factory and vice versa?

    - by Bruce
    Hi all Working my way through the Head First Design Patterns book. I believe I understand the simple factory and the factory method, but I'm having trouble seeing what advantages factory method brings over simple factory. If an object A uses a simple factory to create its B objects, then clients can create it like this: A a = new A(new BFactory()); whereas if an object uses a factory method, a client can create it like this: A a = new ConcreteA(); // ConcreteA contains a method for instantiating the same Bs that the BFactory above creates, with the method hardwired into the subclass of A, ConcreteA. So in the case of the simple factory, clients compose A with a B factory, whereas with the factory method, the client chooses the appropriate subclass for the types of B it wants. There really doesn't seem to be much to choose between them. Either you have to choose which BFactory you want to compose A with, or you have to choose the right subclass of A to give you the Bs. Under what circumstances is one better than the other? Thanks all!

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  • Why does C# not provide the C++ style 'friend' keyword?

    - by Ash
    The C++ friend keyword allows a class A to designate class B as it's friend. This allows Class B to access the private/protected members of class A. I've never read anything as to why this was left out of C# (and VB.NET). Most answers to this earlier StackOverflow question seem to be saying it is a useful part of C++ and there are good reasons to use it. In my experience I'd have to agree. Another question seems to me to be really asking how to do something similar to friend in a C# application. While the answers generally revolve around nested classes, it doesn't seem quite as elegant as using the friend keyword. The original Design Patterns book uses the friend keyword regularly throughout its examples. So in summary, why is friend missing from C#, and what is the "best practice" way (or ways) of simulating it in C#? (By the way, the "internal" keyword is not the same thing, it allows ALL classes within the entire assembly to access internal members, friend allows you to give access to a class to just one other class.)

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  • MYSQL - SImple database design

    - by sequelDesigner
    Hello guys, I would like to develop a system, where user will get the data dynamically(what I mean dynamic is, without reloading pages, using AJAX.. but well, it does not matter much). My situation is like this. I have this table, I called it "player", in this player table, I will store the player information like, player name, level, experience etc. Each player can have different clothes, start from tops(shirts), bottoms, shoes, and hairstyle, and each player can have more than 1 tops, bottoms, shoes etc. What I am hesitated or not very sure about is, how do you normally store the data? My current design is like this: Player Table =========================================================================================== id | name | (others player's info) | wearing | tops | bottoms =========================================================================================== 1 | player1 | | top=1;bottom=2;shoes=5;hair=8 | 1,2,3| 7,2,3 Tops Table ===================== id | name | etc... ===================== 1 | t-shirt | ... I am not sure if this design is good. If you are the database designer, how would you design the database? Or how you will store them? Please advise. Thanks

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  • Combining template method with strategy

    - by Mekswoll
    An assignment in my software engineering class is to design an application which can play different forms a particular game. The game in question is Mancala, some of these games are called Wari or Kalah. These games differ in some aspects but for my question it's only important to know that the games could differ in the following: The way in which the result of a move is handled The way in which the end of the game is determined The way in which the winner is determined The first thing that came to my mind to design this was to use the strategy pattern, I have a variation in algorithms (the actual rules of the game). The design could look like this: I then thought to myself that in the game of Mancala and Wari the way the winner is determined is exactly the same and the code would be duplicated. I don't think this is by definition a violation of the 'one rule, one place' or DRY principle seeing as a change in rules for Mancala wouldn't automatically mean that rule should be changed in Wari as well. Nevertheless from the feedback I got from my professor I got the impression to find a different design. I then came up with this: Each game (Mancala, Wari, Kalah, ...) would just have attribute of the type of each rule's interface, i.e. WinnerDeterminer and if there's a Mancala 2.0 version which is the same as Mancala 1.0 except for how the winner is determined it can just use the Mancala versions. I think the implementation of these rules as a strategy pattern is certainly valid. But the real problem comes when I want to design it further. In reading about the template method pattern I immediately thought it could be applied to this problem. The actions that are done when a user makes a move are always the same, and in the same order, namely: deposit stones in holes (this is the same for all games, so would be implemented in the template method itself) determine the result of the move determine if the game has finished because of the previous move if the game has finished, determine who has won Those three last steps are all in my strategy pattern described above. I'm having a lot of trouble combining these two. One possible solution I found would be to abandon the strategy pattern and do the following: I don't really see the design difference between the strategy pattern and this? But I am certain I need to use a template method (although I was just as sure about having to use a strategy pattern). I also can't determine who would be responsible for creating the TurnTemplate object, whereas with the strategy pattern I feel I have families of objects (the three rules) which I could easily create using an abstract factory pattern. I would then have a MancalaRuleFactory, WariRuleFactory, etc. and they would create the correct instances of the rules and hand me back a RuleSet object. Let's say that I use the strategy + abstract factory pattern and I have a RuleSet object which has algorithms for the three rules in it. The only way I feel I can still use the template method pattern with this is to pass this RuleSet object to my TurnTemplate. The 'problem' that then surfaces is that I would never need my concrete implementations of the TurnTemplate, these classes would become obsolete. In my protected methods in the TurnTemplate I could just call ruleSet.determineWinner(). As a consequence, the TurnTemplate class would no longer be abstract but would have to become concrete, is it then still a template method pattern? To summarize, am I thinking in the right way or am I missing something easy? If I'm on the right track, how do I combine a strategy pattern and a template method pattern? This is part of a homework assignment but I'm not looking to be gifted the answer, I have deliberately been very verbose in my question to show that I have thought about it before coming here to ask a question

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