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• CodeIgniter based e-shop, shipping and gift address design problem

  - by alexander

  While building an ecommerce platform I have run into design problems. I'm working with the built-in CodeIgniter's cart class. It stores all the cart information in session. Let say that cart has already been filled with products and user clicks checkout. When should I store order in database? Just after that click or after several steps of gathering information and stoing it in session? How to deal with additional features like different shipping methods? Should I add it to the basket first and get additional (gift address) to session? I dont want to store it in database because of the relation between gift address and order is needed and since I dont know what's the ID of the order. I'm puzzled :) Additionally I think its crucial to keep cart aware of shipping methods and additional bought services (by selecting gift address there is an extra fee) because the cart content is just like an reciept? In brief, what is the best practice to process checkout?

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• Reference for good Android UI design patterns.

  - by sat

  Hi, I would like to get some links for getting started with design patterns.My requirement is , (at Initial stage) How to go about developing a particular pattern , say customized ListView which can be shared across applications . e.g. Applications will call something like drawCustomizedListView(params...) and my code will draw the listview according to the parameters supplied. This is particularly useful when across the applications I have to draw customized views. My intention is, I should not repeat the same code everywhere for doing similar task. Any references for the above requirement ?

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• Best design for generating code from an AST?

  - by Sam Washburn

  I'm working on a pretty complex DSL that I want to compile down into a few high level languages. The whole process has been a learning experience. The compiler is written in java. I was wondering if anyone knew a best practice for the design of the code generator portion. I currently have everything parsed into an abstract syntax tree. I was thinking of using a template system, but I haven't researched that direction too far yet as I would like to hear some wisdom first from stack overflow. Thanks!

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• Error Messaged and Error Code design

  - by Ved

  We are designing set of web services which will return XML string in response. These are RESTFul services so I will have to send exception inside element. I am planing to design set of Error code which can help me determine where level occured just by looking at the code. For Example 1000 - Application Level 2000 - DB level 3000 - Network level so if I have error message then I can know right away that this was an application level error and it came from 1st business module. I am not very experience in this so I would love to here your thoughts and criticism. Thanks

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• Java appliction design question

  - by ring bearer

  Hi I have a hobby project, which is basically to maintain 'todo' tasks in the way I like. One task can be described as: public class TodoItem { private String subject; private Date dueBy; private Date startBy; private Priority priority; private String category; private Status status; private String notes; } as you can imagine I would have 1000 todo items at a given time. What is the best strategy to store a todo item? (currently on an XML file) such that all the items are loaded quickly up on app start up(the application shows kind of a dashboard of all the items at start up) What is the best way to design its back-end so that it can be ported to android/or a J2ME based phone Currently this is done using java swing. What should be the concerns so that it works efficiently on a device where memory is limited? Thanks!

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• How do I design a cryptographic hash function?

  - by Eyal

  After reading the following about why one-way hash functions are one-way, I would like to know how to design a hash function. http://stackoverflow.com/questions/1038307/help-me-better-understand-cryptographic-hash-functions/1047106#1047106 Before everyone gets on my case: Yes, I know that it's a bad idea to not use a proven and tested hash function. I would still like to know how it's done. I'm familiar with Feistel-network ciphers but those are necessarily reversible, horrible for a cryptographic hash. Is there some sort of construction that is well-used in cryptographic hashing? Something that makes it very one-way?

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• Is this a correct Interlocked synchronization design?

  - by Dan Bryant

  I have a system that takes Samples. I have multiple client threads in the application that are interested in these Samples, but the actual process of taking a Sample can only occur in one context. It's fast enough that it's okay for it to block the calling process until Sampling is done, but slow enough that I don't want multiple threads piling up requests. I came up with this design (stripped down to minimal details): public class Sample { private static Sample _lastSample; private static int _isSampling; public static Sample TakeSample(AutomationManager automation) { //Only start sampling if not already sampling in some other context if (Interlocked.CompareExchange(ref _isSampling, 0, 1) == 0) { try { Sample sample = new Sample(); sample.PerformSampling(automation); _lastSample = sample; } finally { //We're done sampling _isSampling = 0; } } return _lastSample; } private void PerformSampling(AutomationManager automation) { //Lots of stuff going on that shouldn't be run in more than one context at the same time } } Is this safe for use in the scenario I described?

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• Advice Needed To Normalise Database

  - by c11ada

  hey all, im trying to create a database for a feedback application in ASP.net i have the following database design. Username (PK) QuestionNo (PK) QuestionText FeedbackNo (PK) Username UserFeedbackNo (PK) FeedbackNo (FK) QuestionNo (FK) Answer Comment a user has a unique username a user can have multiple feedbacks i was wondering if the database design i have here is normalised and suitable for the application

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• Future proof Primary Key design in postgresql

  - by John P

  I've always used either auto_generated or Sequences in the past for my primary keys. With the current system I'm working on there is the possibility of having to eventually partition the data which has never been a requirement in the past. Knowing that I may need to partition the data in the future, is there any advantage of using UUIDs for PKs instead of the database's built-in sequences? If so, is there a design pattern that can safely generate relatively short keys (say 6 characters instead of the usual long one e6709870-5cbc-11df-a08a-0800200c9a66)? 36^6 keys per-table is more than sufficient for any table I could imagine. I will be using the keys in URLs so conciseness is important.

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• Is a base class with shared fields and functions good design

  - by eych

  I've got a BaseDataClass with shared fields and functions Protected Shared dbase as SqlDatabase Protected Shared dbCommand as DBCommand ... //also have a sync object used by the derived classes for Synclock'ing Protected Shared ReadOnly syncObj As Object = New Object() Protected Shared Sub Init() //initializes fields, sets connections Protected Shared Sub CleanAll() //closes connections, disposes, etc. I have several classes that derive from this base class. The derived classes have all Shared functions that can be called directly from the BLL with no instantiation. The functions in these derived classes call the base Init(), call their specific stored procs, call the base CleanAll() and then return the results. So if I have 5 derived classes with 10 functions each, totaling 50 possible function calls, since they are all Shared, the CLR only calls one at a time, right? All calls are queued to wait until each Shared function completes. Is there a better design with having Shared functions in your DAL and still have base class functions? Or since I have a base class, is it better to move towards instance methods within the DAL?

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• Value object or not for 3d points ?

  - by Stefano Borini

  I need to develop a geometry library in python, describing points, lines and planes in 3d space, and various geometry operations. Related to my previous question. The main issue in the design is if these entities should have identity or not. I was wondering if there's a similar library out there (developed in another language) to take inspiration from, what is the chosen design, and in particular the reason for one choice vs. the other.

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• A series of simple Aggregate Root questions (Domain Driven Design)

  - by Robert

  I have a few (hopefully) simple questions about aggregate roots in domain driven design: Is it okay to have an aggregate root as a property of another aggregate root? Is it okay to have a given entity inside two or more aggregate roots? My final question is a bit more involved. I have a website that has a few entities that really belong to a "website" aggregate root. They are 'News', 'Products', and 'Users'. There isn't a 'Website' table in the database, but a 'Website' seems like a good aggregate root for these three entities. How is this usually achieved? Thanks!

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• What are possible designs for the DCI architecture?

  - by Gabriel Šcerbák

  What are possibles designs for implementation of the DCI (data, contexts, interactions) architecture in different OOP languages? I thought of Policy based design (Andrei Alexandrescu) for C++, DI and AOP for Java. However, I also thought about using State design pattern for representing roles and some sort of Template method for the interactions... What are the other possibilities?

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• any practices ,samples for ERD?

  - by just_name

  Q: I wanna any web sites , any books just for training on ERD and normalization ,, i wanna a lot of samples ,practices,and case studies with recommended answers, to strength myself in database design.and avoid the poor data base design i made . note:i don't need books to explain the concepts , what i need is practices ,examples,case studies with recommended answers. Thanks in advance.

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• Set both Text and Value property of ComboBox in design time

  - by The King

  I need to add the following items to a combo box. Value DisplayText Mpost Posted Call Calling RScan Re-Scan These items are fairly static, and is not retrieved from any database... Hence thought of assigning these in design time itself. I'm Unable to use Items property as it asks only one value per item... Could you please help. Ps : In case you are suggesting BindingSource, could you please give me an example. I was not able to find one.

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• Design an api using rails and change the forgot password functionality

  - by ragupathi

  I have been using rails for developing web applications and now i need to do design an api for iphone application and since i used respond to json it also produces json but i use devise for authentication in my web application and when i send email and password along with the api it gives out {"user":{"authentication_token":"Lsusyd27ewgasga63","email":"[email protected]"}} and there is forgot password functionality in the iphone app but in the web application when clicking on forgot password button it sends an email to the users email, whereby the user has to go to his mail and click on the link sent and it will take to the change password path and after changing it the user will be login but in this iphone app i want to send the password to the user mail and the user can use that password and login. How can i do this? Also do i have to create new controllers for api or the web application controller is enough if it respond as json? please help me.

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• NoSQL vs. MySQL when scalability is irrelevant

  - by Bryan Ward

  Recently I have read a lot about different NoSQL databases and how they are being effectively deployed by some major websites out there. I'm starting a project in which I think the schema-free nature of a database such as MongoDB would be tremendously useful. Everything I have read though seems to indicate that the main advantage of a NoSQL database is scalability. Is choosing a NoSQL database for the schema-free design just as legitimate a design decision as that of scalability?

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• Form.cs not being updated by changes to Form.cs[Design]

  - by Kevin

  I am new to Visual Studio and I am just messing around with the controls to see how things work. I made one form that had a single button that, when pushed, simply printed "Hello World" to the screen. To try something more complicated I deleted that button and added various other tools to the Form. However the code in the Form.cs file was not updated to reflect these changes to the design and I can find no way to update it manually. Any advice is appreciated. Regards.

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• Find the right parameters for an event without using Design Mode in Visual Studio 2010

  - by Jason

  Is there a way to know what parameters are needed by an event in Visual Studio 2010? Let's say I have a DropDownList control and I want to bind a method to the "OnSelectedIndexChanged", I would do something like this In the ASPX File: <asp:DropDownList ID="lstMyList" runat="server" OnSelectedIndexChanged="lstMyList_SelectedIndexChanged"></asp:DropDownList> In the codebehind: protected void lstMyList_SelectedIndexChanged(object sender, EventArgs e) { ... } Is there a way to know what parameters the method needs? (In this case, an object for the sender and an EventArgs parameter for the event.) I know you can easily create the method by double-clicking the right event in Design Mode, but it does a mess with your code so I prefer not to use it. Thanks!

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• Design interoperable web services

  - by Zyd

  Hi everyone, I'm designing a set of web services to allow our clients to connect from their apps to one of our systems. Our clients have their apps developed in all varieties of frameworks (.NET, Java, PHP, Python and even the occasional all JS app), so obviously WS is the way to go. Investigating a little about truly interop WS I've found that the way to go is to design first the WSDL and XSD and derive the implementations from there. What i'm really looking for is guidance if this is really the way to go. I've read that WCF creates interoperable WS but i'm not a fan of MS creating something standard. Should i use WCF or there is a good set of tools for designing WSDL and XSD without the pain i'm expecting. Thanks in advance

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• How to design this simple database?

  - by Vafello

  I have 2 tables - one storing user information (id, username, password) and the second one storing information about events (id, name, description, date, username(represents the user who created the event)). I would like to implement 'favourite events' functionality. This would allow the user to store his favourite events and later display them in a list. I am not sure how to implement this in terms of design. I need a simple solution. Something like storing the IDs of favourite events in a field in the user table. I am using mysql and php. Can anyone point me to the right direction?

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• Django design question: extending User to make users that can't log in

  - by jobrahms

  The site I'm working on involves teachers creating student objects. The teacher can choose to make it possible for a student to log into the site (to check calendars, etc) OR the teacher can choose to use the student object only for record keeping and not allow the student to log in. In the student creation form, if the teacher supplies a username and a password, it should create an object of the first kind - one that can log in, i.e. a regular User object. If the teacher does not supply a username/password, it should create the second type. The other requirement is that the teacher should be able to go in later and change a non-logging-in student to the other kind. What's the best way to design for this scenario? Subclass User and make username and password not required? What else would this affect?

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• JavaScript Library Design

  - by JSMan2034

  I have a general question about the design of JavaScript Libraries. I am trying to consolidate common methods into one js file so they can be reused by different scripts. I have taken a look at how the JSON library is structured and believe it was a good approach. JSON for Javascript. So they start off creating an instance of the class: if (!this.JSON) { this.JSON = {}; } Then they do this: (function () { if (typeof JSON.stringify !== 'function') { JSON.stringify = function (value, replacer, space) { This is works perfect if you just want to do JSON.[function_name], but what if I want to have a more structured library such that I want: JSON.[subgroup].[function]. How would I structure my JS library in such a way? Any links to resources are greatly appreciated, thanks.

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• How to design WCF Contracts?

  - by Amitabh

  We are designing a WCF layer which can be invoked either by a Asp.Net or a WinForm application. Our Application contains too many Entities. If we design WCF Contract around these entities then we get too many Contracts e.g IPartyService, IUserService, IPaymentService etc. So, I may end up with 30-40 Contracts? Is it a good idea or should we go for one huge contracts with around 100 operations? What are the pros and cons of each approach or is there a better way.

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• How can I display a full designer file in c#?

  - by George Tyler

  So I just got a C# program from someone that compiles and gives me a fully functional application. However, when I want to see the .cs{Design] file it gives me the following error: .ErrorStyle { font-family: tahoma; font-size: 11 pt; .... How can I convert this to an actual Design file? I am working on Visual Studio C#. Thank you very much.

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