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  • Database access through collections

    - by Mike
    Hi All, I have an 3 tiered application where I need to get database results and populated the UI. I have a MessagesCollection class that deals with messages. I load my user from the database. On the instantiation of a user (ie. new User()), a MessageCollection Messages = new MessageCollection(this) is performed. Message collection accepts a user as a parameter. User user = user.LoadUser("bob"); I want to get the messages for Bob. user.Messages.GetUnreadMessages(); GetUnreadMessages calls my Business Data provider which in turn calls the data access layer. The Business data provider returns List. My question is - I am not sure what the best practice is here - If I have a collection of messages in an array inside the MessagesCollection class, I could implement ICollection to provide GetEnumerator() and ability to traverse the messages. But what happens if the messages change and the the user has old messages loaded? What about big message collections? What if my user had 10,000 unread messages? I don't think accessing the database and returning 10,000 Message objects would be efficient.

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  • IList<Item> Collection Class accessing database

    - by Mike
    Hi, I have a database with Users. Users have Items. These Items can change actively. How do you access the items in a collection type format? For the user, I fill all the user properties at the time of instantiation. If I load the user's items at the time of the instantiation, and the items change, they will have old data. I was thinking, maybe I need an ItemCollection class and have that a field/property apart of the user class, that way to traverse all the user's items I could use a foreach loop. So, my question is, what is the best practice/best way of accessing the items from a database using some sort of collection? On accessing the particular Item, it needs to get the latest database information, and when the user does do a foreach loop, the latest item information must be available. I.e. What I'm trying to do Console.WriteLine(User.Items[3].ID); returns 5. //this updates the item information and saves it to the database. User.Items[3].ID = 13; //Add a new item to the database. User.Items.Add(new Item { id = 17}); foreach (Item item in User.Items) { //this would traverse all items in the database. //not some cached copy at the time of instantiation of the user. }

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  • Star-schema: Separate dimensions for clients and non-clients or shared dimension for attendants?

    - by celopes
    I'm new to modeling star schemas, fresh from reading the Data Warehouse Toolkit. I have a business process that has clients and non-clients calling into conference calls with some of our employees. My fact table, call it "Audience", will contain a measure of how long an attending person was connected to the call, and the cost per minute of this person's connection to the call. The grain is "individual connection to the conference call". Should I use my conformed Client dimension and create a non-client dimension (for the callers that are not yet clients) this way (omitting dimensions that are not part of this questions): Or would it be OK/better to have a non-conformed Attending dimension related to the conformed Client dimension in this manner: Or is there a better/standard mechanism to model business processes like this one?

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  • Is it a good idea to cache data from web services into a database?

    - by Thierry Lam
    Let's assume that Stackoverflow offers web services where you can retrieve all the questions asked by a specific user. A request to get all question from user A can result in the following json output: { { "question": "What is rest?", "date_created": "20/02/2010", "votes": 1, }, { "question": "Which database to use for ...", "date_created": "20/07/2009", "votes": 5, }, } If I want to manipulate and present the data in any ways that I want, will it be wise to dump it in a local database? At some point, I will also want to retrieve all answers for each question and store them in a local database. The workflow that I'm thinking is: User logs in. Web services retrieve all questions asked by the logged in user, dump them in a local database. User wants all answers for a specific question, another web service does the retrieval and dump them in a local database. After user logs out, delete from the local database all questions and answers from that user.

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  • MYSQL Event to update another database table

    - by Lee
    Hey All, I have just taken over a project for a client and the database schema is in a total mess. I would like to rename a load of fields make it a relationship database. But doing this will be a painstaking process as they have an API running of it also. So the idea would be to create a new database and start re-writing the code to use this instead. But I need a way to keep these tables in sync during this process. Would you agree that I should use MYSQL EVENT's to keep updating the new table on Inserts / updates & deletes?? Or can you suggest a better way?? Hope you can advise !! thanks for any input I get

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  • In .NET, Why Can I Access Private Members of a Class Instance within the Class?

    - by AMissico
    While cleaning some code today written by someone else, I changed the access modifier from Public to Private on a class variable/member/field. I expected a long list of compiler errors that I use to "refactor/rework/review" the code that used this variable. Imagine my surprise when I didn't get any errors. After reviewing, it turns out that another instance of the Class can access the private members of another instance declared within the Class. Totally unexcepted. Is this normal? I been coding in .NET since the beginning and never ran into this issue, nor read about it. I may have stumbled onto it before, but only "vaguely noticed" and move on. Can anyone explain this behavoir to me? I would like to know the "why" I can do this. Please explain, don't just tell me the rule. Am I doing something wrong? I found this behavior in both C# and VB.NET. The code seems to take advantage of the ability to access private variables. Sincerely, Totally Confused Class Jack Private _int As Integer End Class Class Foo Public Property Value() As Integer Get Return _int End Get Set(ByVal value As Integer) _int = value * 2 End Set End Property Private _int As Integer Private _foo As Foo Private _jack As Jack Private _fred As Fred Public Sub SetPrivate() _foo = New Foo _foo.Value = 4 'what you would expect to do because _int is private _foo._int = 3 'TOTALLY UNEXPECTED _jack = New Jack '_jack._int = 3 'expected compile error _fred = New Fred '_fred._int = 3 'expected compile error End Sub Private Class Fred Private _int As Integer End Class End Class

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  • Images not responsive although in responsive container

    - by Darren Sweeney
    I have the following: <div id="hp_imgs"> <img src="/images/hp/1.jpg"> <img src="/images/hp/2.jpg"> <img src="/images/hp/3.jpg"> <img src="/images/hp/4.jpg"> <img src="/images/hp/5.jpg"> <img src="/images/hp/6.jpg"> <img src="/images/hp/7.jpg"> <img src="/images/hp/8.jpg"> </div> The images were sized when created to form a grid of sorts, so need to be in the order where they are. Consequently, when/if the page is resized I want the images to resize and stay where they are. Here's what I'm trying but images are simply staying the same size and not resizing: #hp_imgs { width:66%; float:left; } #hp_imgs img { float:left; margin:2px; border-radius:4px; display: block; max-width:100%; height:100%; } Is there a better/different way to achieve this? FIDDLE Here's a sample to play with: Fiddle

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  • How to fluent-map this (using fluent nhibernate)?

    - by vikasde
    I have two tables in my database "Styles" and "BannedStyles". They have a reference via the ItemNo. Now styles can be banned per store. So if style x is banned at store Y then its very possible that its not banned at store Z or vice verse. What is the best way now to map this to a single entity? Should I be mapping this to a single entity? My Style entity looks like this: public class Style { public virtual int ItemNo { get; set;} public virtual string SKU { get; set; } public virtual string StyleName { get; set; } public virtual string Description { get; set; } public virtual Store Store { get; set; } public virtual bool IsEntireStyleBanned { get; set; } }

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  • How to apply Single Responsibility Principle to a service class

    - by Shekhar
    Hello Suppose we are designing a UserServiceImpl class which does CRUD(Create, Read, Update, and Delete) operations. In my view Create, Read, Update, and Delete are four reasons for a class to change. Does this class violates Single Responsibility Principle? If it violates, then should we have four classes like CreateUserServiceImpl, ReadUserServiceImpl, UpdateUserServiceImpl, and DeleteUserServiceImpl. Isn't it an overkill to have lots of classes? Thanks Shekhar

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  • Communication between modules

    - by David Elentok
    I have an application that consists from the following three modules: Search (to search for objects) List (to display the search results) Painter (to allow me to edit objects) - this module isn't always loaded (Each object is a figure that I can edit in the painter). When I open an object in the painter it's added to the objects that are already in the painter and I can move it and alter it. I'm using an object similar to the EventAggregator to communicate between the modules. For example, to show the search results I publish a "ShowList" event that is caught by the List module (I'm not sure this is the best way to do this, if anyone has better idea please comment...). One of the features of the search module requires it to get the selected object in the painter (if the painter is available), and I'm not sure what would be the best way to do that... I thought of these solutions: Whenever the selected object in the painter changes it will publish a "PainterSelectedObjectChanged" event which will be caught by the search module and stored for later use. When the selected object is needed by the search module it will publish a "RequestingPainterSelectedObject" event which will be caught by the painter module. The painter module will then set the "SelectedObject" property in the EventArgs object, and when the publish is complete and we're back in the search module we will have the painter's selected object in the EventArgs object. What do you think? what is the right way to do this?

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  • Writing fortran robust and "modern" code

    - by Blklight
    In some scientific environments, you often cannot go without FORTRAN as most of the developers only know that idiom, and there is lot of legacy code and related experience. And frankly, there are not many other cross-platform options for high performance programming ( C++ would do the task, but the syntax, zero-starting arrays, and pointers are too much for most engineers ;-) ). I'm a C++ guy but I'm stuck with some F90 projects. So, let's assume a new project must use FORTRAN (F90), but I want to build the most modern software architecture out of it. while being compatible with most "recent" compilers (intel ifort, but also including sun/HP/IBM own compilers) So I'm thinking of imposing: global variable forbidden, no gotos, no jump labels, "implicit none", etc. "object-oriented programming" (modules with datatypes + related subroutines) modular/reusable functions, well documented, reusable libraries assertions/preconditions/invariants (implemented using preprocessor statements) unit tests for all (most) subroutines and "objects" an intense "debug mode" (#ifdef DEBUG) with more checks and all possible Intel compiler checks possible (array bounds, subroutine interfaces, etc.) uniform and enforced legible coding style, using code processing tools C stubs/wrappers for libpthread, libDL (and eventually GPU kernels, etc.) C/C++ implementation of utility functions (strings, file operations, sockets, memory alloc/dealloc reference counting for debug mode, etc.) ( This may all seem "evident" modern programming assumptions, but in a legacy fortran world, most of these are big changes in the typical programmer workflow ) The goal with all that is to have trustworthy, maintainable and modular code. Whereas, in typical fortran, modularity is often not a primary goal, and code is trustworthy only if the original developer was very clever, and the code was not changed since then ! (i'm a bit joking here, but not much) I searched around for references about object-oriented fortran, programming-by-contract (assertions/preconditions/etc.), and found only ugly and outdated documents, syntaxes and papers done by people with no large-scale project involvement, and dead projects. Any good URL, advice, reference paper/books on the subject?

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  • Best solution for a comment table for multiple content types

    - by KRTac
    I'm currently designing a comments table for a site I'm building. Users will be able to upload images, link videos and add audio files to the profile. Each of these types of content must be commentable. Now I'm wondering what's the best approach to this. My current options are: 1. to have one big comments table and a link tables for every content type (comments_videos, ...) with comment_id and _id. 2. to have comments separated by the type of content their for. So each type of content would have his own comments table with the comments for that type.

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  • Database Table of Boolean Values

    - by guazz
    What's the best method of storing a large number of booleans in a database table? Should I create a column for each boolean value or is there a more optimal method? Employee Table IsHardWorking IsEfficient IsCrazy IsOverworked IsUnderpaid ...etc.

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  • Advantage of using a static member function instead of an equivalent non-static member function?

    - by jonathanasdf
    I was wondering whether there's any advantages to using a static member function when there is a non-static equivalent. Will it result in faster execution (because of not having to care about all of the member variables), or maybe less use of memory (because of not being included in all instances)? Basically, the function I'm looking at is an utility function to rotate an integer array representing pixel colours an arbitrary number of degrees around an arbitrary centre point. It is placed in my abstract Bullet base class, since only the bullets will be using it and I didn't want the overhead of calling it in some utility class. It's a bit too long and used in every single derived bullet class, making it probably not a good idea to inline. How would you suggest I define this function? As a static member function of Bullet, of a non-static member function of Bullet, or maybe not as a member of Bullet but defined outside of the class in Bullet.h? What are the advantages and disadvantages of each?

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  • Should a developer be a designer?

    - by nepb
    I have been developing websites for quite some time and I am not so good in designing websites? My Boss is refering me to take some lessons on it. But I really want to stick to development rather than designing?

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  • How to make this OO?

    - by John
    Hello, Sorry for the poor title,I'm new to OOP so I don't know what is the term for what I need to do. I have, say, 10 different Objects that inherit one Object.They have different amount and type of class members,but all of them have one property in common - Visible. type TObj1=class(TObject) private a:integer; ...(More members) Visible:Boolean; end; TObj2=class(TObject) private b:String; ...(More members) Visible:Boolean; end; ...(Other 8 objects) For each of them I have a variable. var Obj1:TObj1; Obj2:TObj2; Obj3:TObj3; ....(Other 7 objects) Rule 1: Only one object can be initialized at a time(others have to be freed) to be visible. For this rule I have a global variable var CurrentVisibleObj:TObject; //Because they all inherit TObject Finally there is a procedure that changes visibility. procedure ChangeObjVisibility(newObj:TObject); begin CurrentVisibleObj.Free; //Free the old object CurrentVisibleObj:=newObj; //assign the new object CurrentVisibleObj:= ??? //Create new object CurrentVisibleObj.Visible:=true; //Set visibility to new object end; There is my problem,I don't know how to initialize it,because the derived class is unknown. How do I do this? I simplified the explanation,in the project there are TFrames each having different controls and I have to set visible/not visible the same way(By leaving only one frame initialized). Sorry again for the title,I'm very new to OOP.

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  • Multiple Tables or Multiple Schema

    - by Yan Cheng CHEOK
    http://stackoverflow.com/questions/1152405/postgresql-is-better-using-multiple-databases-with-1-schema-each-or-1-database I am new in schema concept for PostgreSQL. For the above mentioned scenario, I was wondering Why don't we use a single database (with default schema named public) Why don't we have a single table, to store multiple users row? Other tables which hold users related information, with foreign key point to the user table. Can anyone provide me a real case scenario, which single database, multiple schema will be extremely useful, and can't solve by conventional single database, single schema.

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  • How to build a web site which gives a sub-domain dynamically to every registered user?

    - by coderex
    Suppose i have a site and i wish to give a sub-domain for each registered users. like my site http://site.com/ and the test-user is a user registered on my site and site want to make sub-domain for that user. Like http://test-user.site.com Like http://test-user1.site.com for test-user1. Hop you understood the requirement. How can i create a sub-domain using my sites back-end. or dynamically while register

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  • many-to-many query

    - by kofto4ka
    Hello, guys! I have a problem and I dont know what is better solution. Okay, I have 2 tables: posts(id, title), posts_tags(post_id, tag_id). I have next task: must select posts with tags ids for example 4, 10 and 11. Not exactly, post could have any other tags at the same time. So, how I could do it more optimized? Creating temporary table in each query? Or may be some kind of stored procedure? In the future, user could ask script to select posts with any count of tags (it could be 1 tag only or 10 at the same time) and I must be sure that method that I will choose would be the best method for my problem. Sorry for my english, thx for attention.

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  • algorithm || method to write prog

    - by fatai
    I am one of the computer science student. My wonder is everyone solve problem with different or same method, but actually I dont know whether they use method or I dont know whether there are such common method to approach problem. All teacher give us problem which in simple form sometimes, but they dont introduce any approach or method(s) so that we can first choose method then apply that one to problem , afterward find solution then write code. I have found one method when I failed the course, More accurately, When I counter problem in language , I will get more paper and then ; first, input/ output step ; my prog will take this / these there argument(s) and return namely X , ex : in c, input length is not known and at same type , so I must use pointer desired output is in form of package , so use structure second, execution part ; in that step , I am writing all step which are goes to final output ex : in python ; 1.) [ + , [- , 4 , [ * , 1 , 2 ]], 5] 2.) [ + , [- , 4 , 2 ],5 ] 3.) [ + , 2 , 5] 4.) 7 ==> return 7 third, I will write test code ex : in c++ input : append 3 4 5 6 vector_x remove 0 1 desired output vector_x holds : 5 6 But now, I wonder other method ; used to construct class :::: for c++ , python, java used to communicate classes / computers used for solving embedded system problem ::::: for c Why I wonder , because I learn if you dont costruct algorithm on paper, you may achieve your goal. Like no money no lunch , I can say no algorithm no prog therefore , feel free when you write your own method , a way which is introduced by someone else but you are using and you find it is so efficient

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  • How do I correctly model data in SQL-based databases that have some columns in common, but also have

    - by Brandon Weiss
    For instance, let's say I have a User model. Users have things like logins, passwords, e-mail addresses, avatars, etc. But there are two types of Users that will be using this site, let's say Parents and Businesses. I need to store some different information for the Parents (e.g. childrens' names, domestic partner, salaries, etc.) than for the Businesses (e.g. industry, number of employees, etc.), but also some of it is the same, like logins and passwords. How do I correctly structure this in a SQL-based database? Thanks!

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  • Structuring Win32 GUI code

    - by kraf
    I wish to improve my code and file structure in larger Win32 projects with plenty of windows and controls. Currently, I tend to have one header and one source file for the entire implementation of a window or dialog. This works fine for small projects, but now it has come to the point where these implementations are starting to reach 1000-2000 lines, which is tedious to browse. A typical source file of mine looks like this: static LRESULT CALLBACK on_create(const HWND hwnd, WPARAM wp, LPARAM lp) { setup_menu(hwnd); setup_list(hwnd); setup_context_menu(hwnd); /* clip */ return 0; } static LRESULT CALLBACK on_notify(HWND hwnd, UINT msg, WPARAM wp, LPARAM lp) { const NMHDR* header = (const NMHDR*)lp; /* At this point I feel that the control's event handlers doesn't * necessarily belong in the same source file. Perhaps I could move * each control's creation code and event handlers into a separate * source file? Good practice or cause of confusion? */ switch (header->idFrom) { case IDC_WINDOW_LIST: switch (header->code) { case NM_RCLICK: return on_window_list_right_click(hwnd, wp, lp); /* clip */ } } } static LRESULT CALLBACK wndmain_proc(HWND hwnd, UINT msg, WPARAM wp, LPARAM lp) { switch (msg) { case WM_CREATE: return on_create(hwnd, wp, lp); case WM_CLOSE: return on_close(hwnd, wp, lp); case WM_NOTIFY: return on_notify(hwnd, wp, lp); /* It doesn't matter much how the window proc looks as it just forwards * events to the appropriate handler. */ /* clip */ default: return DefWindowProc(hwnd, msg, wp, lp); } } But now as the window has a lot more controls, and these controls in turn have their own message handlers, and then there's the menu click handlers, and so on... I'm getting lost, and I really need advice on how to structure this mess up in a good and sensible way. I have tried to find good open source examples of structuring Win32 code, but I just get more confused since there are hundreds of files, and within each of these files that seem GUI related, the Win32 GUI code seems so far encapsulated away. And when I finally find a CreateWindowEx statement, the window proc is nowhere to be found. Any advice on how to structure all the code while remaining sane would be greatly appreciated. Thanks! I don't wish to use any libraries or frameworks as I find the Win32 API interesting and valuable for learning. Any insight into how you structure your own GUI code could perhaps serve as inspiration.

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