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• OOP App Architecture: Which layer does a lazy loader sit in?

  - by JW

  I am planning the implemention an Inheritance Mapper pattern for an application component http://martinfowler.com/eaaCatalog/inheritanceMappers.html One feature it needs to have is for a domain object to reference a large list of aggreageted items (10,000 other domain objects) So I need some kind of lazy loading collection to be passed out of the aggregate root domain object to other domain objects. To keep my (php) model scripts organised i am storing them in two folders: MyComponent\ controllers\ models\ domain\ <- domain objects, DDD repository, DDD factory daccess\ <- PoEAA data mappers, SQL queries etc views\ But now I am racking my brains wondering where my lazy loading collection sits. Any suggestions / justifications for putting it in one place over another another? DDD = Domain Driven Design Patterns, Eric Evans - book PoEAA = Patterns of Application Architecture Patterns, Martin Fowler - book

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• Is there such a thing as too many tables?

  - by Stacey

  I've been searching stackoverflow for about an hour now and couldn't find any topics related, so I apologize if this is a duplicate question. My inquery is this. Is there a point at which there are too many tables in a database? Even if the structure is well organized, thought out, and perfectly facilitates the design intent? I have a database that is quickly approaching 40 tables - about 10 main ones, and over 30 ancillary tables (junction tables, 'enumeration' tables, etc). Am I just a bad developer - or should I be trying something different? It seems like so many to me, I'm really afraid at how it will impact the performance of the project. I have done a lot of condensing where possible, grouped similar things where possible, etc. The database is built in MS-SQL 2008.

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• Fitts Law, applying it to touch screens

  - by Caylem

  Been reading a lot into UI design lately and Fitts Law keeps popping up. Now from what i gather its basically the larger an item is, and the closer it is to your cursor, the easier it is to click on. So what about touch screen devices where the input comes from multiple touches or just single touches. What are the fundamentals to take into account considering this? Should it be something like, the hands of the user are on the sides of the device so the buttons should be close to the left and right hand sides of the device? Thanks

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• Sharing [config] data across modules,functions

  - by williamstw

  I have some configuration data in a config file that I read off disk when the app starts. I need to make that configuration data available to other functions/modules in the application. I started down the path of looking into ets/mnesia to store the data on startup to make it shared among all processes, but then my inner voice cautioned me that there must be a more functional, erlang-y way to do this. The only alternate approach I've come up with so far is setting up a module that has an actor loop that reads the data on startup and responds to messages like {Key, From} and responds by From ! {ok,Value}. Then, I gave up and decided to ask... Thanks, --tim

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• receiving data from serialport stops when main form is minimized or moved

  - by Rahul

  Sir, I apologize if this is already covered somewhere. I did a search and find something which I have already implemented. I am developing an application which receives data from a device connected via serialport. I am using SerialPort datareceived event to capture data. I am to display data in text boxes of the main form. Data is received frequently. I used Timer to send command to the device, in response device send some data. Timer interval is 100 ms. In every 100 ms interval some command is sent and correspondingly data is received. I used Invoke function to update the GUI elements like TExtbox, labels etc. Everything is fine. All the elements are updating beautifully. But during receiving data if I make any change in main form like moving form, minimizing, maximizing, or clicking somewhere in the form, then data receiving stops. I couldnot find the reason why its happening ? I also changed the timer interval to 200,300,400,500 but same problem is there. Please tell me why its happening? And possible solution... Thanks In advance.... :)

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• Benefit of outputting JSON as opposed to plain HTML

  - by Franco

  Hey guys, Just wondering which is best here. I want to output data from a table in my DB then put a lot of this data into a html table on the fly on my page. Im working with Java on the server side. Basically I pull the results form the DB and have the raw data..just what next? There is a chance I may want to take data from multiple tables in order to combine it into one table for my site. I retrieve the results of the query from the DB, now do i create a text from it in the form of json which i can parse as json using jquery upon the return of the object to my browser?(kind of a sub question of this question: Is just using a stringbuilder the correct way to make a json object to output?) Or.. Should i build the HTML as a string and output that to the browser instead? Which is better and why? Thanks in advance!

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• how to merge ecommerce transaction data between two databases

  - by yamspog

  We currently run an ecommerce solution for a leisure and travel company. Everytime we have a release, we must bring the ecommerce site down as we update database schema and the data access code. We are using a custom built ORM where each data entity is responsible for their own CRUD operations. This is accomplished by dynamically generating the SQL based on attributes in the data entity. For example, the data entity for an address would be... [tableName="address"] public class address : dataEntity { [column="address1"] public string address1; [column="city"] public string city; } So, if we add a new column to the database, we must update the schema of the database and also update the data entity. As you can expect, the business people are not too happy about this outage as it puts a crimp in their cash-flow. The operations people are not happy as they have to deal with a high-pressure time when database and applications are upgraded. The programmers are upset as they are constantly getting in trouble for the legacy system that they inherited. Do any of you smart people out there have some suggestions?

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• Migrate Data and Schema from MySQL to MSSQL

  - by colithium

  Are there any free solutions for automatically migrating a database from MySQL to MSSQL Server that "just works"? I've been attempting this simple (at least I thought so) task all day now. I've tried: MSSQL Server Management Studio's Import Data feature Create an empty database Tasks - Import Data... .NET Framework Data Provider for Odbc Valid DSN (verified it connects) Copy data from one or more tables or views Check 1 VERY simple table Click Preview Get Error: The preview data could not be retrieved. ADDITIONAL INFORMATION: ERROR [42000] [MySQL][ODBC 5.1 Driver][mysqld-5.1.45-community]You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '"table_name"' at line 1 (myodbc5.dll) A similar error occurs if I go through the rest of the wizard and perform the operation. The failed step is "Setting Source Connection" the error refers to retrieving column information and then lists the above error. It can retrieve column information just fine when I modify column mappings so I really don't know what the issue is. I've also tried getting various MySql tools to output ddl statements that MSSQL understand but haven't succeeded. I've tried with MySQL v5.1.11 to SQL Server 2005 and with MySQL v5.1.45 to SQL Server 2008 (with ODBC drivers 3.51.27.00 and 5.01.06.00 respectively)

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• RAII: Initializing data member in const method

  - by Thomas Matthews

  In RAII, resources are not initialized until they are accessed. However, many access methods are declared constant. I need to call a mutable (non-const) function to initialize a data member. Example: Loading from a data base struct MyClass { int get_value(void) const; private: void load_from_database(void); // Loads the data member from database. int m_value; }; int MyClass :: get_value(void) const { static bool value_initialized(false); if (!value_initialized) { // The compiler complains about this call because // the method is non-const and called from a const // method. load_from_database(); } return m_value; } My primitive solution is to declare the data member as mutable. I would rather not do this, because it suggests that other methods can change the member. How would I cast the load_from_database() statement to get rid of the compiler errors?

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• Select a data template by item type programatically in WPF

  - by Michael Stoll

  Hi all, unfortunately the WPF ToolbarTray does not support binding to a collection of ToolbarViewModels (Correct me, if I'm wrong). Thus I want to create the Toolbars programmatically. So there are two tasks, which I don't know how to do: Select the data template based on the item type. Instantiate the data template as toolbar Both should do the same as WPF does, when we use ItemsControl with an enumerable content and empty template. I used reflector to anaylse what WPF does. Task 1 is done by FrameworkElement.FindTemplateResourceInternal, but this is internal, and I couldn't find any public methods to acomplish the task. Of course one could enumerate all resources and match the data template data type property, but this seems sub-optimal. Who know's how to acomplish these tasks?

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• Validate data before uploading through SSIS

  - by The King

  I have a SSIS package to upload data from Excel file into an Sql Server 2005 table. The excel file will have varied lines of data ranging from 20k - 30k lines. The upload works fine, when all the data are correct. But obviously fails when there is a small problem even in a single row. Examples like mandatory values presented null, inconvertable values (data type mismatch) etc. I want to validate the excel file before the upload and want to tell the user which row and column has got the error... Any idea as to how to accomplish this, without consuming much time and resources. Thanks

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• Storing header and data sections in a CSV file

  - by morpheous

  This should be relatively easy to do, but after several hours straight programming my mind seems a bit frazzled and could do with some help. I have a C++ class which I am currently using to store read/write data to file. I was initially using binary data, but have decided to store the data as CSV in order to let programs written in other languages be able to load the data. The C++ class looks a bit like this: class BinaryData { public: BinaryData(); void serialize(std::ostream& output) const; void deserialize(std::istream& input); private: Header m_hdr; std::vector<Row> m_rows; }; I am simply rewriting the serialize/deserialize methods to write to a CSV file. I am not sure on the "best" way to store a header section and a "data" section in a "flat" CSV file though - any suggestions on the most sensible way to do this?

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• What's the proper way of importing option lists into an Android app?

  - by Scott

  I have been storing option lists for my Android app in a cloud table. For example, categories like "historical fiction","biography","science fiction", etc. I see the following pros and cons: Pro: I can make changes to the list without sending an app update to Google Play Not normalized - I can use the text in my other data tables instead of a reference ID Con: App needs to take time to download from the web each time (or at least check for changes) English only I believe the "proper" way to do this is the use the XML resource files. But I need to make sure the selection references correctly with my data. That is, my app needs to understand that "Poetry" and "Poesía" are the same thing. Is the correct thing to do: Forget about it since I'll never get to the point where I'm translating my app anyway Use a string-array and use the index (0...x) to know what the selection is Use a 2-dimensional string-array with a reference ID in the first column and the text in the second?

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• SQL query to retrieve financial year data grouped by the year

  - by mlevit

  Hi, I have a database with lets assume two columns (service_date & invoice_amount). I would like to create an SQL query that would retrieve and group the data for each financial year (July to June). I have two years of data so that is two financial years (i.e. 2 results). I know I can do this manually by creating an SQL query to group by month then run the data through PHP to create the financial year data but I'd rather have an SQL query. All ideas welcome. Thanks

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• Insert a Join Statement - (Insert Data to Multiple Tables) - C#/SQL/T-SQL/.NET

  - by peace

  I have a Winform that has fields need to be filled by a user. All the fields doesn't belong to one table, the data will go to Customer table and CustomerPhone table, so i decided to do multiple inserts. I will insert appropriate data to CustomerPhone first then Insert the rest data to Customer table. Is it possible to Join an Insert OR Insert a Join? If show me a rough sample, i will be grateful. Many Thanks

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• What do you do before starting on a project?

  - by hahuang65

  I'm still a pretty new project, and I haven't really worked on any large projects yet. However a few projects for school has shown me something I have never really thought of before. Pre-Project planning. One project we ran into a huge problem at the very last minute, and the other project was not divided up between partners very evenly, such that all the work was actually done at the end. So my question to everyone here is: How do you plan out the project beforehand? Please try to cover the following: Design (draw out UI by hand, UMLs, etc.) Division of Labor Timeline (especially how you estimate how much time is needed for certain things) and anything else you can think of. Thanks for all the help!

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• Designing constructors around type erasure in Java

  - by Internet Friend

  Yesterday, I was designing a Java class which I wanted to be initalized with Lists of various generic types: TheClass(List<String> list) { ... } TheClass(List<OtherType> list) { ... } This will not compile, as the constructors have the same erasure. I just went with factory methods differentiated by their names instead: public static TheClass createWithStrings(List<String> list) public static TheClass createWithOtherTypes(List<OtherType> list) This is less than optimal, as there isn't a single obvious location where all the different options for creating instances are available. I tried to search for better design ideas, but found surprisingly few results. What other patterns exist for designing around this problem?

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• How to prepare data for display on a silverlight chart using WCF RIA Services + Entity Framework

  - by Banford

  I've used WCF RIA services with Entity Framework to build a simple application which can display and updates data about school courses. This was done by following the Microsoft tutorials. Now I would like to have a chart which shows a count for how many courses are on a key stage. Example: Key Stage 3 - 20 courses Key Stage 4 - 32 courses Key Stage 5 - 12 courses Displayed on any form of chart. I have no problem binding data to the chart in XAML. My problem is that I do not know how to correct way of getting the data into that format. The generated CRUD methods are basic. I have a few thoughts about possible ways, but don't know which is correct, they are: Create a View in SQL server and map this to a separate Entity in the Entity Data Model. Generating new CRUD methods for this automatically. Customise the read method in the existing DomainService using .Select() .Distinct() etc. Don't know this syntax very well labda expressions/LINQ??? what is it? Any good quickstarts on it? Create a new class to store only the data required and create a read method for it. Tried this but didn't know how to make it work without a matching entity in the entity model. Something I am not aware of. I'm very new to this and struggling with the concepts so if there are useful blogs or documentation I've missed feel free to point me towards them. But I'm unsure of the terminology to use in my searches at the moment.

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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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• Problem convert column values from VARCHAR(n) to DECIMAL

  - by Kevin Babcock

  I have a SQL Server 2000 database with a column of type VARCHAR(255). All the data is either NULL, or numeric data with up to two points of precision (e.g. '11.85'). I tried to run the following T-SQL query but received the error 'Error converting data type varchar to numeric' SELECT CAST([MyColumn] AS DECIMAL) FROM [MyTable]; I tried a more specific cast, which also failed. SELECT CAST([MyColumn] AS DECIMAL(6,2)) FROM [MyTable]; I also tried the following to see if any data is non-numeric, and the only values returned were NULL. SELECT ISNUMERIC([MyColumn]), [MyColumn] FROM [MyTable] WHERE ISNUMERIC([MyColumn]) = 0; I tried to convert to other data types, such as FLOAT and MONEY, but only MONEY was successful. So I tried the following: SELECT CAST(CAST([MyColumn] AS MONEY) AS DECIMAL) FROM [MyTable]; ...which worked just fine. Any ideas why the original query failed? Will there be a problem if I first convert to MONEY and then to DECIMAL? Thanks!

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• How to secure authiorization of methods

  - by Kurresmack

  I am building a web site in C# using MVC.Net How can I secure that no unauthorized persons can access my methods? What I mean is that I want to make sure that only admins can create articles on my page. If I put this logic in the method actually adding this to the database, wouldn't I have business logic in my data layer? Is it a good practise to have a seperate security layer that is always in between of the data layer and the business layer to make? The problem is that if I protect at a higher level I will have to have checks on many places and it is more likely that I miss one place and users can bypass security. Thanks!

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• C# Running several tasks at different intervals

  - by Nir

  A design question: I'd like to build a Windows service that executes different commands at different intervals. For simplicity's sake, let's say I want to run some batch files. The input it gets is a list of files and the intervals at which to execute. For example: a.bat - 4 minutes b.bat - 1 minute c.bat - 1 minute d.bat - 2 minutes I was thinking about sorting them according to intervals, and then setting a timer for each of the intervals. I'm not sure this is the best solution and I'd be happy to hear some feedbacks. Thanks!

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• Is this class + constructor definition pattern overly redundant?

  - by Protector one

  I often come across a pattern similar to this: class Person { public string firstName, lastName; public Person(string firstName, string lastName) { this.firstName = firstName; this.lastName = lastName; } } This feels overly redundant (I imagine typing "firstName" once, instead of thrice could be enough…), but I can't think of a proper alternative. Any ideas? Maybe I just don't know about a certain design pattern I should be using here? Edit - I think I need to elaborate a little. I'm not asking how to make the example code "better", but rather, "shorter". In its current state, all member names appear 3 times (declaration, initialization, constructor arguments), and it feels rather redundant. So I'm wondering if there is a pattern (or semantic sugar) to get (roughly) the same behavior, but with less bloat. I apologize for being unclear initially.

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• Three level heirarchal data-linq

  - by user326010

  Hi I have three level heirarchal data. using the statement below i managed to display two level data. I need to extend it to one more level. Current heirachy is Modules--Documents I need to extend it as Packages--Modules--Documents var data = (from m in DataContext.SysModules join d in DataContext.SysDocuments on m.ModuleID equals d.ModuleID into tempDocs from SysDocument in tempDocs.DefaultIfEmpty() group SysDocument by m).ToList(); Regards Tassadaque

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• Getting JSON data on server side with Grails

  - by maximus

  Once I post JSON data to a url in Grails, how can I get access to that data inside of the controller?

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