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• MySql - only update some rows if the table exists - do not want an error thrown

  - by Pete Oakey

  I want to run an update query. The query will be run against multiple databases - not every database will have the table. I don't want the update to be attempted if the table does not exist. I don't want any error to be thrown - I just want the update to be ignored. Any ideas? EDIT: just to be clear - the query is executed in an automated deployment - no human interaction possible. EDIT2: the logic to say whether the update should run or not will need to be in the MySql query itself. This is not being run through a command prompt or batch or managed code.

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• Testing a (big) collection retrieved from a db

  - by Bas

  I'm currently doing integration testing on a live database and I have the following sql statement: var date = DateTime.Parse("01-01-2010 20:30:00"); var result = datacontext.Repository<IObject>().Where(r => r.DateTime > date).First(); Assert.IsFalse(result.Finished); I need to test if the results retrieved from the statement, where the given date is less then the date of the object, have Finished set to False. I do not know how many results I get back and currently I'm getting the first object of the list and check if that object has Finished set to false. I know testing only the first item of the list is not valid testing, as a solution for that I could iterate through the list and check all items on Finished, but putting logic in a Test is kinda going against the concept of writing 'good' tests. So my question is: Does anyone have a good solution of how to properly test the results of this list?

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• Need help understanding the MVC design pattern

  - by Doron Sinai

  Hi, I am trying to find a ood example of MVC design pattern in java. This is what i understood from reading about it, please correct me if I am wrong: I have the Model part which is the logic behind the program, let's say if we have a phonebook, so adding and removing contact from the Array will be the model. The Gui is the view and it contains buttons that upon clicking them, the model is changing. What I am trying to undersand what is the controller part, is it the ActionListeners? how to you seperate those modules in practice. thank you

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• Business Object desgin

  - by Dan

  I have a question about how I setup my BO's. I setup the BO's to contain all of my properties of the object as well as the business logic to satisfy the business rules. I decided to make all of the methods static, but I'm not sure if that was the right decision. Someone told me to split my BO's into an Entity Object of just properties and then a BO of just methods that do business rules, and don't make the methods static. Does anyone have some experience with the way i've set this up? Any examples of how it might work better for future growth? Thanks!

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• Surface Detection in 2d Game?

  - by GamiShini

  I'm working on a 2D Platform game, and I was wondering what's the best (performance-wise) way to implement Surface (Collision) Detection. So far I'm thinking of constructing a list of level objects constructed of a list of lines, and I draw tiles along the lines. ( http://img375.imageshack.us/img375/1704/lines.png ). I'm thinking every object holds the ID of the surface that he walks on, in order to easily manipulate his y position while walking up/downhill. Something like this: //Player/MovableObject class MoveLeft() { this.Position.Y = Helper.GetSurfaceById(this.SurfaceId).GetYWhenXIs(this.Position.X) } So the logic I use to detect "droping/walking on surface" is a simple point (player's lower legs)-touches-line (surface) check (with some safety approximation - let`s say 1-2 pixels over the line). Is this approach OK? I`ve been having difficulty trying to find reading material for this problem, so feel free to drop links/advice.

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• J2EE: Default values for custom tag attributes

  - by Nick

  So according to Sun's J2EE documentation (http://docs.sun.com/app/docs/doc/819-3669/bnani?l=en&a=view), "If a tag attribute is not required, a tag handler should provide a default value." My question is how in the hell do I define a default value as per the documentation's description. Here's the code: <%@ attribute name="visible" required="false" type="java.lang.Boolean" %> <c:if test="${visible}"> My Tag Contents Here </c:if> Obviously, this tag won't compile because it's lacking the tag directive and the core library import. My point is that I want the "visible" property to default to TRUE. The "tag attribute is not required," so the "tag handler should provide a default value." I want to provide a default value, so what am I missing? Any help is greatly appreciated.

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• Sqlite3 Database versus populating Arrays

  - by Kenoy

  hi, I am working on a program that requires me to input values for 12 objects, each with 4 arrays, each with 100 values. (4800) values. The 4 arrays represent possible outcomes based on 2 boolean values... i.e. YY, YN, NN, NY and the 100 values to the array are what I want to extract based on another inputted variable. I previously have all possible outcomes in a csv file, and have imported these into sqlite where I can query then for the value using sql. However, It has been suggested to me that sqlite database is not the way to go, and instead I should populate using arrays hardcoded. Which would be better during run time and for memory management?

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• VB.Net List.Find. Pass values to predicate

  - by Beta033

  Having a bit of trouble using the List.Find with a custom predicate i have a function that does this private function test () Dim test As Integer = keys.Find(AddressOf FindByOldKeyAndName).NewKey here's the function for the predicate Private Shared Function FindByOldKeyAndName(ByVal k As KeyObj) As Boolean If k.OldKey = currentKey.OldKey And k.KeyName = currentKey.KeyName Then Return True Else Return False End If End Function by doing it this way means i have to have a shared "currentKey" object in the class, and i know there has to be a way to pass in the values i'm interested in of CurrentKey (namely, keyname, and oldkey) ideally i'd like to call it by something like keys.Find(AddressOf FindByOldKeyAndName(Name,OldVal)) however when i do this i get compiler errors. How do i call this method and pass in the values?

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• Unit testing custom controls in Silverlight

  - by Hrvoje

  I have several custom controls (some kind of frames for content and layout management, like wrap panel), and would like to write unit tests for them. It's hard to find any good examples except Silverlight control toolkit, which has some helper classes to do unit tests and it's quite complicated. For MVVM classes it's easy to write tests because they don't use SL dependency system and infrastructure. Questions: how to unit test DepedenyProperty, what do I need to test how to test attached property do I test bindings with theme or UserControl, like simple textblock content binding, or command/event binding in MVVM with UserControl what else do I test in my custom controls, beside my business logic any good tutorial to achieve tests like those in control toolkit How do I start? Is SL controls toolkit only option for learning? For testing framework i'm using one from control toolkit, and for continuus integration on TFS build server I planned to use Statlight (from codeplex). Any advice on that?

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• Style of if: to nest or not to nest

  - by Marco

  A colleague of mine and me had a discussion about the following best-practice issue. Most functions/methods start with some parameter checking. I advocate the following style, which avoids nesting. if (parameter one is ugly) return ERROR; if (parameter two is nonsense || it is raining) return ERROR; // do the useful stuff return result; He, who comes from a more functional/logic programming background, prefers the following, because it reduces the number of exit points from the function. if (parameter one is ok) { if (parameter two is ok && the sun is shining) { // do the useful stuff return result } } return ERROR; Which one would you prefer and why?

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• StructureMap - Injecting a dependency into a base class?

  - by David

  In my domain I have a handful of "processor" classes which hold the bulk of the business logic. Using StructureMap with default conventions, I inject repositories into those classes for their various IO (databases, file system, etc.). For example: public interface IHelloWorldProcessor { string HelloWorld(); } public class HelloWorldProcessor : IHelloWorldProcessor { private IDBRepository _dbRepository; public HelloWorldProcessor(IDBRepository dbRepository) { _dbRepository = dbrepository; } public string HelloWorld(){ return _dbRepository.GetHelloWorld(); } } Now, there are some repositories that I'd like to be available to all processors, so I made a base class like this: public class BaseProcessor { protected ICommonRepository _commonRepository; public BaseProcessor(ICommonRepository commonRepository) { _commonRepository = commonRepository; } } But when my other processors inherit from it, I get a compiler error on each one saying that there's no constructor for BaseProcessor which takes zero arguments. Is there a way to do what I'm trying to do here? That is, to have common dependencies injected into a base class that my other classes can use without having to write the injections into each one?

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• how to return the current object?

  - by ajsie

  in code igniter you can type: $query = $this->db->query("YOUR QUERY"); foreach ($query->result() as $row) { echo $row->title; echo $row->name; echo $row->body; } i guess that the query method returns the object it's part of. am i correct? if i am, how do you type the line where it returns the object? so what i wonder is how it looks like inside the query method for the above code to be functional. public function query($sql) { // some db logic here with the $sql and saves the values to the properties (title, name and body) return X } with other words, what should X be?

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• Evenly distribute items on the screen

  - by abolotnov

  I am trying to solve this little puzzle (the algorithm): I have N image icons and I want to distribute them evenly on users screen. Say, I put them in a table. If there is one image, there will be one cell in a table. If two - one row with two columns, if three - one row and three columns, if four - two rows, two columns... and so on until row space is gone and since then the table should only grow in columns without adding extra rows. I'm trying to figure an algorithm for this and perhaps this is something that has a solution already somewhere? My attempt is so far something like this: obtain_max_rows() obtain_visible_columns() if (number_of_pictures > max_rows*max_columns) { columns = roundup(number_of_pictures/max_rows) for(max_rows){generate row;for columns{generate column}} } else { **here comes to trouble...** } This logic is bit silly though - it somehow needs to think cases where there are 12 pictures on first screen and 2 on the other trying to balance it say 8/6 or somehow like that.

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• constructing dynamic In Statements with sql

  - by nitroxn

  Suppose we need to check three boolean conditions to perform a select query. Let the three flags be 'A', 'B' and 'C'. If all of the three flags are set to '1' then the query to be generated is SELECT * FROM Food WHERE Name In ('Apple, 'Biscuit', 'Chocolate'); If only the flags 'A' and 'B' are set to '1' with C set to '0'. Then the following query is generated. SELECT * FROM Food WHERE Name In ('Apple, 'Biscuit'); What is the best way to do it?

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• In ASP.NET MVC (3.0/Razor), do you prefer multiple views, or conditionals within views? Why?

  - by Chad

  For my new web app, I'm debating on using multiple views, or conditionals within views. An example scenario would be showing different info to users who are authenticated vs non-authenticated. This could be handled a couple ways. In the controller, check IsAuthenticated and return a view based on that In the view, check IsAuthenticated and show blocks of info based on that Pros of multiple views: Smaller, less complicated view - next to no logic in the view Pros of single views: less view files to maintain The obvious cons are the opposites of the pros: more files to maintain or more complicated view files. Which do you prefer? Why? Any pros/cons I haven't outlined here? Update: Assume each view uses a layout page and partial views to abstract the obviously repetitive code.

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• Error : Implementation for method missing (Delphi Prism)

  - by Ilya

  I wrote my method: LangChange type MainForm = partial class(System.Windows.Forms.Form) private ... method LangChange(); protected method Dispose(disposing: Boolean); override; public constructor; end; implementation ... method LangChange(); begin ... end; However,I have an error Error 1 (PE33) Implementation for method "Compiler.MainForm.LangChange" missing What is wrong?Help please!

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• Avoiding "variable might not have been initialized"

  - by Mason Wheeler

  I recently ran across a routine that looks something like this: procedure TMyForm.DoSomething(list: TList<TMyObject>; const flag: boolean); var local: integer; begin if flag then //do something else local := ExpensiveFunctionCallThatCalculatesSomething; //do something else for i := 0 to list.Count do if flag then //do something else if list[i].IntValue > local then //WARNING HERE //do something else end; This gives Variable 'local' might not have been initialized even though you can tell by reading the code that you won't hit that line unless the code branch that initializes it has run. Now, I could get rid of this warning by adding a useless local := 0; at the top of the procedure, but I wonder if there might not be a better way to structure this to avoid the issue. Anyone have any ideas?

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• Interview question: How do I detect a loop in this linked list?

  - by jjujuma

  Say you have a linked list structure in Java. It's made up of Nodes: class Node { Node next; // some user data } and each Node points to the next node, except for the last Node, which has null for next. Say there is a possibility that the list can contain a loop - i.e. the final Node, instead of having a null, has a reference to one of the nodes in the list which came before it. What's the best way of writing boolean hasLoop(Node first) which would return true if the given Node is the first of a list with a loop, and false otherwise? How could you write so that it takes a constant amount of space and a reasonable amount of time? Here's a picture of what a list with a loop looks like: Node->Node->Node->Node->Node->Node--\ \ | ----------------

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• Entity Framework 4.1 (Code First) audit column

  - by Ken Pespisa

  I'm using Entity Framework 4.1 with a Code-First approach on an ASP.NET MVC site Say I have an entity named Profile that keeps track of a user's favorite book, and I want to track when the user updates their favorite book. UPDATED: Using the class below as an example, I want to set the FavoriteBookLastUpdated property to the current date whenever the value of the FavoriteBook property changes. public class Profile { public int Id { get; set; } public string Name { get; set; } public string FavoriteBook { get; set; } public DateTime? FavoriteBookLastUpdated { get; set; } } Right now I just update that field, if appropriate, in the controller's Edit action before calling the DBContext's SaveChanges() method. Is there a way I can put that logic in my model somehow? I'd prefer not to use triggers on the database side.

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• How can I determine if a file I want to read from actually exists?

  - by Imray

  I'm learning Java, and I'm trying to write a program that can read from a .ser file, which I've already created with a writeTo method. I want to know a given file exists in the system before I tell the program to read from it. My code looks like this: public boolean readFromSerializedFile(String fileName){ FileInputStream fileInStream = null; ObjectInputStream objectInStream = null; try{ fileInStream = new FileInputStream(fileName); objectInStream = new ObjectInputStream(fileInStream); Is there a simple way I can determine if the file with the name of the parameter exists in the root directory (or wherever else specified)?

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• release vs setting-to-nil to free memory

  - by Dan Ray

  In my root view controller, in my didReceiveMemoryWarning method, I go through a couple data structures (which I keep in a global singleton called DataManager), and ditch the heaviest things I've got--one or maybe two images associated with possibly twenty or thirty or more data records. Right now I'm going through and setting those to nil. I'm also setting myself a boolean flag so that various view controllers that need this data can easily know to reload. Thusly: DataManager *data = [DataManager sharedDataManager]; for (Event *event in data.eventList) { event.image = nil; event.thumbnail = nil; } for (WondrMark *mark in data.wondrMarks) { mark.image = nil; } [DataManager sharedDataManager].cleanedMemory = YES; Today I'm thinking, though... and I'm not actually sure all that allocated memory is really being freed when I do that. Should I instead release those images and maybe hit them with a new alloc and init when I need them again later?

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• DataBind and Postback

  - by Michael La Voie

  This is a general how does DataBind work questions... I have a simple page with a GridView that is bound (in the aspx code) to an ObjectDataSource. I can look in the Select() function called by the ObjectDataSource to see that it is called on the initial load and on every post back. I have some logic that happens on post backs that will affect the GridView's data, and I want to call GridView.DataBind() later on in the post back, after I've made some changes. Is there a way to prevent the automatic rebinding that happens on each post back? Does this mean I can't use an ObjectDataSource for this control?

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• Update query with conditional?

  - by dmontain

  I'm not sure if this possible. If not, let me know. I have a PDO mysql that updates 3 fields. $update = $mypdo->prepare("UPDATE tablename SET field1=:field1, field2=:field2, field3=:field3 WHERE key=:key"); But I want field3 to be updated only when $update3 = true; (meaning that the update of field3 is controlled by a conditional statement) Is this possible to accomplish with a single query? I could do it with 2 queries where I update field1 and field2 then check the boolean and update field3 if needed in a separate query. //run this query to update only fields 1 and 2 $update_part1 = $mypdo->prepare("UPDATE tablename SET field1=:field1, field2=:field2 WHERE key=:key"); //if field3 should be update, run a separate query to update it separately if ($update3){ $update_part2 = $mypdo->prepare("UPDATE tablename SET field3=:field3 WHERE key=:key"); } But hopefully there is a way to accomplish this in 1 query?

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• Trouble rendering a view inside a generic class

  - by Horace Loeb

  I'm trying to encapsulate the logic for generating my sitemap in a separate class so I can use Delayed::Job to generate it out of band: class ViewCacher include ActionController::UrlWriter def initialize @av = ActionView::Base.new(Rails::Configuration.new.view_path) @av.class_eval do include ApplicationHelper end end def cache_sitemap songs = Song.all sitemap = @av.render 'sitemap/sitemap', :songs => songs Rails.cache.write('sitemap', sitemap) end end But whenever I try ViewCacher.new.cache_sitemap I get this error: ActionView::TemplateError: ActionView::TemplateError (You have a nil object when you didn't expect it! The error occurred while evaluating nil.url_for) on line #5 of app/views/sitemap/_sitemap.builder: I assume this means that ActionController::UrlWriter is not included in the right place, but I really don't know

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• Do I still have to implement a singleton class by hand in .net, even when using .Net4.0?

  - by Hamish Grubijan

  Once the singleton pattern is understood, writing subsequent singleton classes in C# is a brainless exercise. I would hope that the framework would help you by providing an interface or a base class to do that. Here is how I envision it: public sealed class Schablone : ISingleton<Schablone> { // Stuff forced by the interface goes here // Extra logic goes here } Does what I am looking for exist? Is there some syntactic sugar for constructing a singleton class - whether with an interface, a class attribute, etc.? Can one write a useful and bullet-proof ISingleton themselves? Care to try? Thanks!

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