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  • Dependency Injection & Singleton Design pattern

    - by SysAdmin
    How do we identify when to use dependency injection or singleton pattern. I have read in lot of websites where they say "Use Dependency injection over singleton pattern". But I am not sure if I totally agree with them. For my small or medium scale projects I definitely see the use of singleton pattern straightforward. For example Logger. I could use Logger.GetInstance().Log(...) But, instead of this, why do I need to inject every class I create, with the logger's instance?.

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  • What is the best practice when coding math class/functions ?

    - by Isaac Clarke
    Introductory note : I voluntarily chose a wide subject. You know that quote about learning a cat to fish, that's it. I don't need an answer to my question, I need an explanation and advice. I know you guys are good at this ;) Hi guys, I'm currently implementing some algorithms into an existing program. Long story short, I created a new class, "Adder". An Adder is a member of another class representing the physical object actually doing the calculus , which calls adder.calc() with its parameters (merely a list of objects to do the maths on). To do these maths, I need some parameters, which do not exist outside of the class (but can be set, see below). They're neither config parameters nor members of other classes. These parameters are D1 and D2, distances, and three arrays of fixed size : alpha, beta, delta. I know some of you are more comfortable reading code than reading text so here you go : class Adder { public: Adder(); virtual Adder::~Adder(); void set( float d1, float d2 ); void set( float d1, float d2, int alpha[N_MAX], int beta[N_MAX], int delta[N_MAX] ); // Snipped prototypes float calc( List& ... ); // ... inline float get_d1() { return d1_ ;}; inline float get_d2() { return d2_ ;}; private: float d1_; float d2_; int alpha_[N_MAX]; // A #define N_MAX is done elsewhere int beta_[N_MAX]; int delta_[N_MAX]; }; Since this object is used as a member of another class, it is declared in a *.h : private: Adder adder_; By doing that, I couldn't initialize the arrays (alpha/beta/delta) directly in the constructor ( int T[3] = { 1, 2, 3 }; ), without having to iterate throughout the three arrays. I thought of putting them in static const, but I don't think that's the proper way of solving such problems. My second guess was to use the constructor to initialize the arrays Adder::Adder() { int alpha[N_MAX] = { 0, -60, -120, 180, 120, 60 }; int beta[N_MAX] = { 0, 0, 0, 0, 0, 0 }; int delta[N_MAX] = { 0, 0, 180, 180, 180, 0 }; set( 2.5, 0, alpha, beta, delta ); } void Adder::set( float d1, float d2 ) { if (d1 > 0) d1_ = d1; if (d2 > 0) d2_ = d2; } void Adder::set( float d1, float d2, int alpha[N_MAX], int beta[N_MAX], int delta[N_MAX] ) { set( d1, d2 ); for (int i = 0; i < N_MAX; ++i) { alpha_[i] = alpha[i]; beta_[i] = beta[i]; delta_[i] = delta[i]; } } My question is : Would it be better to use another function - init() - which would initialize arrays ? Or is there a better way of doing that ? My bonus question is : Did you see some mistakes or bad practice along the way ?

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  • TCP Message Structure with XML

    - by metdos
    Hello Everybody, I'm sending messages over TCP/IP and on the other side I parse TCP message.For example this is one of the sent messages. $DKMSG(requestType=REQUEST_LOGIN&requestId=123&username=metdos&password=123)$EDKMSG Clarification: $DKMSG( //Start )$EDKMSG //End requestType //Parameter REQUEST_LOGIN //Parameter Value Now I also want to add an Xml file to my message. I'm considering this option: $DKMSG(requestType=REQUEST_LOGIN&xmlData= <Item id="56D@MIT" type="SIGNAL"> <Label> <Text>56D</Text> <X1>10</X1> <Y1>40</Y1> <RotateAngle>90</RotateAngle> </Label> <X1>0</X1> <Y1>20</Y1> <Width>35</Width> <Height>10</Height> <Source>sgs3lr</Source> </Item> )$EDKMSG There are problems with this way: 1-)It doesn't seem right to me. 2-)I have to handle delimeter "=" with much more care or I need to change it in parameters. What are your suggestions, thanks.

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  • How do you clear your mind after 8-10 hours per day of coding?

    - by Bryan
    Related Question- Ways to prepare your mind before coding?. I'm having a hard time taking my mind off of work projects in my personal time. It's not that I have a stressful job or tight deadlines; I love my job. I find that after spending the whole day writing code & trying to solve problems, I have an extremely hard time getting it out of my mind. I'm constantly thinking about the current project/problem/task all the time. It's keeping me from relaxing, and in the long run it just builds stress. Personal projects help to some extent, but mostly just to distract me. I still have source code bouncing around my head 16 hours a day. I'm still relatively new to the workforce. Have you struggled with this, perhaps as a young developer? How did you overcome it? Can anyone offer general advice on winding down after a long programming session?

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  • Should checkins be small steps or complete features?

    - by Caspin
    Two of version controls uses seem to dictate different checkin styles. distibution centric: changesets will generally reflect a complete feature. In general these checkins will be larger. This style is more user/maintainer friendly. rollback centric: changesets will be individual small steps so the history can function like an incredibly powerful undo. In general these checkins will be smaller. This style is more developer friendly. I like to use my version control as really powerful undo while while I banging away at some stubborn code/bug. In this way I'm not afraid to make drastic changes just to try out a possible solution. However, this seems to give me a fragmented file history with lots of "well that didn't work" checkins. If instead I try to have my changeset reflect complete features I loose the use of my version control software for experimentation. However, it is much easier for user/maintainers to figure out how the code is evolving. Which has great advantages for code reviews, managing multiple branches, etc. So what's a developer to do? checkin small steps or complete features?

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  • Database Structure for CakePHP Models

    - by Michael T. Smith
    We're building a data tracking web app using CakePHP, and I'm having some issues getting the database structure right. We have Companies that haveMany Sites. Sites haveMany DataSamples. Tags haveAndBelongToMany Sites. That is all set up fine. The problem is "ranking" the sites within tags. We need to store it in the database as an archive. I created a Rank model that is setup like this: rank ( id (int), sample_id (int), tag_id (int), site_id (int), rank (int), total_rows) ) So, the question is, how do I create the associations for tag, site and sample to rank? I originally set them as haveMany. But the returned structures don't get me where I'd like to be. It looks like: [Site] => Array ( [Sample] = Array(), [Tag] = Array() ) When I'm really looking for: [Site] => Array ( [Tag] = Array ( [Sample] => Array ( [Rank] => Array ( ...data... ) ) ) ) I think that I may not be structuring the database properly; so if I need to update please let me know. Otherwise, how do I write a find query that gets me where I need to be? Thanks! Thoughts? Need more details? Just ask!

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  • Unit testing huge applications - Proven methodologies?

    - by NLV
    Hello members I've been working in windows forms applications and ASP.Net applications for the past 10 months. I've always wondered how to perform proper unit testing on the complete application in a robust manner covering all the scenarios. I've the following questions regarding them - What are the standard mechanisms in performing unit testing and writing test cases? Does the methodologies change based on the application nature such as Windows Forms, Web applications etc? What is the best approach to make sure we cover all the scenarios? Any popular books on this? Popular tools for performing unit testing?

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  • how to handle exceptions/errors in php?

    - by fayer
    when using 3rd part libraries they tend to throw exceptions to the browser and hence kill the script. eg. if im using doctrine and insert a duplicate record to the database it will throw an exception. i wonder, what is best practice for handling these exceptions. should i always do a try...catch? but doesn't that mean that i will have try...catch all over the script and for every single function/class i use? Or is it just for debugging? i don't quite get the picture. Cause if a record already exists in a database, i want to tell the user "Record already exists". And if i code a library or a function, should i always use "throw new Expcetion($message, $code)" when i want to create an error? Please shed a light on how one should create/handle exceptions/errors. Thanks

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  • C++ Matrix class hierachy

    - by bpw1621
    Should a matrix software library have a root class (e.g., MatrixBase) from which more specialized (or more constrained) matrix classes (e.g., SparseMatrix, UpperTriangluarMatrix, etc.) derive? If so, should the derived classes be derived publicly/protectively/privately? If not, should they be composed with a implementation class encapsulating common functionality and be otherwise unrelated? Something else? I was having a conversation about this with a software developer colleague (I am not per se) who mentioned that it is a common programming design mistake to derive a more restricted class from a more general one (e.g., he used the example of how it was not a good idea to derive a Circle class from an Ellipse class as similar to the matrix design issue) even when it is true that a SparseMatrix "IS A" MatrixBase. The interface presented by both the base and derived classes should be the same for basic operations; for specialized operations, a derived class would have additional functionality that might not be possible to implement for an arbitrary MatrixBase object. For example, we can compute the cholesky decomposition only for a PositiveDefiniteMatrix class object; however, multiplication by a scalar should work the same way for both the base and derived classes. Also, even if the underlying data storage implementation differs the operator()(int,int) should work as expected for any type of matrix class. I have started looking at a few open-source matrix libraries and it appears like this is kind of a mixed bag (or maybe I'm looking at a mixed bag of libraries). I am planning on helping out with a refactoring of a math library where this has been a point of contention and I'd like to have opinions (that is unless there really is an objective right answer to this question) as to what design philosophy would be best and what are the pros and cons to any reasonable approach.

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  • Removing a pattern from the beggining and end of a string in ruby

    - by seaneshbaugh
    So I found myself needing to remove <br /> tags from the beginning and end of strings in a project I'm working on. I made a quick little method that does what I need it to do but I'm not convinced it's the best way to go about doing this sort of thing. I suspect there's probably a handy regular expression I can use to do it in only a couple of lines. Here's what I got: def remove_breaks(text) if text != nil and text != "" text.strip! index = text.rindex("<br />") while index != nil and index == text.length - 6 text = text[0, text.length - 6] text.strip! index = text.rindex("<br />") end text.strip! index = text.index("<br />") while index != nil and index == 0 text = test[6, text.length] text.strip! index = text.index("<br />") end end return text end Now the "<br />" could really be anything, and it'd probably be more useful to make a general use function that takes as an argument the string that needs to be stripped from the beginning and end. I'm open to any suggestions on how to make this cleaner because this just seems like it can be improved.

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  • How can I sync three classes?

    - by TheMachineCharmer
    class Foo { Bar b; List<Foo> Neighbours; } class Bar { Spam s; List<Bar> Neighbours; } class Spam { List<string> Neighbours; } Each of these classes have AddNeighbour,RemoveNeighbour methods. User can add/remove Neighbours from any of the class at random. I want these three objects to be in sync. How can I do this?

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  • C# MultiThread Safe Class Design

    - by Robert
    I'm trying to designing a class and I'm having issues with accessing some of the nested fields and I have some concerns with how multithread safe the whole design is. I would like to know if anyone has a better idea of how this should be designed or if any changes that should be made? using System; using System.Collections; namespace SystemClass { public class Program { static void Main(string[] args) { System system = new System(); //Seems like an awkward way to access all the members dynamic deviceInstance = (((DeviceType)((DeviceGroup)system.deviceGroups[0]).deviceTypes[0]).deviceInstances[0]); Boolean checkLocked = deviceInstance.locked; //Seems like this method for accessing fields might have problems with multithreading foreach (DeviceGroup dg in system.deviceGroups) { foreach (DeviceType dt in dg.deviceTypes) { foreach (dynamic di in dt.deviceInstances) { checkLocked = di.locked; } } } } } public class System { public ArrayList deviceGroups = new ArrayList(); public System() { //API called to get names of all the DeviceGroups deviceGroups.Add(new DeviceGroup("Motherboard")); } } public class DeviceGroup { public ArrayList deviceTypes = new ArrayList(); public DeviceGroup() {} public DeviceGroup(string deviceGroupName) { //API called to get names of all the Devicetypes deviceTypes.Add(new DeviceType("Keyboard")); deviceTypes.Add(new DeviceType("Mouse")); } } public class DeviceType { public ArrayList deviceInstances = new ArrayList(); public bool deviceConnected; public DeviceType() {} public DeviceType(string DeviceType) { //API called to get hardwareIDs of all the device instances deviceInstances.Add(new Mouse("0001")); deviceInstances.Add(new Keyboard("0003")); deviceInstances.Add(new Keyboard("0004")); //Start thread CheckConnection that updates deviceConnected periodically } public void CheckConnection() { //API call to check connection and returns true this.deviceConnected = true; } } public class Keyboard { public string hardwareAddress; public bool keypress; public bool deviceConnected; public Keyboard() {} public Keyboard(string hardwareAddress) { this.hardwareAddress = hardwareAddress; //Start thread to update deviceConnected periodically } public void CheckKeyPress() { //if API returns true this.keypress = true; } } public class Mouse { public string hardwareAddress; public bool click; public Mouse() {} public Mouse(string hardwareAddress) { this.hardwareAddress = hardwareAddress; } public void CheckClick() { //if API returns true this.click = true; } } }

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  • How to refactor this Ruby on Rails code?

    - by yuval
    I want to fetch posts based on their status, so I have this code inside my PostsController index action. It seems to be cluttering the index action, though, and I'm not sure it belongs here. How could I make it more concise and where would I move it in my application so it doesn't clutter up my index action (if that is the correct thing to do)? if params[:status].empty? status = 'active' else status = ['active', 'deleted', 'commented'].include?(params[:status]) ? params[:status] : 'active' end case status when 'active' #active posts are not marked as deleted and have no comments is_deleted = false comments_count_sign = "=" when 'deleted' #deleted posts are marked as deleted and have no comments is_deleted = true comments_count_sign = "=" when 'commented' #commented posts are not marked as deleted and do have comments is_deleted = false comments_count_sign = ">" end @posts = Post.find(:all, :conditions => ["is_deleted = ? and comments_count_sign #{comments_count_sign} 0", is_deleted])

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  • Asp.Net MVC Handle Drop Down Boxes that are not part of the Model

    - by Pino
    I have a small form which the user must fill in and consists of the following fields. Name (Text) Value (Text) Group (Group - Is a list of option pulled from a database table) Now the Model for this View looks like so, public string Name { get; set; } public string Value { get; set; } public int GroupID { get; set; } Now the view is Strongly Typed to the above model. What method would one use to populate the drop down list? Since the data is not contained within the Model (It could be contained in the Model) should we be using Temp/View data? A HTML Helper? What would be the ideal way to achieve this.

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  • How to check for undefined or null variable in javascript

    - by Thomas Wanner
    We are frequently using the following code pattern in our javascript code if(typeof(some_variable) != 'undefined' && some_variable != null) { // do something with some_variable } and I'm wondering whether there is a less verbose way of checking that has the same effect. According to some forums and literature saying simply if(some_variable) { // do something with some_variable } should have the same effect. Unfortunately, Firebug evaluates such a statement as error on runtime when some_variable is undefined, whereas the first one is just fine for him. Is this only an (unwanted) behavior of Firebug or is there really some difference between those two ways ?

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  • How should I architect JasperReports with a PHP front+backend system

    - by Itay Moav
    Our system is written completely in PHP. For various business reasons (which are a given) I need to build the reports of the system using JasperReports. What architecture should I use? Should I put the Jasper as a stand alone server (if possible) and let the php query against it, should I have it generate the reports with a cron, and then let the PHP scoop up the files and send them to the web client/browser...

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  • How do I create a new AnyType[] array?

    - by cb
    Which is the best practice in this situation? I would like an un-initialized array of the same type and length as the original. public static <AnyType extends Comparable<? super AnyType>> void someFunction(AnyType[] someArray) { AnyType[] anotherArray = (AnyType[]) new Comparable[someArray.length]; ...or... AnyType[] anotherArray = (AnyType[]) new Object[someArray.length]; ...some other code... } Thanks, CB

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  • What's the preferred way to use helper methods in Ruby?

    - by DR
    Disclaimer: Although I'm asking in context of a Rails application, I'm not talking about Rails helpers (i.e. view helpers) Let's say I have a helper method/function: def dispatch_job(job = {}) #Do something end Now I want to use this from several places (mostly controllers, but also a few BackgrounDRb workers) What's the preferred way to do this? I can think of two possibilities: 1. Use a class and make the helper a static method: class MyHelper def self.dispatch_job(job = {}) end end class MyWorker def run MyHelper.dispatch_job(...) end end 2. Use a module and include the method into whatever class I need this functionality module MyHelper def self.dispatch_job(job = {}) end end class MyWorker include MyHelper def run dispatch_job(...) end end 3. Other possibilities I don't know yet ... The first one is more Java-like, but I'm not sure if the second one is really an appropriate use of Ruby's modules.

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  • The Java interface doesn't declare any exception. How to manage checked exception of the implementat

    - by Frór
    Let's say I have the following Java interface that I may not modify: public interface MyInterface { public void doSomething(); } And now the class implementing it is like this: class MyImplementation implements MyInterface { public void doSomething() { try { // read file } catch (IOException e) { // what to do? } } } I can't recover from not reading the file. A subclass of RuntimeException can clearly help me, but I'm not sure if it's the right thing to do: the problem is that that exception would then not be documented in the class and a user of the class would possibly get that exception an know nothing about solving this. What can I do?

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  • Atomic operations on several transactionless external systems

    - by simendsjo
    Say you have an application connecting 3 different external systems. You need to update something in all 3. In case of a failure, you need to roll back the operations. This is not a hard thing to implement, but say operation 3 fails, and when rolling back, the rollback for operation 1 fails! Now the first external system is in an invalid state... I'm thinking a possible solution is to shut down the application and forcing a manual fix of the external system, but then again... It might already have used this information (and perhaps that's why it failed), or we might not have sufficient access. Or it might not even be a good way to rollback the action! Are there some good ways of handling such cases? EDIT: Some application details.. It's a multi user web application. Most of the work is done with scheduled jobs (through Quartz.Net), so most operations is run in it's own thread. Some user actions should trigger jobs that update several systems though. The external systems are somewhat unstable. I Was thinking of changing the application to use the Command and Unit Of Work pattern

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  • What is this Design Pattern?

    - by Can't Tell
    I read the Wikipedia articles on FactoryMethod and AbstractFactory but the following code doesn't seem to fit anywhere. Can someone explain to me what the following pattern is or if it is an anti-pattern? interace PaymentGateway{ void makePayment(); } class PaypalPaymentGateway implements PaymentGateway { public void makePayment() { //some implementation } } class AuthorizeNetPaymentGateway implements PaymentGateway { public void makePayment() { //some implementation } } class PaymentGatewayFacotry{ PaymentGateway createPaymentGateway(int gatewayId) { if(gatewayId == 1) return PaypalPaymentGateway(); else if(gatewayId == 2) return AuthorizeNetPaymentGateway(); } } Let's say the user selects the payment method using a radio button on an html page and the gatewayId is derived from the radio button value. I have seen code like this and thought it was the AbstractFactory pattern but after reading the Wikipedia article, I'm having doubts.

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  • Me As Child Type In General Function

    - by Steven
    I have a MustInherit Parent class with two Child classes which Inherit from the Parent. How can I use (or Cast) Me in a Parent function as the the child type of that instance? EDIT: My actual goal is to be able to serialize (BinaryFormatter.Serialize(Stream, Object)) either of my child classes. However, "repeating the code" in each child "seems" wrong. EDIT2: This is my Serialize function. Where should I implement this function? Copying and pasting to each child doesn't seem right, but casting the parent to a child doesn't seem right either. Public Function Serialize() As Byte() Dim bFmt As New BinaryFormatter() Dim mStr As New MemoryStream() bFmt.Serialize(mStr, Me) Return mStr.ToArray() End Function

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