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• "Do it right, against customer's wishes" - how is it called?

  - by SF.

  We know the optimal situation of negotiating corrections of specifications with the customer, getting the specs to do what the client wanted, not what they said or thought they wanted. That's negotiating, explaining. Sometimes, we're unable to convince the client. We're forced to produce broken as designed. This, called "demonology" by merit of mages summoning demons and demons fulfilling their wishes very literally, causing the mage's demise as result, is another approach that will leave the customer very dissatisfied once they realize their error, and of course try to pin the blame on the developer. Now I just faced a very different approach: the customer created simple specs that fail to account for some critical caveat, and is completely unwilling to fix them, admit the obvious errors and accept suggested corrections. The product made to these specs will be critically broken, and possibly might cost human lives. Still, it's too late to drop the contract entirely. The contract has punitive clauses for that, ones we can't really accept. The boss' decision? We do the work right and lie to the customer that we did it according to the specs. The algorithms in question are hidden deep enough under the surface, the product will do the work just fine, won't fail in the caveat situation, and unless someone digs too deep, they will never discover we didn't break it as requested. Is there some common name for this tactics of execution of specs?

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• Any tips/tricks/resources on actually TEACHING a class on OOP? [closed]

  - by Sempus

  I may slowly be getting into teaching an Object-Orientated Programming class at my school in a year or two. I just graduated and work at my school as an Application Programmer. I'd first start off as a TA/grader and then slowly move into the Professor role. The class would be in Java. I always see resources on this fine site about HOW to program, but does anyone know any tips/tricks/resources on how to TEACH a programming class? It would be full of all different skills levels(but still semi-technical) so it would have to be a little more understandable than if it was just CS kids.

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• how to stop enemies from moving to one point when lots of them are chasing one object [duplicate]

  - by BBgun

  This question already has an answer here: Is there a simple way to stop enemies standing in the same spot? 8 answers i am making a top down game which lots of enemies are chasing one guy. then,enemies would move to one point without any collision,they just overlay each other. so ,is there any simple way to make them feel more real? make them not overlay with each other? ================================= i have tried the solution using boundbox to check collision, but i still very puzzled about what to do with the collision. i have a bad solution.it doesn't work well. my solution in simple: foreach(around_enemy_arr in other) { vector a = normalize(self.positionvector - other.positionvector); self.move_vector = self.move_vector + a; } this can work,but when plenty of enemies come very close to each other,they would shake. i am sooooo confused. please help.

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• Architecture driven by users, or by actions/content?

  - by hugerth

  I have a question about designing MVC app architecture. Let's say our application has three main categories of views (items of type 1, items of type 2...). And we have three (or more in future) types of users - Admins, let's say Moderators and typical Users. And in the future there might be more of them. Admins have full access to app, Moderators can visit only 2/3 type of items, and Users can visit only basic type of items. Should I divide my controllers/views/whatever like this: Items "A", Items "B", Items "C", then make them 100% finished and at the end add access privileges? Pros: DRY option Cons Conditional expressions in views Or another options: Items "A" / Admin, Items "A" / Moderator / Items "B" Admin ...? Pros: Divided parts of application for specific user (is that pros?) Cons: A lot of repeated code I don't have great experience in planning such things so it would nice if you can give me some tips or links to learn something about it.

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• Do I need to add an index on a table with one row?

  - by briddums

  I'm creating a parameter table in our database. This table will have 1 row with values that are environment specific (production, development, etc). Is there any reason why I should define an index on this table? Update This table is a parameter table which will be used to drive our job queue system. The table will be defined like this: QueuePrm LogLvl integer ShowMs boolean Restart boolean This table will only ever have 1 row. No other table in our system will reference it.

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• How is this paradigm/style called?

  - by McMannus

  I have the following situation: I'm developing an add-in for a UML modeling tool. The models that can be created by the user are stored inside the main application and a limited access to the models is given through its API. However, the add-in has a lot of callbacks for events that are triggered by the main application, when changes to the model occur by the user. Since the models are already stored once in the main application, I considered it not practicable to duplicate the models in the add-in, which leads to the fact that I have only behavior in the add-in, rather than having a state. This behavior is mainly expressed by static functions, that are organized in functional cohesive classes. The callbacks for the events have always references to the model elements relevant for the specifc event that ocurred. First, it seemed to me that this is a procedural style in general, but procedural style doesn't consider events/callbacks, so this boils down to the question. How is this programming style called?

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• Characteristics, what's the inverse of (x*(x+1))/2? [closed]

  - by Valmond

  In my game you can spend points to upgrade characteristics. Each characteristic has a formula like: A) out = in : for one point spent, one pont gained (you spend 1 point on Force so your force goes from 5 to 6) B) out = last level (starting at 1) : so the first point spent earns you 1 point, the next point spent earns you an additional 2 and so on (+3,+4,+5...) C) The inverse of B) : You need to spend 1 point to earn one, then you need to spend 2 to earn another one and so on. I have already found the formula for calculating the actual level of B when points spent = x : charac = (x*(x+1))/2 But I'd like to know what the "reverse" version of B) (usable for C) is, ie. if I have spent x points, how many have I earned if 1 spent gives 1, 1+2=3 gives 2, 1+2+3=6 gives 3 and so on. I know I can just calculate the numbers but I'd like to have the formula because its neater and so that I can stick it in an excel sheet for example... Thanks! ps. I think I have nailed it down to something like charac = sqrt( x*m +k) but then I'm stuck doing number guessing for k and m and I feel I might be wrong anyway as I get close but never hits the spot.

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• Scala regex Named Capturing Groups

  - by Brent

  In scala.util.matching.Regex trait MatchData I see that there support for groupnames (Named Capturing Groups) But since Java does not support groupnames until version 7 as I understand it, Scala version 2.8.0.RC4 (Java HotSpot(TM) 64-Bit Server VM, Java 1.6. gives me this exception: scala> val pattern = """(?<login>\w+) (?<id>\d+)""".r java.util.regex.PatternSyntaxException: Look-behind group does not have an obvio us maximum length near index 11 (?<login>\w+) (?<id>\d+) ^ at java.util.regex.Pattern.error(Pattern.java:1713) at java.util.regex.Pattern.group0(Pattern.java:2488) at java.util.regex.Pattern.sequence(Pattern.java:1806) at java.util.regex.Pattern.expr(Pattern.java:1752) at java.util.regex.Pattern.compile(Pattern.java:1460) So the question is Named Capturing Groups supported in Scala? If so any examples out there? If not I might look into the Named-Regexp lib from clement.denis.

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• Add multiple entities to Javascript namespace from different files

  - by Brian M. Hunt

  Given a namespaces ns used in two different files: abc.js ns = ns || (function () { foo = function() { ... }; return { abc : foo }; }()); def.js // is this correct? ns = ns || {} ns.def = ns.def || (function () { defoo = function () { ... }; return { deFoo: defoo }; }()); Is this the proper way to add def to the ns to a namespace? In other words, how does one merge two contributions to a namespace in javascript? If abc.js comes before def.js I'd expect this to work. If def.js comes before abc.js I'd expect ns.abc to not exist because ns is defined at the time. It seems there ought to be a design pattern to eliminate any uncertainty of doing inclusions with the javascript namespace pattern. I'd appreciate thoughts and input on how best to go about this sort of 'inclusion'. Thanks for reading. Brian

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• VMware vSphere cluster design for site redundancy

  - by Stefan Radovanovici

  I have a question about the best design for site redudancy when using vSphere clusters. A bit of background info about our situation first though. We are a medium-sized company with two main offices, located in different countries. Our networks are linked by a Layer2 150Mbps leased line which is currently underused. We have a variety of services running for internal use within the company, some on physycal servers and some on existing vSphere clusters. In our department we also run several services (almost all running under various forms of Linux) like NTP, Syslog, jump servers, monitoring servers and so on. We have now the requirement that those servers need to be redundant within each location (which they are not at the moment) and also site redudant (which they are to some extent, the servers are duplicated in the 2nd location with configurations kept in sync via various methods at the application layer). There is no SAN available for us, at least not something that we can use at the moment. Cost is also an issue. While we do have some budget available for this, we can't afford to buy SANs for both locations for example. I looked at the VSA feature and it seems that this could be something for us but I am unsure how to solve the site-redudancy requirement. At the moment for testing purposes I am setting up in a lab a vSphere 5 with VSA on two ESXi hosts. I am currently using the Essentials Plus kit with VSA license, which allows me to build a VSA cluster on up to 3 hosts, together with a vCenter license to manage them. The hosts each have two dual-port network cards and two 600GB drives, running in Raid1. Hardware-wise this will be enough for us to run the all the services we need as VMs and will provide redundandcy within the site. At the moment I see only two option to have site redundancy: build an identical VSA cluter in the second location and keep the various services sync'ed at application layer (database sync, rsync and so on). simply move one of the hosts from the existing cluster to the second location, basically having the VSA cluster span the 150Mbps link between the sites. I would very much prefer the second option but I am unsure how well it'll work, if it can work at all. Technically it should, we can span the needed VLANs across the leased line and have them available in the second location. The advantage would be that we don't need to worry at all about sync'ing databases and the like. But I have the feeling that the bandwidth will not be enough, I have no way of knowing how much traffic will the VSA cluster generate between the hosts. I realize that this will most likely depend on the individual usage of the VMs but still, I have no idea how VSA replicates data between the ESXi hosts. Are these my only options or can my goals be achieved in some other way ? Is there perhaps a way to have some sort of "cold stand by" cluster in the second location where the VMs would be sync'ed once per night from the main location ? The idea is that in case the first site becomes unavailable, we would be able to bring all those VMs online there. We would be ok with the data being 1 day old. Any answers are appreciated. Best regards, Stefan

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• Silverlight child windows in MVVM pattern

  - by rrejc

  Hello, I am trying to find the right way to get the data from a ChildWindow/popup using a MVVM pattern in Silverlight (3). For example: I have a main page with a data entry form and I want to open a popup with a list of customers. When user selects a customer I want to transfer selected customer into the main page. This is what the (example) code which I am using at the moment: Main page public partial class MainPage : UserControl { public MainPageViewModel ViewModel { get; private set; } public MainPage() { InitializeComponent(); ViewModel = new MainPageViewModel(); DataContext = ViewModel; } private void SearchCustomer_Click(object sender, RoutedEventArgs e) { ViewModel.SearchCustomer(); } } public class MainPageViewModel: ViewModel { private string customer; public string Customer { get { return customer; } set { customer = value; RaisePropertyChanged("Customer"); } } public void SearchCustomer() { // Called from a view SearchWindow searchWindow = new SearchWindow(); searchWindow.Closed += (sender, e) => { if ((bool)searchWindow.DialogResult) { Customer = searchWindow.ViewModel.SelectedCustomer.ToString(); } }; searchWindow.Show(); } } Child window public partial class SearchWindow : ChildWindow { public SearchWindowViewModel ViewModel { get; private set; } public SearchWindow() { InitializeComponent(); ViewModel = new SearchWindowViewModel(); DataContext = ViewModel; } private void OKButton_Click(object sender, RoutedEventArgs e) { DialogResult = ViewModel.OkButtonClick(); } private void CancelButton_Click(object sender, RoutedEventArgs e) { DialogResult = ViewModel.CancelButtonClick(); } } public class SearchWindowViewModel: ViewModel { private Customer selectedCustomer; private ObservableCollection<Customer> customers; public ObservableCollection<Customer> Customers { get { return customers; } set {customers = value; RaisePropertyChanged("Customers"); } } public Customer SelectedCustomer { get { return selectedCustomer; } set { selectedCustomer = value; RaisePropertyChanged("SelectedCustomer"); } } public SearchWindowViewModel() { Customers = new ObservableCollection<Customer>(); ISearchService searchService = new FakeSearchService(); foreach (Customer customer in searchService.FindCustomers("dummy")) Customers.Add(customer); } public bool? OkButtonClick() { if (SelectedCustomer != null) return true; else return null; // show some error message before that } public bool? CancelButtonClick() { return false; } } Is this the right way or is there anything more "simple"? Cheers, Rok

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• Java Builder pattern with Generic type bounds

  - by I82Much

  Hi all, I'm attempting to create a class with many parameters, using a Builder pattern rather than telescoping constructors. I'm doing this in the way described by Joshua Bloch's Effective Java, having private constructor on the enclosing class, and a public static Builder class. The Builder class ensures the object is in a consistent state before calling build(), at which point it delegates the construction of the enclosing object to the private constructor. Thus public class Foo { // Many variables private Foo(Builder b) { // Use all of b's variables to initialize self } public static final class Builder { public Builder(/* required variables */) { } public Builder var1(Var var) { // set it return this; } public Foo build() { return new Foo(this); } } } I then want to add type bounds to some of the variables, and thus need to parametrize the class definition. I want the bounds of the Foo class to be the same as that of the Builder class. public class Foo<Q extends Quantity> { private final Unit<Q> units; // Many variables private Foo(Builder<Q> b) { // Use all of b's variables to initialize self } public static final class Builder<Q extends Quantity> { private Unit<Q> units; public Builder(/* required variables */) { } public Builder units(Unit<Q> units) { this.units = units; return this; } public Foo build() { return new Foo<Q>(this); } } } This compiles fine, but the compiler is allowing me to do things I feel should be compiler errors. E.g. public static final Foo.Builder<Acceleration> x_Body_AccelField = new Foo.Builder<Acceleration>() .units(SI.METER) .build(); Here the units argument is not Unit<Acceleration> but Unit<Length>, but it is still accepted by the compiler. What am I doing wrong here? I want to ensure at compile time that the unit types match up correctly.

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• Implementing EAV pattern with Hibernate for User -> Settings relationship

  - by Trevor

  I'm trying to setup a simple EAV pattern in my web app using Java/Spring MVC and Hibernate. I can't seem to figure out the magic behind the hibernate XML setup for this scenario. My database table "SETUP" has three columns: user_id (FK) setup_item setup_value The database composite key is made up of user_id | setup_item Here's the Setup.java class: public class Setup implements CommonFormElements, Serializable { private Map data = new HashMap(); private String saveAction; private Integer speciesNamingList; private User user; Logger log = LoggerFactory.getLogger(Setup.class); public String getSaveAction() { return saveAction; } public void setSaveAction(String action) { this.saveAction = action; } public User getUser() { return user; } public void setUser(User user) { this.user = user; } public Integer getSpeciesNamingList() { return speciesNamingList; } public void setSpeciesNamingList(Integer speciesNamingList) { this.speciesNamingList = speciesNamingList; } public Map getData() { return data; } public void setData(Map data) { this.data = data; } } My problem with the Hibernate setup, is that I can't seem to figure out how to map out the fact that a foreign key and the key of a map will construct the composite key of the table... this is due to a lack of experience using Hibernate. Here's my initial attempt at getting this to work: <composite-id> <key-many-to-one foreign-key="id" name="user" column="user_id" class="Business.User"> <meta attribute="use-in-equals">true</meta> </key-many-to-one> </composite-id> <map lazy="false" name="data" table="setup"> <key column="user_id" property-ref="user"/> <composite-map-key class="Command.Setup"> <key-property name="data" column="setup_item" type="string"/> </composite-map-key> <element column="setup_value" not-null="true" type="string"/> </map> Any insight into how to properly map this common scenario would be most appreciated!

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• C# Finalize/Dispose pattern

  - by robUK

  Hello, C# 2008 I have been working on this for a while now. And I am still confused about some issues. My questions below 1) I know that you only need a finalizer if you are disposing of unmanaged resources. However, if you are using managed resources that make calls to unmanaged resources. Would you still need to implement a finalizer? 2) However, if you develop a class that doesn't use any unmanged resources directly or indirectly and you implement the IDisposable so that clients of your class can use the 'using statement'. Would it be acceptable to implement the IDisposable just so that clients of your class can use the using statement? using(myClass objClass = new myClass()) { // Do stuff here } 3) I have developed this simple code below to demostrate the Finalize/dispose pattern: public class NoGateway : IDisposable { private WebClient wc = null; public NoGateway() { wc = new WebClient(); wc.DownloadStringCompleted += wc_DownloadStringCompleted; } // Start the Async call to find if NoGateway is true or false public void NoGatewayStatus() { // Start the Async's download // Do other work here wc.DownloadStringAsync(new Uri(www.xxxx.xxx)); } private void wc_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e) { // Do work here } // Dispose of the NoGateway object public void Dispose() { wc.DownloadStringCompleted -= wc_DownloadStringCompleted; wc.Dispose(); GC.SuppressFinalize(this); } } Question about the source code: 1) Here I have not added the finalizer. And normally the finalizer will be called by the GC, and the finalizer will call the Dispose. As I don't have the finalizer, when do I call the Dispose method? Is it the client of the class that has to call it? So my class in the example is called NoGateway and the client could use and dispose of the class like this: Would the Dispose method be automatically called when execution reaches the end of the using block? using(NoGateway objNoGateway = new NoGateway()) { // Do stuff here } Or does the client have to manually call the dispose method i.e.? NoGateway objNoGateway = new NoGateway(); // Do stuff with object objNoGateway.Dispose(); // finished with it Many thanks for helping with all these questions, 2) I am using the webclient class in my 'NoGateway' class. Because the webclient implements the IDisposable interface. Does this mean that the webclient indirectly uses unmanaged resources? Is there any hard and fast rule to follow about this. How do I know that a class uses unmanaged resources?

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• Dependency Injection and Unit of Work pattern

  - by sunwukung

  I have a dilemma. I've used DI (read: factory) to provide core components for a homebrew ORM. The container provides database connections, DAO's,Mappers and their resultant Domain Objects on request. Here's a basic outline of the Mappers and Domain Object classes class Mapper{ public function __constructor($DAO){ $this->DAO = $DAO; } public function load($id){ if(isset(Monitor::members[$id]){ return Monitor::members[$id]; $values = $this->DAO->selectStmt($id); //field mapping process omitted for brevity $Object = new Object($values); return $Object; } } class User(){ public function setName($string){ $this->name = $string; //mark modified by means fair or foul } } The ORM also contains a class (Monitor) based on the Unit of Work pattern i.e. class Monitor(){ private static array modified; private static array dirty; public function markClean($class); public function markModified($class); } The ORM class itself simply co-ordinates resources extracted from the DI container. So, to instantiate a new User object: $Container = new DI_Container; $ORM = new ORM($Container); $User = $ORM->load('user',1); //at this point the container instantiates a mapper class //and passes a database connection to it via the constructor //the mapper then takes the second argument and loads the user with that id $User->setName('Rumpelstiltskin');//at this point, User must mark itself as "modified" My question is this. At the point when a user sets values on a Domain Object class, I need to mark the class as "dirty" in the Monitor class. I have one of three options as I can see it 1: Pass an instance of the Monitor class to the Domain Object. I noticed this gets marked as recursive in FirePHP - i.e. $this-Monitor-markModified($this) 2: Instantiate the Monitor directly in the Domain Object - does this break DI? 3: Make the Monitor methods static, and call them from inside the Domain Object - this breaks DI too doesn't it? What would be your recommended course of action (other than use an existing ORM, I'm doing this for fun...)

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• PHP Regex: How to match anything except a pattern between two tags

  - by Ryan

  Hello, I am attempting to match a string which is composed of HTML. Basically it is an image gallery so there is a lot of similarity in the string. There are a lot of <dl> tags in the string, but I am looking to match the last <dl>(.?)+</dl> combo that comes before a </div>. The way I've devised to do this is to make sure that there aren't any <dl's inside the <dl></dl> combo I'm matching. I don't care what else is there, including other tags and line breaks. I decided I had to do it with regular expressions because I can't predict how long this substring will be or anything that's inside it. Here is my current regex that only returns me an array with two NULL indicies: preg_match_all('/<dl((?!<dl).)+<\/dl>(?=<\/div>)/', $foo, $bar) As you can see I use negative lookahead to try and see if there is another <dl> within this one. I've also tried negative lookbehind here with the same results. I've also tried using +? instead of just + to no avail. Keep in mind that there's no pattern <dl><dl></dl> or anything, but that my regex is either matching the first <dl> and the last </dl> or nothing at all. Now I realize . won't match line breaks but I've tried anything I could imagine there and it still either provides me with the NULL indicies or nearly the whole string (from the very first occurance of <dl to </dl></div>, which includes several other occurances of <dl>, exactly what I didn't want). I honestly don't know what I'm doing incorrectly. Thanks for your help! I've spent over an hour just trying to straighten out this one problem and it's about driven me to pulling my hair out.

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• Problem with Command Pattern under Visual Studio 2008 (C++)

  - by D.Giunchi

  Dear All, I've a problem with this pattern under c++ on VS 2008. The same code has been tested in gcc (linux, mac and mingw for widnows) and it works. I copy/paste the code here: class MyCommand { public: virtual void execute() = 0; virtual ~MyCommand () {}; }; class MyOperation { public: virtual void DoIt() {}; //I also write it not inline }; class MyOperationDerived : public MyOperation { public: virtual void DoIt() {}; //I also write it not inline }; class MyUndoStackCommand : public MyCommand { public: typedef void(MyOperation::*Action)(); MyUndoStackCommand(MyOperation *rec, Action action); /*virtual*/ void execute(); /*virtual*/ ~MyUndoStackCommand(); private: MyOperation *myReceiver; Action myAction ; }; in cpp: #include "MyUndoStackCommand.h" #include "MyOperation.h" MyUndoStackCommand::~MyUndoStackCommand() { } MyUndoStackCommand::MyUndoStackCommand(myOperation *rec, Action action): myReceiver(rec), myAction(action) { } void MyUndoStackCommand::execute() { ((myReceiver)->*(myAction))(); } use in main.cpp: MyReceiver receiver; MyUndoStackCommand usc(&receiver, &MyOperation::DoIt); usc.execute(); when I debug under visual studio only if I set inside MyUndoStackCommand, directly myAction = &MyOperation::DoIt , it works, otherwise not. Any advice? thank you very much, dan Edit: The following code compiles with g++ - changes by Neil Butterworth flagged as //NB. class MyCommand { public: virtual void execute() = 0; virtual ~MyCommand () {}; }; class MyOperation { public: virtual void DoIt() {}; //I also write it not inline }; class MyOperationDerived : public MyOperation { public: virtual void DoIt() {}; //I also write it not inline }; class MyUndoStackCommand : public MyCommand { public: typedef void(MyOperation::*Action)(); MyUndoStackCommand(MyOperation *rec, Action action); /*virtual*/ void execute(); /*virtual*/ ~MyUndoStackCommand(); private: MyOperation *myReceiver; Action myAction ; }; MyUndoStackCommand::~MyUndoStackCommand() { } MyUndoStackCommand::MyUndoStackCommand(MyOperation *rec, //NB Action action) : myReceiver(rec), myAction(action) { } void MyUndoStackCommand::execute() { ((myReceiver)->*(myAction))(); } int main() { MyOperation receiver; //NB MyUndoStackCommand usc(&receiver, &MyOperation::DoIt); usc.execute(); }

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• Is it bad practice to make a setter return "this"?

  - by Ken Liu

  Is it a good or bad idea to make setters in java return "this"? public Employee setName(String name){ this.name = name; return this; } This pattern can be useful because then you can chain setters like this: list.add(new Employee().setName("Jack Sparrow").setId(1).setFoo("bacon!")); instead of this: Employee e = new Employee(); e.setName("Jack Sparrow"); ...and so on... list.add(e); ...but it sort of goes against standard convention. I suppose it might be worthwhile just because it can make that setter do something else useful. I've seen this pattern used some places (e.g. JMock, JPA), but it seems uncommon, and only generally used for very well defined APIs where this pattern is used everywhere. Update: What I've described is obviously valid, but what I am really looking for is some thoughts on whether this is generally acceptable, and if there are any pitfalls or related best practices. I know about the Builder pattern but it is a little more involved then what I am describing - as Josh Bloch describes it there is an associated static Builder class for object creation.

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• What do you call a generalized (non-GUI-related) "Model-View-Controller" architecture?

  - by dcuccia

  I am currently refactoring code that coordinates multiple hardware components for data acquisition, and feeling a bit like I'm recreating the wheel. In particular, an MVC-like pattern seems to be emerging. Except, this has nothing to do with a GUI and I'm worried that I'm forcing this particular pattern where another might be more appropriate. Here's my scenario: Individual hardware "component" classes obey interface contracts for each hardware type. Previously, component instances were orchestrated by a single monolithic InstrumentController class, which relied heavily on configuration + branching logic for executing a specific acquisition sequence. After an iteration, I have a separate controller for each component, with these controllers all managed by a small InstrumentControllerBase (or its derivatives). The composite system will receive "input" either programmatically or via inter-hardware component triggering - in either case these interactions are routed to, and handled by, the appropriate controller. So, I have something that feels MVC-esque, but I don't know if that's because I'm forcing the point. With little direct MVC experience in application development, it's hard to know if I'm just trying to make my scenario fit MVC, where another pattern might be a good alternative or complimentary. My problem is, search results and wiki documentation of these family of patterns seems to immediately drop me into GUI-specific discussions. I understand "M means Model data and the V means View" - but do you call the superset pattern? Component-Commander-Controller? Whence can I exhume examples exemplary?

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• WPF TabControl - how to preserve control state within tab items (MVVM pattern)

  - by Tim Coulter

  I am a newcomer to WPF, attempting to build a project that follows the recommendations of Josh Smith's excellent article describing The Model-View-ViewModel Design Pattern. Using Josh's sample code as a base, I have created a simple application that contains a number of "workspaces", each represented by a tab in a TabControl. In my application, a workspace is a document editor that allows a hierarchical document to be manipulated via a TreeView control. Although I have succeeded in opening multiple workspaces and viewing their document content in the bound TreeView control, I find that the TreeView "forgets" its state when switching between tabs. For example, if the TreeView in Tab1 is partially expanded, it will be shown as fully collapsed after switching to Tab2 and returning to Tab1. This behaviour appears to apply to all aspects of control state for all controls. After some experimentation, I have realized that I can preserve state within a TabItem by explicitly binding each control state property to a dedicated property on the underlying ViewModel. However, this seems like a lot of additional work, when I simply want all my controls to remember their state when switching between workspaces. I assume I am missing something simple, but I am not sure where to look for the answer. Any guidance would be much appreciated. Thanks, Tim Update: As requested, I will attempt to post some code that demonstrates this problem. However, since the data that underlies the TreeView is complex, I will post a simplified example that exhibits the same symtoms. Here is the XAML from the main window: <TabControl IsSynchronizedWithCurrentItem="True" ItemsSource="{Binding Path=Docs}"> <TabControl.ItemTemplate> <DataTemplate> <ContentPresenter Content="{Binding Path=Name}" /> </DataTemplate> </TabControl.ItemTemplate> <TabControl.ContentTemplate> <DataTemplate> <view:DocumentView /> </DataTemplate> </TabControl.ContentTemplate> </TabControl> The above XAML correctly binds to an ObservableCollection of DocumentViewModel, whereby each member is presented via a DocumentView. For the simplicity of this example, I have removed the TreeView (mentioned above) from the DocumentView and replaced it with a TabControl containing 3 fixed tabs: <TabControl> <TabItem Header="A" /> <TabItem Header="B" /> <TabItem Header="C" /> </TabControl> In this scenario, there is no binding between the DocumentView and the DocumentViewModel. When the code is run, the inner TabControl is unable to remember its selection when the outer TabControl is switched. However, if I explicitly bind the inner TabControl's SelectedIndex property ... <TabControl SelectedIndex="{Binding Path=SelectedDocumentIndex}"> <TabItem Header="A" /> <TabItem Header="B" /> <TabItem Header="C" /> </TabControl> ... to a corresponding dummy property on the DocumentViewModel ... public int SelecteDocumentIndex { get; set; } ... the inner tab is able to remember its selection. I understand that I can effectively solve my problem by applying this technique to every visual property of every control, but I am hoping there is a more elegant solution.

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• Solutions for exercises in The Algorithm Design Manual

  - by mpm

  Does anybody know where to find solutions for the exercises in the book The Algorithm Design Manual?

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• Database design - alternatives for Entity Attribute Value (EAV)

  - by Bob

  Hi, see http://stackoverflow.com/questions/695752/product-table-many-kinds-of-product-each-product-has-many-parameters for similar topic. My question: i want to design a database, that will be used for a production facility of different types of products where each product has its own (number of) parameters. because i want the serial numbers to be in one tabel for overview purposes i have a problem with these different paraeters . One solution could be EAV, but it has its downsides, certainly because we have +- 5 products with every product +- 20.000 serial numbers (records). it looks a bit overkill to me... I just don't know how one could design a database so that you have an attribute in a mastertable that says: 'hey, you could find details of this record in THAT detail-table". 'in a way that you qould easely query the results) currenty i am using Visual Basic & Acces 2007. but i'm going to Visual Basic & MySQL. thanks for your help. Bob

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• WPF - Have a list source defined at runtime but still have sample data for design time

  - by Vaccano

  I have some ListBoxes in my WPF app. I would like to be able to view how the design looks with out having to run the app. But I still want to be able to bind to ItemsSource to my View Model. I know I saw a blog post on how to do this, but I cannot seem to find it now. To reiterate, I want dummy data at design time, but real data at run time and not break the MVVM pattern. Any ideas?

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• subsonic in visual studio design host

  - by csizo

  Hi, I'm facing currently a problem regarding Subsonic configuration. What I want to achieve is using subsonic data access in a System.Web.UI.Design.ControlDesigner class. This class is hosted in Visual Studio Environment and enables design time operations on the attached System.Web.UI.WebControls.Control. The only problem is SubSonic seems always looking for SubSonicSection in the application configuration regardless passing connection string to it. The relevant code snippet: using (SharedDbConnectionScope dbScope = new SharedDbConnectionScope(new SqlDataProvider(), ConnectionString)) { Table1 _table1 = new Select().From<..().Where(...).IsEqualTo(...).ExecuteSingle<...>(); Throws exception on ExecuteSingle() method (configuration section was not found) while using (SharedDbConnectionScope dbScope = new SharedDbConnectionScope(ConnectionString)) { Throws exception on new SharedDbConnectionScope() (configuration section was not found) So the question is: Is there any way to pass the settings runtime to bypass the configuration section lookup as I don't want to add any subsonic specific configuration to devenv.configuration Thanks

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• css3 design tutorial/template etc

  - by Adam

  Hello, I search some tutorial/templates how made easy (lightwight) and nice css3 design, or made with some "css firmware" etc

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