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• AD-DirectoryServices: .NET2.0 - Speaking architecture, approach and best practices... Suggestions?

  - by Will Marcouiller

  I've been mandated to write an application to migrate the Active Directory access models to another environment. Here's the context: I'm stuck with VB.NET 2005 and .NET Framework 2.0; The application must use the Windows authenticated user to manage AD; The objects I have to handle are Groups, Users and OrganizationalUnits; I intend to use the Façade design pattern to provider ease of use and a fully reusable code; I plan to write a factory for each of the objects managed (group, ou, user); The use of Attributes should be useful here, I guess; As everything is about the DirectoryEntry class when accessing the AD, it seems a good candidate for generic types. Obligatory features: User creates new OUs manually; User creates new group manually; User creates new user (these users are services accounts) manually; Application reads an XML file which contains the OUs, groups and users to create; Application informs the user about the OUs, groups and users that shall be created; User specifies the domain environment where to migrate the XML input file designated objects; User makes changes if needed, and launches the task operations; Application performs required by the XML input file operations against the underlying AD as specified by the user; Application informs the user upon completion. Linear features: User fetches OUs, groups, users; User changes OUs, groups, users; User deletes OUs, groups, users; The application logs AD entries and operations performed, plus errors and exceptions; Nice-to-have features: Application rollbacks operations on error or exception. I've been working for weeks now to get acquainted with the AD and the System.DirectoryServices assembly. But I don't seem to find a way to be fully satisfied with what I'm doing and always looking for better. I have studied Bret de Smet's Linq to AD on CodePlex, but then again, I can't use it as I'm stuck with .NET 2.0, so no Linq! But I've learned about Attributes, and seen that he's working with generic types as he codes a DirectorySource class to perform the operations for OUs, groups and users. I have been able to add groups to the AD; I have been able to add users to the AD; The created user is automatically disabled? I seem to get confused with the use of a LDAP path to add objects. For instance, one needs two instances of a System.DirectoryServices.DirectoryEntry class to add a group, for instance. Why this? Any suggestions? Thanks for any help, code sample, ideas, architural solution, everything!

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• How to combine designable components with dependency injection

  - by Wim Coenen

  When creating a designable .NET component, you are required to provide a default constructor. From the IComponent documentation: To be a component, a class must implement the IComponent interface and provide a basic constructor that requires no parameters or a single parameter of type IContainer. This makes it impossible to do dependency injection via constructor arguments. (Extra constructors could be provided, but the designer would ignore them.) Some alternatives we're considering: Service Locator Don't use dependency injection, instead use the service locator pattern to acquire dependencies. This seems to be what IComponent.Site.GetService is for. I guess we could create a reusable ISite implementation (ConfigurableServiceLocator?) which can be configured with the necessary dependencies. But how does this work in a designer context? Dependency Injection via properties Inject dependencies via properties. Provide default instances if they are necessary to show the component in a designer. Document which properties need to be injected. Inject dependencies with an Initialize method This is much like injection via properties but it keeps the list of dependencies that need to be injected in one place. This way the list of required dependencies is documented implicitly, and the compiler will assists you with errors when the list changes. Any idea what the best practice is here? How do you do it? edit: I have removed "(e.g. a WinForms UserControl)" since I intended the question to be about components in general. Components are all about inversion of control (see section 8.3.1 of the UMLv2 specification) so I don't think that "you shouldn't inject any services" is a good answer. edit 2: It took some playing with WPF and the MVVM pattern to finally "get" Mark's answer. I see now that visual controls are indeed a special case. As for using non-visual components on designer surfaces, I think the .NET component model is fundamentally incompatible with dependency injection. It appears to be designed around the service locator pattern instead. Maybe this will start to change with the infrastructure that was added in .NET 4.0 in the System.ComponentModel.Composition namespace.

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• how much time does grid.py take to run ?

  - by trinity

  Hello all , I am using libsvm for binary classification.. I wanted to try grid.py , as it is said to improve results.. I ran this script for five files in separate terminals , and the script has been running for more than 12 hours.. this is the state of my 5 terminals now : [root@localhost tools]# python grid.py sarts_nonarts_feat.txt>grid_arts.txt Warning: empty z range [61.3997:61.3997], adjusting to [60.7857:62.0137] line 2: warning: Cannot contour non grid data. Please use "set dgrid3d". Warning: empty z range [61.3997:61.3997], adjusting to [60.7857:62.0137] line 4: warning: Cannot contour non grid data. Please use "set dgrid3d". [root@localhost tools]# python grid.py sgames_nongames_feat.txt>grid_games.txt Warning: empty z range [64.5867:64.5867], adjusting to [63.9408:65.2326] line 2: warning: Cannot contour non grid data. Please use "set dgrid3d". Warning: empty z range [64.5867:64.5867], adjusting to [63.9408:65.2326] line 4: warning: Cannot contour non grid data. Please use "set dgrid3d". [root@localhost tools]# python grid.py sref_nonref_feat.txt>grid_ref.txt Warning: empty z range [62.4602:62.4602], adjusting to [61.8356:63.0848] line 2: warning: Cannot contour non grid data. Please use "set dgrid3d". Warning: empty z range [62.4602:62.4602], adjusting to [61.8356:63.0848] line 4: warning: Cannot contour non grid data. Please use "set dgrid3d". [root@localhost tools]# python grid.py sbiz_nonbiz_feat.txt>grid_biz.txt Warning: empty z range [67.9762:67.9762], adjusting to [67.2964:68.656] line 2: warning: Cannot contour non grid data. Please use "set dgrid3d". Warning: empty z range [67.9762:67.9762], adjusting to [67.2964:68.656] line 4: warning: Cannot contour non grid data. Please use "set dgrid3d". [root@localhost tools]# python grid.py snews_nonnews_feat.txt>grid_news.txt Wrong input format at line 494 Traceback (most recent call last): File "grid.py", line 223, in run if rate is None: raise "get no rate" TypeError: exceptions must be classes or instances, not str I had redirected the outputs to files , but those files for now contain nothing.. And , the following files were created : sbiz_nonbiz_feat.txt.out sbiz_nonbiz_feat.txt.png sarts_nonarts_feat.txt.out sarts_nonarts_feat.txt.png sgames_nongames_feat.txt.out sgames_nongames_feat.txt.png sref_nonref_feat.txt.out sref_nonref_feat.txt.png snews_nonnews_feat.txt.out (-- is empty ) There's just one line of information in .out files.. the ".png" files are some GNU PLOTS . But i dont understand what the above GNUplots / warnings convey .. Should i re-run them ? Can anyone please tell me on how much time this script might take if each input file contains about 144000 lines.. Thanks and regards

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• AlarmManager triggers PendingIntent too soon

  - by Wezelkrozum

  I've searched for 3 days now but didn't find a solution or similar problem/question anywhere else. Here is the deal: Trigger in 1 hour - works correct Trigger in 2 hours - Goes of in 1:23 Trigger in 1 day - Goes of in ~11:00 So why is the AlarmManager so unpredictable and always too soon? Or what am I doing wrong? And is there another way so that it could work correctly? This is the way I register my PendingIntent in the AlarmManager (stripped down): AlarmManager alarmManager = (AlarmManager)parent.getSystemService(ALARM_SERVICE); Intent myIntent = new Intent(parent, UpdateKlasRoostersService.class); PendingIntent pendingIntent = PendingIntent.getService(parent, 0, myIntent, PendingIntent.FLAG_UPDATE_CURRENT); //Set startdate of PendingIntent so it triggers in 10 minutes Calendar start = Calendar.getInstance(); start.setTimeInMillis(SystemClock.elapsedRealtime()); start.add(Calendar.MINUTE, 10); //Set interval of PendingIntent so it triggers every day Integer interval = 1*24*60*60*1000; //Cancel any similar instances of this PendingIntent if already scheduled alarmManager.cancel(pendingIntent); //Schedule PendingIntent alarmManager.setRepeating(AlarmManager.ELAPSED_REALTIME_WAKEUP, start.getTimeInMillis(), interval, pendingIntent); //Old way I used to schedule a PendingIntent, didn't seem to work either //alarmManager.set(AlarmManager.RTC_WAKEUP, start.getTimeInMillis(), pendingIntent); It would be awesome if anyone has a solution. Thanks for any help! Update: 2 hours ago it worked to trigger it with an interval of 2 hours, but after that it triggered after 1:20 hours. It's getting really weird. I'll track the triggers down with a logfile and post it here tomorrow. Update: The PendingIntent is scheduled to run every 3 hours. From the log's second line it seems like an old scheduled PendingIntent is still running: [2012-5-3 2:15:42 519] Updating Klasroosters [2012-5-3 4:15:15 562] Updating Klasroosters [2012-5-3 5:15:42 749] Updating Klasroosters [2012-5-3 8:15:42 754] Updating Klasroosters [2012-5-3 11:15:42 522] Updating Klasroosters But, I'm sure I cancelled the scheduled PendingIntent's before I schedule a new one. And every PendingIntent isn't recreated in the same way, so it should be exactly the same. If not , this threads question isn't relevant anymore.

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• Comparing Nested object properties using C#

  - by Kumar

  I have a method which compares two objects and returns a list of all the property names which are different. public static IList<string> GetDifferingProperties(object source, object) { var sourceType = source.GetType(); var sourceProperties = sourceType.GetProperties(); var targetType = target.GetType(); var targetProperties = targetType.GetProperties(); var properties = (from s in sourceProperties from t in targetProperties where s.Name == t.Name && s.PropertyType == t.PropertyType && s.GetValue(source,null) != t.GetValue(target,null) select s.Name).ToList(); return properties; } For example if I have two classes as follows: public class Address { public string AddressLine1 { get; set; } public string AddressLine2 { get; set; } public string City { get; set; } public string State { get; set; } public string Zip { get; set; } } public class Employee { public string FirstName { get; set; } public string MiddleName { get; set; } public string LastName { get; set; } public Address EmployeeAddress { get; set; } } I am trying to compare the following two employee instances: var emp1Address = new Address(); emp1Address.AddressLine1 = "Microsoft Corporation"; emp1Address.AddressLine2 = "One Microsoft Way"; emp1Address.City = "Redmond"; emp1Address.State = "WA"; emp1Address.Zip = "98052-6399"; var emp1 = new Employee(); emp1.FirstName = "Bill"; emp1.LastName = "Gates"; emp1.EmployeeAddress = emp1Address; var emp2Address = new Address(); emp2Address.AddressLine1 = "Gates Foundation"; emp2Address.AddressLine2 = "One Microsoft Way"; emp2Address.City = "Redmond"; emp2Address.State = "WA"; emp2Address.Zip = "98052-6399"; var emp2 = new Employee(); emp2.FirstName = "Melinda"; emp2.LastName = "Gates"; emp2.EmployeeAddress = emp2Address; So when I pass these two employee objects to my GetDifferingProperties method currently it returns FirstName and EmployeeAddress, but it does not tell me which exact property (which in this case is Address1) in the EmployeeAddress has changed. How can I tweak this method to get something like EmployeeAddress.Address1?

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• idiomatic property changed notification in scala?

  - by Jeremy Bell

  I'm trying to find a cleaner alternative (that is idiomatic to Scala) to the kind of thing you see with data-binding in WPF/silverlight data-binding - that is, implementing INotifyPropertyChanged. First, some background: In .Net WPF or silverlight applications, you have the concept of two-way data-binding (that is, binding the value of some element of the UI to a .net property of the DataContext in such a way that changes to the UI element affect the property, and vise versa. One way to enable this is to implement the INotifyPropertyChanged interface in your DataContext. Unfortunately, this introduces a lot of boilerplate code for any property you add to the "ModelView" type. Here is how it might look in Scala: trait IDrawable extends INotifyPropertyChanged { protected var drawOrder : Int = 0 def DrawOrder : Int = drawOrder def DrawOrder_=(value : Int) { if(drawOrder != value) { drawOrder = value OnPropertyChanged("DrawOrder") } } protected var visible : Boolean = true def Visible : Boolean = visible def Visible_=(value: Boolean) = { if(visible != value) { visible = value OnPropertyChanged("Visible") } } def Mutate() : Unit = { if(Visible) { DrawOrder += 1 // Should trigger the PropertyChanged "Event" of INotifyPropertyChanged trait } } } For the sake of space, let's assume the INotifyPropertyChanged type is a trait that manages a list of callbacks of type (AnyRef, String) = Unit, and that OnPropertyChanged is a method that invokes all those callbacks, passing "this" as the AnyRef, and the passed-in String). This would just be an event in C#. You can immediately see the problem: that's a ton of boilerplate code for just two properties. I've always wanted to write something like this instead: trait IDrawable { val Visible = new ObservableProperty[Boolean]('Visible, true) val DrawOrder = new ObservableProperty[Int]('DrawOrder, 0) def Mutate() : Unit = { if(Visible) { DrawOrder += 1 // Should trigger the PropertyChanged "Event" of ObservableProperty class } } } I know that I can easily write it like this, if ObservableProperty[T] has Value/Value_= methods (this is the method I'm using now): trait IDrawable { // on a side note, is there some way to get a Symbol representing the Visible field // on the following line, instead of hard-coding it in the ObservableProperty // constructor? val Visible = new ObservableProperty[Boolean]('Visible, true) val DrawOrder = new ObservableProperty[Int]('DrawOrder, 0) def Mutate() : Unit = { if(Visible.Value) { DrawOrder.Value += 1 } } } // given this implementation of ObservableProperty[T] in my library // note: IEvent, Event, and EventArgs are classes in my library for // handling lists of callbacks - they work similarly to events in C# class PropertyChangedEventArgs(val PropertyName: Symbol) extends EventArgs("") class ObservableProperty[T](val PropertyName: Symbol, private var value: T) { protected val propertyChanged = new Event[PropertyChangedEventArgs] def PropertyChanged: IEvent[PropertyChangedEventArgs] = propertyChanged def Value = value; def Value_=(value: T) { if(this.value != value) { this.value = value propertyChanged(this, new PropertyChangedEventArgs(PropertyName)) } } } But is there any way to implement the first version using implicits or some other feature/idiom of Scala to make ObservableProperty instances function as if they were regular "properties" in scala, without needing to call the Value methods? The only other thing I can think of is something like this, which is more verbose than either of the above two versions, but is still less verbose than the original: trait IDrawable { private val visible = new ObservableProperty[Boolean]('Visible, false) def Visible = visible.Value def Visible_=(value: Boolean): Unit = { visible.Value = value } private val drawOrder = new ObservableProperty[Int]('DrawOrder, 0) def DrawOrder = drawOrder.Value def DrawOrder_=(value: Int): Unit = { drawOrder.Value = value } def Mutate() : Unit = { if(Visible) { DrawOrder += 1 } } }

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• How to generate and encode (for use in GA), random, strict, binary rooted trees with N leaves?

  - by Peter Simon

  First, I am an engineer, not a computer scientist, so I apologize in advance for any misuse of nomenclature and general ignorance of CS background. Here is the motivational background for my question: I am contemplating writing a genetic algorithm optimizer to aid in designing a power divider network (also called a beam forming network, or BFN for short). The BFN is intended to distribute power to each of N radiating elements in an array of antennas. The fraction of the total input power to be delivered to each radiating element has been specified. Topologically speaking, a BFN is a strictly binary, rooted tree. Each of the (N-1) interior nodes of the tree represents the input port of an unequal, binary power splitter. The N leaves of the tree are the power divider outputs. Given a particular power divider topology, one is still free to map the power divider outputs to the array inputs in an arbitrary order. There are N! such permutations of the outputs. There are several considerations in choosing the desired ordering: 1) The power ratio for each binary coupler should be within a specified range of values. 2) The ordering should be chosen to simplify the mechanical routing of the transmission lines connecting the power divider. The number of ouputs N of the BFN may range from, say, 6 to 22. I have already written a genetic algorithm optimizer that, given a particular BFN topology and desired array input power distribution, will search through the N! permutations of the BFN outputs to generate a design with compliant power ratios and good mechanical routing. I would now like to generalize my program to automatically generate and search through the space of possible BFN topologies. As I understand it, for N outputs (leaves of the binary tree), there are $C_{N-1}$ different topologies that can be constructed, where $C_N$ is the Catalan number. I would like to know how to encode an arbitrary tree having N leaves in a way that is consistent with a chromosomal description for use in a genetic algorithm. Also associated with this is the need to generate random instances for filling the initial population, and to implement crossover and mutations operators for this type of chromosome. Any suggestions will be welcome. Please minimize the amount of CS lingo in your reply, since I am not likely to be acquainted with it. Thanks in advance, Peter

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• JSF inner datatable not respecting rendered condition of outer table.

  - by Marc

  <h:dataTable cellpadding="0" cellspacing="0" styleClass="list_table" id="OuterItems" value="#{valueList.values}" var="item" border="0"> <h:column rendered="#{item.typeA"> <h:dataTable cellpadding="0" cellspacing="0" styleClass="list_table" id="InnerItems" value="#{item.options}" var="option" border="0"> <h:column > <h:outputText value="Option: #{option.displayValue}"/> </h:column> </h:dataTable> </h:column> <h:column rendered="#{item.typeB"> <h:dataTable cellpadding="0" cellspacing="0" styleClass="list_table" id="InnerItems" value="#{item.demands}" var="demand" border="0"> <h:column > <h:outputText value="Demand: #{demand.displayValue}"/> </h:column> </h:dataTable> </h:column> </h:dataTable> public class Item{ ... public boolean isTypeA(){ return this instanceof TypeA; } public boolean isTypeB(){ return this instanceof TypeB; } ... } public class typeA extends Item(){ ... public List getOptions(){ .... } ... } public class typeB extends Item(){ ... public List getDemands(){ ... } .... } I'm having an issue with JSF. I've abstracted the problem out here, and I'm hoping someone can help me understand how what I'm doing fails. I'm looping over a list of Items. These Items are actually instances of the subclasses TypeA and TypeB. For Type A, I want to display the options, for Type B I want to display the demands. When rendering the page for the first time, this works fine. However, when I post back to the page for some action, I get an error: [3/26/10 12:52:32:781 EST] 0000008c SystemErr R javax.faces.FacesException: Error getting property 'options' from bean of type TypeB at com.sun.faces.lifecycle.ApplyRequestValuesPhase.execute(ApplyRequestValuesPhase.java:89) at com.sun.faces.lifecycle.LifecycleImpl.phase(LifecycleImpl.java(Compiled Code)) at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:91) at com.ibm.faces.portlet.FacesPortlet.processAction(FacesPortlet.java:193) My grasp on the JSF lifecyle is very rough. At this point, i understand there is an error in the ApplyRequestValues Phases which is very early and so the previous state is restored and nothing changes. What I don't understand is that in order to fufill the condition for rendering "item.typeA" that object has to be an instance of TypeA. But here, it looks like that object passed the condition even though it was an instance of TypeB. It is like it is evaluating the inner dataTable (InnerItems) before evaluating the outer (outerItems). My working assumption is that I just don't understand how/when the rendered attribute is actually evaluated.

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• question about book example - Java Concurrency in Practice, Listing 4.12

  - by mike

  Hi, I am working through an example in Java Concurrency in Practice and am not understanding why a concurrent-safe container is necessary in the following code. I'm not seeing how the container "locations" 's state could be modified after construction; so since it is published through an 'unmodifiableMap' wrapper, it appears to me that an ordinary HashMap would suffice. EG, it is accessed concurrently, but the state of the map is only accessed by readers, no writers. The value fields in the map are syncronized via delegation to the 'SafePoint' class, so while the points are mutable, the keys for the hash, and their associated values (references to SafePoint instances) in the map never change. I think my confusion is based on what precisely the state of the collection is in the problem. Thanks!! -Mike Listing 4.12, Java Concurrency in Practice, (this listing available as .java here, and also in chapter form via google) /////////////begin code @ThreadSafe public class PublishingVehicleTracker { private final Map<String, SafePoint> locations; private final Map<String, SafePoint> unmodifiableMap; public PublishingVehicleTracker( Map<String, SafePoint> locations) { this.locations = new ConcurrentHashMap<String, SafePoint>(locations); this.unmodifiableMap = Collections.unmodifiableMap(this.locations); } public Map<String, SafePoint> getLocations() { return unmodifiableMap; } public SafePoint getLocation(String id) { return locations.get(id); } public void setLocation(String id, int x, int y) { if (!locations.containsKey(id)) throw new IllegalArgumentException( "invalid vehicle name: " + id); locations.get(id).set(x, y); } } // monitor protected helper-class @ThreadSafe public class SafePoint { @GuardedBy("this") private int x, y; private SafePoint(int[] a) { this(a[0], a[1]); } public SafePoint(SafePoint p) { this(p.get()); } public SafePoint(int x, int y) { this.x = x; this.y = y; } public synchronized int[] get() { return new int[] { x, y }; } public synchronized void set(int x, int y) { this.x = x; this.y = y; } } ///////////end code

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• How to avoid repetition when working with primitive types?

  - by I82Much

  I have the need to perform algorithms on various primitive types; the algorithm is essentially the same with the exception of which type the variables are. So for instance, /** * Determine if <code>value</code> is the bitwise OR of elements of <code>validValues</code> array. * For instance, our valid choices are 0001, 0010, and 1000. * We are given a value of 1001. This is valid because it can be made from * ORing together 0001 and 1000. * On the other hand, if we are given a value of 1111, this is invalid because * you cannot turn on the second bit from left by ORing together those 3 * valid values. */ public static boolean isValid(long value, long[] validValues) { for (long validOption : validValues) { value &= ~validOption; } return value != 0; } public static boolean isValid(int value, int[] validValues) { for (int validOption : validValues) { value &= ~validOption; } return value != 0; } How can I avoid this repetition? I know there's no way to genericize primitive arrays, so my hands seem tied. I have instances of primitive arrays and not boxed arrays of say Number objects, so I do not want to go that route either. I know there are a lot of questions about primitives with respect to arrays, autoboxing, etc., but I haven't seen it formulated in quite this way, and I haven't seen a decisive answer on how to interact with these arrays. I suppose I could do something like: public static<E extends Number> boolean isValid(E value, List<E> numbers) { long theValue = value.longValue(); for (Number validOption : numbers) { theValue &= ~validOption.longValue(); } return theValue != 0; } and then public static boolean isValid(long value, long[] validValues) { return isValid(value, Arrays.asList(ArrayUtils.toObject(validValues))); } public static boolean isValid(int value, int[] validValues) { return isValid(value, Arrays.asList(ArrayUtils.toObject(validValues))); } Is that really much better though? Any thoughts in this matter would be appreciated.

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• How to set text above and below a JButton icon?

  - by mre

  I want to set text above and below a JButton's icon. At the moment, in order to achieve this, I override the layout manager and use three JLabel instances (i.e. 2 for text and 1 for the icon). But this seems like a dirty solution. Is there a more direct way of doing this? Note -I'm not looking for a multi-line solution, I'm looking for a multi-label solution. Although this article refers to it as a multi-line solution, it actually seems to refer to a multi-label solution. EXAMPLE import java.awt.Component; import java.awt.FlowLayout; import javax.swing.BoxLayout; import javax.swing.Icon; import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.SwingUtilities; import javax.swing.UIManager; public final class JButtonDemo { public static void main(String[] args) { SwingUtilities.invokeLater(new Runnable(){ @Override public void run() { createAndShowGUI(); } }); } private static void createAndShowGUI(){ final JFrame frame = new JFrame(); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setLayout(new FlowLayout()); frame.add(new JMultiLabelButton()); frame.pack(); frame.setLocationRelativeTo(null); frame.setVisible(true); } private static final class JMultiLabelButton extends JButton { private static final long serialVersionUID = 7650993517602360268L; public JMultiLabelButton() { super(); setLayout(new BoxLayout(this, BoxLayout.Y_AXIS)); add(new JCenterLabel("Top Label")); add(new JCenterLabel(UIManager.getIcon("OptionPane.informationIcon"))); add(new JCenterLabel("Bottom Label")); } } private static final class JCenterLabel extends JLabel { private static final long serialVersionUID = 5502066664726732298L; public JCenterLabel(final String s) { super(s); setAlignmentX(Component.CENTER_ALIGNMENT); } public JCenterLabel(final Icon i) { super(i); setAlignmentX(Component.CENTER_ALIGNMENT); } } }

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• MVC validation error with strongly typed view

  - by Remnant

  I have a simple form that I would like to validate on form submission. Note I have stripped out the html for ease of viewing <%=Html.TextBox("LastName", "")%> //Lastname entry <%=Html.ValidationMessage("LastName")%> <%=Html.TextBox("FirstName", "")%>//Firstname entry <%=Html.ValidationMessage("FirstName")%> <%=Html.DropDownList("JobRole", Model.JobRoleList)%> //Dropdownlist of job roles <% foreach (var record in Model.Courses) // Checkboxes of different courses for user to select { %> <li><label><input type="checkbox" name="Courses" value="<%=record.CourseName%>" /><%= record.CourseName%></label></li> <% } %> On submission of this form I would like to check that both FirstName and LastName are populated (i.e. non-zero length). In my controller I have: public ActionResult Submit(string FirstName, string LastName) { if (FirstName.Trim().Length == 0) ModelState.AddModelError("FirstName", "You must enter a first name"); if (LastName.Trim().Length == 0) ModelState.AddModelError("LastName", "You must enter a first name"); if (ModelState.IsValid) { //Update database + redirect to action } return View(); //If ModelState not valid, return to View and show error messages } Unfortunately, this code logic produces an error that states that no objects are found for JobRole and Courses. If I remove the dropdownlist and checkboxes then all works fine. The issue appears to be that when I return the View the view is expecting objects for the dropwdownlist and checkboxes (which is sensible as that is what is in my View code) How can I overcome this problem? Things I have considered: In my controller I could create a JobRoleList object and Course object to pass to the View so that it has the objects to render. The issue with this is that it will overwrite any dropdownlist / checkbox selections that the user has already made. In the parameters of my controller method Submit I could aslo capture the JobRoleList object and Course object to pass back to the View. Again, not sure this would capture any items the user has already selected. I have done much googling and reading but I cannot find a good answer. When I look at examples in books or online (e.g. Nerddinner) all the validation examples involve simple forms with TextBox inputs and don't seems to show instances with multiple checkboxes and dropdownlists. Have I missed something obvious here? What would be best practice in this situation? Thanks

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• WLI domain with 3 servers - issues on JPD process startup

  - by XpiritO

  Hi there. I'm currently working on a clustered WLI environment which comprehends 3 servers: 1 admin server ("AdminServer") and 2 managed servers ("mn1" and "mn2") grouped as a cluster, as follows: Architecture diagram: http://img72.imageshack.us/img72/4112/clusterdiagram.jpg I've developed a JPD process to execute some scheduled tasks, invoked using a Message Broker. I've deployed this project into a single-server WLI domain (with AdminServer only) and it works as expected: the JPD process is invoked (I've configured a Timer Event Generator instance to start it up). Message broker: http://img532.imageshack.us/img532/1443/wlimessagebroker.jpg Timer event generator: http://img408.imageshack.us/img408/7358/wlitimereventgenerator.jpg In order to achieve fail-over and load-balancing capabilities, I'm currently trying to deploy this JPD process into this clustered WLI environment. Although, I'm having some issues with this, as I cannot get it to work properly, even if it still works. Here is a screenshot of the "WLI Process Instance Monitor" (with AdminServer and mn1 instances up and running): http://img710.imageshack.us/img710/8477/wliprocessinstancemonit.jpg According to this screen the process seems to be running, as it shows in this instance monitor screen. However, I don't see any output coming out neither at AdminServer console or mn1 console. In single-server domain it was visible output from JPD process "timeout" callback method, wich implementation is shown below: @com.bea.wli.control.broker.MessageBroker.StaticSubscription(xquery = "", filterValueMatch = "", channelName = "/SamplePrefix/Samples/SampleStringChannel", messageBody = "{x0}") public void subscription(java.lang.String x0) { String toReturn=""; try { Context myCtx = new InitialContext(); MBeanHome mbeanHome = (MBeanHome)myCtx.lookup("weblogic.management.home.localhome"); toReturn=mbeanHome.getMBeanServer().getServerName(); System.out.println("**** executed at **** " + System.currentTimeMillis() + " by: " + toReturn); } catch (Exception e) { System.out.println("Exception!"); e.printStackTrace(); } } (...) @org.apache.beehive.controls.api.events.EventHandler(field = "myT", eventSet = com.bea.control.WliTimerControl.Callback.class, eventName = "onTimeout") public void myT_onTimeout(long time, java.io.Serializable data) { // #START: CODE GENERATED - PROTECTED SECTION - you can safely add code above this comment in this method. #// // input transform System.out.println("**** published at **** " + System.currentTimeMillis()); publishControl.publish("aaaa"); // parameter assignment // #END : CODE GENERATED - PROTECTED SECTION - you can safely add code below this comment in this method. #// } and here is the output visible at "AdminServer" console in single-server domain testing: **** published at **** 1273238090713 **** executed at **** 1273238132123 by: AdminServer **** published at **** 1273238152462 **** executed at **** 1273238152562 by: AdminServer (...) What may be wrong with my clustered configuration? Am I missing something to accomplish clustered deployment? Thanks in advance for your help.

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• CoreData : App crashes when deleting last instance created

  - by Leo

  Hello, I have a 2 tabs application. In the first one, I'm creating objects of the "Sample" and "SampleList" entities. Each sampleList contains an ID and a set of samples. Each sample contains a date and temperature property. In the second tab, I'm displaying my data in a tableView. I implemented the - (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath method in order to delete SampleLists. In my xcdatamodel the delete rule for my relationship between SampleList and Sample is Cascade. My problem is that when I try to delete SampleList I just created, the app crashes and I receive a EXC_BAD_ACCESS signal. If I restart it, then I'm able to delete "old" sampleList without any problems. Earlier, I had the following problem : I couldn't display the the sampleLists I created since I launched the app, because it crashed too. I received also the EXC_BAD_ACCESS signal. Actually, it seemed that the date of the last sample created of the set was nil. If I am not releasing the NSDate I'm using to set the sample's date, I don't have this problem anymore... If anyone could help me to find out what could cause my troubles it would be great !! Here is the method I'm using to create new instances : SampleList *newSampleList = (SampleList *)[NSEntityDescription insertNewObjectForEntityForName:@"SampleList" inManagedObjectContext:managedObjectContext]; [newSampleList setPatchID:patchID]; NSMutableSet *newSampleSet = [[NSMutableSet alloc] init]; NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar]; for (int i = 0; i < [byteArray count]; i=i+4, sampleCount++) { NSDateComponents *comps = [[NSDateComponents alloc] init]; [comps setYear:year]; [comps setMonth:month]; [comps setDay:day]; [comps setHour:hours]; [comps setMinute:minutes]; NSDate *sampleDate = [gregorian dateFromComponents:comps]; Sample *newSample = (Sample *)[NSEntityDescription insertNewObjectForEntityForName:@"Sample" inManagedObjectContext:managedObjectContext]; [newSample setSampleDate:sampleDate]; [newSample setSampleTemperature:[NSNumber numberWithInt:temperature]]; [newSampleSet addObject:newSample]; [comps release]; //[sampleDate release]; } [newSampleList setSampleSet:newSampleSet]; // [newSampleSet release]; NSError *error; if (![managedObjectContext save:&error]) { NSLog(@"Could not Save the context !!"); } [gregorian release];

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• Class template specializations with shared functionality

  - by Thomas

  I'm writing a simple maths library with a template vector type: template<typename T, size_t N> class Vector { public: Vector<T, N> &operator+=(Vector<T, N> const &other); // ... more operators, functions ... }; Now I want some additional functionality specifically for some of these. Let's say I want functions x() and y() on Vector<T, 2> to access particular coordinates. I could create a partial specialization for this: template<typename T> class Vector<T, 3> { public: Vector<T, 3> &operator+=(Vector<T, 3> const &other); // ... and again all the operators and functions ... T x() const; T y() const; }; But now I'm repeating everything that already existed in the generic template. I could also use inheritance. Renaming the generic template to VectorBase, I could do this: template<typename T, size_t N> class Vector : public VectorBase<T, N> { }; template<typename T> class Vector<T, 3> : public VectorBase<T, 3> { public: T x() const; T y() const; }; However, now the problem is that all operators are defined on VectorBase, so they return VectorBase instances. These cannot be assigned to Vector variables: Vector<float, 3> v; Vector<float, 3> w; w = 5 * v; // error: no conversion from VectorBase<float, 3> to Vector<float, 3> I could give Vector an implicit conversion constructor to make this possible: template<typename T, size_t N> class Vector : public VectorBase<T, N> { public: Vector(VectorBase<T, N> const &other); }; However, now I'm converting from Vector to VectorBase and back again. Even though the types are the same in memory, and the compiler might optimize all this away, it feels clunky and I don't really like to have potential run-time overhead for what is essentially a compile-time problem. Is there any other way to solve this?

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• In a PHP project, how do you organize and access your helper objects?

  - by Pekka

  How do you organize and manage your helper objects like the database engine, user notification, error handling and so on in a PHP based, object oriented project? Say I have a large PHP CMS. The CMS is organized in various classes. A few examples: the database object user management an API to create/modify/delete items a messaging object to display messages to the end user a context handler that takes you to the right page a navigation bar class that shows buttons a logging object possibly, custom error handling etc. I am dealing with the eternal question, how to best make these objects accessible to each part of the system that needs it. my first apporach, many years ago was to have a $application global that contained initialized instances of these classes. global $application; $application->messageHandler->addMessage("Item successfully inserted"); I then changed over to the Singleton pattern and a factory function: $mh =&factory("messageHandler"); $mh->addMessage("Item successfully inserted"); but I'm not happy with that either. Unit tests and encapsulation become more and more important to me, and in my understanding the logic behind globals/singletons destroys the basic idea of OOP. Then there is of course the possibility of giving each object a number of pointers to the helper objects it needs, probably the very cleanest, resource-saving and testing-friendly way but I have doubts about the maintainability of this in the long run. Most PHP frameworks I have looked into use either the singleton pattern, or functions that access the initialized objects. Both fine approaches, but as I said I'm happy with neither. I would like to broaden my horizon on what is possible here and what others have done. I am looking for examples, additional ideas and pointers towards resources that discuss this from a long-term, real-world perspective. Also, I'm interested to hear about specialized, niche or plain weird approaches to the issue. Bounty I am following the popular vote in awarding the bounty, the answer which is probably also going to give me the most. Thank you for all your answers!

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• Objective-c design advice for use of different data sources, swapping between test and live

  - by user200341

  I'm in the process of designing an application that is part of a larger piece of work, depending on other people to build an API that the app can make use of to retrieve data. While I was thinking about how to setup this project and design the architecture around it, something occurred to me, and I'm sure many people have been in similar situations. Since my work is depending on other people to complete their tasks, and a test server, this slows work down at my end. So the question is: What's the best practice for creating test repositories and classes, implementing them, and not having to depend on altering several places in the code to swap between the test classes and the actual repositories / proper api calls. Contemplate the following scenario: GetDataFromApiCommand *getDataCommand = [[GetDataFromApiCommand alloc]init]; getDataCommand.delegate = self; [getDataCommand getData]; Once the data is available via the API, "GetDataFromApiCommand" could use the actual API, but until then a set of mock data could be returned upon the call of [getDataCommand getData] There might be multiple instances of this, in various places in the code, so replacing all of them wherever they are, is a slow and painful process which inevitably leads to one or two being overlooked. In strongly typed languages we could use dependency injection and just alter one place. In objective-c a factory pattern could be implemented, but is that the best route to go for this? GetDataFromApiCommand *getDataCommand = [GetDataFromApiCommandFactory buildGetDataFromApiCommand]; getDataCommand.delegate = self; [getDataCommand getData]; What is the best practices to achieve this result? Since this would be most useful, even if you have the actual API available, to run tests, or work off-line, the ApiCommands would not necessarily have to be replaced permanently, but the option to select "Do I want to use TestApiCommand or ApiCommand". It is more interesting to have the option to switch between: All commands are test and All command use the live API, rather than selecting them one by one, however that would also be useful to do for testing one or two actual API commands, mixing them with test data. EDIT The way I have chosen to go with this is to use the factory pattern. I set up the factory as follows: @implementation ApiCommandFactory + (ApiCommand *)newApiCommand { // return [[ApiCommand alloc]init]; return [[ApiCommandMock alloc]init]; } @end And anywhere I want to use the ApiCommand class: GetDataFromApiCommand *getDataCommand = [ApiCommandFactory newApiCommand]; When the actual API call is required, the comments can be removed and the mock can be commented out. Using new in the message name implies that who ever uses the factory to get an object, is responsible for releasing it (since we want to avoid autorelease on the iPhone). If additional parameters are required, the factory needs to take these into consideration i.e: [ApiCommandFactory newSecondApiCommand:@"param1"]; This will work quite well with repositories as well.

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• HttpWebResponse get mixed up when used inside multiple threads

  - by Holli

  In my Application I have a few threads who will get data from a web service. Basically I just open an URL and get an XML output. I have a few threads who do this continuously but with different URLs. Sometimes the results are mixed up. The XML output doesn't belong to the URL of a thread but to the URL of another thread. In each thread I create an instance of the class GetWebPage and call the method Get from this instance. The method is very simple and based mostly on code from the MSDN documentation. (See below. I removed my error handling here!) public string Get(string userAgent, string url, string user, string pass, int timeout, int readwriteTimeout, WebHeaderCollection whc) { string buffer = string.Empty; HttpWebRequest myWebRequest = (HttpWebRequest)WebRequest.Create(url); if (!string.IsNullOrEmpty(userAgent)) myWebRequest.UserAgent = userAgent; myWebRequest.Timeout = timeout; myWebRequest.ReadWriteTimeout = readwriteTimeout; myWebRequest.Credentials = new NetworkCredential(user, pass); string[] headers = whc.AllKeys; foreach (string s in headers) { myWebRequest.Headers.Add(s, whc.Get(s)); } using (HttpWebResponse myWebResponse = (HttpWebResponse)myWebRequest.GetResponse()) { using (Stream ReceiveStream = myWebResponse.GetResponseStream()) { Encoding encode = Encoding.GetEncoding("utf-8"); StreamReader readStream = new StreamReader(ReceiveStream, encode); // Read 1024 characters at a time. Char[] read = new Char[1024]; int count = readStream.Read(read, 0, 1024); int break_counter = 0; while (count > 0 && break_counter < 10000) { String str = new String(read, 0, count); buffer += str; count = readStream.Read(read, 0, 1024); break_counter++; } } } return buffer; As you can see I have no public properties or any other shared resources. At least I don't see any. The url is the service I call in the internet and buffer is the XML Output from the server. Like I said I have multiple instances of this class/method in a few threads (10 to 12) and sometimes buffer does not belong the the url of the same thread but another thread.

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• Java Swing: JWindow appears behind all other process windows, and will not disappear

  - by Kim Jong Woo

  I am using JWindow to display my splash screen during the application start up. however it will not appear in front of all windows as it should, and it will not disappear as well. import java.awt.BorderLayout; import java.awt.Color; import java.awt.Dimension; import java.awt.Font; import java.awt.Toolkit; import javax.swing.BorderFactory; import javax.swing.ImageIcon; import javax.swing.JLabel; import javax.swing.JPanel; import javax.swing.JWindow; public class MySplash { public static MySplash INSTANCE; private static JWindow jw; public MySplash(){ createSplash(); } private void createSplash() { jw = new JWindow(); JPanel content = (JPanel) jw.getContentPane(); content.setBackground(Color.white); // Set the window's bounds, centering the window int width = 328; int height = 131; Dimension screen = Toolkit.getDefaultToolkit().getScreenSize(); int x = (screen.width - width) / 2; int y = (screen.height - height) / 2; jw.setBounds(x, y, width, height); // Build the splash screen JLabel label = new JLabel(new ImageIcon("splash.jpg")); JLabel copyrt = new JLabel("SplashScreen Test", JLabel.CENTER); copyrt.setFont(new Font("Sans-Serif", Font.BOLD, 12)); content.add(label, BorderLayout.CENTER); content.add(copyrt, BorderLayout.SOUTH); Color oraRed = new Color(156, 20, 20, 255); content.setBorder(BorderFactory.createLineBorder(oraRed, 0)); } public synchronized static MySplash getInstance(){ if(INSTANCE==null){ INSTANCE = new MySplash(); } return INSTANCE; } public void showSplash(){ jw.setAlwaysOnTop(true); jw.toFront(); jw.setVisible(true); return; } public void hideSplash(){ jw.setAlwaysOnTop(false); jw.toBack(); jw.setVisible(false); return; } } So in my main class which extends JFrame, I call my splash screen by SwingUtilities.invokeLater(new Runnable(){ @Override public void run() { MySplash.getInstance().showSplash(); } }); However, the JWindow appears behind the all open instances of windows on my computer. Hiding the JWindow also doesn't work. SwingUtilities.invokeLater(new Runnable(){ @Override public void run() { MySplash.getInstance().hideSplash(); } });

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• deleting element objects of a std vector using erase : a) memory handling and b) better way?

  - by memC

  hi, I have a vec_A that stores instances of class A as: vec_A.push_back(A()); I want to remove some elements in the vector at a later stage and have two questions: a) The element is deleted as: vec_A.erase(iterator) Is there any additional code I need to add to make sure that there is no memory leak? . b) Assume that condition if(num <5) is if num is among a specific numberList. Given this, is there a better way to delete the elements of a vector than what I am illustrating below? #include<vector> #include<stdio.h> #include<iostream> class A { public: int getNumber(); A(int val); ~A(){}; private: int num; }; A::A(int val){ num = val; }; int A::getNumber(){ return num; }; int main(){ int i =0; int num; std::vector<A> vec_A; std::vector<A>::iterator iter; for ( i = 0; i < 10; i++){ vec_A.push_back(A(i)); } iter = vec_A.begin(); while(iter != vec_A.end()){ std::cout << "\n --------------------------"; std::cout << "\n Size before erase =" << vec_A.size(); num = iter->getNumber() ; std::cout << "\n num = "<<num; if (num < 5){ vec_A.erase(iter); } else{ iter++; } std::cout << "\n size after erase =" << vec_A.size(); } std::cout << "\nPress RETURN to continue..."; std::cin.get(); return 0; }

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• how to develop a program to minimize errors in human transcription of hand written surveys

  - by Alex. S.

  I need to develop custom software to do surveys. Questions may be of multiple choice, or free text in a very few cases. I was asked to design a subsystem to check if there is any error in the manual data entry for the multiple choices part. We're trying to speed up the user data entry process and to minimize human input differences between digital forms and the original questionnaires. The surveys are filled with handwritten marks and text by human interviewers, so it's possible to find hard to read marks, or also the user could accidentally select a different value in some question, and we would like to avoid that. The software must include some automatic control to detect possible typing differences. Each answer of the multiple choice questions has the same probability of being selected. This question has two parts: The GUI. The most simple thing I have in mind is to implement the most usable design of the questions display: use of large and readable fonts and space generously the choices. Is there something else? For faster input, I would like to use drop down lists (favoring keyboard over mouse). Given the questions are grouped in sections, I would like to show the answers selected for the questions of that section, but this could slow down the process. Any other ideas? The error checking subsystem. What else can I do to minimize or to check human typos in the multiple choice questions? Is this a solvable problem? is there some statistical methodology to check values that were entered by the users are the same from the hand filled forms? For example, let's suppose the survey has 5 questions, and each has 4 options. Let's say I have n survey forms filled in paper by interviewers, and they're ready to be entered in the software, then how to minimize the accidental differences that can have the manual transcription of the n surveys, without having to double check everything in the 5 questions of the n surveys? My first suggestion is that at the end of the processing of all the hand filled forms, the software could choose some forms randomly to make a double check of the responses in a few instances, but on what criteria can I make this selection? This validation would be enough to cover everything in a significant way? The actual survey is nation level and it has 56 pages with over 200 questions in total, so it will be a lot of hand written pages by many people, and the intention is to reduce the likelihood of errors and to optimize speed in the data entry process. The surveys must filled in paper first, given the complications of taking laptops or handhelds with the interviewers.

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• Greasemonkey is getting an empty document.body on select Google pages.

  - by Brock Adams

  Hi, I have a Greasemonkey script that processes Google search results. But it's failing in a few instances, when xpath searches (and document body) appear to be empty. Running the code in Firebug's console works every time. It only fails in a Greasemonkey script. Greasemonkey sees an empty document.body. I've boiled the problem down to a test, greasemonkey script, below. I'm using Firefox 3.5.9 and Greasemonkey 0.8.20100408.6 (but earlier versions had the same problem). Problem: Greasemonkey sees an empty document.body. Recipe to Duplicate: Install the Greasemonkey script. Open a new tab or window. Navigate to Google.com (http://www.google.com/). Search on a simple term like "cats". Check Firefox's Error console (Ctrl-shift-J) or Firebug's console. The script will report that document body is empty. Hit refresh. The script will show a good result (document body found). Note that the failure only reliably appears on Google results obtained this way, and on a new tab/window. Turn javascript off globally (javascript.enabled set to false in about:config). Repeat steps 2 thru 5. Only now the Greasemonkey script will work. It seems that Google javascript is killing the DOM tree for greasemonkey, somehow. I've tried a time-delayed retest and even a programmatic refresh; the script still fails to see the document body. Test Script: // // ==UserScript== // @name TROUBLESHOOTING 2 snippets // @namespace http://www.google.com/ // @description For code that has funky misfires and defies standard debugging. // @include http://*/* // ==/UserScript== // function LocalMain (sTitle) { var sUserMessage = ''; //var sRawHtml = unsafeWindow.document.body.innerHTML; //-- unsafeWindow makes no difference. var sRawHtml = document.body.innerHTML; if (sRawHtml) { sRawHtml = sRawHtml.replace (/^\s\s*/, ''). substr (0, 60); sUserMessage = sTitle + ', Doc body = ' + sRawHtml + ' ...'; } else { sUserMessage = sTitle + ', Document body seems empty!'; } if (typeof (console) != "undefined") { console.log (sUserMessage); } else { if (typeof (GM_log) != "undefined") GM_log (sUserMessage); else if (!sRawHtml) alert (sUserMessage); } } LocalMain ('Preload'); window.addEventListener ("load", function() {LocalMain ('After load');}, false);

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• Configuration Element Collection Section

  - by Matt

  I would like to set up a custom app configuration element collection section like this <logSectionGroup> <logSection name="Testttt"> <properties name ="Pride"> <pathName="TestingLog.txt"/> <deleteRetention="100"/> <deleteZeroRetention="5"/> <wildcard="*.txt"/> </properties> <properties name ="Adhoc"> <pathName="blah.txt"/> <deleteRetention="70"/> <deleteZeroRetention="3"/> <wildcard="*.*"/> </properties> </logSection> </logSectionGroup> Is this possible? Properties would be the configuration element, and log section would be the configuration element collection. The problem is, I've only seen where you can have multiple instances of a single element instead of multiple elements. <Section name="Section1"> <Section name="Section1"> <SubSection name="SubSection1"> <Item name="Item1" /> <Item name="Item2" /> </SubSection> <SubSection name="SubSection2"> <Item name="Item1" /> <Item name="Item2" /> </SubSection> </Section> When you use GetElementKey() you have it return element "name" in the above example but how would you return 4 different elements like "pathName" "deleteRetention" etc. Here is my Definition for PropElement Public Class PropElement Inherits ConfigurationElement <ConfigurationProperty("pathName", IsRequired:=True)> _ Public Property PathName() As String Get Return CStr(Me("pathName")) End Get Set(ByVal value As String) Me("pathName") = value End Set End Property <ConfigurationProperty("deleteRetention", DefaultValue:="0", IsRequired:=False)> _ Public Property DeleteRetention() As Integer Get Return CStr(Me("deleteRetention")) End Get Set(ByVal value As Integer) Me("deleteRetention") = value End Set End Property <ConfigurationProperty("deleteZeroRetention", DefaultValue:="0", IsRequired:=False)> _ Public Property DeleteZeroRetention() As Integer Get Return CStr(Me("deleteZeroRetention")) End Get Set(ByVal value As Integer) Me("deleteZeroRetention") = value End Set End Property <ConfigurationProperty("wildcard", DefaultValue:="*.*", IsRequired:=False)> _ Public Property Wildcard() As String Get Return CStr(Me("wildcard")) End Get Set(ByVal value As String) Me("wildcard") = value End Set End Property End Class

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• Converting C source to C++

  - by Barry Kelly

  How would you go about converting a reasonably large (300K), fairly mature C codebase to C++? The kind of C I have in mind is split into files roughly corresponding to modules (i.e. less granular than a typical OO class-based decomposition), using internal linkage in lieu private functions and data, and external linkage for public functions and data. Global variables are used extensively for communication between the modules. There is a very extensive integration test suite available, but no unit (i.e. module) level tests. I have in mind a general strategy: Compile everything in C++'s C subset and get that working. Convert modules into huge classes, so that all the cross-references are scoped by a class name, but leaving all functions and data as static members, and get that working. Convert huge classes into instances with appropriate constructors and initialized cross-references; replace static member accesses with indirect accesses as appropriate; and get that working. Now, approach the project as an ill-factored OO application, and write unit tests where dependencies are tractable, and decompose into separate classes where they are not; the goal here would be to move from one working program to another at each transformation. Obviously, this would be quite a bit of work. Are there any case studies / war stories out there on this kind of translation? Alternative strategies? Other useful advice? Note 1: the program is a compiler, and probably millions of other programs rely on its behaviour not changing, so wholesale rewriting is pretty much not an option. Note 2: the source is nearly 20 years old, and has perhaps 30% code churn (lines modified + added / previous total lines) per year. It is heavily maintained and extended, in other words. Thus, one of the goals would be to increase mantainability. [For the sake of the question, assume that translation into C++ is mandatory, and that leaving it in C is not an option. The point of adding this condition is to weed out the "leave it in C" answers.]

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• Patterns: Local Singleton vs. Global Singleton?

  - by Mike Rosenblum

  There is a pattern that I use from time to time, but I'm not quite sure what it is called. I was hoping that the SO community could help me out. The pattern is pretty simple, and consists of two parts: A singleton factory, which creates objects based on the arguments passed to the factory method. Objects created by the factory. So far this is just a standard "singleton" pattern or "factory pattern". The issue that I'm asking about, however, is that the singleton factory in this case maintains a set of references to every object that it ever creates, held within a dictionary. These references can sometimes be strong references and sometimes weak references, but it can always reference any object that it has ever created. When receiving a request for a "new" object, the factory first searches the dictionary to see if an object with the required arguments already exits. If it does, it returns that object, if not, it returns a new object and also stores a reference to the new object within the dictionary. This pattern prevents having duplicative objects representing the same underlying "thing". This is useful where the created objects are relatively expensive. It can also be useful where these objects perform event handling or messaging - having one object per item being represented can prevent multiple messages/events for a single underlying source. There are probably other reasons to use this pattern, but this is where I've found this useful. My question is: what to call this? In a sense, each object is a singleton, at least with respect to the data it contains. Each is unique. But there are multiple instances of this class, however, so it's not at all a true singleton. In my own personal terminology, I tend to call the factory method a "global singleton". I then call the created objects "local singletons". I sometimes also say that the created objects have "reference equality", meaning that if two variables reference the same data (the same underlying item) then the reference they each hold must be to the same exact object, hence "reference equality". But these are my own invented terms, and I am not sure that they are good ones. Is there standard terminology for this concept? And if not, could some naming suggestions be made? Thanks in advance...

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