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  • I can not get the text from a selected item in a listview...pleeeeasss help.

    - by Miguel
    I always get an ClassCastException error... i do not what else to do... - I'm using a data biding concept to populated the listview from a sqlite3 database. - I just want to get the selected item text after a long press click. This is the code of the activity: public class ItemConsultaGastos extends ListActivity { private DataHelper dh ; TextView seleccion; private static String[] FROM = {DataHelper.MES, DataHelper.ANO}; private static int[] TO = {R.id.columnaMes, R.id.columnaAno }; public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.muestrafechas); this.dh = new DataHelper(this); Cursor cursor = dh.selectAllMeses(); startManagingCursor(cursor); this.mostrarFechas(cursor); ListView lv = getListView(); lv.setOnItemLongClickListener(new OnItemLongClickListener(){ @Override public boolean onItemLongClick(AdapterView<?> arg0, View arg1,int row, long arg3) { //here is where i got the classCastException. String[] tmp = (String[]) arg0.getItemAtPosition(row); //tmp[0] ist the Text of the first TextView displayed by the clicked ListItem Log.w("Gastos: ", "El texto: " + tmp[0].toString()); return true; } }); } private void mostrarFechas(Cursor cursor) { SimpleCursorAdapter adapter = new SimpleCursorAdapter(this,R.layout.muestrafechasitem,cursor, FROM, TO); setListAdapter(adapter); } } ///// This is the xml where a define the rows to show on the listview <TextView android:id="@+id/espacio" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text=" " /> <TextView android:id="@+id/columnaAno" android:layout_width="wrap_content" android:layout_height="wrap_content" android:textSize="20sp" android:layout_toRightOf="@+id/espacio"/> <TextView android:id="@+id/separador1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text=" -- " android:layout_toRightOf="@+id/columnaAno" android:textSize="20sp" /> <TextView android:id="@+id/columnaMes" android:layout_width="fill_parent" android:layout_height="wrap_content" android:layout_toRightOf="@+id/separador1" android:textSize="20sp"/>

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  • Linked lists in Java - help with assignment

    - by user368241
    Representation of a string in linked lists In every intersection in the list there will be 3 fields : The letter itself. The number of times it appears consecutively. A pointer to the next intersection in the list. The following class CharNode represents a intersection in the list : public class CharNode { private char _data; private int _value; private charNode _next; public CharNode (char c, int val, charNode n) { _data = c; _value = val; _next = n; } public charNode getNext() { return _next; } public void setNext (charNode node) { _next = node; } public int getValue() { return _value; } public void setValue (int v) { value = v; } public char getData() { return _data; } public void setData (char c) { _data = c; } } The class StringList represents the whole list : public class StringList { private charNode _head; public StringList() { _head = null; } public StringList (CharNode node) { _head = node; } } Add methods to the class StringList according to the details : (I will add methods gradually according to my specific questions) (Pay attention, these are methods from the class String and we want to fulfill them by the representation of a string by a list as explained above) public int indexOf (int ch) - returns the index in the string it is operated on of the first appeareance of the char "ch". If the char "ch" doesn't appear in the string, returns -1. If the value of fromIndex isn't in the range, returns -1. Pay attention to all the possible error cases. Write what is the time complexity and space complexity of every method that you wrote. Make sure the methods you wrote are effective. It is NOT allowed to use ready classes of Java. It is NOT allowed to move to string and use string operations. Here is my try to write the method indexOf (int ch). Kindly assist me with fixing the bugs so I can move on. public int indexOf (int ch) { int count = 0; charNode pose = _head; if (pose == null ) { return -1; } for (pose = _head; pose!=null && pose.getNext()!='ch'; pose = pose.getNext()) { count++; } if (pose!=null) return count; else return -1; }

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  • JApplet behaving unexpectedly

    - by JohnW
    import java.awt.Graphics; import java.awt.Image; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import javax.swing.JApplet; import javax.swing.Timer; public class CountingSheep extends JApplet { private Image sheepImage; private Image backgroundImage; private GameBoard gameBoard; private scoreBoard scoreBoard; public void init() { loadImages(); gameBoard = new GameBoard(sheepImage, backgroundImage); scoreBoard = new scoreBoard(); getContentPane().add(gameBoard); getContentPane().add(scoreBoard); } public void loadImages() { sheepImage = getImage(getDocumentBase(), "sheep.png"); backgroundImage = getImage(getDocumentBase(), "bg.jpg"); } } Update guys: Alright, first of all, thank you very much for all the help you've given so far (specifically creemam and Hovercraft Full of Eels), and your persistence. You've helped me out a lot as this is incredibly important (i.e. me passing my degree). The problem now is: The program works correctly when nothing but the GameBoard class is added to the JApplet, however, when I try to add the ScoreBoard class, both Panel classes do not show on the Applet. I'm guessing this is now down to positioning? Any ideas? EDIT: Gone back to the previously asked question Hovercraft, and found it was due to the layout of the contentPane and the order at with the components were added. Thanks to all of you so much. People like you make the development community a bit of alright.

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  • How to add a gwt widget to a gwt Composite already visible at runtime using MVP?

    - by mary4pfc
    Hi! I'm building an application whose menus depend on user roles. Once user is logged in and, therefore, her roles are known, I want to create the Hyperlinks related to the user and add them to the menu. I'm using MVP. Here's my code for the presenter: public class AdminMenuAreaPresenter extends WidgetPresenter<AdminMenuAreaPresenter.Display> { public interface Display extends WidgetDisplay{ public void addLink(String link); } private DispatchAsync dispatcher; private SessionManager sessionManager; @Inject public AdminMenuAreaPresenter(AdminMenuAreaPresenter.Display display, EventBus bus, DispatchAsync dispatcher, SessionManager sessionManager){ super(display, bus); this.dispatcher = dispatcher; this.sessionManager = sessionManager; this.bind(); } @Override protected void onBind() { super.onBind(); registerHandler(eventBus.addHandler(LoginEvent.TYPE, new LoginEventHandler() { @Override public void onLogin(LoginEvent event) { display.addLink("register user"); } })); } @Override protected void onUnbind() { // TODO Auto-generated method stub } @Override protected void onRevealDisplay() { // TODO Auto-generated method stub } } And here's the View: public class AdminMenuAreaView extends Composite implements AdminMenuAreaPresenter.Display{ private VerticalPanel vPanel; private Hyperlink registerUserLink; public AdminMenuAreaView(){ vPanel = new VerticalPanel(); initWidget(vPanel); } @Override public Widget asWidget() { return this; } public void addLink(String s){ registerUserLink = new Hyperlink(s, "this is new target"); this.vPanel.add(registerUserLink); registerUserLink.setVisible(true); } public HasClickHandlers getRegisterUserLink(){ return registerUserLink; } What am I doing wrong? Flow program goes throgh the addLink() method, but nothing is added to the view either dom document. Thank you.

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  • How to attach Gtk::Menu to Gtk::Widget

    - by krokoziabla
    Gtk::Menu has void Gtk::Menu::attach_to_widget(Widget& attach_widget, GtkMenuDetachFunc detacher) void Gtk::Menu::attach_to_widget (Widget& attach_widget) wrapper methods for void gtk_menu_attach_to_widget(GtkMenu *menu, GtkWidget *attach_widget, GtkMenuDetachFunc detacher) But why are they protected? If I want to make a pop-up menu on a widget, how, then, can I get access to it from the menu's activate call-back if not via these methods?

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  • Implement a threading to prevent UI block on a bug in an async function

    - by Marcx
    I think I ran up againt a bug in an async function... Precisely the getDirectoryListingAsync() of the File class... This method is supposted to return an object containing the lists of files in a specified folder. I found that calling this method on a direcory with a lot of files (in my tests more than 20k files), after few seconds there is a block on the UI until the process is completed... I think that this method is separated in two main block: 1) get the list of files 2) create the array with the details of the files The point 1 seems to be async (for a few second the ui is responsive), then when the process pass from point 1 to point 2 the block of the UI occurs until the complete event is dispathed... Here's some (simple) code: private function checkFiles(dir:File):void { if (dir.exists) { dir.addEventListener( FileListEvent.DIRECTORY_LISTING, listaImmaginiLocale); dir.getDirectoryListingAsync(); // after this point, for the firsts seconds the UI respond well (point 1), // few seconds later (point 2) the UI is frozen } } private function listaImmaginiLocale( event:FileListEvent ):void { // from this point on the UI is responsive again... } Actually in my projects there are some function that perform an heavy cpu usage and to prevent the UI block I implemented a simple function that after some iteration will wait giving time to UI to be refreshed. private var maxIteration:int = 150000; private function sampleFunct(offset:int = 0) :void { if (offset < maxIteration) { // do something // call the recursive function using a timeout.. // if the offset in multiple by 1000 the function will wait 15 millisec, // otherwise it will be called immediately // 1000 is a random number for the pourpose of this example, but I usually change the // value based on how much heavy is the function itself... setTimeout(function():void{aaa(++offset);}, (offset%1000?15:0)); } } Using this method I got a good responsive UI without afflicting performance... I'd like to implement it into the getDirectoryListingAsync method but I don't know if it's possibile how can I do it where is the file to edit or extend.. Any suggestion???

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  • NSNotifications vs delegate for multiple instances of same protocol

    - by Brent Traut
    I could use some architectural advice. I've run into the following problem a few times now and I've never found a truly elegant way to solve it. The issue, described at the highest level possible:I have a parent class that would like to act as the delegate for multiple children (all using the same protocol), but when the children call methods on the parent, the parent no longer knows which child is making the call. I would like to use loose coupling (delegates/protocols or notifications) rather than direct calls. I don't need multiple handlers, so notifications seem like they might be overkill. To illustrate the problem, let me try a super-simplified example: I start with a parent view controller (and corresponding view). I create three child views and insert each of them into the parent view. I would like the parent view controller to be notified whenever the user touches one of the children. There are a few options to notify the parent: Define a protocol. The parent implements the protocol and sets itself as the delegate to each of the children. When the user touches a child view, its view controller calls its delegate (the parent). In this case, the parent is notified that a view is touched, but it doesn't know which one. Not good enough. Same as #1, but define the methods in the protocol to also pass some sort of identifier. When the child tells its delegate that it was touched, it also passes a pointer to itself. This way, the parent know exactly which view was touched. It just seems really strange for an object to pass a reference to itself. Use NSNotifications. The parent defines a separate method for each of the three children and then subscribes to the "viewWasTouched" notification for each of the three children as the notification sender. The children don't need to attach themselves to the user dictionary, but they do need to send the notification with a pointer to themselves as the scope. Same as #4, but rather than using separate methods, the parent could just use one with a switch case or other branching along with the notification's sender to determine which path to take. Create multiple man-in-the-middle classes that act as the delegates to the child views and then call methods on the parent either with a pointer to the child or with some other differentiating factor. This approach doesn't seem scalable. Are any of these approaches considered best practice? I can't say for sure, but it feels like I'm missing something more obvious/elegant.

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  • Call to a member function get_segment() error

    - by hogofwar
    I'm having this problem with this piece of PHP code: class Core { public function start() { require("funk/funks/libraries/uri.php"); $this->uri = new uri(); require("funk/core/loader.php"); $this->load = new loader(); if($this->uri->get_segment(1) != "" and file_exists("funk/pages/".$uri->get_segment(1).".php")){ Only a snippet of the code The best way I can explain it is that it is a class calling upon another class (uri.php) and i am getting the error: Fatal error: Call to a member function get_segment() on a non-object in /home/eeeee/public_html/private/funkyphp/funk/core/core.php on line 11 (the if($this-uri-get_segment(1) part) I'm having this problem a lot and it is really bugging me. the library code is: <?php class uri { private $server_path_info = ''; private $segment = array(); private $segments = 0; public function __construct() { $segment_temp = array(); $this->server_path_info = preg_replace("/\?/", "", $_SERVER["PATH_INFO"]); $segment_temp = explode("/", $this->server_path_info); foreach ($segment_temp as $key => $seg) { if (!preg_match("/([a-zA-Z0-9\.\_\-]+)/", $seg) || empty($seg)) unset($segment_temp[$key]); } foreach ($segment_temp as $k => $value) { $this->segment[] = $value; } unset($segment_temp); $this->segments = count($this->segment); } public function segment_exists($id = 0) { $id = (int)$id; if (isset($this->segment[$id])) return true; else return false; } public function get_segment($id = 0) { $id--; $id = (int)$id; if ($this->segment_exists($id) === true) return $this->segment[$id]; else return false; } } ?>

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  • Sub-millisecond precision timing in C or C++

    - by andand
    What techniques / methods exist for getting sub-millisecond precision timing data in C or C++, and what precision and accuracy do they provide? I'm looking for methods that don't require additional hardware. The application involves waiting for approximately 50 microseconds +/- 1 microsecond while some external hardware collects data. EDIT: OS is Wndows, probably with VS2010. If I can get drivers and SDK's for the hardware on Linux, I can go there. Thanks.

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  • Difference between abstract class and interface

    - by nectar
    A class implementing an interface has to implement all the methods of the interface, but if that class is implementing an abctract class is it necessary to implement all abstract methods? If not, can we create the object of that class which is implementing the Abstract class???

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  • How to easily Generate Synth Chords Sounds in Android?

    - by barata7
    How to easily Generate Synth Chords Sounds in Android? I wanna be able to generate dynamically an in game Music using 8bit. Tried with AudioTrack, but did not get good results of nice sounds yet. Any examples out there? I have tried the following code without success: public class BitLoose { private final int duration = 1; // seconds private final int sampleRate = 4200; private final int numSamples = duration * sampleRate; private final double sample[] = new double[numSamples]; final AudioTrack audioTrack; public BitLoose() { audioTrack = new AudioTrack(AudioManager.STREAM_MUSIC, sampleRate, AudioFormat.CHANNEL_CONFIGURATION_MONO, AudioFormat.ENCODING_PCM_8BIT, numSamples, AudioTrack.MODE_STREAM); audioTrack.play(); } public void addTone(final int freqOfTone) { // fill out the array for (int i = 0; i < numSamples; ++i) { sample[i] = Math.sin(2 * Math.PI * i / (sampleRate / freqOfTone)); } // convert to 16 bit pcm sound array // assumes the sample buffer is normalised. final byte generatedSnd[] = new byte[numSamples]; int idx = 0; for (final double dVal : sample) { // scale to maximum amplitude final short val = (short) ((((dVal * 255))) % 255); // in 16 bit wav PCM, first byte is the low order byte generatedSnd[idx++] = (byte) (val); } audioTrack.write(generatedSnd, 0, sampleRate); } public void stop() { audioTrack.stop(); }

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  • Cannot Find Symbol Method?

    - by Aaron
    In my driver program, This line gives me cannot find symbol error and I don't know why, the method is clearly defined in the SavingsAccount class, and I can refer to all other methods in my driver program but just not that one, I tried changing the type to double, and etc but still not working. Refer to ** Account acct2 = new SavingsAccount (name); acct2.calculateBalance(); SavingsAccount Class Inherited from Account Class: public class SavingsAccount extends Account { private final short minBalance = 0; private double overdraftFee; private double yearlyInterestRate = 0.02; private double interestAmount; public SavingsAccount (String name) { super(name); } public double withdraw (double amount) { if (accountBalance - amount >= minBalance) { accountBalance -= amount; System.out.print ("Withdraw Successful"); } else { accountBalance -= amount; overdraftFee = accountBalance * (0.10); accountBalance += overdraftFee; System.out.print ("Withdraw Succesful, however overdraft fee of 10% has been applied to your account"); } return accountBalance; } **public void calculateBalance () { interestAmount = (accountBalance * yearlyInterestRate); accountBalance += interestAmount; }** public String toString() { return super.toString() + " Interest Received: " + interestAmount; } } Account class, if needed import java.util.Random; import java.text.NumberFormat; public abstract class Account { protected double accountBalance; protected long accountNumber; protected String accountHolder; public Account (String name) { accountHolder = name; accountBalance = 0; Random accountNo = new Random(); accountNumber = accountNo.nextInt(100000); } public double deposit (double amount) { accountBalance += amount; return accountBalance; } public String toString() { NumberFormat accountBal = NumberFormat.getCurrencyInstance(); return "Account Balance: " + accountBal.format(accountBalance) + "\nAccount Number: " + accountNumber; } public String getAccountHolder() { return accountHolder; } public double getAccountBalance() { return accountBalance; } public abstract double withdraw (double amount); }

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  • How to refer to enum values inside nhibernate formula mapping specification?

    - by mark
    Dear ladies and sirs. I have two entities types: RunContainer parent entity type Run child entity type Run has a property Status, which is of type RunStatus, like so: public enum RunStatus { Created, Starting, // ... } public class Run { public int ContainerId { get; private set; } // ... public RunStatus Status { get; private set; } } RunContainer has a calculated property ActiveRunCount, like so: public class RunContainer { public int Id { get; private set; } // ... public int ActiveRunCount { get; private set; } } In the mapping for the RunContainer.ActiveRunCount property, I use the formula specification like so: <property name="ActiveRunCount" formula="(select count(r.Id) from Run r where r.ContainerId = Id and r.Status = 1)"/> My problem is that I refer to the RunStatus enum values in the formula by their respective numeric value, rather than the appropriate symbolic name. Can anyone tell me how can I use the symbolic name instead? Thanks.

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  • Changing the Hibernate 3 settings

    - by Bogdanel
    I use Hibernate3 and Hibernate Tools 3.2.4 to generate hbm.xml and java files and I want to use List instead of HashSet(...). I've tried to modify the hbm.xml files, putting list instead of set. Is there any way to specify to hibernate tools that I want to generate automatically a list not a HashSet? This is an exemple: Java class public class Test implements java.io.Serializable { private Long testId; private Course course; private String testName; private Set<Question> questions = new HashSet<Question>( 0 ); } Test.hbm.xml: <set name="questions" inverse="true" lazy="true" table="questions" fetch="select"> <key> <column name="test_id" not-null="true" /> </key> <one-to-many class="com.app.objects.Question" /> ... </set> I thought that I could find a clue in the "reveng.xml" file, but I failed.

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  • Checking method visibility in PHP

    - by phobia
    Is there any way of checking if a class method has been declared as private or public? I'm working on a controller where the url is mapped to methods in the class, and I only want to trigger the methods if they are defined as public.

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  • Good books and resources on user interface testing

    - by josefx
    I am looking for good books and articles on user-interface testing. What they should contain (one or more of): different test methods/strategies examples, use cases naming pros and cons for different methods something important I might have forgotten :-) What they should not be: Only about general tests and not gui tests describing a test framework limited to a single language What are the best resources you know of? (preferably language agnostic)

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  • Python required variable style

    - by Adam Nelson
    What is the best style for a Python method that requires the keyword argument 'required_arg': def test_method(required_arg, *args, **kwargs: def test_method(*args, **kwargs): required_arg = kwargs.pop('required_arg') if kwargs: raise ValueError('Unexpected keyword arguments: %s' % kwargs) Or something else? I want to use this for all my methods in the future so I'm kind of looking for the best practices way to deal with required keyword arguments in Python methods.

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  • Compile C++ in Visual Studio

    - by Kasun
    Hi All.. I use this method to compile C++ file in VS. But even i provide the correct file it returns false. Can any one help me... This is class called CL class CL { private const string clexe = @"cl.exe"; private const string exe = "Test.exe", file = "test.cpp"; private string args; public CL(String[] args) { this.args = String.Join(" ", args); this.args += (args.Length > 0 ? " " : "") + "/Fe" + exe + " " + file; } public Boolean Compile(String content, ref string errors) { if (File.Exists(exe)) File.Delete(exe); if (File.Exists(file)) File.Delete(file); File.WriteAllText(file, content); Process proc = new Process(); proc.StartInfo.UseShellExecute = false; proc.StartInfo.RedirectStandardOutput = true; proc.StartInfo.RedirectStandardError = true; proc.StartInfo.FileName = clexe; proc.StartInfo.Arguments = this.args; proc.StartInfo.CreateNoWindow = true; proc.Start(); //errors += proc.StandardError.ReadToEnd(); errors += proc.StandardOutput.ReadToEnd(); proc.WaitForExit(); bool success = File.Exists(exe); return success; } } This is my button click event private void button1_Click(object sender, EventArgs e) { string content = "#include <stdio.h>\nmain(){\nprintf(\"Hello world\");\n}\n"; string errors = ""; CL k = new CL(new string[] { }); if (k.Compile(content, ref errors)) Console.WriteLine("Success!"); else MessageBox.Show("Errors are : ", errors); }

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  • Why does this code sample produce a memory leak?

    - by citronas
    In the university we were given the following code sample and we were being told, that there is a memory leak when running this code. The sample should demonstrate that this is a situation where the garbage collector can't work. As far as my object oriented programming goes, the only codeline able to create a memory leak would be items=Arrays.copyOf(items,2 * size+1); The documentation says, that the elements are copied. Does that mean the reference is copied (and therefore another entry on the heap is created) or the object itself is being copied? As far as I know, Object and therefore Object[] are implemented as a reference type. So assigning a new value to 'items' would allow the garbage collector to find that the old 'item' is no longer referenced and can therefore be collected. In my eyes, this the codesample does not produce a memory leak. Could somebody prove me wrong? =) import java.util.Arrays; public class Foo { private Object[] items; private int size=0; private static final int ISIZE=10; public Foo() { items= new Object[ISIZE]; } public void push(final Object o){ checkSize(); items[size++]=o; } public Object pop(){ if (size==0) throw new ///... return items[--size]; } private void checkSize(){ if (items.length==size){ items=Arrays.copyOf(items,2 * size+1); } } }

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  • How to choose between UUIDs, autoincrement/sequence keys and sequence tables for database primary keys?

    - by Tim
    I'm looking at the pros and cons of these three primary methods of coming up with primary keys for database rows. So assuming I am using a database that supports more than one of these methods, is there a simple heuristic to determine what the best option would be for me? How do considerations such a distributed/multiple masters, performance requirements, ORM use, security and testing have on the choice? Any unexpected drawbacks that one might run into?

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  • ASP.Net MVC TDD using Moq

    - by Nicholas Murray
    I am trying to learn TDD/BDD using NUnit and Moq. The design that I have been following passes a DataService class to my controller to provide access to repositories. I would like to Mock the DataService class to allow testing of the controllers. There are lots of examples of mocking a repository passed to the controller but I can't work out how to mock a DataService class in this scenerio. Could someone please explain how to implement this? Here's a sample of the relevant code: [Test] public void Can_View_A_Single_Page_Of_Lists() { var dataService = new Mock<DataService>(); var controller = new ListsController(dataService); ... } namespace Services { public class DataService { private readonly IKeyedRepository<int, FavList> FavListRepository; private readonly IUnitOfWork unitOfWork; public FavListService FavLists { get; private set; } public DataService(IKeyedRepository<int, FavList> FavListRepository, IUnitOfWork unitOfWork) { this.FavListRepository = FavListRepository; this.unitOfWork = unitOfWork; FavLists = new FavListService(FavListRepository); } public void Commit() { unitOfWork.Commit(); } } } namespace MyListsWebsite.Controllers { public class ListsController : Controller { private readonly DataService dataService; public ListsController(DataService dataService) { this.dataService = dataService; } public ActionResult Index() { var myLists = dataService.FavLists.All().ToList(); return View(myLists); } } }

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  • Array of function pointers in Java

    - by Waltzy
    I have read this question and I'm still not sure whether it is possible to keep pointers to methods in an array in Java, if anyone knows if this is possible or not it would be a real help. I'm trying to find an elegant solution of keeping a list of Strings and associated functions without writing a mess of hundreds of 'if's. Cheers edit- 'functions' changed to 'methods', seems to bug people.

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  • How do you use boost iterators

    - by Neil G
    It worked, and then I added the typedefs so that I could have a const_sparse_iterator as well. Now, when I compile this and try to use sparse_iterator, it says: /Users/neilrg/nn/src/./core/sparse_vector.h:331: error: invalid use of incomplete type 'struct sparse_vector<A>::sparse_iterator' Here's the code. More code here. tempalte<typename T> class sparse_vector { // There is more code at my previous question, but this might be enough...? private: template<typename base_type> class sparse_iterator_private : public boost::iterator_adaptor< sparse_iterator_private<base_type> // Derived , base_type // Base , value_type // Value , boost::random_access_traversal_tag // CategoryOrTraversal > { private: struct enabler {}; // a private type avoids misuse public: sparse_iterator_private() : sparse_iterator_private<base_type>::iterator_adaptor_(0) {} explicit sparse_iterator_private(typename array_type::iterator&& p) : sparse_iterator_private<base_type>::iterator_adaptor_(p) {} private: friend class boost::iterator_core_access; reference dereference() const { return this->base()->value; } }; public: typedef sparse_iterator_private<typename array_type::iterator> sparse_iterator; typedef sparse_iterator_private<typename array_type::const_iterator> const_sparse_iterator; };

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  • Who needs singletons?

    - by sexyprout
    Imagine you access your MySQL database via PDO. You got some functions, and in these functions, you need to access the database. The first thing I thought of is global, like: $db = new PDO('mysql:host=127.0.0.1;dbname=toto', 'root', 'pwd'); function some_function() { global $db; $db->query('...'); } But it's considered as a bad practice. So, after a little search, I ended up with the Singleton pattern, which "applies to situations in which there needs to be a single instance of a class." According to the example of the manual, we should do this: class Database { private static $instance, $db; private function __construct(){} static function singleton() { if(!isset(self::$instance)) self::$instance = new __CLASS__; return self:$instance; } function get() { if(!isset(self::$db)) self::$db = new PDO('mysql:host=127.0.0.1;dbname=toto', 'user', 'pwd') return self::$db; } } function some_function() { $db = Database::singleton(); $db->get()->query('...'); } some_function(); But I just can't understand why you need that big class when you can do it merely with: class Database { private static $db; private function __construct(){} static function get() { if(!isset(self::$rand)) self::$db = new PDO('mysql:host=127.0.0.1;dbname=toto', 'user', 'pwd'); return self::$db; } } function some_function() { Database::get()->query('...'); } some_function(); This last one works perfectly and I don't need to worry about $db anymore. But maybe I'm forgetting something. So, who's wrong, who's right?

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