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  • Using the AND and NOT Operator in Python

    - by NoahClark
    Here is my custom class that I have that represents a triangle. I'm trying to write code that checks to see if self.a, self.b, and self.c are greater than 0, which would mean that I have Angle, Angle, Angle. Below you will see the code that checks for A and B, however when I use just self.a != 0 then it works fine. I believe I'm not using & correctly. Any ideas? Here is how I am calling it: print myTri.detType() class Triangle: # Angle A To Angle C Connects Side F # Angle C to Angle B Connects Side D # Angle B to Angle A Connects Side E def __init__(self, a, b, c, d, e, f): self.a = a self.b = b self.c = c self.d = d self.e = e self.f = f def detType(self): #Triangle Type AAA if self.a != 0 & self.b != 0: return self.a #If self.a > 10: #return AAA #Triangle Type AAS #elif self.a = 0: #return AAS #Triangle Type ASA #Triangle Type SAS #Triangle Type SSS #else: #return unknown

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  • how can i update view when fragment change?

    - by user1524393
    i have a activity that have 2 sherlockfragment in this The first two pages display fragments with custom list views which are built from xml from server using AsyncTask. However, when the app runs, only one list view is displayed, the other page is just blank public class VpiAbsTestActivity extends SherlockFragmentActivity { private static final String[] CONTENT = new String[] { "1","2"}; TestFragmentAdapter mAdapter; ViewPager mPager; PageIndicator mIndicator; protected void onCreate(Bundle savedInstanceState) { setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT); super.onCreate(savedInstanceState); setContentView(R.layout.simple_tabs); mAdapter = new TestFragmentAdapter(getSupportFragmentManager()); mPager = (ViewPager)findViewById(R.id.pager); mPager.setAdapter(mAdapter); mIndicator = (TabPageIndicator)findViewById(R.id.indicator); mIndicator.setViewPager(mPager); mIndicator.notifyDataSetChanged(); } class TestFragmentAdapter extends FragmentPagerAdapter { private int mCount = CONTENT.length; public TestFragmentAdapter(FragmentManager fm) { super(fm); } @Override public Fragment getItem(int position) { switch(position) { case 0: return new customlist(); case 1: return new customlistnotuser(); default: return null; } } @Override public int getCount() { return mCount; } public CharSequence getPageTitle(int position) { return VpiAbsTestActivity.CONTENT[position % VpiAbsTestActivity.CONTENT.length].toUpperCase(); } @Override public void destroyItem(View collection, int position, Object view) { ((ViewPager) collection).removeView((View) view); } } } what can i update viewpager when change pages ? the customlistnotuser page likes customlist page but not show public class customlistnotuser extends SherlockFragment { // All static variables static final String URL = "url"; // XML node keys static final String KEY_TEST = "test"; // parent node static final String KEY_ID = "id"; static final String KEY_TITLE = "title"; static final String KEY_Description = "description"; static final String KEY_DURATION = "duration"; static final String KEY_THUMB_URL = "thumb_url"; static final String KEY_PRICE = "price"; static final String KEY_URL = "url"; private ProgressDialog pDialog; ListView list; LazyAdapterbeth adapter; XMLParser parser = new XMLParser(); public void onActivityCreated(Bundle savedInstanceState) { super.onActivityCreated(savedInstanceState); } public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); new getFeed().execute(); } public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { View thisfragment = inflater.inflate(R.layout.dovomi, container, false); return thisfragment; } private class getFeed extends AsyncTask<Void, Void, Document> { } protected Document doInBackground(Void... params) { XMLParser parser = new XMLParser(); String xml = parser.getXmlFromUrl(URL); // getting XML from URL Document doc = parser.getDomElement(xml); // getting DOM element return doc; } protected void onPostExecute(Document doc) { ArrayList<HashMap<String, String>> songsList = new ArrayList<HashMap<String, String>>(); NodeList nl = doc.getElementsByTagName(KEY_TEST); // looping through all song nodes <song> for (int i = 0; i < nl.getLength(); i++) { // creating new HashMap HashMap<String, String> map = new HashMap<String, String>(); Element e = (Element) nl.item(i); // adding each child node to HashMap key => value map.put(KEY_ID, parser.getValue(e, KEY_ID)); map.put(KEY_TITLE, parser.getValue(e, KEY_TITLE)); map.put(KEY_Description, parser.getValue(e, KEY_Description)); map.put(KEY_DURATION, parser.getValue(e, KEY_DURATION)); map.put(KEY_THUMB_URL, parser.getValue(e, KEY_THUMB_URL)); map.put(KEY_PRICE, parser.getValue(e, KEY_PRICE)); map.put(KEY_URL, parser.getValue(e, KEY_URL)); // adding HashList to ArrayList songsList.add(map); pDialog.dismiss(); } list=(ListView)getActivity().findViewById(R.id.list); // Getting adapter by passing xml data ArrayList adapter=new LazyAdapterbeth(getActivity(), songsList); list.setAdapter(adapter); // Click event for single list row list.setOnItemClickListener(new OnItemClickListener() {

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  • Should I skip authorization, with CanCan, of an action that instantiates a resource?

    - by irkenInvader
    I am writing a web app to pick random lists of cards from larger, complete sets of cards. I have a Card model and a CardSet model. Both models have a full RESTful set of 7 actions (:index, :new, :show, etc). The CardSetsController has an extra action for creating random sets: :random. # app/models/card_set.rb class CardSet < ActiveRecord::Base belongs_to :creator, :class_name => "User" has_many :memberships has_many :cards, :through => :memberships # app/models/card.rb class Card < ActiveRecord::Base belongs_to :creator, :class_name => "User" has_many :memberships has_many :card_sets, :through => :memberships I have added Devise for authentication and CanCan for authorizations. I have users with an 'editor' role. Editors are allowed to create new CardSets. Guest users (Users who have not logged in) can only use the :index and :show actions. These authorizations are working as designed. Editors can currently use both the :random and the :new actions without any problems. Guest users, as expected, cannot. # app/controllers/card_sets_controller.rb class CardSetsController < ApplicationController before_filter :authenticate_user!, :except => [:show, :index] load_and_authorize_resource I want to allow guest users to use the :random action, but not the :new action. In other words, they can see new random sets, but not save them. The "Save" button on the :random action's view is hidden (as designed) from the guest users. The problem is, the first thing the :random action does is build a new instance of the CardSet model to fill out the view. When cancan tries to load_and_authorize_resource a new CardSet, it throws a CanCan::AccessDenied exception. Therefore, the view never loads and the guest user is served a "You need to sign in or sign up before continuing" message. # app/controllers/card_sets_controllers.rb def random @card_set = CardSet.new( :name => "New Set of 10", :set_type => "Set of 10" ) I realize that I can tell load_and_authorize_resource to skip the :random action by passing :except => :random to the call, but that just feels "wrong" for some reason. What's the "right" way to do this? Should I create the new random set without instantiating a new CardSet? Should I go ahead and add the exception?

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  • Can running object be garbage collected?

    - by Kugel
    I have a simple class: public class Runner { public void RunAndForget(RunDelegate method) { ThreadPool.QueueUserWorkItem(new WaitCallback(Run), method); } private void Run(object o) { ((RunDelegate )o).Invoke(); } } And if I use this like so: private void RunSomethingASync() { Runner runner = new Runner(); runner.FireAndForget(new RunDelegate(Something)); } Is there any danger using it like this? My C++ guts tell me that runner object should be destroyed after RunSomethingASync is finished. Am I right? What happens then to the method running on different thread? Or perhaps it is other way around and runner will not be collected? That would be a problem considering I may call RunSomethingASync() many times.

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  • What is the proper way to declare a specialization of a template for another template type?

    - by Head Geek
    The usual definition for a specialization of a template function is something like this: class Foo { [...] }; namespace std { template<> void swap(Foo& left, Foo& right) { [...] } } // namespace std But how do you properly define the specialization when the type it's specialized on is itself a template? Here's what I've got: template <size_t Bits> class fixed { [...] }; namespace std { template<size_t Bits> void swap(fixed<Bits>& left, fixed<Bits>& right) { [...] } } // namespace std Is this the right way to declare swap? It's supposed to be a specialization of the template function std::swap, but I can't tell whether the compiler is seeing it as such, or whether it thinks that it's an overload of it or something.

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  • converting string to int in C++

    - by xbonez
    I am trying to convert a string I read in from a file to an int value so I can store it in an integer variable. This is what my code looks like: ifstream sin; sin.open("movie_output.txt"); string line; getline(sin,line); myMovie.setYear(atoi(line)); Over here, setYear is a mutator in the Movie class (myMovie is an object of Movie class) that looks like this: void Movie::setYear(unsigned int year) { year_ = year; } When I run the code, I get the following error: error C2664: 'atoi' : cannot convert parameter 1 from 'std::string' to 'const char *' 1> No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called

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  • ProgrammingError: (1146, "Table 'test_<DB>.<TABLE>' doesn't exist") when running unit test for Djang

    - by abigblackman
    I'm running a unit test using the Django framework and get this error. Running the actual code does not have this problem, running the unit tests creates a test database on the fly so I suspect the issue lies there. The code that throws the error looks like this member = Member.objects.get(email=email_address) and the model looks like class Member(models.Model): member_id = models.IntegerField(primary_key=True) created_on = models.DateTimeField(editable=False, default=datetime.datetime.utcnow()) flags = models.IntegerField(default=0) email = models.CharField(max_length=150, blank=True) phone = models.CharField(max_length=150, blank=True) country_iso = models.CharField(max_length=6, blank=True) location_id = models.IntegerField(null=True, blank=True) facebook_uid = models.IntegerField(null=True, blank=True) utc_offset = models.IntegerField(null=True, blank=True) tokens = models.CharField(max_length=3000, blank=True) class Meta: db_table = u'member' there's nothing too odd there i can see. the user running the tests has the same permissions to the database server as the user that runs the website where else can I look to see what's going wrong, why is this table not being created?

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  • How do I get element's className inside loop of elements?

    - by crosenblum
    I am doing a loop of all elements inside a div, and I now need to get the classname of the element that I am looping by. Then i can check if the current element's class is one, I need to do something with... // var children = parent.childNodes, child; var parentNode = divid; // start loop thru child nodes for(var node=parentNode.firstChild;node!=null;node=node.nextSibling){ var myclass = (node.className ? node.className.baseVal : node.getAttribute('class')); } But this code for getting the classname only get's null values. Any suggestions?

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  • iPhone noob - different method types?

    - by codemonkey
    My apologies in advance for what is probably a really dumb question. I'm familiar (or at least getting familiar) with instance and class methods in objective-c, but have also seen method implementations that look like this: #import "Utilities.h" #import "CHAPPAppDelegate.h" #import "AppState.h" @implementation Utilities CHAPPAppDelegate* GetAppDelegate() { return (CHAPPAppDelegate *)[UIApplication sharedApplication].delegate; } AppState* GetAppState() { return [GetAppDelegate() appState]; } @end What are these? While I'm sure this is documented somewhere, I don't know what term to use in searching for an explanation of what's being done here. I like the syntax methods like this let me use when calling them, but I'm not sure exactly what I'm doing, what the implications are, how to send parameters to these types of functions, etc? To clarify how I ended up in this position, I started using these methods in a "utilities" class of mine after reading some online blog describing the author's preference for declaring these functions this way. Now I can't seem to track down a more detailed explanation of what exactly the differences are, etc.

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  • In what circumstances are instance variables declared as '_var' in 'use fields' private?

    - by Pedro Silva
    I'm trying to understand the behavior of the fields pragma, which I find poorly documented, regarding fields prefixed with underscores. This is what the documentation has to say about it: Field names that start with an underscore character are made private to the class and are not visible to subclasses. Inherited fields can be overridden but will generate a warning if used together with the -w switch. This is not consistent with its actual behavior, according to my test, below. Not only are _-prefixed fields visible within a subclass, they are visible within foreign classes as well (unless I don't get what 'visible' means). Also, directly accessing the restricted hash works fine. Where can I find more about the behavior of the fields pragma, short of going at the source code? { package Foo; use strict; use warnings; use fields qw/a _b __c/; sub new { my ( $class ) = @_; my Foo $self = fields::new($class); $self->a = 1; $self->b = 2; $self->c = 3; return $self; } sub a : lvalue { shift->{a} } sub b : lvalue { shift->{_b} } sub c : lvalue { shift->{__c} } } { package Bar; use base 'Foo'; use strict; use warnings; use Data::Dumper; my $o = Bar->new; print Dumper $o; ##$VAR1 = bless({'_b' => 2, '__c' => 3, 'a' => 1}, 'Foo'); $o->a = 4; $o->b = 5; $o->c = 6; print Dumper $o; ##$VAR1 = bless({'_b' => 5, '__c' => 6, 'a' => 4}, 'Foo'); $o->{a} = 7; $o->{_b} = 8; $o->{__c} = 9; print Dumper $o; ##$VAR1 = bless({'_b' => 8, '__c' => 9, 'a' => 7}, 'Foo'); }

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  • Static vs Non Static constructors

    - by Neil N
    I can't think of any reasons why one is better than the other. Compare these two implementations: public class MyClass { public myClass(string fileName) { // some code... } } as opposed to: public class MyClass { private myClass(){} public static Create(string fileName) { // some code... } } There are some places in the .Net framework that use the static method to create instances. At first I was thinking, it registers it's instances to keep track of them, but regular constructors could do the same thing through the use of private static variables. What is the reasoning behind this style?

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  • iPhone - UITableViewController not loading table

    - by RyanJM
    I'm pushing a UITableViewController onto a navigationController. The title (set in the viewDidLoad) shows up but not the table. numberOfSectionsInTableView is called. But tableView:numberOfRowsInSection: is not called. I'm passing in 1 so it should be looking for number of rows. - (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView { return 1; } I'm setting up the view in the following manner: SelectUserViewController *nextController = [[SelectUserViewController alloc] initWithStyle:UITableViewStyleGrouped]; nextController.managedObjectContext = managedObjectContext; OrangeQCAppDelegate *delegate = [[UIApplication sharedApplication] delegate]; [delegate.navigationController pushViewController:nextController animated:YES]; Again, the viewDidLoad method is called. And my class is set up as follows: @interface SelectUserViewController : UITableViewController <UITableViewDelegate, UITableViewDataSource> {...} What else should I be looking at? When I go through the debugger, after it looks at numberOfSectionsInTableView it just disappears (I think it is in the UITableViewController class) and never comes back.

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  • Accessing Session and IPrinciple data in a Master View in Asp.Net MCV

    - by bplus
    I currently have a abstract controller class that I all my controllers inherit from. In my master page I want to be able to access some data that will be in Session and also the currently user (IPrinciple). I read that I could use the contructor of by abstract base controller class, that is I could do something like public BaseController() { ViewData["SomeData"] = Session["SomeData"]; ViewData["UserName"] = this.User.Identity.Name; } I could then access ViewData["UserName"] etc from my master page. My problem is that both Session and User are null at this point. Does anybody know of a different approach? Thanks in advance.

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  • Rails STI validation inheritance

    - by KARASZI István
    Dear Rails users! I have STI models in my Rails application. The ancestor model has validations with the validates_... methods which are working fine. But I have custom validations as well, and I would like to add more different custom validations in the descendants. These custom validations would depend on the class. If I write class DescendantA < Ancestor protected def validate # ... end end It simply overwrites the original validations. Is there a convention to do this in Rails?

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  • Should I create subclass NSManagedObject or not?

    - by TP
    Hi, I have spent a few days learning and writing NSCoding and finally got it working. However, it took very long to archive and unarchive the (quite complex) object graph, which is unacceptable. After searching the internet for some time, I think the better way is to use core data. Do you recommend that 1) I should rewrite all my classes as subclasses of NSManagedObject or 2) should I create an instance variable of NSManagedObject in each of my class so that any changes to the class also updates its core data representation? Doing either way will need significant changes to the exiting classes and I think I have to update lots of unit test cases as well if it changes the way the classes are initialized. What do you recommend? I really don't want to head to the wrong approach again... Thanks!

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  • Displaying list of objects as single column in a bound gridview (Winforms)?

    - by Carrie Nelson
    I have a gridview that is bound to a datasource on a Windows Form (VB.NET). The grid displays a list of "certifications", and each "certification" can be associated with many languages. So in the grid, I'd like to display "languages" as a column, and display a comma delimited list of the language names for each "certification". In the "certification" class, one of the properties is a list of "language" objects, and each "language" has an ID (guid), name (string), and value (integer). So in the datasource, I have the list of "languages", but I can't figure out how to display them in a column on the grid. The gridview won't let me add the language list property as a column. So is the ONLY way to add a new property on the "certification" class, which returns a string that contains the comma delimited list, and show THAT on the grid? Or is there a way to display that list of "languages"?

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  • some confusions to singleton pattern in PHP

    - by SpawnCxy
    Hi all, In my team I've been told to write resource class like this style: class MemcacheService { private static $instance = null; private function __construct() { } public static function getInstance($fortest = false) { if (self::$instance == null) { self::$instance = new Memcached(); if ($fortest) { self::$instance->addServer(MEMTEST_HOST, MEMTEST_PORT); } else { self::$instance->addServer(MEM_HOST, MEM_PORT); } } return self::$instance; } } But I think in PHP resource handles will be released and initialized again every time after a request over. That means MemcacheService::getInstance() is totally equal new Memcached() which cannot be called singleton pattern at all. Please correct me if I'm wrong. Regards

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  • what is wrong: "value Parsers is not a member of package scala.util.parsing.combinator"?

    - by Nick Fortescue
    I've got the above odd error message that I don't understand "value Parsers is not a member of package scala.util.parsing.combinator". I'm trying to learn Parser combinators by writing a C parser step by step. I started at token, so I have the classes: import util.parsing.combinator.JavaTokenParsers object CeeParser extends JavaTokenParsers { def token: Parser[CeeExpr] = ident } abstract class CeeExpr case class Token(name: String) extends CeeExpr This is as simple as I could make it. The code below works fine, but if I uncomment the commented line I get the error message given above: object Play { def main(args: Array[String]) { //val parser: _root_.scala.util.parsing.combinator.Parsers.Parser[CeeExpr] CeeParser.token val x = CeeParser.token print(x) } } In case it is a problem with my setup, I'm using scala 2.7.6 via the scala-plugin for intellij. Can anyone shed any light on this? The message is wrong, Parsers is a member of scala.util.parsing.combinator.

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  • How to create file of files?

    - by TheMachineCharmer
    class Node { FooType Data; // I can save Data to file with extension .foo void Save() { // save Data to .foo file } } Now , class Graph { List<Node> Nodes; void Save() { foreach(Node node in Nodes) { node.Save(); } } } Now when I invoke someGraph.Save(); then it creates Nodes.Count number of files. I would like to appear those files as one file with extension somename.graph and be able to read it again as Nodes. How can I do this? Is there a way to bundle files into a single different file?

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  • Error with connection in my database servlet

    - by Zerobu
    Hello, I am writing a Database servlet, all seems well except that there seems to be an error in my connection import java.io.IOException; import java.sql.Connection; import java.sql.DriverManager; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement; import java.util.ArrayList; import javax.servlet.RequestDispatcher; import javax.servlet.ServletContext; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class DBServlet3 extends HttpServlet { private static final long serialVersionUID = 1L; @Override public void init() throws ServletException { super.init(); try { String jdbcDriverClass= getServletContext().getInitParameter( "jdbcDriverClass" ); if (jdbcDriverClass == null) throw new ServletException( "Could not find jdbcDriverClass initialization parameter" ); Class.forName( jdbcDriverClass ); } catch (ClassNotFoundException e) { throw new ServletException( "Could not load JDBC driver class", e ); } } @Override protected void doGet( HttpServletRequest request, HttpServletResponse response ) throws ServletException, IOException { RequestDispatcher dispatcher= request.getRequestDispatcher( "/db.jsp" ); ServletContext application= getServletContext(); ArrayList<String> names= new ArrayList<String>(); try { Connection connection= null; Statement statement= null; ResultSet results= null; try { String jdbcUrl= application.getInitParameter( "jdbcUrl" ); String jdbcUser= application.getInitParameter( "jdbcUser" ); String jdbcPassword= application.getInitParameter( "jdbcPassword" ); connection= DriverManager.getConnection( jdbcUrl, jdbcUser, jdbcPassword ); statement= connection.createStatement(); results= statement.executeQuery( "SELECT * FROM students" ); while (results.next()) { String name= results.getString( "name" ); names.add( name ); } } finally { if (results != null) results.close(); if (statement != null) statement.close(); if (connection != null) connection.close(); } } catch (SQLException e) { throw new ServletException( e ); } request.setAttribute( "names", names ); dispatcher.forward( request, response ); } @Override protected void doPost( HttpServletRequest request, HttpServletResponse response ) throws ServletException, IOException { String sql= "INSERT INTO students VALUES (" + request.getParameter( "id" ) + ", '" + request.getParameter( "name" ) + "')"; sql= "INSERT INTO students VALUES (?, ?, ?, ?)"; PreparedStatement statement= connection.prepareStatement( sql ); //error on this line statement.setString( 1, request.getParameter( "id" ) ); statement.setString( 2, request.getParameter( "name" ) ); } }

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  • WPF multibound textblock not updating

    - by Superstringcheese
    I want to create a program which calculates how long it will take to repeat a process a certain number of times. I've scaled this down a lot for this example. So, I have some textboxes which are bound to properties in a class: Count: <TextBox x:Name="txtCount" Text="{Binding Count, Mode=TwoWay}" Width="50"/> Days: <TextBox x:Name="txtDays" Text="{Binding Days, Mode=TwoWay}" Width="50"/> and a textblock which is multibound like so: <TextBlock x:Name="tbkTotal"> <TextBlock.Text> <MultiBinding StringFormat="Days: {0}, Count: {1}"> <Binding Path="Days" /> /* This isn't updating */ <Binding Path="Count" /> </MultiBinding> </TextBlock.Text> </TextBlock> My DataContext is set in the Window1.xaml.cs file. public Window1() { InitializeComponent(); Sample sample = new Sample(); this.DataContext = sample; } I can update the multibound textblock with the Count property just fine, but the Days property always shows 0, even though the Days input accurately reflects changes. I believe that this is because my accessors are different for Days - namely, the Set method. This class is in a different file. public class Sample : INotifyPropertyChanged { private int _count; private TimeSpan _span; public int Count { get { return _count; } set { _count = value; NotifyPropertyChanged("Count"); /* Doesn't seem to be needed, actually */ } } public TimeSpan Span { get { return _span; } } /* The idea is to provide a property for Days, Hours, Minutes, etc. as conveniences to the inputter */ public double Days { get { return _span.Days; } set { TimeSpan ts = new TimeSpan(); double val = value > 0 ? value : 0; ts = TimeSpan.FromDays(val); _span.Add(ts); NotifyPropertyChanged("Span"); /* Here I can only get it to work if I notify that Span has changed - doesn't seem to be aware that the value behind Days has changed. */ } } private void NotifyPropertyChanged(string property) { if (null != this.PropertyChanged) { PropertyChanged(this, new PropertyChangedEventArgs(property)); } } public Sample() { _count = 0; _span = new TimeSpan(); } public event PropertyChangedEventHandler PropertyChanged; }

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  • Reverse List<Object>

    - by Mercer
    Hello, i have a List List<DataClient> listDataClient; My class DataCLient: Client client; List<String> phoneNumber; i have a second list List<DataPhoneNumber> listPhoneNumber; My class DataPhoneNumber: String phoneNumber; List<Client> client; In my code i put data in my first list but now i want to reverse my list in the second. In the first list i have a Client wiht x NumberPhone now i want to have NumberPhone for x Client

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  • Why is there no parameter contra-variance for overriding?

    - by Oak
    C++ and Java support return-type covariance when overriding methods. Neither, however, support contra-variance in parameter types - instead, it translates to overloading (Java) or hiding (C++). Why is that? It seems to me that there is no harm in allowing that. I can find one reason for it in Java - since it has the "choose-the-most-specific-version" mechanism for overloading anyway - but can't think of any reason for C++. Example (Java): class A { public void f(String s) {...} } class B extends A { public void f(Object o) {...} // Why doesn't this override A.f? }

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  • IconDownloader, problem with lazy downloading

    - by Junior B.
    My problem is simple to be described but it seems to be hard to solve. The problem is loading icons, with a custom class like IconDownloader.m provided by an official example from Apple, avoiding crashes if I release the view. I've added the IconDownloader class to my app, but it's clear that this approach is good only if the tableview is the root. The big problem is when the view is not the root one. F.e: if I start to scroll my second view (the app now load the icons) and, without leaving it the time to finish the download, I go back to root, the app crash because the view that have to be updated with new icons doesn't exist anymore. One possible solution could be implement an OperationQueue in the view, but with this approach I've to stop the queue when I change the view and restart it when I come back and the idea to have N queues don't make me enthusiastic. Anyone found a good solution for this problem?

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  • How can I handle multiple views of a data object? Which design pattern is acceptable?

    - by tranquil.byte
    I have a person object. class Person { private $name; ... } I need to be able to change how they are displayed on the front-end ( visitors have control ). They can choose list view, grid view, photo view for example. class PersonDisplay { public function displayList() { // Query database // Output html to display in list mode } public function displayPhoto() { // Query database // Output html to display in photo mode } } Is this an acceptable way to handle the presentation of the items on the front-end or is there a specific design pattern I should be researching to help me with this task? Does anyone have any suggestions or ideas where this could go wrong or if this could potentially make maintenance a nightmare? The Person object was just an example very similiar to what I am using.

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