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  • Django - 2 fields unique together

    - by webvulture
    Suppose, I want to record say poll choices by users everyday. In this case, i have a table named vote which has columns poll , choice and user-id . So how can i out the constraint (maybe in the django models or wherever possible) that poll and user-id both should not be the same for any entry but like the same user can vote for various different polls once and obviously various users can vote for the same poll. I hope I am clear.

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  • Loosely coupled implicit conversion

    - by ltjax
    Implicit conversion can be really useful when types are semantically equivalent. For example, imagine two libraries that implement a type identically, but in different namespaces. Or just a type that is mostly identical, except for some semantic-sugar here and there. Now you cannot pass one type into a function (in one of those libraries) that was designed to use the other, unless that function is a template. If it's not, you have to somehow convert one type into the other. This should be trivial (or otherwise the types are not so identical after-all!) but calling the conversion explicitly bloats your code with mostly meaningless function-calls. While such conversion functions might actually copy some values around, they essentially do nothing from a high-level "programmers" point-of-view. Implicit conversion constructors and operators could obviously help, but they introduce coupling, so that one of those types has to know about the other. Usually, at least when dealing with libraries, that is not the case, because the presence of one of those types makes the other one redundant. Also, you cannot always change libraries. Now I see two options on how to make implicit conversion work in user-code: The first would be to provide a proxy-type, that implements conversion-operators and conversion-constructors (and assignments) for all the involved types, and always use that. The second requires a minimal change to the libraries, but allows great flexibility: Add a conversion-constructor for each involved type that can be externally optionally enabled. For example, for a type A add a constructor: template <class T> A( const T& src, typename boost::enable_if<conversion_enabled<T,A>>::type* ignore=0 ) { *this = convert(src); } and a template template <class X, class Y> struct conversion_enabled : public boost::mpl::false_ {}; that disables the implicit conversion by default. Then to enable conversion between two types, specialize the template: template <> struct conversion_enabled<OtherA, A> : public boost::mpl::true_ {}; and implement a convert function that can be found through ADL. I would personally prefer to use the second variant, unless there are strong arguments against it. Now to the actual question(s): What's the preferred way to associate types for implicit conversion? Are my suggestions good ideas? Are there any downsides to either approach? Is allowing conversions like that dangerous? Should library implementers in-general supply the second method when it's likely that their type will be replicated in software they are most likely beeing used with (I'm thinking of 3d-rendering middle-ware here, where most of those packages implement a 3D vector).

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  • What's the worst name you've seen for a product? [closed]

    - by Dean J
    (Community wiki from the start.) What's the worst name you've seen for a product? It might be a euphemism the company didn't know about, maybe something like Penetrode (from Office Space). It might be something impossible to do a web search on, like the band named "Download". It might be some combination of random syllables that's just awful. But no matter what, it's bad. What's the worst you've seen?

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  • How do I convert jstring to wchar_t *

    - by Obediah Stane
    Let's say that on the C++ side my function takes a variable of type jstring named myString. I can convert it to an ANSI string as follows: const char* ansiString = env-GetStringUTFChars(myString, 0); is there a way of getting const wchar_t* unicodeString = ...

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  • How to hide and show silvelight user control on main Silverlight Control?

    - by Steve Johnson
    Hi all I have a main silverlight control named MainPage.xaml in an asp.net web site. I want to dynamically add and remove control at run time. So, I have created another control Top10.xaml and added to selected canvas area on MainPage.xaml as described on this page(Click Me): Now i need to modify Top10 visibility in MainPage.xaml dynamically when a button is clicked on MainPage.xaml using C# code in MainPage.xaml.cs. Can anybody help me out? Thanks

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  • Select into from one sql server into another?

    - by blasto
    I want to select data from one table (T1, in DB1) in one server (Data.Old.S1) into data in another table (T2, in DB2) in another server (Data.Latest.S2). How can I do this ? Please note the way the servers are named. The query should take care of that too. That is, SQL server should not be confused about fully qualified table names. For example - this could confuse SQL server - Data.Old.S1.DB1.dbo.T1.

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  • How do I translate a ISO 8601 datetime string into a Python datetime object?

    - by Andrey Fedorov
    I'm getting a datetime string in a format like "2009-05-28T16:15:00" (this is ISO 8601, I believe) one hack-ish option seems to be to parse the string using time.strptime and passing the first 6 elements of the touple into the datetime constructor, like: datetime.datetime(*time.strptime("2007-03-04T21:08:12", "%Y-%m-%dT%H:%M:%S")[:6]) I haven't been able to find a "cleaner" way of doing this, is there one?

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  • Is is possible to create a factory class in PHP?

    - by user198729
    Like the BeanFactory in java: In the much more common case where the BeanFactory itself directly creates the bean by calling its constructor (equivalent to Java code calling new), the class attribute specifies the class of the bean to be constructed. In the less common case where the BeanFactory calls a static, so-called factory method on a class to create the bean, the class attribute specifies the actual class containing the static factory method. Note:it's not the factory method

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  • case insensitive for sql LIKE wildcard statement

    - by David Morrow
    sorry if this is a repeat, i looked around some and didnt find what i was after so here goes SELECT * FROM trees WHERE trees.`title` LIKE '%elm%' this works fine, but not if the tree is named Elm or ELM ect... how do i make sql case insensitive for this wild-card search? again apologies if this is repeated. oh, using MySql 5 on apache

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  • How do I get the year drop down with a textfield

    - by Sanjib Karmakar
    I am creating a domain class named HOLIDAY in grails.I need to have a year dropdown in my Holiday year field. Hear is my domain:- class Holiday extends CategoryMaster { String holidayName Date startDate int year Date dateCreated static constraints = { holidayName(blank:false,nullable:false) } } I need to a year dropdown in year field, Should it come dynamically from a domain method that will discard the month & day and reflect only year in that dropdown adding +50 -50 to that?... How can I get it?

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  • Environment variable expansion in persistence.xml (JPA)

    - by user342495
    I am developing a Eclipse RCP plugin which uses JPA. I tried to specify the database path via a variable give to the JVM on runtime. The property is set correctly but the database is created in a folder named after the variable name (here: ${DBHOME}). <property name="javax.persistence.jdbc.url" value="jdbc:derby:${DBHOME};create=true"/> Is there a possibility to fix this? Thx

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  • Exception throws: encapsulate them or not?

    - by Simon
    Hi there. Once I read an MSDN article that encouraged the following programming paradigm: public class MyClass { public void Method1() { NewCustomException(); } public void Method2() { NewCustomException(); } void NewCustomException() { throw new CustomException("Exception message"); } } Do you think this paradigm makes sense? Wouldn't it be enough to store the exception message in a static const field and then pass it to the exception's constructor, instead of encapsulating the whole exception throw?

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  • Multiple Timers with setTimeInterval

    - by visibleinvisibly
    I am facing a problem with setInterval being used in a loop. I have a function subscribeFeed( ) which takes an array of urls as input. It loops through the url array and subscribes each url to getFeedAutomatically() using a setInterval function. so if three URL's are there in the array, then 3 setInterval's will be called. The problem is 1)how to distinguish which setInterval is called for which URL. 2)it is causing Runtime exception in setInterval( i guess because of closure problem in javascript) //constructor function myfeed(){ this.feedArray = []; } myfeed.prototype.constructor= myfeed; myfeed.prototype.subscribeFeed =function(feedUrl){ var i=0; var url; var count = 0; var _this = this; var feedInfo = { url : [], status : "" }; var urlinfo = []; feedUrl = (feedUrl instanceof Array) ? feedUrl : [feedUrl]; //notifyInterval = (notifyInterval instanceof Array) ? notifyInterval: [notifyInterval]; for (i = 0; i < feedUrl.length; i++) { urlinfo[i] = { url:'', notifyInterval:5000,// Default Notify/Refresh interval for the feed isenable:true, // true allows the feed to be fetched from the URL timerID: null, //default ID is null called : false, position : 0, getFeedAutomatically : function(url){ _this.getFeedUpdate(url); }, }; urlinfo[i].url = feedUrl[i].URL; //overide the default notify interval if(feedUrl[i].NotifyInterval /*&& (feedUrl[i] !=undefined)*/){ urlinfo[i].notifyInterval = feedUrl[i].NotifyInterval; } // Trigger the Feed registered event with the info about URL and status feedInfo.url[i] = feedUrl[i].URL; //Set the interval to get the feed. urlinfo[i].timerID = setInterval(function(){ urlinfo[i].getFeedAutomatically(urlinfo[i].url); }, urlinfo[i].notifyInterval); this.feedArray.push(urlinfo[i]); } } // The getFeedUpate function will make an Ajax request and coninue myfeed.prototype.getFeedUpdate = function( ){ } I am posting the same on jsfiddle http://jsfiddle.net/visibleinvisibly/S37Rj/ Thanking you in advance

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  • WP7 databinding displays int but not string?

    - by user1794106
    Whenever I test my app.. it binds the data from Note class and displays it if it isn't a string. But for the string variables it wont bind. What am I doing wrong? Inside my main: <Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0"> <ListBox x:Name="Listbox" SelectionChanged="listbox_SelectionChanged" ItemsSource="{Binding}"> <ListBox.ItemTemplate> <DataTemplate> <Border Width="800" MinHeight="60"> <StackPanel> <TextBlock x:Name="Title" VerticalAlignment="Center" FontSize="{Binding TextSize}" Text="{Binding Name}"/> <TextBlock x:Name="Date" VerticalAlignment="Center" FontSize="{Binding TextSize}" Text="{Binding Modified}"/> </StackPanel> </Border> </DataTemplate> </ListBox.ItemTemplate> </ListBox> </Grid> </Grid> in code behind: protected override void OnNavigatedTo(System.Windows.Navigation.NavigationEventArgs e) { MessageBox.Show("enters onNav Main"); DataContext = null; DataContext = Settings.NotesList; Settings.CurrentNoteIndex = -1; Listbox.SelectedIndex = -1; if (Settings.NotesList != null) { if (Settings.NotesList.Count == 0) { Notes.Text = "No Notes"; } else { Notes.Text = ""; } } } and public static class Settings { public static ObservableCollection<Note> NotesList; static IsolatedStorageSettings settings; private static int currentNoteIndex; static Settings() { NotesList = new ObservableCollection<Note>(); settings = IsolatedStorageSettings.ApplicationSettings; MessageBox.Show("enters constructor settings"); } notes class: public class Note { public DateTimeOffset Modified { get; set; } public string Title { get; set; } public string Content { get; set; } public int TextSize { get; set; } public Note() { MessageBox.Show("enters Note Constructor"); Modified = DateTimeOffset.Now; Title = "test"; Content = "test"; TextSize = 32; } }

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  • Missing Project templates in XCode

    - by coure06
    I have installed xcode 3.2 with iphone SDK. (without Mac OS 10.4 SDK). WHen i create new project i only got these options for Mac OS -- Application -- Framework and Library -- Application plugin -- System plugin --Other But a book named: Programming Object C 2.0. From which i am learning object C. Its showing XCode with these templates for Mac OS --Application --Audio Units --Automater actions --Bundles --Command Line Utility --dynamic library --Framework --Java --Kernal Extensions --Standard Apple plugin --Static Library --Other I need the Command Line Utility template so that can create sample projects mentioned in book.

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