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  • Setting initial state of a JSF component to invalid

    - by user359391
    Hi there I have a small JSF application where the user is required to enter some data about themselves. For each component on the page that has required="true" I want to show an icon depending if there is data in the field or not. My problem is that when the page is initially shown all fields are valid, even if they do not have any data in them. So my question is how I can set a component to be invalid based on if there is data in the field or not? After a submit of the page (or after the component loses focus) the icon is shown properly, it is only on the initial page load I have a problem. (i.e there is no post data) Here is my xhtml for a component that needs to be validated: <s:decorate id="employeeIdDecoration" template="/general/util/errorStyle.xhtml"> <ui:define name="label">#{messages['userdetails.employeeId']}</ui:define> <h:inputText value="#{authenticator.user.employeeId}" required="true"> <a4j:support event="onblur" reRender="employeeIdDecoration" bypassUpdates="true"/> </h:inputText> the template: <s:label styleClass="#{invalid?'error':''}"> <ui:insert name="label"/> <s:span styleClass="required" rendered="#{required}">*</s:span> </s:label> <span class="#{invalid?'error':''}"> <s:validateAll> <ui:insert/> </s:validateAll> <h:graphicImage value="/resources/redx.png" rendered="#{invalid}" height="16" width="16" style="vertical-align:middle;"/> <h:graphicImage value="/resources/Checkmark.png" rendered="#{!invalid}" height="16" width="16" style="vertical-align:middle;"/> </span> Any help will be appreciated.

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  • ListSelector applies to the entire list

    - by jax
    I have a simple list with a listselector like so. <ListView android:id="@+id/list" android:layout_width="fill_parent" android:layout_height="fill_parent" android:layout_below="@+id/round" android:listSelector="#99000000" android:clickable="true" android:cacheColorHint="#00000000" android:background="#00000000"> </ListView> As you can see android:listSelector="#99000000" but the "black alpha" color is applied to the entire list, not the selected item. So this is what I have now but the entire list still turns black ::listview_background.xml <?xml version="1.0" encoding="utf-8"?> <selector xmlns:android="http://schemas.android.com/apk/res/android"> <item android:state_enabled="false" android:state_focused="true" android:drawable="@drawable/list_normal" /> <item android:state_pressed="true" android:drawable="@drawable/list_pressed" /> <item android:state_focused="true" android:drawable="@drawable/list_active" /> </selector> ::colors.xml <resources> <drawable name="list_normal">#96FFFFFF</drawable> <drawable name="list_active">#66000000</drawable> <drawable name="list_pressed">#CA000000</drawable> </resources> ::the xml tag in my list android:listSelector="@drawable/listview_background"

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  • Insertion sort invariant assertion fails

    - by user1661211
    In the following code at the end of the for loop I use the assert function in order to test that a[i+1] is greater than or equal to a[i] but I get the following error (after the code below). Also in c++ the assert with the following seems to work just fine but in python (the following code) it does not seem to work...anyone know why? import random class Sorting: #Precondition: An array a with values. #Postcondition: Array a[1...n] is sorted. def insertion_sort(self,a): #First loop invariant: Array a[1...i] is sorted. for j in range(1,len(a)): key = a[j] i = j-1 #Second loop invariant: a[i] is the greatest value from a[i...j-1] while i >= 0 and a[i] > key: a[i+1] = a[i] i = i-1 a[i+1] = key assert a[i+1] >= a[i] return a def random_array(self,size): b = [] for i in range(0,size): b.append(random.randint(0,1000)) return b sort = Sorting() print sort.insertion_sort(sort.random_array(10)) The Error: Traceback (most recent call last): File "C:\Users\Albaraa\Desktop\CS253\Programming 1\Insertion_Sort.py", line 27, in <module> print sort.insertion_sort(sort.random_array(10)) File "C:\Users\Albaraa\Desktop\CS253\Programming 1\Insertion_Sort.py", line 16, in insertion_sort assert a[i+1] >= a[i] AssertionError

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  • Does implementing a Java class under an open-source library's package name constitutes a modificatio

    - by Minyu
    Greetings, I understand that this is not the best forum for getting legal advices. But I am still wondering if anybody has some experience around this topic, or can point me to relevant resources that explain it. I have tried to search it online but could not find clear answers. Assuming I am using a Java open-source library from "somecompany", specifically its entities in the "org.somecompany.somepackage". During development, I found that I need to access some of the internals of that package that are not exposed through its public interface. So I thought maybe creating my own classes under the same "org.somecompany.somepackage" name would make that easier. My question is: does this constitutes a modification of the open-source library? The fully qualified name of my classes look like "org.somecompany.somepackage.myclass". It does seem an "extension" of the original library, even though I am not modifying the original library source or binary. I am also not adding my classes to the open-source jar files. Any advice or pointer to resources will be appreciated!

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  • is there a Java GUI for dummies ?

    - by MHero
    Hello, first I want to apologize about my english, it may be not clear enough. Well, I'm new to Java programming, and I search over this web about use of Swing, AWT, 2D, etc. but I didn't get the answer I was looking for. I want to know about a book or method to learn Java GUI programming (not even sure this is a propper term). Previous answers guide me to Filthy Rich Clients by Romain Guy and also to The Swing Tutorial in Sun Web Page. and No offense, but...the first one seems too complex and the second one a bit disorganize. so I ask about a more "for dummies" method. Thanks EDIT: Thanks everyboy, you're very kind and serious. I want to clear some things that I didn't state for being my first question. I dont' want to use autogenerated code(Don't want to say why only focus on my question for consistency) Also I've read Deitel & Deitel and it's a good beginners book but it seems to me that doesn't cover layout(and other details) Finally, I tried to read netbeans generated code but it's a mess find method by method and function by function the way that the IDE does it I hope this edition helps to solve my question

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  • Use of Java [Interfaces / Abstract classes]

    - by Samuel
    Hello, Lately i decided to take a look at Java so i am still pretty new to it and also to the approach of OO programming, so i wanted to get some things straight before learning more, (i guess it's never to soon to start with good practices). I am programming a little 2D game for now but i think my question applies to any non trivial project. For the simplicity i'll provide examples from my game. I have different kinds of zombies, but they all have the same attributes (x, y, health, attack etc) so i wrote an interface Zombie which i implement by WalkingZombie, RunningZombie TeleportingZombie etc. Is this the best thing to do? Am i better of with an abstract class? Or with a super class? (I am not planning to partially implement functions - therefor my choice for an interface instead of an abstract class) I have one class describing the main character (Survivor) and since it is pretty big i wanted to write an interface with the different functions, so that i can easily see and share the structure of it. Is it good practice? Or is it simply a waste of space and time? I hope this question will not be rated as subjective because i thought that experienced programmers won't disagree about this kind of topic since the use of interfaces / super classes / abstract classes follows logical rules and is thereby not simply a personal choice. Thank you for your time -Samuel

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  • Have a clickable button on top of a combobox in WPF

    - by Travyguy9
    I can get a button to appear and be clickable in the drop down list of a combo box, but I cannot get the selected combo box item (the drop list is closed) to have the button be clickable. It always skips the button click and just opens the drop down list. I basically want the Button_Click event handler that I setup to be called once it is clicked. Here is my sample combo box that shows the button but is not clickable once it is in the selected item: <ComboBox x:Name="MyCombo" Width="200" Height="30" ItemsSource="{Binding ListCombo}"> <ComboBox.Resources> <DataTemplate DataType="{x:Type local:ComboItemClass}"> <StackPanel Orientation="Horizontal"> <TextBlock Text="{Binding Path=SampleText}" Width="120" /> <Button Width="20" Content="..." Click="Button_Click"/> </StackPanel> </DataTemplate> </ComboBox.Resources> </ComboBox>

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  • Problem with Java FX Look and Feel

    - by drachenfels
    Hi, I was looking at some of the examples from the Deitel and Deitel's book for Programming in Java, and one of the first examples is a very simple Swing display. Hence this snippet of code : import javax.swing.*; public class cdea { public static void main(String args[]){ JOptionPane.showMessageDialog(null,"\"Welcome to Java Programming!\""); System.exit(0); //end method main } } I read some stuff regarding how one can get native UI look and feel by using UIManager.setLookAndFeel( UIManager.getSystemLookAndFeelClassName()); to the program. However, when I just add this to my main method, it gives me a host of errors. Specifically : Multiple markers at this line - Unhandled exception type IllegalAccessException - Unhandled exception type InstantiationException - Unhandled exception type ClassNotFoundException - Unhandled exception type UnsupportedLookAndFeelException However when I use it as part of a try/catch exception loop (is that what it is called?) as detailed on http://stackoverflow.com/questions/1590863/getting-java-applications-to-look-native-on-windows-how , I get the program running properly. Could anyone tell me in simple language why this is so? As in, why can't I directly get the System look and feel; why do I have to use it with exception handling? I'm new to Java, and OOP in general, so I'm sorry if I'm being too simplistic.

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  • in haskell, why do I need to specify type constraints, why can't the compiler figure them out?

    - by Steve
    Consider the function, add a b = a + b This works: *Main> add 1 2 3 However, if I add a type signature specifying that I want to add things of the same type: add :: a -> a -> a add a b = a + b I get an error: test.hs:3:10: Could not deduce (Num a) from the context () arising from a use of `+' at test.hs:3:10-14 Possible fix: add (Num a) to the context of the type signature for `add' In the expression: a + b In the definition of `add': add a b = a + b So GHC clearly can deduce that I need the Num type constraint, since it just told me: add :: Num a => a -> a -> a add a b = a + b Works. Why does GHC require me to add the type constraint? If I'm doing generic programming, why can't it just work for anything that knows how to use the + operator? In C++ template programming, you can do this easily: #include <string> #include <cstdio> using namespace std; template<typename T> T add(T a, T b) { return a + b; } int main() { printf("%d, %f, %s\n", add(1, 2), add(1.0, 3.4), add(string("foo"), string("bar")).c_str()); return 0; } The compiler figures out the types of the arguments to add and generates a version of the function for that type. There seems to be a fundamental difference in Haskell's approach, can you describe it, and discuss the trade-offs? It seems to me like it would be resolved if GHC simply filled in the type constraint for me, since it obviously decided it was needed. Still, why the type constraint at all? Why not just compile successfully as long as the function is only used in a valid context where the arguments are in Num? Thank you.

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  • Thread is being killed by the OS

    - by Or.Ron
    I'm currently programming an app that extracts frames from a movie clip. I designed it so that the extraction will be done on a separate thread to prevent the application from freezing. The extraction process itself is taking a lot of resources, but works fine when used in the simulator. However, there are problems when building it for the iPad. When I perform another action (I'm telling my AV player to play while I extract frames), the thread unexpectedly stops working, and I believe it's being killed. I assume it's becauase I'm using a lot of resources, but not entirely sure. Here are my questions: 1. How can I tell if/why my thread stopping? 2. If it's really from over processing what should I do? I really need this action to be implemented. Heres some code im using: To create the thread: [NSThread detachNewThreadSelector:@selector(startReading) toTarget:self withObject:nil]; I'll post any information you need, Thanks so much! Update I'm using GCD now and it populates the threads for me. However the OS still kills the threads. I know exactly when is it happening. when i tell my [AVplayer play]; it kills the thread. This issue is only happening in the actual iPad and not on the simulator

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  • Localization of DisplayNameAttribute

    - by PowerKiKi
    Hi, I am looking for a way to localize properties names displayed in a PropertyGrid. The property's name may be "overriden" using the DisplayNameAttribute attribute. Unfortunately attributes can not have non constant expressions. So I can not use strongly typed resources such as: class Foo { [DisplayAttribute(Resources.MyPropertyNameLocalized)] // do not compile string MyProperty {get; set;} } I had a look around and found some suggestion to inherit from DisplayNameAttribute to be able to use resource. I would end up up with code like: class Foo { [MyLocalizedDisplayAttribute("MyPropertyNameLocalized")] // not strongly typed string MyProperty {get; set;} } However I lose strongly typed resource benefits which is definitely not a good thing. Then I came across DisplayNameResourceAttribute which may be what I'm looking for. But it's supposed to be in Microsoft.VisualStudio.Modeling.Design namespace and I can't find what reference I am supposed to add for this namespace. Anybody know if there's a easier way to achieve DisplayName localization in a good way ? or if there is as way to use what Microsoft seems to be using for Visual Studio ?

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  • Coding the R-ight way - avoiding the for loop

    - by mropa
    I am going through one of my .R files and by cleaning it up a little bit I am trying to get more familiar with writing the code the r-ight way. As a beginner, one of my favorite starting points is to get rid of the for() loops and try to transform the expression into a functional programming form. So here is the scenario: I am assembling a bunch of data.frames into a list for later usage. dataList <- list (dataA, dataB, dataC, dataD, dataE ) Now I like to take a look at each data.frame's column names and substitute certain character strings. Eg I like to substitute each "foo" and "bar" with "baz". At the moment I am getting the job done with a for() loop which looks a bit awkward. colnames(dataList[[1]]) [1] "foo" "code" "lp15" "bar" "lh15" colnames(dataList[[2]]) [1] "a" "code" "lp50" "ls50" "foo" matchVec <- c("foo", "bar") for (i in seq(dataList)) { for (j in seq(matchVec)) { colnames (dataList[[i]])[grep(pattern=matchVec[j], x=colnames (dataList[[i]]))] <- c("baz") } } Since I am working here with a list I thought about the lapply function. My attempts handling the job with the lapply function all seem to look alright but only at first sight. If I write f <- function(i, xList) { gsub(pattern=c("foo"), replacement=c("baz"), x=colnames(xList[[i]])) } lapply(seq(dataList), f, xList=dataList) the last line prints out almost what I am looking for. However, if i take another look at the actual names of the data.frames in dataList: lapply (dataList, colnames) I see that no changes have been made to the initial character strings. So how can I rewrite the for() loop and transform it into a functional programming form? And how do I substitute both strings, "foo" and "bar", in an efficient way? Since the gsub() function takes as its pattern argument only a character vector of length one.

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  • What happens when you create an instance of an object containing no state in C#?

    - by liquorice
    I am I think ok at algorithmic programming, if that is the right term? I used to play with turbo pascal and 8086 assembly language back in the 1980s as a hobby. But only very small projects and I haven't really done any programming in the 20ish years since then. So I am struggling for understanding like a drowning swimmer. So maybe this is a very niave question or I'm just making no sense at all, but say I have an object kind of like this: class Something : IDoer { void Do(ISomethingElse x) { x.DoWhatEverYouWant(42); } } And then I do var Thing1 = new Something(); var Thing2 = new Something(); Thing1.Do(blah); Thing2.Do(blah); does Thing1 = Thing2? does "new Something()" create anything? Or is it not much different different from having a static class, except I can pass it around and swap it out etc. Is the "Do" procedure in the same location in memory for both the Thing1(blah) and Thing2(blah) objects? I mean when executing it, does it mean there are two Something.Do procedures or just one?

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  • Use AttachedProperty in Style in ControlTemplate

    - by Andrey
    Here is my simple app: <Window x:Class="WpfApplication1.Window1" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:app="clr-namespace:WpfApplication1" Title="Window1" Height="300" Width="300"> <Window.Resources> <Style x:Key="Test"> <Setter Property="Button.Template"> <Setter.Value> <ControlTemplate> <Border BorderBrush="Blue" BorderThickness="3" Background="Black" CornerRadius="{Binding app:Extras.CornerRadius}" > </Border> </ControlTemplate> </Setter.Value> </Setter> </Style> </Window.Resources> <Grid> <Button Height="23" HorizontalAlignment="Left" Margin="29,26,0,0" Name="button1" VerticalAlignment="Top" Width="75" app:Extras.CornerRadius="10" Style="{StaticResource Test}" >Button</Button> </Grid> </Window> Here is my AttachedPropery: namespace WpfApplication1 { public class Extras { public static readonly DependencyProperty CornerRadiusProperty = DependencyProperty.RegisterAttached( "CornerRadius", typeof(double), typeof(Button), new FrameworkPropertyMetadata(1.0d, FrameworkPropertyMetadataOptions.AffectsRender) ); public static void SetCornerRadius(UIElement element, double value) { element.SetValue(CornerRadiusProperty, value); } public static double GetCornerRadius(UIElement element) { return (double)element.GetValue(CornerRadiusProperty); } } } CornerRadius="{Binding app:Extras.CornerRadius}" this of course doesn't work. so how can I get value from here app:Extras.CornerRadius="10" thanks in advance!

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  • C++ IDE for Linux?

    - by Sven
    I want to expand my programming horizons to Linux. A good, dependable basic toolset is important, and what is more basic than an IDE? I could find these SO topics: Lightweight IDE for linux and What tools do you use to develop C++ applications on Linux? I'm not looking for a lightweight IDE. If an IDE is worth the money, then I will pay for it, so it need not be free. My question, then: What good, C++ programming IDE is available for Linux? The minimums are fairly standard: syntax highlighting, code completion (like intellisense or its Eclipse counterpart) and integrated debugging (e.g., basic breakpoints). I have searched for it myself, but there are so many that it is almost impossible to separate the good from the bads by hand, especially for someone like me who has little C++ coding experience in Linux. I know that Eclipse supports C++, and I really like that IDE for Java, but is it any good for C++ and is there something better? The second post actually has some good suggestions, but what I am missing is what exactly makes the sugested IDE so good for the user, what are its (dis)advantages? Maybe my question should therefore be: What IDE do you propose (given your experiences), and why?

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  • Rails - Dynamic name routes namespace

    - by Kuro
    Hi, Using Rails 2.3, I'm trying to configure my routes but I uncounter some difficulties. I would like to have something like : http:// mydomain.com/mycontroller/myaction/myid That should respond with controllers in :front namespace http:// mydomain.com/aname/mycontroller/myaction/mydi That should respond with controllers in :custom namespace I try something like this, but I'm totaly wrong : map.namespace :front, :path_prefix => "" do |f| f.root :controller => :home, :action => :index f.resources :home ... end map.namespace :custom, :path_prefix => "" do |m| m.root :controller => :home, :action => :index m.resources :home ... m.match ':sub_url/site/:controller/:action/:id' m.match ':sub_url/site/:controller/:action/:id' m.match ':sub_url/site/:controller/:action/:id.:format' m.match ':sub_url/site/:controller/:action.:format' end I put matching instruction in custom namespace but I'm not sure it's the right place for it. I think I really don't get the way to customize fields in url matching and I don't know how to find documentation about Rails 2.3, most of my research drove me to Rails 3 doc about the topic... Somebody to help me ?

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  • Parser Error Problem

    - by user177140
    Hi I have found a problem in Multilingual Asp.Net Web Application I have Created a Global.asax file and write the code private void Application_BeginRequest(Object source, EventArgs e) { string[] languages = HttpContext.Current.Request.UserLanguages; if (languages[0].ToLower() != null && languages[0].ToLower()!="") { System.Threading.Thread.CurrentThread.CurrentUICulture = new System.Globalization.CultureInfo(languages[0].ToLower()); System.Threading.Thread.CurrentThread.CurrentCulture = System.Globalization.CultureInfo.CreateSpecificCulture(languages[0].ToLower()); } } and define Label Like this <asp:Label ID="Labeldg" runat="server" Text="<%$ Resources:Resource, Labeldg %>"</asp:Label> But it through Parser error like: Parser Error Description: An error occurred during the parsing of a resource required to service this request. Please review the following specific parse error details and modify your source file appropriately. Parser Error Message: The resource object with key 'LblUsrName_Login' was not found. Source Error: </div> <div class="impcLoginText_Login"> <asp:Label ID="LblUsrName" runat="server" Text="<%$ Resources:PageResource, LblUsrName_Login %>" "></asp:Label>

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  • How to implement the API/SPI Pattern in Java?

    - by Adam Tannon
    I am creating a framework that exposes an API for developers to use: public interface MyAPI { public void doSomeStuff(); public int getWidgets(boolean hasRun); } All the developers should have to do is code their projects against these API methods. I also want them to be able to place different "drivers"/"API bindings" on the runtime classpath (the same way JDBC or SLF4J work) and have the API method calls (doSomeStuff(), etc.) operate on different 3rd party resources (files, servers, whatever). Thus the same code and API calls will map to operations on different resources depending on what driver/binding the runtime classpath sees (i.e. myapi-ftp, myapi-ssh, myapi-teleportation). How do I write (and package) an SPI that allows for such runtime binding, and then maps MyAPI calls to the correct (concrete) implementation? In other words, if myapi-ftp allows you to getWidgets(boolean) from an FTP server, how would I could this up (to make use of both the API and SPI)? Bonus points for concrete, working Java code example! Thanks in advance!

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  • How to use the Zend_Log instance that was created using the Zend_Application_Resource_Log in a model

    - by Alex
    Our Zend_Log is initialized by only adding the following lines to application.ini resources.log.stream.writerName = "Stream" resources.log.stream.writerParams.mode = "a" So Zend_Application_Resource_Log will create the instance for us. We are already able to access this instance in controllers via the following: public function getLog() { $bootstrap = $this->getInvokeArg('bootstrap'); //if (is_null($bootstrap)) return false; if (!$bootstrap->hasPluginResource('Log')) { return false; } $log = $bootstrap->getResource('Log'); return $log; } So far, so good. Now we want to use the same log instance in model classes, where we can not access the bootstrap. Our first idea was to register the very same Log instance in Zend_Registry to be able to use Zend_Registry::get('Zend_Log') everywhere we want: in our Bootstrap class: protected function _initLog() { if (!$this->hasPluginResource('Log')) { throw new Zend_Exception('Log not enabled'); } $log = $this->getResource('Log'); assert( $log != null); Zend_Registry::set('Zend_Log', $log); } Unfortunately this assertion fails == $log IS NULL --- but why?? It is clear that we could just initialize the Zend_Log manually during bootstrapping without using the automatism of Zend_Application_Resource_Log, so this kind of answers will not be accepted.

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  • Practice of checking 'trueness' or 'equality' of conditional statements - does it really make sense?

    - by senthilkumar1033
    I remember many years back, when I was in school, one of my computer science teachers taught us that it was better to check for 'trueness' or 'equality' of a condition and not the negative stuff like 'inequality'. Let me elaborate - If a piece of conditional code can be written by checking whether an expression is true or false, we should check the 'trueness'. Example: Finding out whether a number is odd - it can be done in two ways: if ( num % 2 != 0 ) { // Number is odd } or if ( num % 2 == 1 ) { // Number is odd } When I was beginning to code, I knew that num % 2 == 0 implies the number is even, so I just put a ! there to check if it is odd. But he was like 'Don't check NOT conditions. Have the practice of checking the 'trueness' or 'equality' of conditions whenever possible.' And he recommended that I use the second piece of code. I am not for or against either but I just wanted to know - what difference does it make? Please don't reply 'Technically the output will be the same' - we ALL know that. Is it a general programming practice or is it his own programming practice that he is preaching to others?

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  • Testing variable types in Python

    - by Jasper
    Hello, I'm creating an initialising function for the class 'Room', and found that the program wouldn't accept the tests I was doing on the input variables. Why is this? def __init__(self, code, name, type, size, description, objects, exits): self.code = code self.name = name self.type = type self.size = size self.description = description self.objects = objects self.exits = exits #Check for input errors: if type(self.code) != type(str()): print 'Error found in module rooms.py!' print 'Error number: 110' elif type(self.name) != type(str()): print 'Error found in module rooms.py!' print 'Error number: 111' elif type(self.type) != type(str()): print 'Error found in module rooms.py!' print 'Error number: 112' elif type(self.size) != type(int()): print 'Error found in module rooms.py!' print 'Error number: 113' elif type(self.description) != type(str()): print 'Error found in module rooms.py!' print 'Error number: 114' elif type(self.objects) != type(list()): print 'Error found in module rooms.py!' print 'Error number: 115' elif type(self.exits) != type(tuple()): print 'Error found in module rooms.py!' print 'Error number: 116' When I run this I get this error: Traceback (most recent call last): File "/Users/Jasper/Development/Programming/MyProjects/Game Making Challenge/Europa I/rooms.py", line 148, in <module> myRoom = Room(101, 'myRoom', 'Basic Room', 5, '<insert description>', myObjects, myExits) File "/Users/Jasper/Development/Programming/MyProjects/Game Making Challenge/Europa I/rooms.py", line 29, in __init__ if type(self.code) != type(str()): TypeError: 'str' object is not callable

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  • Silverlight ~ MVVM ~ Dynamic setting of Style property based on model value

    - by eponymous23
    I have a class called Question that represents a question and it's answer. I have an application that renders an ObservableCollection of Question objects. Each Question is rendered as a StackPanel that contains a TextBlock for the question verbiage, and a TextBox for the user to enter in an answer. The questions are rendered using an ItemsControl, and I have initially set the Style of the Questions's StackPanel using a StaticResource key called 'IncorrectQuestion' (defined in UserControl.Resources section of the page). In the UserControl.Resources section, I've also defined a key calld 'CorrectQuestion' which I need to somehow apply to the Question's StackPanel when the user correctly answers the question. My problem is I'm not sure how to dynamically change the Style of the StackPanel, specifically within the constraints of a ViewModel class (i.e. I don't want to put any style selection code in the View's code-behind). My Question class has an IsCorrect property which is accurately being set when the correction is answered. I'd like to somehow reflect the IsCorrect value in the form of a Style selection. How do I do that?

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  • How to use different providers for Linq to entities?

    - by Anders Svensson
    I'm trying to familiarize myself a bit more with database programming, and I'm looking at different ways of creating a data access layer for applications. I've tried out a few ways but there is such a jungle of different database technologies that I don't know what to learn. For instance I've tried using datasets with tableadapters. Using that I am able to switch data provider rather easily (by programming against the interfaces such as IDbConnection). This is one thing I would want to achieve. But I also know everyone's talking about LINQ, and I'm trying to get to know that a bit better too. So I have tried using Linq to Sql classes as the data access layer as well, but apparently this is not provider independent (works only for SQL Server). So then I read about the Entity Framework (which just as Linq to SQL apparently has gotten its share of bashing already...). It's supposed to be provider independent everybody says, but how? I tried out a tutorial to create an entity data model, but the only providers to choose from were SQL Server/Express. Just for learning purposes, I would like to know how to use the entity framework with MS Access/OleDb. Also, I would appreciate some input on what is the preferred database technology for data access. Is it LINQ still after all the bashing, or should you just use datasets because they are provider independent? Any pointers for what to learn would be great, because it's just too much to learn it all if I'm not going to use it in the end...!

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  • How to synchronize access to many objects

    - by vividos
    I have a thread pool with some threads (e.g. as many as number of cores) that work on many objects, say thousands of objects. Normally I would give each object a mutex to protect access to its internals, lock it when I'm doing work, then release it. When two threads would try to access the same object, one of the threads has to wait. Now I want to save some resources and be scalable, as there may be thousands of objects, and still only a hand full of threads. I'm thinking about a class design where the thread has some sort of mutex or lock object, and assigns the lock to the object when the object should be accessed. This would save resources, as I only have as much lock objects as I have threads. Now comes the programming part, where I want to transfer this design into code, but don't know quite where to start. I'm programming in C++ and want to use Boost classes where possible, but self written classes that handle these special requirements are ok. How would I implement this? My first idea was to have a boost::mutex object per thread, and each object has a boost::shared_ptr that initially is unset (or NULL). Now when I want to access the object, I lock it by creating a scoped_lock object and assign it to the shared_ptr. When the shared_ptr is already set, I wait on the present lock. This idea sounds like a heap full of race conditions, so I sort of abandoned it. Is there another way to accomplish this design? A completely different way?

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  • How can I be a Guru? Is it possible? [closed]

    - by Kev
    Before 1999, I heard about computer. But, I don't know what it look like. TV? Maybe! Before 2001, I only saw it in book. It looks like a TV. Before 2005, I touched it in reality. It still looks like a TV + Black Box. In 2005, I entered university. I had a cource about Mathematica.I loved programming since then. In 2006, I owned a computer. I was coding C every day. if...else..., for..., while..., switch... entered my life. Since 2007, I have learned Data Structures, Algorithms...Then, C#, Java, Python, HTML/CSS/JavaScript, F#... A lot of languages. I'm still learning new lang. Unfortunately, I only know syntax! I'm always a novice(??)! I know some guru start programming at age of 8 or 12. I admire these gurus who are compiler writers, language designers, architecture designers, Linux hackers... Is it possible to become a guru like me. If possible, how? what should I do now? Any advice? Thank you very much.

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