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• C++ Why is the converter constructor implicitly called?

  - by ShaChris23

  Why is the Child class's converter constructor called in the code below? I mean, it automatically converts Base to Child via the Child converter constructor. The code below compiles, but shouldn't it not compile since I haven't provided bool Child::operator!=(Base const&)? class Base { }; class Child : public Base { public: Child() {} Child(Base const& base_) : Base(base_) { std::cout <<"should never called!"; } bool operator!=(Child const&) { return true; } }; void main() { Base base; Child child; if(child != base) std::cout << "not equal"; else std::cout << "equal"; }

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• Dealing with the lack of closures in Objective-C

  - by Sean Clark Hess

  Maybe it's just the fact that I've been using http://nodejs.org/ lately, but the lack of closures in Objective-C (iphone) has been really hard to work around. For example, I'm creating service classes. Each service class can have several methods, each of which makes a different URL request. I can use the delegate pattern, but that means that I have to create a new service each time I want to call a method on it (because it has to store the delegate and selector for that request, and new method calls would overwrite them). Even more difficult for me is the fact that I can't easily keep local variables around in the scope for a callback. I have to store anything I want to send back to the delegate on the service class itself, which makes it harder to have more than one method on each class. How do you pros do it? Should I just quit whining and do it another way?

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• Java HTML Parsing

  - by Richie_W

  Hello everyone. I'm working on an app which scrapes data from a website and I was wondering how I should go about getting the data. Specifically I need data contained in a number of div tags which use a specific CSS class - Currently (for testing purposes) I'm just checking for "div class = "classname"" in each line of HTML - This works, but I can't help but feel there is a better solution out there. Ie. - Is there any nice way where I could give a class a line of HTML and have some nice methods like: boolean usesClass(String CSSClassname); String getText(); String getLink(); Many many thanks!

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• constructor injection using Autofac 2 and Named Registration

  - by Thad

  I am currently attempting to remove a number of .Resolve(s) in our code. I was moving along fine until I ran into a named registration and I have not been able to get Autofac resolve using the name. What am I missing to get the named registration injected into the constructor. Registration builder.RegisterType<CentralDataSessionFactory>().Named<IDataSessionFactory>("central").SingleInstance(); builder.RegisterType<ClientDataSessionFactory>().Named<IDataSessionFactory>("client").SingleInstance(); builder.RegisterType<CentralUnitOfWork>().As<ICentralUnitOfWork>().InstancePerDependency(); builder.RegisterType<ClientUnitOfWork>().As<IClientUnitOfWork>().InstancePerDependency(); Current class public class CentralUnitOfWork : UnitOfWork, ICentralUnitOfWork { protected override ISession CreateSession() { return IoCHelper.Resolve<IDataSessionFactory>("central").CreateSession(); } } Would Like to Have public class CentralUnitOfWork : UnitOfWork, ICentralUnitOfWork { private readonly IDataSessionFactory _factory; public CentralUnitOfWork(IDataSessionFactory factory) { _factory = factory; } protected override ISession CreateSession() { return _factory.CreateSession(); } }

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• C# "Enum" Serialization - Deserialization to Static Instance

  - by Walt W

  Suppose you have the following class: class Test : ISerializable { public static Test Instance1 = new Test { Value1 = "Hello" ,Value2 = 86 }; public static Test Instance2 = new Test { Value1 = "World" ,Value2 = 26 }; public String Value1 { get; private set; } public int Value2 { get; private set; } public void GetObjectData(SerializationInfo info, StreamingContext context) { //Serialize an indicator of which instance we are - Currently //I am using the FieldInfo for the static reference. } } I was wondering if it is possible / elegant to deserialize to the static instances of the class? Since the deserialization routines (I'm using BinaryFormatter, though I'd imagine others would be similar) look for a constructor with the same argument list as GetObjectData(), it seems like this can't be done directly . . Which I would presume means that the most elegant solution would be to actually use an enum, and then provide some sort of translation mechanism for turning an enum value into an instance reference. How might one go about this?

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• Undo "Upgrade Current Target for iPad?

  - by Moshe

  I've upgraded current Target for iPad and I dodn't like the result. Now, i've tried to downgrade by deleting files but it's not working. Help! Do I need to change project settings? Does XCode keep a backup of the project? What to do... It doesn't run on iPhone anymore... EDIT: The console crash log on the iPhone Simulator: 2010-05-10 00:11:02.455 iDecide[9743:207] Unknown class iDecideAppDelegate in Interface Builder file. 2010-05-10 00:11:02.456 iDecide[9743:207] Unknown class iDecideViewController in Interface Builder file. 2010-05-10 00:11:02.465 iDecide[9743:207] *** Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[<UICustomObject 0x391eb80> setValue:forUndefinedKey:]: this class is not key value coding-compliant for the key viewController.' 2010-05-10 00:11:02.466 iDecide[9743:207] Stack: ( 34047067, 2420679945, 34206145, 215656, 214197, 4551796, 33949999, 4546347, 4554615, 2715730, 2754518, 2743092, 2725503, 2752609, 39038297, 33831808, 33827912, 2719253, 2756527 )

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• Explicit C# interface implementation of interfaces that inherit from other interfaces

  - by anthony

  Consider the following three interfaces: interface IBaseInterface { event EventHandler SomeEvent; } interface IInterface1 : IBaseInterface { ... } interface IInterface 2 : IBaseInterface { ... } Now consider the following class that implements both IInterface1 and IInterface 2: class Foo : IInterface1, IInterface2 { event EventHandler IInterface1.SomeEvent { add { ... } remove { ... } } event EventHandler IInterface2.SomeEvent { add { ... } remove { ... } } } This results in an error because SomeEvent is not part of IInterface1 or IInterface2, it is part of IBaseInterface. How can the class Foo implement both IInterface1 and IInterface2?

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• Difference between Singleton implemention using pointer and using static object

  - by Anon

  EDIT: Sorry my question was not clear, why do books/articles prefer implementation#1 over implementation#2? What is the actual advantage of using pointer in implementation of Singleton class vs using a static object? Why do most books prefer this class Singleton { private: static Singleton *p_inst; Singleton(); public: static Singleton * instance() { if (!p_inst) { p_inst = new Singleton(); } return p_inst; } }; over this class Singleton { public: static Singleton& Instance() { static Singleton inst; return inst; } protected: Singleton(); // Prevent construction Singleton(const Singleton&); // Prevent construction by copying Singleton& operator=(const Singleton&); // Prevent assignment ~Singleton(); // Prevent unwanted destruction };

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• C# inheritance XmlSerializer

  - by ikurtz

  greetngs, i have two classes: [Serializable] public class FireGridUnit { public GridUnit FireGridLocation { get; set; } } [Serializable] public class FireResult: FireGridUnit { public bool Hit { get; set; } public bool ShipDestroyed { get; set; } public Ship.ValidShips DestroyedShipType {get; set;} public bool Win { get; set; } } as you see FireResult inherits FireGrdUnit. in my code when i try to use them i get a runtime error: Unable to cast object of type 'NietzscheBattleships.FireGridUnit' to type 'NietzscheBattleships.FireResult'. is this because if i am serializing the class has to be independant ie not be inherited? many thanks.

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• How to properly match varargs in Mockito

  - by qualidafial

  I've been trying to get to mock a method with vararg parameters using Mockito: interface A { B b(int x, int y, C... c); } A a = mock(A.class); B b = mock(B.class); when(a.b(anyInt(), anyInt(), any(C[].class))).thenReturn(b); assertEquals(b, a.b(1, 2)); This doesn't work, however if I do this instead: when(a.b(anyInt(), anyInt())).thenReturn(b); assertEquals(b, a.b(1, 2)); This works, despite that I have completely omitted the varargs argument when stubbing the method. Any clues?

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• How to read verbose VC++ linker output

  - by Assaf Lavie

  Trying to debug some linker errors, I turned on /VERBOSE and I'm trying to make sense of the output. It occurs to me that I really don't know how to read it. For example: 1>Compiling version info 1>Linking... 1>Starting pass 1 1>Processed /DEFAULTLIB:mfc80.lib 1>Processed /DEFAULTLIB:mfcs80.lib 1>Processed /DEFAULTLIB:msvcrt.lib 1>Processed /DEFAULTLIB:kernel32.lib 1>Processed /DEFAULTLIB:user32.lib .... 1>Processed /DEFAULTLIB:libgslcblasMD.lib 1>Searching libraries 1> Searching V:\Src\Solutions\\..\..\\Common\Win32\Lib\PlxApi.lib: 1> Searching ..\..\..\..\out\win32\release\lib\camerageometry.lib: 1> Searching ..\..\..\..\out\win32\release\lib\geometry.lib: 1> Found "public: __thiscall VisionMap::Geometry::Box2d::operator class VisionMap::Geometry::Box2DInt(void)const " (??BBox2d@Geometry@VisionMap@@QBE?AVBox2DInt@12@XZ) 1> Referenced in FocusDlg.obj 1> Loaded geometry.lib(Box2d.obj) 1>Processed /DEFAULTLIB:CGAL-vc80-mt.lib 1>Processed /DEFAULTLIB:boost_thread-vc80-mt-1_33_1.lib What's going on here? I think I understand this bit: 1>Processed /DEFAULTLIB:libgslcblasMD.lib 1>Searching libraries 1> Searching V:\Src\Solutions\\..\..\\Common\Win32\Lib\PlxApi.lib: 1> Searching ..\..\..\..\out\win32\release\lib\camerageometry.lib: 1> Searching ..\..\..\..\out\win32\release\lib\geometry.lib: 1> Found "public: __thiscall VisionMap::Geometry::Box2d::operator class VisionMap::Geometry::Box2DInt(void)const " (??BBox2d@Geometry@VisionMap@@QBE?AVBox2DInt@12@XZ) 1> Referenced in FocusDlg.obj 1> Loaded geometry.lib(Box2d.obj) It's trying to find the implementation of the above operator, which is used somewhere in FocusDlg.cpp, and it finds it in geometry.lib. But what does 1>Processed /DEFAULTLIB:libgslcblasMD.lib mean? What determines the order of symbol resolution? Why is it loading this particular symbol while processing libgslcblasMD.lib which is a 3rd party library? Or am I reading it wrong? It seems that the linker is going through the symbols referenced in the project's various object files, but I have no idea in what order. It then searches the static libraries the project uses - by project reference, explicit import and automatic default library imports; but it does so in an order that, again, seems arbitrary to me. When it finds a symbol, for example in geometry.lib, it then continues to find a bunch of other symbols from the same lib: 1> Searching V:\Src\Solutions\\..\..\\Common\Win32\Lib\PlxApi.lib: 1> Searching ..\..\..\..\out\win32\release\lib\camerageometry.lib: 1> Searching ..\..\..\..\out\win32\release\lib\geometry.lib: 1> Found "public: __thiscall VisionMap::Geometry::Box2d::operator class VisionMap::Geometry::Box2DInt(void)const " (??BBox2d@Geometry@VisionMap@@QBE?AVBox2DInt@12@XZ) 1> Referenced in FocusDlg.obj 1> Loaded geometry.lib(Box2d.obj) 1>Processed /DEFAULTLIB:CGAL-vc80-mt.lib 1>Processed /DEFAULTLIB:boost_thread-vc80-mt-1_33_1.lib 1> Found "public: __thiscall VisionMap::Geometry::Box2DInt::Box2DInt(int,int,int,int)" (??0Box2DInt@Geometry@VisionMap@@QAE@HHHH@Z) 1> Referenced in FocusDlg.obj 1> Referenced in ImageView.obj 1> Referenced in geometry.lib(Box2d.obj) 1> Loaded geometry.lib(Box2DInt.obj) 1> Found "public: virtual __thiscall VisionMap::Geometry::Point3d::~Point3d(void)" (??1Point3d@Geometry@VisionMap@@UAE@XZ) 1> Referenced in GPSFrm.obj 1> Referenced in MainFrm.obj 1> Loaded geometry.lib(Point3d.obj) 1> Found "void __cdecl VisionMap::Geometry::serialize<class boost::archive::binary_oarchive>(class boost::archive::binary_oarchive &,class VisionMap::Geometry::Point3d &,unsigned int)" (??$serialize@Vbinary_oarchive@archive@boost@@@Geometry@VisionMap@@YAXAAVbinary_oarchive@archive@boost@@AAVPoint3d@01@I@Z) 1> Referenced in GPSFrm.obj 1> Referenced in MainFrm.obj 1> Loaded geometry.lib(GeometrySerializationImpl.obj) But then, for some reason, it goes on to find symbols that are defined in other libs, and returns to geometry later on (a bunch of times). So clearly it's not doing "look in geometry and load every symbol that's references in the project, and then continue to other libraries". But it's not clear to me what is the order of symbol lookup. And what's the deal with all those libraries being processed at the beginning of the linker's work, but not finding any symbols to load from them? Does this project really not use anything from msvcrt.lib, kernel32.lib? Seems unlikely. So basically I'm looking to decipher the underlying order in the linker's operation.

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• Heap Dump Root Classes

  - by Adnan Memon

  We have production system going into infinite loop of full gc and memory drops form 8 gigs to like 1 MB in just 2 minutes. After taking heap dump it tells me there an is an array of java.lang.Object ([Ljava.lang.Object) with millions of java.lang.String objects having same String taking 99% of heap. But it doesn't tell me which class is referencing to this array so that I can fix it in the code. I took the heap dump using jmap tool on JDK 6 and used JProfiler, NetBeans, SAP Memory Analyzer and IBM Memory Analyzer but none of those tell me what is causing this huge array of objects?? ... like what class is referencing to it or contains it. Do I have to take a different dump with different config in order to get that info? ... Or anything else that can help me find out the culprit class causing this ... it will help a lot.

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• ClassNotFoundException error in implementing Bayesian algorithm in Apache Mahout on Hadoop

  - by Shweta

  Hi, I have a problem in executing the Bayesian algorithm in Mahout. I built it with Maven and the job file is in target directory. When run from terminal using hadoop, I'm getting the ClassNotFoundException error. What should be done? $HADOOP_HOME/bin/hadoop jar mahout-core-0.3-SNAPSHOT.job org.apache.mahout.classifier.bayes.mapreduce.bayes.bayesdriver -i test -o output Exception in thread "main" java.lang.ClassNotFoundException: org.apache.mahout.classifier.bayes.mapreduce.bayes.bayesdriver at java.net.URLClassLoader$1.run(URLClassLoader.java:200) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:188) at java.lang.ClassLoader.loadClass(ClassLoader.java:307) at java.lang.ClassLoader.loadClass(ClassLoader.java:252) at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320) at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Class.java:247) at org.apache.hadoop.util.RunJar.main(RunJar.java:149)

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• forloop and table in latex

  - by Tim

  Hi, Here is the latex code for my table: \begin{table}{| c || c | c | c || c | c | c | } \caption{Examples of the concepts. \label{tab:conceptsimgs}}\\ \hline \backslashbox{Concept}{Class} &\multicolumn{3}{|c||}{Negative Class} & \multicolumn{3}{|c|}{Positive Class} \\ \hline \forloop{themenumber}{1}{\value{themenumber} < 4}{ %\hline \arabic{themenumber} \forloop{classnumber}{0}{\value{classnumber} < 2}{ \forloop{imagenumber}{1}{\value{imagenumber} < 4}{ & 0 } } \\ \hline } \end{table} Something is wrong in the result however. There is some extra thing at the end of the table, as shown in this image. How can I fix it? Thanks and regards!

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• DataAnnotations multiple property validation in MVC

  - by scottrakes

  I am struggling with DataAnnotations in MVC. I would like to validate a specific property, not the entire class but need to pass in another property value to validate against. I can't figure out how to pass the other property's value, ScheduleFlag, to the SignUpType Validation Attribute. public class Event { public bool ScheduleFlag {get;set;} [SignupType(ScheduleFlag=ScheduleFlag)] } public class SignupTypeAttribute : ValidationAttribute { public bool ScheduleFlag { get; set; } public override bool IsValid(object value) { var DonationFlag = (bool)value; if (DonationFlag == false && ScheduleFlag == false) return false; return true; } }

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• Efficient counting of an association’s association

  - by Matthew Robertson

  In my app, when a User makes a Comment in a Post, Notifications are generated that marks that comment as unread. class Notification < ActiveRecord::Base belongs_to :user belongs_to :post belongs_to :comment class User < ActiveRecord::Base has_many :notifications class Post < ActiveRecord::Base has_many :notifications I’m making an index page that lists all the posts for a user and the notification count for each post for just that user. # posts controller @posts = Post.where( :user_id => current_user.id ) .includes(:notifications) # posts view @posts.each do |post| <%= post.notifications.count %> This doesn’t work because it counts notifications for all users. What’s an efficient way to do this without running a separate query for each post?

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• C# WinForms problem with draw image

  - by Paul

  Hi I have this class: class OriginalImage: Form { private Image image; private PictureBox pb; public OriginalImage() { pb = new PictureBox {SizeMode = PictureBoxSizeMode.CenterImage}; pb.SizeMode = PictureBoxSizeMode.StretchImage; Controls.Add(pb); image = Image.FromFile(@"Image/original.jpg"); this.Width = image.Width; this.Height = image.Height; this.Text = "Original image"; this.Paint += new PaintEventHandler(Drawer); } public virtual void Drawer(object source, PaintEventArgs e) { Graphics g = pb.CreateGraphics(); g.DrawImage(image,0,0); } I call this create object OriginalImage in other form on button click, but image is not draw? Where is problem? public partial class Form1 : Form { public Form1() { InitializeComponent(); } private void button1_Click(object sender, EventArgs e) { var oi = new OriginalImage(); oi.Show(); } }

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• Protected Members of Other Instances in Scala

  - by Masterofpsi

  I just ran into a difficulty while learning Scala. I have an inheritance hierarchy that is essentially equivalent to this: class A { protected def myMethod() = println("myMethod() from A") } class B extends A { def invokeMyMethod(a: A) = a.myMethod() } But trying to compile this sample, I get the error "test.scala:7: error: method myMethod cannot be accessed in A". Coming from Java, my understanding is that protected members should be accessible at any point from a derived class, and nowhere have I seen anything that tells me that protected members in Scala are limited by instance. Does anyone have an explanation for this?

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• Django Managers

  - by owca

  I have the following models code : from django.db import models from categories.models import Category class MusicManager(models.Manager): def get_query_set(self): return super(MusicManager, self).get_query_set().filter(category='Music') def count_music(self): return self.all().count() class SportManager(models.Manager): def get_query_set(self): return super(MusicManager, self).get_query_set().filter(category='Sport') class Event(models.Model): title = models.CharField(max_length=120) category = models.ForeignKey(Category) objects = models.Manager() music = MusicManager() sport = SportManager() Now by registering MusicManager() and SportManager() I am able to call Event.music.all() and Event.sport.all() queries. But how can I create Event.music.count() ? Should I call self.all() in count_music() function of MusicManager to query only on elements with 'Music' category or do I still need to filter through them in search for category first ?

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• Spring MVC defaultValue for Double

  - by mlathe

  Hi All, I'm trying to build a controller like this: @RequestMapping(method = {RequestMethod.GET}, value = "/users/detail/activities.do") public View foo(@RequestParam(value = "userCash", defaultValue="0.0") Double userCash) { System.out.println("foo userCash=" + userCash); } This works fine: http://localhost/app/users/detail/activities.do?userCash=123& but in this one userCash==null despite the default value http://localhost/app/users/detail/activities.do?userCash=& From some digging it seems like the first one works b/c of a Editor binding like this: binder.registerCustomEditor(Double.class, new CustomNumberEditor(Double.class, false)); The trouble is that the second param (ie false) defines whether blank values are allowed. If i set that to true, than the system considers the blank input as valid so i get a null Double class. If i set it to false then the system chokes on the blank input string with: org.springframework.beans.TypeMismatchException: Failed to convert value of type 'java.lang.String' to required type 'double'; nested exception is java.lang.NumberFormatException: empty String Does anyone know how to get the defaultValue to work for Doubles? Thanks --Matthias

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• django-admin formfield_for_* change default value per/depending on instance

  - by Nick Ma.

  Hi, I'm trying to change the default value of a foreignkey-formfield to set a Value of an other model depending on the logged in user. But I'm racking my brain on it... This: Changing ForeignKey’s defaults in admin site would an option to change the empty_label, but I need the default_value. #Now I tried the following without errors but it didn't had the desired effect: class EmployeeAdmin(admin.ModelAdmin): ... def formfield_for_foreignkey(self, db_field, request=None, **kwargs): formfields= super(EmployeeAdmin, self).formfield_for_foreignkey(db_field, request, **kwargs) if request.user.is_superuser: return formfields if db_field.name == "company": #This is the RELEVANT LINE kwargs["initial"] = request.user.default_company return db_field.formfield(**kwargs) admin.site.register(Employee, EmployeeAdmin) ################################################################## # REMAINING Setups if someone would like to know it but i think # irrelevant concerning the problem ################################################################## from django.contrib.auth.models import User, UserManager class CompanyUser(User): ... objects = UserManager() company = models.ManyToManyField(Company) default_company= models.ForeignKey(Company, related_name='default_company') #I registered the CompanyUser instead of the standard User, # thats all up and working ... class Employee(models.Model): company = models.ForeignKey(Company) ... Hint: kwargs["default"] ... doesn't exist. Thanks in advance, Nick

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• Javassist: how to create proxy of proxy?

  - by Bozho

  I'm creating proxies with javassist ProxyFactory. When creating a single proxy all works fine. However, when I pass a proxied class to the proxying mechanism, it fails with javassist.bytecode.DuplicateMemberException: duplicate method: setHandler in com.mypackage.Bean_$$_javassist_0_$$_javassist_1 I'm creating the proxies with this: public Object createProxiedInstance(Object originalInstance) throws Exception { Class<?> originalClass = instance.getClass(); ProxyFactory factory = new ProxyFactory(); factory.setSuperclass(originalClass); factory.setHandler(new MethodHandler() {..}); Class<T> proxyClass = factory.createClass(); return proxyClass.newInstance(); } So, how do I create proxies of proxies? Update: The actual problems is that each proxy implements the ProxyObject which defines setHandler(..) method. So the 2nd proxy is trying to redefine the method, instead of overriding it in the subclass.

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• Good Async pattern for sequential WebClient requests

  - by Omar Shahine

  Most of the code I've written in .NET to make REST calls have been synchronous. Since Silverlight on Windows Phone only supports Async WebClient and HttpWebRequest calls, I was wondering what a good async pattern is for a Class that exposes methods that make REST calls. For example, I have an app that needs to do the following. Login and get token Using token from #1, get a list of albums Using token from #1 get a list of categories etc my class exposes a few methods: Login() GetAlbums() GetCategories() since each method needs to call WebClient using Async calls what I need to do is essentially block calling Login till it returns so that I can call GetAlbums(). What is a good way to go about this in my class that exposes those methods?

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• Google App Engine (python): TemplateSyntaxError: 'for' statements with five words should end in 'rev

  - by Phil

  This is using the web app framework, not Django. The following template code is giving me an TemplateSyntaxError: 'for' statements with five words should end in 'reversed' error when I try to render a dictionary. I don't understand what's causing this error. Could somebody shed some light on it for me? {% for code, name in charts.items %} <option value="{{code}}">{{name}}</option> {% endfor %} I'm rendering it using the following: class GenerateChart(basewebview): def get(self): values = {"datepicker":True} values["charts"] = {"p3": "3D Pie Chart", "p": "Segmented Pied Chart"} self.render_page("generatechart.html", values) class basewebview(webapp.RequestHandler): ''' Base class for all webapp.RequestHandler type classes ''' def render_page(self, filename, template_values=dict()): filename = "%s/%s" % (_template_dir, filename) path = os.path.join(os.path.dirname(__file__), filename) self.response.out.write(template.render(path, template_values))

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• Covariance and Contravariance on the same type argument

  - by William Edmondson

  The C# spec states that an argument type cannot be both covariant and contravariant at the same time. This is apparent when creating a covariant or contravariant interface you decorate your type parameters with "out" or "in" respectively. There is not option that allows both at the same time ("outin"). Is this limitation simply a language specific constraint or are there deeper, more fundamental reasons based in category theory that would make you not want your type to be both covariant and contravariant? Edit: My understanding was that arrays were actually both covariant and contravariant. public class Pet{} public class Cat : Pet{} public class Siamese : Cat{} Cat[] cats = new Cat[10]; Pet[] pets = new Pet[10]; Siamese[] siameseCats = new Siamese[10]; //Cat array is covariant pets = cats; //Cat array is also contravariant since it accepts conversions from wider types cats = siameseCats;

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