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  • Python overriding class (not instance) special methods

    - by André
    How do I override a class special method? I want to be able to call the __str__() method of the class without creating an instance. Example: class Foo: def __str__(self): return 'Bar' class StaticFoo: @staticmethod def __str__(): return 'StaticBar' class ClassFoo: @classmethod def __str__(cls): return 'ClassBar' if __name__ == '__main__': print(Foo) print(Foo()) print(StaticFoo) print(StaticFoo()) print(ClassFoo) print(ClassFoo()) produces: <class '__main__.Foo'> Bar <class '__main__.StaticFoo'> StaticBar <class '__main__.ClassFoo'> ClassBar should be: Bar Bar StaticBar StaticBar ClassBar ClassBar Even if I use the @staticmethod or @classmethod the __str__ is still using the built in python definition for __str__. It's only working when it's Foo().__str__() instead of Foo.__str__().

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  • Swapping UIImages causing 'unrecognized selector sent to instance' ?

    - by user158103
    Error: [__NSCFDate drawAtPoint:]: unrecognized selector sent to instance 0xd251e0 Termininating app due to uncaught exception 'NSInvalidArgumentException' Scenario: for the most part this works. But I notice this error, even on the simulator, when I swapping UIImages, slowly, but consistently. For example, I have a retained reference to a UIImage that im drawing. By the click of a picker control I am changing the face image (this occurs in another view-controller). I can consistently recreate this error by continuously changing the faces. It usually crashes at about the 4th swap or more. My theory: It's not loading the image, therefore the image reference is nil. I know ive read a bit about UIImage being cached, so I wouldnt think im running out of memory. Any ideas? Thanks!

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  • Objective-C convention to prevent "local declaration hides instance variable" warning

    - by Nippysaurus
    Is there a common convention for dealing with these scenarios? The following code is what I am using .. -(id) initWithVariableName: (NSString*)variableName withComparisonValue:(NSString*)comparisonValue { self.mustExist = NO; self.reverseCondition = NO; self.regularExpression = NO; self.variableName = variableName; self.comparisonValue = comparisonValue; return self; } But I am getting "Local declaration of 'variableName' hides instance variable" and the same for "comparisonValue". The function signature seems logical to me, but surely there must be a more "acceptable" standard which will still make sense and be accurate but not generate annoying warnings?

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  • Adding Class instance as a new Row in DataGridView (c#)

    - by Amit Shah
    Hi All, I have a class say [Serializable] public class Answer { [DisplayName("ID")] public string ID { get; set; } [DisplayName("Value")] public string Value { get; set; } } and I have a datagridview with bounded columns to the above class. instances of this class Answer are created dynamically as and when required. How do I update datagridview when each and every instance of class is created. is it possible to do something of this sort. dataGridView.Rows.Add(classInstance); Thanks in Advance, Amit

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  • arguments into instance methods in ruby

    - by aharon
    So, I'd like to be able to make a call x = MyClass.new('good morning', 'good afternoon', 'good evening', 'good night', ['hello', 'goodbye']) that would add methods to the class whose values are the values of the arguments. So now: p x.methods #> [m_greeting, a_greeting, e_greeting, n_greeting, r_greeting, ...] And p x.m_greeting #> "good morning" p x.r_greeting #> ['hello', 'goodbye'] I realize that this is sort of what instance variables are to do (and that if I wanted them immutable I could make them frozen constants) but, for reasons beyond my control, I need to make methods instead. Thanks!

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  • Subsonic 3.0 - .Net - Error : Can not ceate an instance of an interface

    - by George
    Hi, I am new to Subsonic, I have configured Subsonic3.0 T4 Template and created classes for my project. I have taken GridView and Object Datasource. Object datasource will connect to the one of the classes which is created from subsonic. I have set object datasource for g\fetch, Insert, Update and delete methods. Then i set the datasource of grid witht he object datasource. Grid view successfully showing me all the records. But at the time of Update, Insert or delete it throws an exception that "Can not ceate an instance of an interface". And also i am not able to dwbug in the code of the subsonic. May be because of partial classes. Can anyone please let me know what is happening at the backgrund? Or may be one can give me sample example which contains subsonic 3.0 and grid add, edit and delete so it will be really helpful for me.... Please... :) Thanks, George

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  • Haskell Ord instance with a Set

    - by mvid
    I have some code that I would like to use to append an edge to a Node data structure: import Data.Set (Set) import qualified Data.Set as Set data Node = Vertex String (Set Node) deriving Show addEdge :: Node -> Node -> Node addEdge (Vertex name neighbors) destination | Set.null neighbors = Vertex name (Set.singleton destination) | otherwise = Vertex name (Set.insert destination neighbors) However when I try to compile I get this error: No instance for (Ord Node) arising from a use of `Set.insert' As far as I can tell, Set.insert expects nothing but a value and a set to insert it into. What is this Ord?

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  • Extend a direct instance

    - by Diolor
    We have a new instance of an object with four properties: person={firstname:"John",lastname:"Doe",age:50,eyecolor:"blue"}; What is the best way to many other properties to that object? If we wanted few couple more sure we would: person[address_no] = 4; .... person[country] = 'Netherlands'; But what if we have a lot properties. Is there any minimalistic way like the one below? (I know it doesn't work) person +={address_no: '4', .... , country: 'Netherlands'};

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  • Profile:Object reference not set to an instance of an object

    - by sallalman83
    Hi, i just lunch my web site i used the asp.net routing technology on it, and its work fine in my localhost but when i moved the project to the hosting server(Godaddy.com) its just work fine when there is no virtual sub directories like this(havebreak.com) but when u click on this link (havebreak.com/Registration/) or any other links that contain a virtual sub-directories its give Object reference not set to an instance of an object error on the profile object if (!Profile.IsAnonymous) Line 18: mlvRegistratioin.ActiveViewIndex = 1; i check my IIS settings and found it using the "Integrated pipeline" as recommended (at least at my knowledge), i checked the httpModules and httpHandlers tags under the system.webServer (since my hosting plan use the IIS7) and under the normal tag and every thing is fine then i used the url-rewriting instead of URL-Routing and the same problem exist and i notice that the session also not working in the virtual sub-directories too and by the way the ASP.NET routing work fine with my site its just the profile and session objects that not workin any help will be appreciated

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  • Ruby: Calling class method from instance

    - by Peter
    In Ruby, how do you call a class method from one of that class's instances? Say I have class Truck def self.default_make # Class method. "mac" end def initialize # Instance method. Truck.default_make # gets the default via the class's method. # But: I wish to avoid mentioning Truck. Seems I'm repeating myself. end end the line Truck.default_make retrieves the default. But is there a way of saying this without mentioning Truck? It seems like there should be.

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  • iphone instance / class method issue

    - by user290031
    Hey All, Okay, so I have a viewController method that has some elements created with interface builder and some I coded myself. I created a view in the IB...lets call it viewOne. I created a loop that creates buttons (through code) and places them on a separate view (viewTwo). This is done in a class method. However, I want the view I made to be opened everytime one of the buttons is clicked. So I did: [button addTarget:self action:@selector(woogoo:) forControlEvents:UIControlEventTouchUpInside]; The woogoo class does the following: +(void) woogoo:(id)sender { //back button [self.view addSubview:viewOne] } However, the program crashes when a button is clicked. I did try making woogoo an instance method but it also crashes in this case too. All I want to do is show viewOne when a button is clicked. Any ideas what I can do?

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  • Cannot create instance of 'Ribbon'

    - by user354433
    I'm having trouble using the Ribbon control from the Office 2007 RibbonControlsLibrary.dll. It works for most people but not for me. The fault I get is: Cannot create instance of 'Ribbon' defined in assembly 'RibbonControlsLibrary, Version=3.5.31016.1, Culture=neutral, PublicKeyToken=31bf3856ad364e35'. Exception has been thrown by the target of an invocation The problem is probably not with the code since it works for other people. Its the Ribbon class thats causing the problem. If I remove any references to the Ribbon class but keep the references to RibbonWindow I don't get any exceptions. Any help appreciated

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  • Active Record like functionality on array instance variable

    - by rube_noob
    I would like to write a module that provides active record like functionality on an array instance variable. Examples of its use would be x = Container.new x.include(ContainerModule) x.elements << Element.new x.elements.find id module ContainerModule def initialize(*args) @elements = [] class << @elements def <<(element) #do something with the Container... super(element) end def find(id) #find an element using the Container's id self #=> #<Array..> but I need #<Container..> end end super(*args) end end The problem is that I need the Container object within these methods. Any reference to self will return the Array, not the Container object. Is there any way to do this? Thanks!

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  • Creating a method that is simultaneously an instance and class method

    - by Mike Axiak
    In Python, I'd like to be able to create a function that behaves both as a class function and an instance method, but with the ability to change behaviors. The use case for this is for a set of serializable objects and types. As an example: >>> class Thing(object): #... >>> Thing.to_json() 'A' >>> Thing().to_json() 'B' I know that given the definition of classmethod() in funcobject.c in the Python source, this looks like it'd be simple with a C module. Is there a way to do this from within python? Thanks!

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  • Rails: unexpected behavior updating a shared instance

    - by Pascal Lindelauf
    I have a User object, that is related to a Post object via two different association paths: Post --(has_many)-- comments --(belongs to)-- writer (of type User) Post --(belongs to)-- writer (of type User) Say the following hold: user1.name == "Bill" post1.comments[1].writer == user1 post1.writer == user1 Now when I retrieve the post1 and its comments from the database and I update post1.comments[1].writer like so: post1.comments[1].writer.name = "John" I would expect post1.writer to equal "John" too. But it doesn't! It still equals "Bill". So there seems to be some caching going on, but the kind I would not expect. I would expect Rails to be clever enough to load exactly one instance of the user with name "Bill"; instead is appears to load two individual ones: one for each association path. Can someone explain how this works exactly and how I am to handle these types of situations the "Rails way"?

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  • Create Generic Class Instance from Static Method in a Derived Class

    - by user343547
    I have a class in C# with a template and static method similar to class BClass<T> { public static BClass<T> Create() { return new BClass<T>(); } } From this I derive a class and specify a template parameter to the base class class DClass : BClass<int> { } A problem occurs when I try to use the static method to create an instance of D class Program { static void Main(string[] args) { DClass d = DClass.Create(); } } Gives a compiler error "Cannot implicitly convert type 'Test.BClass<int ' to 'Test.DClass'." Adding the below cast leads to a runtime casting exception. DClass d = (DClass)DClass.Create(); Is there any succint way to allow the static method to create instances of the derived class? Ideally I would like the equivalent of a c++ typedef and I don't want the below syntax (which does work). BClass<int> d = DClass.Create();

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  • Weblogic server lib VS instance libext

    - by Sebastien Lorber
    Hello, I use weblogic 10. Its provide an Oracle JDBC driver 10.2.0.2 (in the server/lib on weblogic home). Actually someone at work put a long time ago a 10.2.0.3 driver in instance libext folder. But in production we got a jdbc driver stack (nullpointer :O) and by reverse engineering it seems we are using driver 10.2.0.2. We know that we could change the driver in the server/lib of weblogic but i want to understand. Isn't libext supposed to override server libs like META-INF libs override libext? By the way we are in a strange situation: - We have 2 EAR, and for the exact same treatment in those 2, one will sometime throw the oracle driver nullpointer while the other doesn't - I wonder if one ear isn't using 10.2.0.2 while the other is using 10.2.0.3 (i saw a bug fixed that could fit to our problem for this version). - I need to look better but at first sight both ear use the exact same datasource set in weblogic JNDI resources Any idea?

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  • Creating Instance of Python Extension Type in C

    - by Brad Zeis
    I am writing a simple Vector implementation as a Python extension module in C that looks mostly like this: typedef struct { PyObject_HEAD double x; double y; } Vector; static PyTypeObject Vector_Type = { ... }; It is very simple to create instances of Vector while calling from Python, but I need to create a Vector instance in the same extension module. I looked in the documentation but I couldn't find a clear answer. What's the best way to do this?

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  • Copying blocks (ie: copying them to instance variables) in Objective-C

    - by RyanWilcox
    I'm trying to understand blocks. I get how to use them normally, when passed directly to a method. I'm interested now in taking a block, storing it (say) in an instance variable and calling it later. The blocks programming guide makes it sound like I can do this, by using Block_copy / retain to copy the block away, but when I try to run it I crash my program. - (void) setupStoredBlock { int salt = 42; m_storedBlock = ^(int incoming){ return 2 + incoming + salt; }; [m_storedBlock retain]; } I try to call it later: - (void) runStoredBlock { int outputValue = m_storedBlock(5); NSLog(@"When we ran our stored blockwe got back: %d", outputValue); [m_storedBlock release]; } Anyone have any insights? (Or, is there something I'm not getting with blocks?) Thank you very much!

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  • unrecognized selector sent to instance

    - by iamsmug
    My app works fine in the simulator but when I run it on my phone I get this error: 2010-04-05 21:32:45.119 Top Banana[119:207] * Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '* -[MethodViewController setReferringObject:]: unrecognized selector sent to instance 0x16e930' It happens here: -(void)method { [UIView beginAnimations:@"View Flip" context:nil]; [UIView setAnimationDuration:0.50]; [UIView setAnimationCurve:UIViewAnimationCurveEaseInOut]; [UIView setAnimationTransition: UIViewAnimationTransitionFlipFromRight forView:self.navigationController.view cache:NO]; MethodViewController *methodViewController = [[MethodViewController alloc] initWithNibName:@"MethodViewController" bundle:0]; NSManagedObject *selectedObject = self.referringObject; methodViewController.referringObject = selectedObject; [self.navigationController pushViewController:methodViewController animated:NO]; methodViewController.title = @"Method"; [UIView commitAnimations]; [MethodViewController release]; } It crashes on this line: methodViewController.referringObject = selectedObject; Not sure how to resolve this as it works in the simulator, I'm sure it is fairly basic to fix, any help will be appreciated.

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  • Constructor with non-instance variable assistant?

    - by Robert Fischer
    I have a number of classes that look like this: class Foo(val:BasicData) extends Bar(val) { val helper = new Helper(val) val derived1 = helper.getDerived1Value() val derived2 = helper.getDerived2Value() } ...except that I don't want to hold onto an instance of "helper" beyond the end of the constructor. In Java, I'd do something like this: public class Foo { final Derived derived1, derived2; public Foo(BasicData val) { Helper helper = new Helper(val); derived1 = helper.getDerived1Value(); derived2 = helper.getDerived2Value(); } } So how do I do something like that in Scala? I'm aware of creating a helper object of the same name of the class with an apply method: I was hoping for something slightly more succinct.

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  • Inherit appenders from calling instance in log4j or logback

    - by Lord.Quackstar
    In my program I have 2 separate streams of logging events (calling them streams for simplicity, in reality its 2 appenders). Stream1 contains client logging and Stream2 contains control logging. Now this might seem easy, except that certain classes can be both in the client logging and server logging, depending on the situation. Complicating this further is the fact that a command that a client wants takes place in 2 separate threads (one being fetched randomly from a thread pool), so any kind of tracking with MDC or NDC isn't possible. What would really simplify this is if the logger could inherit the appenders from the calling instance. That way I can setup 2 appenders for 2 loggers and be done. However I have no idea how to do it cleanly or easily. Can anyone offer any advice on how to do so? Note: If something needs to be passed around, I do have a event bean that gets passed to everything in the chain that can be used if necessary.

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  • Is an ArrayList automaticaly declared static ,if it is an instance variable?(Java)

    - by Alex
    Hy ,what i`m trying to do is something like this: private class aClass { private ArrayList idProd; aClass(ArrayList prd) { this.idProd=new ArrayList(prd); } public ArrayList getIdProd() { return this.idProd; } } So if i have multiple instances of ArrayLIst (st1 ,st2 ,st3) and I want to make new objects of aClass : { aClass obj1,obj2,obj3; obj1=new aClass(st1); obj2=new aClass(st2); obj3=new aClass(st3); }why all of the aClass objects will return st3 if I access the method getIdProd() for each of them(obj1..obj3)? is an arraylist as a instance variable automatically declared static?

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  • Installing Skype on Amazon EC2 instance

    - by Adrian
    For my application, I need to have Skype working on my Amazon EC2 Windows instance. I got the application installed and am able to log in, however, I can't make a phone call, since I am getting an 'Can't detect your sound card' error. Since I'm trying to inject audio from an audio file into the phone call, I don't need the sound card on the server. Thus, I need a way to bypass this error message. I have tried installing Virtual Audio Cable, which unfortunately didn't work (even though it worked on my desktop machine).

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  • Setting an instance variable from a block

    - by c00lryguy
    How would I achieve something like below so that when I set the s variable within the block, it also sets the @subject instance variable in my Topic class? class Topic def subject(&blk) blk.call(@subject) if block_given? @subject unless block_given? end end my_topic = Topic.new p my_topic.subject #=> nil my_topic.subject do |s| s = ['one', 'two', 'three'] s.pop p s #=> ['one', 'two'] end p my_topic.subject #=> nil... want it to be ['one, 'two']

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