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  • How do I find the "concrete class" of a django model baseclass

    - by Mr Shark
    I'm trying to find the actual class of a django-model object, when using model-inheritance. Some code to describe the problem: class Base(models.model): def basemethod(self): ... class Child_1(Base): pass class Child_2(Base): pass If I create various objects of the two Child classes and the create a queryset containing them all: Child_1().save() Child_2().save() (o1, o2) = Base.objects.all() I want to determine if the object is of type Child_1 or Child_2 in basemethod, I can get to the child object via o1.child_1 and o2.child_2 but that reconquers knowledge about the childclasses in the baseclass. I have come up with the following code: def concrete_instance(self): instance = None for subclass in self._meta.get_all_related_objects(): acc_name = subclass.get_accessor_name() try: instance = self.__getattribute__(acc_name) return instance except Exception, e: pass But it feels brittle and I'm not sure of what happens when if I inherit in more levels.

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  • Observing an NSMutableArray for insertion/removal

    - by Adam Ernst
    A class has a property (and instance var) of type NSMutableArray with synthesized accessors (via @property). If you observe this array using: [myObj addObserver:self forKeyPath:@"theArray" options:0 context:NULL]; And then insert an object in the array like this: [[myObj theArray] addObject:[NSString string]]; An observeValueForKeyPath... notification is not sent. However, the following does send the proper notification: [[myObj mutableArrayValueForKey:@"theArray"] addObject:[NSString string]]; This is because mutableArrayValueForKey returns a proxy object that takes care of notifying observers. But shouldn't the synthesized accessors automatically return such a proxy object? What's the proper way to work around this--should I write a custom accessor that just invokes [super mutableArrayValueForKey...]?

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  • ToolStripComboBox + objects default string value

    - by Martin
    I am using a ToolStripComboBox to list some data. I am populating this combo with some custom objects: For Each obj As myObject In myObjectList myToolStripComboBox.Items.Add(obj) Next This works great except the text displayed in the combo is the name of the object class. I can understand why and realise that I need to do something to make the combo use a property from my class instead. The help files state: To add objects to the list at run time, assign an array of object references with the AddRange method. The list then displays the default string value for each object. You can add individual objects with the Add method. The bit in bold suggests I need to setup the default string value in my class. How would I go about doing this?

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  • Best way to check for null values in Java?

    - by Arty-fishL
    I need to check whether the function of an object returns true or false in Java, but that object may be null, so obviously then the function would throw a NullPointerException. This means I need to check if the object is null before checking the value of the function. What is the best way to go about this? I've listed some methods I considered, I just want to know the most sensible one, the one that is best programming practice for Java (opinion?). // method 1 if (foo != null) { if (foo.bar()) { etc... } } // method 2 if (foo != null ? foo.bar() : false) { etc... } // method 3 try { if (foo.bar()) { etc... } } catch (NullPointerException e) { } // method 4 // would this work all the time, would it still call foo.bar()? if (foo != null && foo.bar()) { etc... }

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  • How can I pass a javaScript function to a Java Method to act as a callback (Rhino)

    - by Dan Howard
    Hi everyone, Basically I'm trying to pass a javaScript function to a Java method to act as a callback to the script. I can do it - sort of - but the object I receive is a sun.org.mozilla.javascript.internal.InterpretedFunction and I don't see a way to invoke it. Any ideas? Here's what I have so far: var someNumber = 0; function start() { // log is just an log4j instance added to the Bindings log.info("started...."); someNumber = 20; // Test is a unit test object with this method on it (taking Object as a param). test.callFromRhino(junk); } function junk() { log.info("called back " + someNumber); }

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  • setting value to the instance of primitive types

    - by Samreen
    I have a function which performs some operation i.e. fetches some data from database. The generic it takes is primitive type always i.e. int, char, bool, string etc. I can easily create its instance. But I can't set the value that I have fetched from database to this instance. public T PerformOperation<T>() { object instance = (T)Activator.CreateInstance(typeof(T)); object result=FetchData(); instance = (T)result; //It gives error on this statement } The function is called as: int result = PerformOperation<int>(); Is there some way of casting the object Type to any generic type which is always primitive?

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  • Adding row to DataGridView from Thread

    - by she hates me
    Hello, I would like to add rows to DataGridView from two seperate threads. I tried something with delegates and BeginInvoke but doesn't work. Here is my row updater function which is called from another function in a thread. public delegate void GRIDLOGDelegate(string ulke, string url, string ip = ""); private void GRIDLOG(string ulke, string url, string ip = "") { if (this.InvokeRequired) { // Pass the same function to BeginInvoke, // but the call would come on the correct // thread and InvokeRequired will be false. object[] myArray = new object[3]; myArray[0] = ulke; myArray[1] = url; myArray[2] = ip; this.BeginInvoke(new GRIDLOGDelegate(GRIDLOG), new object[] { myArray }); return; } //Yeni bir satir daha olustur string[] newRow = new string[] { ulke, url, ip }; dgLogGrid.Rows.Add(newRow); }

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  • WCF hosting in .NET compact framework

    - by jauwaad
    I would like to host a service on a WinCE device. The WinCE device is the host which can be accessed(control and data acquisition) by multiple clients (PC or WinCE) over serial port, TCP, USB etc. I was considering using Protocol Buffers for serialization on the wire. It would be ideal to use WCF or remoting but as far as I see they are not implement on the Compact Framework. Anyone have any ideas how this can be achieved.

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  • readobject method throws ClassNotFoundException

    - by eruina
    Hi all, I'm trying to pick up Java and wanted to test around with Java's client/server to make the client send a simple object of a self defined class(Message) over to the server. The problem was that I kept getting a ClassNotFoundException on the server side. I think the rest of the codes seem to be alright because other objects such as String can go through without problems. I had two different netbeans projects in different locations for client and server each. Each of them have their own copy of Message class under their respective packages. Message class implements Serializable. On the client side, I attempt to send a Message object through. On the server side, upon calling the readObject method, it seems to be finding Message class from the client's package instead of it's own. printStackTrace showed: "java.lang.ClassNotFoundException: client.Message" on the server side I have not even tried to cast or store the object received yet. Is there something I left out?

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  • JQuery-tmpl Template Switching Not working.

    - by Mike
    I'm trying to implement "more/less" functionality using the official jquery-tmpl plugin. I've looked at the examples, but I cannot seem to get the functionality to work in my own implementation. When I click on one of my "More" buttons, I seem to get an error thrown of: Uncaught TypeError: Property 'tmpl' of object #<an Object> is not a function This is my implementation here From what I can tell, the example I'm trying to replace is doing the following: Render the "Master" template On-click: Find the corresponding template object (tmplItem) to the clicked element. Pass in reference to a new template. Call the update function to re-render. Have I understood the documentation wrong? From what I can tell I'm doing the same thing as the example on the official documentation.

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  • Detecting/Repairing NSConnection failure

    - by anthony
    I would like to use NSConnection/NSDistributedObject for interprocess communication. I would like the client to be able to handle the case where the server is only occasionally reachable. How can I determine if sending a message to the NSConnection will fail or has failed? Currently if my server (the process that has vended the remote object) dies, the client will crash if it sends a selector to the remote object. Ideally I'd like to have a wrapper for the remote object that can lazily instantiate (or reinstantiate) the connection, and return a default value in the case where the connection could not be instantiated, or the connection has failed. I don't really know the correct way to do this using objective c. Here's some pseudocode representing this logic: if myConnection is null: instantiate myConnection if MyConnection is null: return defaultValue try return [myConnection someMethod] catch myConnection = null return defaultValue

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  • CORE DATA objectId changes constantly

    - by mongeta
    Hello, I have some data that I export into an XML file and put in a remote FTP Server. I have to identified each object with a unique attribute, it doesn't matter wich is, but must be persistent always = it can never change. I don't want to create a unique attribute, sequence, serial, etc. I'm using the objectID but every time I use it a get a new reference. I know that before the object has been saved, it has a 'temporal id', but once it's saved, it gets the definitive. I'm not seeing this, never. When I export, just fetch all data and loop, and always I get a new reference: NSURL *objectID = [[personalDataObject objectID] URIRepresentation]; // some of id received for the SAME OBJECT (no changes made, saved, ...) // 61993296 // 62194624 thanks, r. edit I was using %d instead of %@, now the returned data is: x-coredata://F46F3300-8FED-4876-B0BF-E4D2A9D80913/DataEntered/p1 x-coredata://F46F3300-8FED-4876-B0BF-E4D2A9D80913/DataEntered/p2

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  • Java Properties and References -- I'm not getting what I expect.

    - by Blumer
    I'm a little embarrassed to ask this as I ought to know better, but here's what I've got. I have an object "Pitcher" with an int property of "runsAllowed". I have an object Batter that has a property of "responsiblePitcher". I have an object Team that has a property "pitcher". When the batter reaches base: Batter.responsiblePitcher = Team.pitcher; All that's well and good. However, if we have a pitching change while the runner is on base, I set a new pitcher in Team.pitcher: Team.pitcher = new Pitcher(); ... and of course this changes the value of Batter.pitcher. How should I be doing things differently such that the Batter.responsiblePitcher property continues to point to the pitcher who let him on base instead of pointing at whever is in the Team.pitcher property? Again, I feel like I ought to know this already ... Thanks.

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  • ASP.NET handling button click event before OnPreInit

    - by Phillykins
    Hello, I have a data access layer, a business logic layer and a presentation layer (ie. the pages themselves). I handle the OnPreInit event and populate collections required for the page. All the data comes from an SQL server database and I do not use caching. I handle a button click event to grab values from a form and insert a new object into the database. The problem is that by the time I handle the click event, the collections have already been populated, so the new item which has been inserted into the database has not been retrieved. What is the accepted solution to this? I could insert the new object directly into the collection and re-bind the GridView, but the SQL query selects only a set of objects and the new object could fall outside of this set. Thanks!

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  • logging in scala

    - by IttayD
    In Java, the standard idiom for logging is to create a static variable for a logger object and use that in the various methods. In Scala, it looks like the idiom is to create a Logging trait with a logger member and mixin the trait in concrete classes. This means that each time an object is created it calls the logging framework to get a logger and also the object is bigger due to the additional reference. Is there an alternative that allows the ease of use of "with Logging" while still using a per-class logger instance? EDIT: My question is not about how one can write a logging framework in Scala, but rather how to use an existing one (log4j) without incurring an overhead of performance (getting a reference for each instance) or code complexity. Also, yes, I want to use log4j, simply because I'll use 3rd party libraries written in Java that are likely to use log4j.

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  • Save in Sessions to reduce database load

    - by Kovu
    at the moment I try to reduce the load on my database extremly, so I had a look in my website and think about - what database calls can I try to avoid. So is there a rule for that? Sould I save every information in a Session that is nearly never changed? e.g.: The User-Table is a 35-coloumn-table which I need so often in so different ways, that in the moment I got this user-object at nearly every PageLoad AND in the master-site-page-load (Settings, display the username for a welcome message, colors etc etc.). So is that good to avoid the database query here, save the User-Object in a Session and call it from the session - and of course destroy the session whereever the User-Object get changed (e.g. User change his settings)?

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  • "dynamic" keyword and JSON data

    - by Peter Perhác
    An action method in my ASP.NET MVC2 application returns a JsonResult object and in my unit test I would like to check that the returned JSON object indeed contains the expected values. I tried this: 1. dynamic json = ((JsonResult)myActionResult).Data; 2. Assert.AreEqual(JsonMessagesHelper.ErrorLevel.ERROR.ToString(), json.ErrorLevel); But I get a RuntimeBinderException "'object' does not contain a definition for 'ErrorLevel'". However, when I place a breakpoint on line 2 and inspect the json dynamic variable (see picture below), it obviously does contain the ErrorLevel string and it has the expected value, so if the runtime binder wasn't playing funny the test would pass. What am I not getting? What am I doing wrong and how can I fix this? How can I make the assertion pass?

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  • Creating New Objects in JavaScript

    - by Ken Ray
    I'm a relatively newbie to object oriented programming in JavaScript, and I'm unsure of the "best" way to define and use objects in JavaScript. I've seen the "canonical" way to define objects and instantiate a new instance, as shown below. function myObjectType(property1, propterty2) { this.property1 = property1, this.property2 = property2 } // now create a new instance var myNewvariable = new myObjectType('value for property1', 'value for property2'); But I've seen other ways to create new instances of objects in this manner: var anotherVariable = new someObjectType({ property1: "Some value for this named property", property2: "This is the value for property 2" }); I like how that second way appears - the code is self documenting. But my questions are: Which way is "better"? Can I use that second way to instantiate a variable of an object type that has been defined using the "classical"way of defining the object type with that implicit constructor? If I want to create an array of these objects, are there any other considerations? Thanks in advance.

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  • pros and cons of TryCatch versus TryParse

    - by Vijesh
    What are the pros and cons of using either of the following approaches to pulling out a double from an object? Beyond just personal preferences, issues I'm looking for feedback on include ease of debugging, performance, maintainability etc. public static double GetDouble(object input, double defaultVal) { try { return Convert.ToDouble(input); } catch { return defaultVal; } } public static double GetDouble(object input, double defaultVal) { double returnVal; if (double.TryParse(input.ToString(), out returnVal)) { return returnVal; } else { return defaultVal; } }

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  • Silverlight 3 DataBinding with ValueConverter: conditionally use the default value for property

    - by eriksmith200
    I have a DatePicker for which I want to set the BorderBrush to SolidColorBrush(Colors.Red) if the SelectedDate is null. If a date has been filled in though, I want to just have the default BorderBrush. I still want to be able to style the default BorderBrush in Blend, so I don't want to hardcode the default borderbrush of the DatePicker. So basically: xaml: <controls:DatePicker BorderBrush="{Binding SelectedDate, RelativeSource={RelativeSource Self}, Converter={StaticResource BrushConverter}, Mode=OneWay}"/> c#: public class BrushConverter : IValueConverter { public object Convert(object value, Type targetType, object parameter, CultureInfo culture) { return value == null ? new SolidColorBrush(Colors.Red) : /* when value != null have the bound property use it's default value */ } is this possible?

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  • inkscape stroke inaccurate

    - by oshirowanen
    I am trying to add a stroke to a rectangle object, but if I add a 1px stroke, it places it 0.5px outside the edge of the rectangle and 0.5px inside the rectangle. I find this to be annoying when I want an object to be exactly 5px by 5px and it ends up becoming 6px by 6px. Is there a setting anywhere which places the stroke within the rectangle edge so a 5px by 5px square remains a 5px by 5px square. Please help.

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  • A* pathfinder obstacle collision problem

    - by Cheesebaron
    I am working on a project with a robot that has to find its way to an object and avoid some obstacles when going to that object it has to pick up. The problem lies in that the robot and the object the robot needs to pick up are both one pixel wide in the pathfinder. In reality they are a lot bigger. Often the A* pathfinder chooses to place the route along the edges of the obstacles, sometimes making it collide with them, which we do not wish to have to do. I have tried to add some more non-walkable fields to the obstacles, but it does not always work out very well. It still collides with the obstacles, also adding too many points where it is not allowed to walk, results in that there is no path it can run on. Do you have any suggestions on what to do about this problem?

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  • Is a base class with shared fields and functions good design

    - by eych
    I've got a BaseDataClass with shared fields and functions Protected Shared dbase as SqlDatabase Protected Shared dbCommand as DBCommand ... //also have a sync object used by the derived classes for Synclock'ing Protected Shared ReadOnly syncObj As Object = New Object() Protected Shared Sub Init() //initializes fields, sets connections Protected Shared Sub CleanAll() //closes connections, disposes, etc. I have several classes that derive from this base class. The derived classes have all Shared functions that can be called directly from the BLL with no instantiation. The functions in these derived classes call the base Init(), call their specific stored procs, call the base CleanAll() and then return the results. So if I have 5 derived classes with 10 functions each, totaling 50 possible function calls, since they are all Shared, the CLR only calls one at a time, right? All calls are queued to wait until each Shared function completes. Is there a better design with having Shared functions in your DAL and still have base class functions? Or since I have a base class, is it better to move towards instance methods within the DAL?

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  • [C#] How to consume web service adheres to the Event-based Asynchronous Pattern?

    - by codemonkie
    I am following the example from http://msdn.microsoft.com/en-us/library/8wy069k1.aspx to consume a web service implemented (by 3rd party) using the Event-based Asynchronous Pattern. However, my program needs to do multiple calls to the DoStuffAsync() hence will get back as many DoStuffCompleted. I chose the overload which takes an extra parameter - Object userState to distinguish them. My first question is: Is it valid to cast a GUID to Object as below, where GUID is used to generate unique taskID? Object userState = Guid.NewGuid(); Secondly, do I need to spawn off a new thread for each DoStuffAsync() call, since I am calling it multiple times? Also, would be nice to have some online examples or tutorials on this subject. (I've been googling for it the whole day and didn't get much back) Many thanks

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