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Best way to databind a Winforms control to a nullable type?

- by Steve Hiner

I'm currently using winforms databinding to wire up a data editing form. I'm using the netTiers framework through CodeSmith to generate my data objects. For database fields that allow nulls it creates nullable types. I've found that using winforms databinding the controls won't bind properly to nullable types. I've seen solutions online suggesting that people create new textbox classes that can handle the nullable types but that could be a pain having to swap out the textboxes on the forms I've already created. Initially I thought it would be great to use an extension method to do it. Basically creating an extension property for the textbox class and bind to that. From my limited extension method experience and doing a bit of checking online it looks like you can't do an extension property. As far as I can tell, binding has to be through a property since it needs to be able to get or set the value so an extension method wouldn't work. I'd love to find a clean way to retrofit these forms using something like extension methods but if I have to create new textbox and combo box controls that's what I'll do. My project is currently limited to .Net 2.0 due to the requirement to run on Windows 2000. Any suggestions?

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Cast errors with IXmlSerializable

- by Nathan

I am trying to use the IXmlSerializable interface to deserialize an Object (I am using it because I need specific control over what gets deserialized and what does not. See my previous question for more information). However, I'm stumped as to the error message I get. Below is the error message I get (I have changed some names for clarity): An unhandled exception of type 'System.InvalidCastException' occurred in App.exe Additional information: Unable to cast object of type 'System.Xml.XmlNode[]' to type 'MyObject'. MyObject has all the correct methods defined for the interface, and regardless of what I put in the method body for ReadXml() I still get this error. It doesn't matter if it has my implementation code or if it's just blank. I did some googling and found an error that looks similar to this involving polymorphic objects that implement IXmlSerializable. However, my class does not inherit from any others (besides Object). I suspected this may be an issue because I never reference XmlNode any other time in my code. Microsoft describes a solution to the polymorphism error: https://connect.microsoft.com/VisualStudio/feedback/details/422577/incorrect-deserialization-of-polymorphic-type-that-implements-ixmlserializable?wa=wsignin1.0#details The code the error occurs at is as follows. The object to be read back in is an ArrayList of "MyObjects" IO::FileStream ^fs = gcnew IO::FileStream(filename, IO::FileMode::Open); array<System::Type^>^ extraTypes = gcnew array<System::Type^>(1); extraTypes[0] = MyObject::typeid; XmlSerializer ^xmlser = gcnew XmlSerializer(ArrayList::typeid, extraTypes); System::Object ^obj; obj = xmlser->Deserialize(fs); fs->Close(); ArrayList ^al = safe_cast<ArrayList^>(obj); MyObject ^objs; for each(objs in al) //Error occurs here { //do some processing } Thanks for reading and for any help.

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How do I write a J2EE/EJB Singleton?

- by Bears will eat you

A day ago my application was one EAR, containing one WAR, one EJB JAR, and a couple of utility JAR files. I had a POJO singleton class in one of those utility files, it worked, and all was well with the world: EAR |--- WAR |--- EJB JAR |--- Util 1 JAR |--- Util 2 JAR |--- etc. Then I created a second WAR and found out (the hard way) that each WAR has its own ClassLoader, so each WAR sees a different singleton, and things break down from there. This is not so good. EAR |--- WAR 1 |--- WAR 2 |--- EJB JAR |--- Util 1 JAR |--- Util 2 JAR |--- etc. So, I'm looking for a way to create a Java singleton object that will work across WARs (across ClassLoaders?). The @Singleton EJB annotation seemed pretty promising until I found that JBoss 5.1 doesn't seem to support that annotation (which was added as part of EJB 3.1). Did I miss something - can I use @Singleton with JBoss 5.1? Upgrading to JBoss AS 6 is not an option right now. Alternately, I'd be just as happy to not have to use EJB to implement my singleton. What else can I do to solve this problem? Basically, I need a semi-application-wide* hook into a whole bunch of other objects, like various cached data, and app config info. As a last resort, I've already considered merging my two WARs into one, but that would be pretty hellish. *Meaning: available basically anywhere above a certain layer; for now, mostly in my WARs - the View and Controller (in a loose sense).

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Generate an ID via COM interop

- by Erik van Brakel

At the moment, we've got an unmaintanable ball of code which offers an interface to a third party application. The third party application has a COM assembly which MUST be used to create new entries. This process involves two steps: generate a new object (basically an ID), and update that object with new field values. Because COM interop is so slow, we only use that to generate the ID (and related objects) in the database. The actual update is done using a regular SQL query. What I am trying to figure out if it's possible to use NHibernate to do some of the heavy lifting for us, without bypassing the COM assembly. Here's the code for saving something to the database as I envision it: using(var s = sessionFactory.OpenSession()) using(var t = s.BeginTransaction()) { MyEntity entity = new MyEntity(); s.Save(entity); t.Commit(); } Regular NH code I'd say. Now, this is where it gets tricky. I think I have to supply my own implementation of NHibernate.Id.IIdentifierGenerator which calls the COM assembly in the Generate method. That's not a problem. What IS a problem is that the COM assembly requires initialisation, which does take a bit of time. It also doesn't like multiple instances in the same process, for some reason. What I would like to know is if there's a way to properly access an external service in the generator code. I'm free to use any technique I want, so if it involves something like an IoC container that's no problem. The thing I am looking for is where exactly to hook-up my code so I can access the things I need in my generator, without having to resort to using singletons or other nasty stuff.

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Facebook SDK Comment Deleting

- by mwoodworth

Working with the Facebook php SDK's, I am having a lot of trouble figuring out how to delete comments, given its id and xid. At first I was using the REST API, where you can call 'comments_remove($xid, $id);' to delete a comment. The problem with this method came when the xid parameter only accepts alphanumeric characters and underscores. Based on the documentation (http://developers.facebook.com/docs/reference/fbml/comments ) a valid XID can be the result of any url_encode. Now I am testing my luck with the new GRAPH api. Looking at http://developers.facebook.com/docs/api under 'Deleting Objects', It seems that comment deleting is definitely supported. However, I have tried sending a DELETE request, and I have also tried sending POST and GET to the object url with the argument 'method=delete'. No matter how I try it, I always get the same error: {"error":{"type":"GraphMethodException","message":"Unsupported delete request."}} I am sending the access token as a parameter as well. The access token that I am sending is the access token saved in the facebook cookie from the single sign on javascript cookie. These are all comments made on my application. Does this happen to anyone else, or am I simply not doing this right? Any help or guidance is GREATLY appreciated.

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C# reflection instantiation

- by NickLarsen

I am currently trying to create a generic instance factory for which takes an interface as the generic parameter (enforced in the constructor) and then lets you get instantiated objects which implement that interface from all types in all loaded assemblies. The current implementation is as follows: public class InstantiationFactory { protected Type Type { get; set; } public InstantiationFactory() { this.Type = typeof(T); if (!this.Type.IsInterface) { // is there a more descriptive exception to throw? throw new ArgumentException(/* Crafty message */); } } public IEnumerable GetLoadedTypes() { // this line of code found in other stack overflow questions var types = AppDomain.CurrentDomain.GetAssemblies() .SelectMany(a = a.GetTypes()) .Where(/* lambda to identify instantiable types which implement this interface */); return types; } public IEnumerable GetImplementations(IEnumerable types) { var implementations = types.Where(/* lambda to identify instantiable types which implement this interface */ .Select(x = CreateInstance(x)); return implementations; } public IEnumerable GetLoadedImplementations() { var loadedTypes = GetLoadedTypes(); var implementations = GetImplementations(loadedTypes); return implementations; } private T CreateInstance(Type type) { T instance = default(T); var constructor = type.GetConstructor(Type.EmptyTypes); if (/* valid to instantiate test */) { object constructed = constructor.Invoke(null); instance = (T)constructed; } return instance; } } It seems useful to me to have my CreateInstance(Type) function implemented as an extension method so I can reuse it later and simplify the code of my factory, but I can't figure out how to return a strongly typed value from that extension method. I realize I could just return an object: public static class TypeExtensions { public object CreateInstance(this Type type) { var constructor = type.GetConstructor(Type.EmptyTypes); return /* valid to instantiate test */ ? constructor.Invoke(null) : null; } } Is it possible to have an extension method create a signature per instance of the type it extends? My perfect code would be this, which avoids having to cast the result of the call to CreateInstance(): Type type = typeof(MyParameterlessConstructorImplementingType); MyParameterlessConstructorImplementingType usable = type.CreateInstance();

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item-not-found(404) when trying to get a node using Smackx pubsub

- by DustMason

I'm trying to use the latest Smackx trunk to get and then subscribe to a pubsub node. However, openfire just sends me a back an error: item not found (404). I am instantiating the java objects from ColdFusion, so my code snippets might look funny but maybe someone will be able to tell me what I've forgotten. Here's how I create the node: ftype = createObject("java", "org.jivesoftware.smackx.pubsub.FormType"); cform = createObject("java", "org.jivesoftware.smackx.pubsub.ConfigureForm").init(ftype.submit); cform.setPersistentItems(true); cform.setDeliverPayloads(true); caccess = createObject("java", "org.jivesoftware.smackx.pubsub.AccessModel"); cform.setAccessModel(caccess.open); cpublish = createObject("java", "org.jivesoftware.smackx.pubsub.PublishModel"); cform.setPublishModel(cpublish.open); cform.setMaxItems(99); manager = createObject("java", "org.jivesoftware.smackx.pubsub.PubSubManager").init(XMPPConnection); myNode = manager.createNode("subber", cform); And here's how I am trying to get to it (in a different section of code): manager = createObject("java", "org.jivesoftware.smackx.pubsub.PubSubManager").init(XMPPConnection); myNode = manager.getNode("subber"); Immediately upon creating the node I seem to be able to publish to it like so: payload = createObject("java", "org.jivesoftware.smackx.pubsub.SimplePayload").init("book","pubsub:test:book","<book xmlns='pubsub:test:book'><title>Lord of the Rings</title></book>"); item = createObject("java", "org.jivesoftware.smackx.pubsub.Item").init(payload); myNode.publish(item); However, it is the getNode() call that is causing my code to error. I have verified that the nodes are being created by checking the DB used by my openfire server. I can see them in there, properly attributed as leaf nodes, etc. Any advice? Anyone else out there doing anything with XMPP and ColdFusion? I have had great success sending and receiving messages with CF and Smack just haven't had the pubsub working yet :) Thanks!

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Using MongoDB's map/reduce to "group by" two fields

- by ibz

I need something slightly more complex than the examples in the MongoDB docs and I can't seem to be able to wrap my head around it. Say I have a collection of objects of the form {date: "2010-10-10", type: "EVENT_TYPE_1", user_id: 123, ...} Now I want to get something similar to a SQL GROUP BY query, grouping over both date and type. That is, I want the number of events of each type in each day. Also, I'd like to make it unique by user_id, ie. if a user has more events in the same day, count it only once. I'm trying to do this with map/reduce. I do db.logs.mapReduce(function() { emit(this.type, 1); }, function(k, vals) { var total = 0; for (var i = 0; i < vals.length; i++) total += vals[i]; return total; }}) which nicely groups by type, but now, how can I group by date at the same time? Seems the key in emit() can't be an array (I thought about doing emit([this.date, this.type], 1)). Also, how can I ensure the per-user uniqueness? I'm just starting with MongoDB and I'm still having trouble grasping the basic concepts. Also, there is not much documentation available out there. Any help from more experienced users is appreciated. Thanks!

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Recommendations of a high volume log event viewer in a Java enviroment

- by Thorbjørn Ravn Andersen

I am in a situation where I would like to accept a LOT of log events controlled by me - notably the logging agent I am preparing for slf4j - and then analyze them interactively. I am not as such interested in a facility that presents formatted log files, but one that can accept log events as objects and allow me to sort and display on e.g. threads and timelines etc. Chainsaw could maybe be an option but is currently not compatible with logback which I use for technical reasons. Is there any project with stand alone viewers or embedded in an IDE which would be suitable for this kind of log handling. I am aware that I am approaching what might be suitable for a profiler, so if there is a profiler projekt suitable for this kind of data acquisition and display where I can feed the event pipe, I would like to hear about it). Thanks for all feedback Update 2009-03-19: I have found that there is not a log viewer which allows me to see what I would like (a visual display of events with coordinates determined by day and time, etc), so I have decided to create a very terse XML format derived from the log4j XMLLayout adapted to be as readable as possible while still being valid XML-snippets, and then use the Microsoft LogParser to extract the information I need for postprocessing in other tools.

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django hidden field error

- by dana

hi, there, i'm building a message system for a virtual community, but i can't take the userprofile id i have in views.py def save_message(request): if request.method == 'POST': form = MessageForm(request.POST) if form.is_valid(): new_obj = form.save(commit=False) new_obj.sender = request.user u = UserProfile.objects.get(request.POST['userprofile_id']) new_obj.owner = u new_obj.save() return HttpResponseRedirect('.') else: form = MessageForm() return render_to_response('messages/messages.html', { 'form': form, }, context_instance=RequestContext(request)) and the template: {% block primary %} <form action="." method="post"> {{ form.as_p }} <p><input type="hidden" value="{{ userprofile.id }}" name = "owner" /></p> <p><input type="submit" value="Send Message!" /></p> </form> {% endblock %} forms.py: class MessageForm(ModelForm): class Meta: model = Messages fields = ['message'] models.py: class Messages(models.Model): message = models.CharField(max_length = 300) read = models.BooleanField(default=False) owner = models.ForeignKey(UserProfile) sender = models.ForeignKey(User) I don't figure out why i get this error,since i'm just trying to get the profileId of a user, using a hiddeen field. the error is: Key 'UserProfile_id' not found in <QueryDict: {u'owner': [u''], u'message': [u'fdghjkl']}> and i'm getting it after i fill out the message text field. Thanks!

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Unit tests - The benefit from unit tests with contract changes?

- by Stefan Hendriks

Recently I had an interesting discussion with a colleague about unit tests. We where discussing when maintaining unit tests became less productive, when your contracts change. Perhaps anyone can enlight me how to approach this problem. Let me elaborate: So lets say there is a class which does some nifty calculations. The contract says that it should calculate a number, or it returns -1 when it fails for some reason. I have contract tests who test that. And in all my other tests I stub this nifty calculator thingy. So now I change the contract, whenever it cannot calculate it will throw a CannotCalculateException. My contract tests will fail, and I will fix them accordingly. But, all my mocked/stubbed objects will still use the old contract rules. These tests will succeed, while they should not! The question that rises, is that with this faith in unit testing, how much faith can be placed in such changes... The unit tests succeed, but bugs will occur when testing the application. The tests using this calculator will need to be fixed, which costs time and may even be stubbed/mocked a lot of times... How do you think about this case? I never thought about it thourougly. In my opinion, these changes to unit tests would be acceptable. If I do not use unit tests, I would also see such bugs arise within test phase (by testers). Yet I am not confident enough to point out what will cost more time (or less). Any thoughts?

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XmlSerialize a custom collection with an Attribute

- by roomaroo

I've got a simple class that inherits from Collection and adds a couple of properties. I need to serialize this class to XML, but the XMLSerializer ignores my additional properties. I assume this is because of the special treatment that XMLSerializer gives ICollection and IEnumerable objects. What's the best way around this? Here's some sample code: using System.Collections.ObjectModel; using System.IO; using System.Xml.Serialization; namespace SerialiseCollection { class Program { static void Main(string[] args) { var c = new MyCollection(); c.Add("Hello"); c.Add("Goodbye"); var serializer = new XmlSerializer(typeof(MyCollection)); using (var writer = new StreamWriter("test.xml")) serializer.Serialize(writer, c); } } [XmlRoot("MyCollection")] public class MyCollection : Collection<string> { [XmlAttribute()] public string MyAttribute { get; set; } public MyCollection() { this.MyAttribute = "SerializeThis"; } } } This outputs the following XML (note MyAttribute is missing in the MyCollection element): <?xml version="1.0" encoding="utf-8"?> <MyCollection xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"> <string>Hello</string> <string>Goodbye</string> </MyCollection> What I want is <MyCollection MyAttribute="SerializeThis" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"> <string>Hello</string> <string>Goodbye</string> </MyCollection> Any ideas? The simpler the better. Thanks.

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Passing data between ViewControllers versus doing local Fetch in each VC

- by Tofrizer

Hi All, I'm developing an iPhone app using Core Data and I'm looking for some general advice and recommendations on whether its acceptable to pass data between ViewControllers versus doing a local fetch in each ViewController as you navigate to it. Ordinarily I would say it all depends on various factors (e.g. performance etc) but the passing data approach is so prevalent in my app and I'm spooked by all the stories about Apple rejecting apps because of not conforming to their standard guidelines. So let me put another way -- is it non-standard to pass data between VC's? The reason I pass data so much is because each ViewController is just another view on to data present in my object model / graph. Once I have a handle on my first object in the first view controller (which I of course do have to fetch), I can use the existing object composition / relationships to drill down into the next level of detail into data and so I just pass these objects to the next VC. Separately, one possible downside with this passing-data-to-each-VC approach is I don't benefit from (what I perceive to be) the optimisation/benefits that NSFetchedResultsController provides in terms of efficient memory usage and section handling. My app is read-only but I do have one table with 5000 rows and I'm curious if I am missing out on NSFetchedResultsController benefits. Any thoughts on this as well? Can I somehow still benefit from NSFetchedResultsController goodness without having to do a full fetch (as I would have already passed in the data from my previous VC)? Thanks a lot.

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GL_COLOR_MATERIAL with lighting on Android

- by kostmo

It appears that glColorMaterial() is absent from OpenGL ES. According to this post (for iPhone), you may still enable GL_COLOR_MATERIAL in OpenGL ES 1.x, but you're stuck with the default settings of GL_FRONT_AND_BACK and GL_AMBIENT_AND_DIFFUSE that you would otherwise set with glColorMaterial(). I would be OK with this, but the diffuse lighting is not working correctly. I set up my scene and tested it with one light, setting glMaterialfv() for GL_AMBIENT and GL_DIFFUSE once in the initialization. The normals have been set correctly, and lighting works the way it's supposed to. I see the Gourad shading. With GL_LIGHTING disabled, the flat colors I have set with glColor4f() appear on the various objects in the scene. This also functions as expected. However, when glEnable(GL_COLOR_MATERIAL) is called, the flat colors remain. I would expect to see the lighting effects. What might be missing? glColorMaterial() is also mentioned on anddev.org, but I'm not sure if the information there is accurate. I'm testing this on an Android 2.1 handset (Motorola Droid). Edit: It works properly on my 1.6 handset (ADP1).

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How to implement custom JSF component for drawing chart?

- by Roman

I want to create a component which can be used like: <mc:chart data="#{bean.data}" width="200" height="300" /> where #{bean.data} returns a collection of some objects or chart model object or something else what can be represented as a chart (to put it simple, let's assume it returns a collection of integers). I want this component to generate html like this: <img src="someimg123.png" width="200" height="300"/> The problem is that I have some method which can receive data and return image, like: public RenderedImage getChartImage (Collection<Integer> data) { ... } and I also have a component for drawing dynamic image: <o:dynamicImage width="200" height="300" data="#{bean.readyChartImage}/> This component generates html just as I need but it's parameter is array of bytes or RenderedImage i.e. it needs method in bean like this: public RenderedImage getReadyChartImage () { ... } So, one approach is to use propertyChangedListener on submit to set data (Collection<Integer>) for drawing chart and then use <o:dynamicImage /> component. But I'd like to create my own component which receives data and draws chart. I'm using facelets but it's not so important indeed. Any ideas how to create the desired component? P.S. One solution I was thinking about is not to use <o:dynamicImage/> and use some servlet to stream image. But I don't know how to implement that correctly and how to tie jsf component with servlet and how to save already built chart images (generating new same image for each request can cause performance problems imho) and so on..

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List<object>.RemoveAll - How to create an appropriate Predicate

- by CJM

This is a bit of noob question - I'm still fairly new to C# and generics and completely new to predicates, delegates and lamda expressions... I have a class 'Enquiries' which contains a generic list of another class called 'Vehicles'. I'm building up the code to add/edit/delete Vehicles from the parent Enquiry. And at the moment, I'm specifically looking at deletions. From what I've read so far, it appears that I can use Vehicles.RemoveAll() to delete an item with a particular VehicleID or all items with a particular EnquiryID. My problem is understanding how to feed .RemoveAll the right predicate - the examples I have seen are too simplistic (or perhaps I am too simplistic given my lack of knowledge of predicates, delegates and lambda expressions). So if I had a List<Of Vehicle> Vehicles where each Vehicle had an EnquiryID, how would I use Vehicles.RemoveAll() to remove all vehicles for a given EnquiryID? I understand there are several approaches to this so I'd be keen to hear the differences between approaches - as much as I need to get something working, this is also a learning exercise. As an supplementary question, is a Generic list the best repository for these objects? My first inclination was towards a Collection, but it appears I am out of date. Certainly Generics seem to be preferred, but I'm curious as to other alternatives. Thanks

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C#/LINQ: How to define generically a keySelector for a templated class before calling OrderBy

- by PierrOz

Hi Folks, I have the following class defined in C# class myClass<T,U> { public T PropertyOne { get; set; } public U PropertyTwo { get; set; } } I need to write a function that reorder a list of myClass objects and takes two other parameters which define how I do this reorder: does my reordering depend on PropertyOne or PropertyTwo and is it ascending or descending. Let's say this two parameters are boolean. With my current knowledge in LINQ, I would write: public IList<myClass<T,U>> ReOrder(IList<myClass<T,U>> myList, bool usePropertyOne, bool ascending) { if (usePropertyOne) { if (ascending) { return myList.OrderBy(o => o.PropertyOne).ToList(); } else { return myList.OrderByDescending(o => o.PropertyOne).ToList(); } } else { if (ascending) { return myList.OrderBy(o => o.PropertyTwo).ToList(); } else { return myList.OrderByDescending(o => o.PropertyTwo).ToList(); } } } What could be a more efficient/elegant way to do that ? How can I declare the Func,TResult keySelector object to reuse when I call either OrderBy or OrderByDescending? I'm interesting in the answer since in my real life, I can have more than two properties.

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Loading from archive?

- by fuzzygoat

Can anyone point me in the right direction, I have two sets of load/save methods below that I am playing with to save an array of objects out to disk and then load them back in. I am getting a little confused after calling "saveMoons" how I should go about loading that data back in ... any pointers would be great. -(void)saveMoons:(NSString *)savePath { NSMutableData *data = [[NSMutableData alloc] init]; NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:data]; [moons encodeWithCoder:archiver]; [archiver finishEncoding]; [data writeToFile:savePath atomically:YES]; [data release]; [archiver release]; } -(void)loadMoons:(NSString *)loadPath { NSMutableData *data = [[NSMutableData alloc] initWithContentsOfFile:loadPath]; NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:data]; // [self setMoons:[unarchiver ??????]]; } . // ------------------------------------------------------------------- ** // SIMPLER // ------------------------------------------------------------------- ** -(void)saveMoons_SIMPLE:(NSString *)savePath { NSData *data = [NSKeyedArchiver archivedDataWithRootObject:moons]; [data writeToFile:savePath atomically:YES]; } -(void)loadMoons_SIMPLE:(NSString *)loadPath { [self setMoons:[NSKeyedUnarchiver unarchiveObjectWithFile:loadPath]]; } // ------------------------------------------------------------------- ** // // ------------------------------------------------------------------- ** gary

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How do I pass parameters between request-scoped beans

- by smayers81

This is a question that has been bothering me for sometime. My application uses ICEFaces for our UI framework and Spring 2.5 for Dependency Injection. In addition, Spring actually maintains all of our backing beans, not the ICEFaces framework, so our faces-config is basically empty. Navigation is not even really handled through navigation-rules. We perform manual redirects to new windows using window.open. All of our beans are defined in our appContext file as being request-scoped. I have Page ABC which is backed by BackingBeanABC. Inside that backing bean, I have a parameter say: private Order order; I then have Page XYZ backed by BackingBeanXYZ. When I redirect from page ABC to page XYZ, I want to transfer the 'order' property from ABC to XYZ. The problem is since everything is request-scoped and I'm performing a redirect, I am losing the value of 'description'. There has got to be an easier way to pass objects between beans in request scope during a redirect. Can anyone assist with this issue?

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constructor function's object literal returns toString() method but no other method

- by JohnMerlino

I'm very confused with javascript methods defined in objects and the "this" keyword. In the below example, the toString() method is invoked when Mammal object instantiated: function Mammal(name){ this.name=name; this.toString = function(){ return '[Mammal "'+this.name+'"]'; } } var someAnimal = new Mammal('Mr. Biggles'); alert('someAnimal is '+someAnimal); Despite the fact that the toString() method is not invoked on the object someAnimal like this: alert('someAnimal is '+someAnimal.toString()); It still returns 'someAnimal is [Mammal "Mr. Biggles"]' . That doesn't make sense to me because the toString() function is not being called anywhere. Then to add even more confusion, if I change the toString() method to a method I make up such as random(): function Mammal(name){ this.name=name; this.random = function(){ return Math.floor(Math.random() * 15); } } var someAnimal = new Mammal('Mr. Biggles'); alert(someAnimal); It completely ignores the random method (despite the fact that it is defined the same way was the toString() method was) and returns: [object object] Another issue I'm having trouble understanding with inheritance is the value of "this". For example, in the below example function person(w,h){ width.width = w; width.height = h; } function man(w,h,s) { person.call(this, w, h); this.sex = s; } "this" keyword is being send to the person object clearly. However, does "this" refer to the subclass (man) or the super class (person) when the person object receives it? Thanks for clearing up any of the confusion I have with inheritance and object literals in javascript.

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Free Memory Occupied by Std List, Vector, Map etc

- by Graviton

Coming from a C# background, I have only vaguest idea on memory management on C++-- all I know is that I would have to free the memory manually. As a result my C++ code is written in such a way that objects of the type std::vector, std::list, std::map are freely instantiated, used, but not freed. I didn't realize this point until I am almost done with my programs, now my code is consisted of the following kinds of patterns: struct Point_2 { double x; double y; }; struct Point_3 { double x; double y; double z; }; list<list<Point_2>> Computation::ComputationJob(list<Point_3> pts3D, vector<Point_2> vectors) { map<Point_2, double> pt2DMap=ConstructPointMap(pts3D); vector<Point_2> vectorList = ConstructVectors(vectors); list<list<Point_2>> faceList2D=ConstructPoints(vectorList , pt2DMap); return faceList2D; } My question is, must I free every.single.one of the list usage ( in the above example, this means that I would have to free pt2DMap, vectorList and faceList2D)? That would be very tedious! I might just as well rewrite my Computation class so that it is less prone to memory leak. Any idea how to fix this?

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How can I create a new Person object correctly in Javascript?

- by TimDog

I'm still struggling with this concept. I have two different Person objects, very simply: ;Person1 = (function() { function P (fname, lname) { P.FirstName = fname; P.LastName = lname; return P; } P.FirstName = ''; P.LastName = ''; var prName = 'private'; P.showPrivate = function() { alert(prName); }; return P; })(); ;Person2 = (function() { var prName = 'private'; this.FirstName = ''; this.LastName = ''; this.showPrivate = function() { alert(prName); }; return function(fname, lname) { this.FirstName = fname; this.LastName = lname; } })(); And let's say I invoke them like this: var s = new Array(); //Person1 s.push(new Person1("sal", "smith")); s.push(new Person1("bill", "wonk")); alert(s[0].FirstName); alert(s[1].FirstName); s[1].showPrivate(); //Person2 s.push(new Person2("sal", "smith")); s.push(new Person2("bill", "wonk")); alert(s[2].FirstName); alert(s[3].FirstName); s[3].showPrivate(); The Person1 set alerts "bill" twice, then alerts "private" once -- so it recognizes the showPrivate function, but the local FirstName variable gets overwritten. The second Person2 set alerts "sal", then "bill", but it fails when the showPrivate function is called. The new keyword here works as I'd expect, but showPrivate (which I thought was a publicly exposed function within the closure) is apparently not public. I want to get my object to have distinct copies of all local variables and also expose public methods -- I've been studying closures quite a bit, but I'm still confused on this one. Thanks for your help.

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Django db encoding

- by realshadow

Hey, I have a little problem with encoding. The data in db is ok, when I select the data in php its ok. Problem comes when I get the data and try to print it in the template, I get - Å port instead of Šport, etc. Everything is set to utf-8 - in settings.py, meta tags in template, db table and I even have unicode method specified for the model, but nothing seems to work. I am getting pretty hopeless here... Here is some code: class Category_info(models.Model): objtree_label_id = models.AutoField(primary_key = True) node_id = models.IntegerField(unique = True) language_id = models.IntegerField() label = models.CharField(max_length = 255) type_id = models.IntegerField() class Meta: db_table = 'objtree_labels' def __unicode__(self): return self.label I have even tried with return u"%s" % self.label. Here is the view: def categories_list(request): categories_list = Category.objects.filter(parent_id = 1, status = 1) paginator = Paginator(categories_list, 10) try: page = int(request.GET.get('page', 1)) except ValueError: page = 1 try: categories = paginator.page(page) except (EmptyPage, InvalidPage): categories = paginator.page(paginator.num_pages) return render_to_response('categories_list.html', {'categories': categories}) Maybe I am just blind and/or stupid, but it just doesnt work. So any help is appreciated, thanks in advance. Regards

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Where can I find a list of all possible messages that an XmlException can contain?

- by Rahul

I'm writing an XML code editor and I want to display syntax errors in the user interface. Because my code editor is strongly constrained to a particular problem domain and audience, I want to rewrite certain XMLException messages to be more meaningful for users. For instance, an exception message like this: '"' is an unexpected token. The expected token is '='. Line 30, position 35 .. is very technical and not very informative to my audience. Instead, I'd like to rewrite it and other messages to something else. For completeness' sake that means I need to build up a dictionary of existing messages mapped to the new message I would like to display instead. To accomplish that I'm going to need a list of all possible messages XMLException can contain. Is there such a list somewhere? Or can I find out the possible messages through inspection of objects in C#? Edit: specifically, I am using XmlDocument.LoadXml to parse a string into an XmlDocument, and that method throws an XmlException when there are syntax errors. So specifically, my question is where I can find a list of messages applied to XmlException by XmlDocument.LoadXml. The discussion about there potentially being a limitless variation of actual strings in the Message property of XmlException is moot.

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Simplifying Testing through design considerations while utilizing dependency injection

- by Adam Driscoll

We are a few months into a green-field project to rework the Logic and Business layers of our product. By utilizing MEF (dependency injection) we have achieved high levels of code coverage and I believe that we have a pretty solid product. As we have been working through some of the more complex logic I have found it increasingly difficult to unit test. We are utilizing the CompositionContainer to query for types required by these complex algorithms. My unit tests are sometimes difficult to follow due to the lengthy mock object setup process that must take place, just right, to allow for certain circumstances to be verified. My unit tests often take me longer to write than the code that I'm trying to test. I realize this is not only an issue with dependency injection but with design as a whole. Is poor method design or lack of composition to blame for my overly complex tests? I've tried base classing tests, creating commonly used mock objects and ensuring that I utilize the container as much as possible to ease this issue but my tests always end up quite complex and hard to debug. What are some tips that you've seen to keep such tests concise, readable, and effective?

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