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• Restricting deletion with NHibernate

  - by FrontSvin

  I'm using NHibernate (fluent) to access an old third-party database with a bunch of tables, that are not related in any explicit way. That is a child tables does have parentID columns which contains the primary key of the parent table, but there are no foreign key relations ensuring these relations. Ideally I would like to add some foreign keys, but cannot touch the database schema. My application works fine, but I would really like impose a referential integrity rule that would prohibit deletion of parent objects if they have children, e.i. something similar 'ON DELETE RESTRICT' but maintained by NHibernate. Any ideas on how to approach this would be appreciated. Should I look into the OnDelete() method on the IInterceptor interface, or are there other ways to solve this? Of course any solution will come with a performance penalty, but I can live with that.

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• Accessing HttpApplication.Application variables from a class

  - by Young Ninja

  I set up various global parameters in Global.asax, as such: Application["PagePolicies"] = "~/Lab/Policies.aspx"; Application["PageShare"] = "/Share.aspx"; Application["FileSearchQueries"] = Server.MapPath("~/Resources/SearchQueries.xml"); ... I have no problem accessing these variables form .ascx.cs or .aspx.cs file -- ie. files that are part of the Web content. However, I can't seem to access 'Application' from basic class objects (ie. standalone .cs files). I read somewhere to use a slight variations in .cs files, as follows, but it always comes throws an exception when in use: String file = (String)System.Web.HttpContext.Current.Application["FileSearchQueries"];

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• getElementsByTagName() equivalent for textNodes

  - by levik

  Is there any way to get the collection of all textNode objects within a document? getElementsByTagName() works great for Elements, but textNodes are not Elements. Update: I realize this can be accomplished by walking the DOM - as many below suggest. I know how to write a DOM-walker function that looks at every node in the document. I was hoping there was some browser-native way to do it. After all it's a little strange that I can get all the <input>s with a single built-in call, but not all textNodes.

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• How do you reference another element in a xaml list

  - by Ball

  I'm using xaml as a datastore because It's quick and we haven't yet defined a file format. But I can only seem to create xaml that is a pure tree, even if it is acyclic. I know how to create a list of items in xaml, but How do I share objects in two lists? Below is an example of what I'm trying to say. <CreaturFile> <CreatureFile.Monsters> <Monster Name="Kobold" x:Name="Mepo"/> <Monster Name="Goblin"/> </CreatureFile.Monsters> <CreatureFile.Encounters> <Encounter> <Reference ElementName="Mepo"/> </Encounter> </CreatureFile.Encounters> </CreatureFile>

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• Proper usage of Java Weak Reference in case of nested collections

  - by Tong Wang

  I need to define a weak reference Map, whose value is a Set. I use Google collections' MapMaker, like this: Map<Class<? extends Object>, Set<Foo>> map = new MapMaker().weakKeys().weakValues().makeMap(); So, for Set<Foo>, can I use a normal HashSet? Or, do I have to create a weak HashSet, like this: Collections.newSetFromMap(new WeakHashMap<Foo, Boolean>()); And why? Another question, the key of my map is Class objects, when will a Class object become weakly reachable? In other words, what is the lifetime of a Class object? Thanks.

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• How do I convert a Python list of lists of lists into a C array by using ctypes?

  - by pc05

  As seen here How do I convert a Python list into a C array by using ctypes? this code will take a python array and transform it to a C array. import ctypes arr = (ctypes.c_int * len(pyarr))(*pyarr) Which would the way of doing the same with a list of lists or a lists of lists of lists? For example, for the following variable list3d = [[[40.0, 1.2, 6.0, 0.3], [50.0, 4.2, 0, 0]], [[40.0, 1.2, 6.0, 0.3], [50.0, 4.2, 0, 0]], [[40.0, 1.2, 6.0, 0.3], [50.0, 4.2, 0, 0]]] I have tried the following with no luck: ([[ctypes.c_double * 4] *2]*3)(*list3d) # *** TypeError: 'list' object is not callable (ctypes.c_double * 4 *2 *3)(*list3d) # *** TypeError: expected c_double_Array_4_Array_2 instance, got list Thank you! EDIT: Just to clarify, I am trying to get one object that contains the whole multidimensional array, not a list of objects. This object's reference will be an input to a C DLL that expects a 3D array.

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• Creating seed model from data already in DB

  - by Nick Brown

  Is there a way to convert data in an existing database into objects that can easily be put into a seed method? Essentially I'd like to let some people add lines to my DB via a form and then convert that into an object that I can re-seed the DB anytime I need to make changes. The database itself is created via code-first using the following model: public class Combo { public int Id { get; set; } public string MainPrefix { get; set; } public string MainDescriptor { get; set; } public string MainDish { get; set; } public string Connector { get; set; } public string SecondaryDescriptor { get; set; } public string SecondaryDish { get; set; } }

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• How can I make a read-only ObservableCollection property?

  - by thrag

  I'd like to expose a property on a view model that contains a list of objects (from database). I need this collection to be read-only. That is, I want to prevent Add/Remove, etc. But allow the foreach and indexers to work. My intent is to declare a private field holding the editable collection and reference it with a read-only Public Property. As follows public ObservableCollection<foo> CollectionOfFoo { get { return _CollectionOfFoo; } } However, that syntax just prevents changing the reference to the collection. It doesn't prevent add/remove, etc. What is the right way to accomplish this?

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• Looking at the C++ new[] cookie. How portable is this code?

  - by carleeto

  I came up with this as a quick solution to a debugging problem - I have the pointer variable and its type, I know it points to an array of objects allocated on the heap, but I don't know how many. So I wrote this function to look at the cookie that stores the number of bytes when memory is allocated on the heap. template< typename T > int num_allocated_items( T *p ) { return *((int*)p-4)/sizeof(T); } //test #include <iostream> int main( int argc, char *argv[] ) { using std::cout; using std::endl; typedef long double testtype; testtype *p = new testtype[ 45 ]; //prints 45 std::cout<<"num allocated = "<<num_allocated_items<testtype>(p)<<std::endl; delete[] p; return 0; } I'd like to know just how portable this code is.

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• Accessing items from a dictionary using pickle efficiently in Python

  - by user248237

  I have a large dictionary mapping keys (which are strings) to objects. I pickled this large dictionary and at certain times I want to pull out only a handful of entries from it. The dictionary has usually thousands of entries total. When I load the dictionary using pickle, as follows: from cPickle import * # my dictionary from pickle, containing thousands of entries mydict = open(load('mypickle.pickle')) # accessing only handful of entries here for entry in relevant_entries: # find relevant entry value = mydict[entry] I notice that it can take up to 3-4 seconds to load the entire pickle, which I don't need, since I access only a tiny subset of the dictionary entries later on (shown above.) How can I make it so pickle only loads those entries that I have from the dictionary, to make this faster? Thanks.

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• Deserializing only select properties of an Entity using JDOQL query string?

  - by user246114

  Hi, I have a rather large class stored in the datastore, for example a User class with lots of fields (I'm using java, omitting all decorations below example for clarity): @PersistenceCapable class User { private String username; private String city; private String state; private String country; private String favColor; } For some user queries, I only need the favColor property, but right now I'm doing this: SELECT FROM " + User.class.getName() + " WHERE username == 'bob' which should deserialize all of the entity properties. Is it possible to do something instead like: SELECT username, favColor FROM " + User.class.getName() + " WHERE username == 'bob' and then in this case, all of the returned User instances will only spend time deserializing the username and favColor properties, and not the city/state/country properties? If so, then I suppose all the other properties will be null (in the case of objects) or 0 for int/long/float? Thank you

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• Substituting variables in a loop?

  - by jksl

  I am trying to write a loop in R but I think the nomenclature is not correct as it does not create the new objects, here is a simplified example of what I am trying to do: for i in (1:8) { List_i <-List colsToGrab_i <-grep(predefinedRegex_i, colnames(List_i$table)) List_i$table <- List_i$table[,predefinedRegex_i] } I have created 'predefinedRegex'es 1:8 which the grep should use to search The loop creates an object called "List_i" and then fails to find "predefinedRegex_i". I have tried putting quotes around the "i" and $ in front of the i but these do not work. Any help much appreciated. Thank you.

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• Improve SQL strategy - denormalize in object-children-images case

  - by fesja

  Hi, I have a Tour object which has many Place objects. For the list of tours, I want to show some info of the tour, the number of places of the tour, and three Place's images. Right one my SQL queries are (i'm using Doctrine with Symfony on MySQL) get Tour get Tour 1 places get Tour 2 places get Tour 3 places ... get Tour n places If I have a three Tour list, it's not so bad; but I'm sure it can get bad if I do a 10-20 tour-list. So, thinking on how to improve the queries I've thought of several measures: Having a place count cache Storing the urls of three images on a new tour field. The problem with 2. is that if I change the image, I have to check all the tours to update that image for another one. What solution do you think is best to scale the system in a near future? Any other suggestion. thanks!

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• Is there a name for a pure-data Objective-C class?

  - by BrianEnigma

  This is less of a code-specific question and more of an Objective-C nomenclature question. In C you have struct for pure data. In Enterprise Java, you have "bean" classes that are purely member variables with getters and setters, but no business logic. In Adobe FLEX, you have "Value Objects". In Objective-C, is there a proper name for an object (descended from NSObject, of course) that simply has ivars and getters/setters (or @property/@synthesize, if you want to get fancy) and no real business logic? A more concrete example might be a simple class with getters and setters for filename, file size, description, and assorted other metadata. You could then take a bunch of these and easily throw them into a container (NSDictionary, NSArray) without the need for messy NSValue wrapping of a C struct. It is also a little more structure than putting, say, a bunch of loosely-typed child NSDictionaries into a parent container object.

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• Combining XmlSerializer and XmlWriter?

  - by num3ric

  In addition to a list of objects I am serializing to an xml file using C#'s XmlSerializer, I would like to store a few more independent elements (mainly strings from textboxes) in the same xml. public static void SaveBehaviors(ObservableCollection<Param> listParams) { XmlSerializer _paramsSerializer = new XmlSerializer(listParams.GetType()); string path = Environment.GetFolderPath(Environment.SpecialFolder.Desktop); path += "\\test.xml"; using (TextWriter writeFileStream = new StreamWriter(path)) { _paramsSerializer.Serialize(writeFileStream, listParams); using (XmlWriter writer = XmlWriter.Create(writeFileStream)) { writer.WriteStartElement("Foo"); //test entry... writer.WriteAttributeString("Bar", "Some & value"); writer.WriteElementString("Nested", "data"); writer.WriteEndElement(); } } } However, deserializing "test.xml" results in an error because of the added element. I suppose writing in the serialized xml file is prohibited and should be avoided?

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• Question about memory usage

  - by sudo rm -rf

  Hi there. I have the following method: +(NSMutableDictionary *)getTime:(float)lat :(float)lon { NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; NSMutableDictionary *dictionary = [[NSMutableDictionary alloc] init]; [dictionary setObject:hour forKey:@"hour"]; [dictionary setObject:minute forKey:@"minute"]; [dictionary setObject:ampm forKey:@"ampm"]; return dictionary; } A lot of the method is chopped off, so I think I need the pool for some other stuff in the method. Here's my question. I know that I need to release the following objects: [dictionary release]; [pool release]; However, I can't release the dictionary before I return it, but as soon as I return it the rest of the method isn't performed. What should I do?

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• Does C++ require a destructor call for each placement new?

  - by Josh Haberman

  I understand that placement new calls are usually matched with explicit calls to the destructor. My question is: if I have no need for a destructor (no code to put there, and no member variables that have destructors) can I safely skip the explicit destructor call? Here is my use case: I want to write C++ bindings for a C API. In the C API many objects are accessible only by pointer. Instead of creating a wrapper object that contains a single pointer (which is wasteful and semantically confusing). I want to use placement new to construct an object at the address of the C object. The C++ object will do nothing in its constructor or destructor, and its methods will do nothing but delegate to the C methods. The C++ object will contain no virtual methods. I have two parts to this question. Is there any reason why this idea will not work in practice on any production compiler? Does this technically violate the C++ language spec?

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• how to access jquery internal data?

  - by Unknown

  As you may or may not be aware as of jQuery 1.7 the whole event system was rewritten from the ground up. The codebase is much faster and with the new .on() method there is a lot of uniformity to wiring up event handlers. One used to be able to access the internal events data and investiate what events are registered on any given element, but recently this internal information has been hidden based on the following scenario... It seems that the "private" data is ALWAYS stored on the .data(jQuery.expando) - For "objects" where the deletion of the object should also delete its caches this makes some sense. In the realm of nodes however, I think we should store these "private" members in a separate (private) cache so that they don't pollute the object returned by $.fn.data()" Although I agree with the above change to hide the internal data, I have found having access to this information can be helpful for debugging and unit testing. What was the new way of getting the internal jquery event object in jQuery 1.7?

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• When designing an event, is it a good idea to prevent listeners from being added twice?

  - by Matt

  I am creating an event-based API where a user can subscribe to an event by adding listener objects (as is common in Java or C#). When the event is raised, all subscribed listeners are invoked with the event information. I initially decided to prevent adding an event listener more than once. If a listener is added that already exists in the listener collection, it is not added again. However, after thinking about it some more, it doesn't seem that most event-based structures actually prevent this. Was my initial instinct wrong? I'm not sure which way to go here. I guess I thought that preventing addition of an existing listener would help to avoid a common programming error. Then again, it could also hide a bug that would lead to code being run multiple times when it shouldn't.

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• Why are there two implementations of std::sort (with and without a comparator) rather than one implementation with a default template parameter?

  - by PolyVox

  In my code I'm adopting a design strategy which is similar to some standard library algorithms in that the exact behavior can be customized by a function object. The simplest example is std::sort, where a function object can control how the comparison is made between objects. I notice that the Visual C++ provides two implementations of std::sort, which naturally involves code duplication. I would have imagined that it was instead possible to have only one implementation, and provide a default comparator (using operator< ) as a default template parameter. What is the rational behind two separate versions? Would my suggestion make the interface more complex in some way? Or result in confusing error messages when the object does not provide operator Thanks, David

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• python mock side_effect or return_value dependent on call_count

  - by user18380

  To test a polling function I want to mock the calling of a sub function so that the first time it is called it will fail, and the second time it is called it will succeed. Here's a very simplified version of it: poll_function(var1): value = sub_function(var1) # First call will return None while not value: time.sleep(POLLING_INTERVAL) value = sub_function(var1) # A subsequent call will return a string, e.g "data" return value Is this possible to do with a Mock object from the mock framework? I know Mock objects have a call_count attribute I should be able to use somehow. Right now I've solved it by creating a custom mock object that I use to monkey patch sub_function(), but I feel there should be a better less verbose way of doing it: def test_poll(): class MyMock(object): def __init__(self, *args): self.call_count = 0 def sub_function(self, *args, **kwargs): if self.call_count > 1: return "data" else: self.call_count += 1 return None my_mock = MyMock() with patch('sub_function', my_mock.sub_function): ok_(poll_function())

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• Is there a way to launch an aggressive and complete garbage collection in Java?

  - by Gnoupi

  For memory optimization reasons, I'm launching myself the garbage collector during profiling, to check if objects are correctly cleaned after disposing of them. The call to garbage collector is not enough, though, and it seems that there is no guarantee of what it will clean. Is there a way to call it, to be sure it will recover as much as it can, in profiling conditions (this would have no point in production, of course)? Or is "calling it several times" the only way to be "almost sure"? Or did I simply misunderstand something about the Garbage Collector?

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• Region or ItemsSource for large data set in ListBox

  - by Ryan

  I'm having trouble figuring out what the best solution is given the following situation. I'm using Prism 4.1, MEF, and .Net 4.0. I have an object Project that could have a large number (~1000) of Line objects. I'm deciding whether it is better to expose an ObservableCollection<LineViewModel> from my ProjectViewModel and manually create the Line viewmodels there OR set the ListBox as it's own region and activate views that way. I'd still want my LineViewModel to have Prism's shared services (IEventAggregator, etc.) injected, but I don't know how to do that when I manually create the LineViewModel. Any suggestions or thoughts?

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• MovieClip changes Stage alignment

  - by Nicholas Cowle

  I am loading a MovieClip using MovieClipLoader. When the MovieClip starts playing, it changes the alignment of my stage to LT, which incorrectly repositions all the other objects on my stage. Is there anyway for me to: Prevent the MovieClip from changing the alignment of my stage? Adding an event handler to an appropriate event, so that I can reset the stage alignment when it gets changed? I have already tried resetting the stage alignment on the onLoadInit event of MovieClipLoader and the onEnterFrame event of MovieClip, but both seem to reset the alignment too soon.

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• WPF Datatemplate + ItemsControl each item uses > 1 MB Memory?

  - by Matt H.

  Does that sound right to anyone???? I have an ItemsControl that displays data from a custom object that implements iNotifyPropertyChanged. The DataTemplate consists of: Border 3 buttons 5 textboxes An ellipse A Bindable RichTextBox (custom class that inherits from RichTextBox... so I could make Document a dependency property (to support binding)) Several grids and stackpanels for layout It uses: Styles (stored in a resource dictionary higher up the tree) Styles affect: colors, thicknesses, and text properties: which are data-bound to a "settings" class that implements iNotifyPropertyChanged, so the user can change display settings That's it! So what gives? I've also noticed that when I empty and remove the ItemsControl, memory isn't freed. over 5000 instances of "CommandBindingCollection" and "WeakReference" are CREATED (using ANTS profiler). And huge number of EffectiveValueEntry objects are created too. So really, what gives!!! :-) Thanks for your insight! Management needs this project soon but in its current state, it's unreleasable.

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