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  • Working with extra fields in an Inline form - save_model, save_formset, can't make sense of the diff

    - by magicrebirth
    Suppose I am in the usual situation where there're extra fields in the many2many relationship: class Person(models.Model): name = models.CharField(max_length=128) class Group(models.Model): name = models.CharField(max_length=128) members = models.ManyToManyField(Person, through='Membership') class Membership(models.Model): person = models.ForeignKey(Person) group = models.ForeignKey(Group) date_joined = models.DateField() invite_reason = models.CharField(max_length=64) # other models which are unrelated to the ones above.. class Trip(models.Model): placeVisited = models.ForeignKey(Place) visitor = models.ForeignKey(Person) pleasuretrip = models.Boolean() class Place(models.Model): name = models.CharField(max_length=128) I want to add some extra fields in the Membership form that gets displayed through the Inline. These fields basically are a shortcut to the instantiation of another model (Trip). Trip can have its own admin views, but these shortcuts are needed because when my project partners are entering 'Membership' data in the system they happen to have also the 'Trip' information handy (and also because some of the info in Membership can just be copied over to Trip etc. etc.). So all I want to have is two extra fields in the Membership Inline - placeVisited and pleasuretrip - which together with the Person instance will let me instantiate the Trip model in the background... I found out I can easily add extra fields to the inline view by defining my own form. But once the data have been entered, how and when to reference to them in order to perform the save operations I need to do? class MyForm(forms.ModelForm): place = forms.ModelChoiceField(required=False, queryset=Place.objects.all(), label="place",) pleasuretrip = forms.BooleanField(required=False, label="...") class MembershipInline(admin.TabularInline): model = Membership form = MyForm def save_model(self, request, obj, form, change): place = form.place pleasuretrip = form.pleasuretrip person = form.person .... # now I can create Trip instances with those data .... obj.save() class GroupAdmin(admin.ModelAdmin): model = Group .... inlines = (MembershipInline,) This doesn't seem to work... I'm also a bit puzzled by the save_formset method... maybe is that the one I should be using? Many thanks in advance for the help!!!!

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  • how to get access to private members of nested class?

    - by macias
    Background: I have enclosed (parent) class E with nested class N with several instances of N in E. In the enclosed (parent) class I am doing some calculations and I am setting the values for each instance of nested class. Something like this: n1.field1 = ...; n1.field2 = ...; n1.field3 = ...; n2.field1 = ...; ... It is one big eval method (in parent class). My intention is -- since all calculations are in parent class (they cannot be done per nested instance because it would make code more complicated) -- make the setters only available to parent class and getters public. And now there is a problem: when I make the setters private, parent class cannot acces them when I make them public, everybody can change the values and C# does not have friend concept I cannot pass values in constructor because lazy evaluation mechanism is used (so the instances have to be created when referencing them -- I create all objects and the calculation is triggered on demand) I am stuck -- how to do this (limit access up to parent class, no more, no less)? I suspect I'll get answer-question first -- "but why you don't split the evaluation per each field" -- so I answer this by example: how do you calculate min and max value of a collection? In a fast way? The answer is -- in one pass. This is why I have one eval function which does calculations and sets all fields at once.

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  • How do you store accented characters coming from a web service into a database?

    - by Thierry Lam
    I have the following word that I fetch via a web service: André From Python, the value looks like: "Andr\u00c3\u00a9". The input is then decoded using json.loads: >>> import json >>> json.loads('{"name":"Andr\\u00c3\\u00a9"}') >>> {u'name': u'Andr\xc3\xa9'} When I store the above in a utf8 MySQL database, the data is stored like the following using Django: SomeObject.objects.create(name=u'Andr\xc3\xa9') Querying the name column from a mysql shell or displaying it in a web page gives: André The web page displays in utf8: <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> My database is configured in utf8: mysql> SHOW VARIABLES LIKE 'collation%'; +----------------------+-----------------+ | Variable_name | Value | +----------------------+-----------------+ | collation_connection | utf8_general_ci | | collation_database | utf8_unicode_ci | | collation_server | utf8_unicode_ci | +----------------------+-----------------+ 3 rows in set (0.00 sec) mysql> SHOW VARIABLES LIKE 'character_set%'; +--------------------------+----------------------------+ | Variable_name | Value | +--------------------------+----------------------------+ | character_set_client | utf8 | | character_set_connection | utf8 | | character_set_database | utf8 | | character_set_filesystem | binary | | character_set_results | utf8 | | character_set_server | utf8 | | character_set_system | utf8 | | character_sets_dir | /usr/share/mysql/charsets/ | +--------------------------+----------------------------+ 8 rows in set (0.00 sec) How can I retrieve the word André from a web service, store it properly in a database with no data loss and display it on a web page in its original form?

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  • Importing data from third party datasource (open architecture design )

    - by mare
    How would you design an application (classes, interfaces in class library) in .NET when we have a fixed database design on our side and we need to support imports of data from third party data sources, which will most likely be in XML? For instance, let us say we have a Products table in our DB which has columns Id Title Description TaxLevel Price and on the other side we have for instance Products: ProductId ProdTitle Text BasicPrice Quantity. Currently I do it like this: Have the third party XML convert to classes and XSD's and then deserialize its contents into strong typed objects (what we get as a result of this process is classes like ThirdPartyProduct, ThirdPartyClassification, etc.). Then I have methods like this: InsertProduct(ThirdPartyProduct newproduct) I do not use interfaces at the moment but I would like them to. What I would like is implement something like public class Contoso_ProductSynchronization : ProductSynchronization InsertProduct(ContosoProduct p) where ProductSynchronization will be an interface or abstract class. There will most likely be many implementations of ProductSynchronization. I cannot hardcode the types - classes like ContosoProduct, NorthwindProduct might be created from the third party XML's (so preferably I would continue to use deserialization). Hopefully someone will understand what I'm trying to explain here. Just imagine you are the seller and you have numerous providers and each one uses their own proprietary XML format. I don't mind the development, which will of course be needed everytime new format appears, because it will only require 10-20 methods to be implemented, I just want the architecture to be open and support that.

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  • ASP.NET MVC application architecture "guidelines"

    - by Joe Future
    I'm looking for some feedback on my ASP.NET MVC based CMS application architecture. Domain Model - depends on nothing but the System classes to define types. For now, mostly anemic. Repository Layer - abstracted data access, only called by the services layer Services Layer - performs business logic on domain models. Exposes view models to the controllers. ViewModelMapper - service that translates back and forth between view models and domain models Controllers - super thin "traffic cop" style functionality that interacts with the service layer and only talks in terms of view models, never domain models My domain model is mostly used as data transfer (DTO) objects and has minimal logic at the moment. I'm finding this is nice because it depends on nothing (not even classes in the services layer). The services layer is a bit tricky... I only want the controllers to have access to viewmodels for ease of GUI programming. However, some of the services need to talk to each other. For example, I have an eventing service that notifies other listener services when content is tagged, when blog posts are created, etc. Currently, the methods that take domain models as inputs or return them are marked internal so they can't be used by the controllers. Sounds like overkill? Not enough abstraction? I'm mainly doing this as a learning exercise in being strict about architecture, not for an actual product, so please no feedback along the lines of "right depends on what you want to do". thanks! Jason

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  • Why is Core Data not persisting these changes to disk?

    - by scott
    I added a new entity to my model and it loads fine but no changes made in memory get persisted to disk. My values set on the car object work fine in memory but aren't getting persisted to disk on hitting the home button (in simulator). I am using almost exactly the same code on another entity in my application and its values persist to disk fine (core data - sqlite3); Does anyone have a clue what I'm overlooking here? Car is the managed object, cars in an NSMutableArray of car objects and Car is the entity and Visible is the attribute on the entity which I am trying to set. Thanks for you assistance. Scott - (void)viewDidLoad { myAppDelegate* appDelegate = (myAppDelegate*)[[UIApplication sharedApplication] delegate]; NSManagedObjectContext* managedObjectContex = appDelegate.managedObjectContext; NSFetchRequest* request = [[NSFetchRequest alloc] init]; NSEntityDescription* entity = [NSEntityDescription entityForName:@"Car" inManagedObjectContext:managedObjectContex]; [request setEntity:entity]; NSSortDescriptor* sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"Name" ascending:YES]; NSArray* sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil]; [request setSortDescriptors:sortDescriptors]; [sortDescriptors release]; [sortDescriptor release]; NSError* error = nil; cars = [[managedObjectContex executeFetchRequest:request error:&error] mutableCopy]; if (cars == nil) { NSLog(@"Can't load the Cars data! Error: %@, %@", error, [error userInfo]); } [request release]; } - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath*)indexPath { Car* car = [cars objectAtIndex:indexPath.row]; if (car.Visible == [NSNumber numberWithBool:YES]) { car.Visible = [NSNumber numberWithBool:NO]; [tableView cellForRowAtIndexPath:indexPath].accessoryType = UITableViewCellAccessoryNone; } else { car.Visible = [NSNumber numberWithBool:YES]; [tableView cellForRowAtIndexPath:indexPath].accessoryType = UITableViewCellAccessoryCheckmark; } }

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  • JFrame that has multiple layers

    - by phunehehe
    Hello, I have a window that has two layers: a static background and a foreground that contains moving objects. My idea is to draw the background just once (because it's not going to change), so I make the changing panel transparent and add it on top of the static background. Here is the code for this: public static void main(String[] args) { JPanel changingPanel = new JPanel() { @Override public void paintComponent(Graphics g) { super.paintComponent(g); g.setColor(Color.RED); g.fillRect(100, 100, 100, 100); } }; changingPanel.setOpaque(false); JPanel staticPanel = new JPanel(); staticPanel.setBackground(Color.BLUE); staticPanel.setLayout(new BorderLayout()); staticPanel.add(changingPanel); JFrame frame = new JFrame(); frame.add(staticPanel); frame.setSize(800, 600); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setVisible(true); } This piece of code gives me the correct image I want, but every time I repaint changingPanel, staticPanel gets repainted as well (which is obviously against the whole idea of painting the static panel just once). Can somebody show me what's wrong? FYI I am using the javax.swing.Timer to recalculate and repaint the changing panel 24 times every second.

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  • c++ multithread

    - by chnet
    I use c++ to implement a thread class. The code is in the following. I initialize two objects, wish it will start two threads (I use pthread_self() to look the thread Id). But the result shows that there is only one thread beside the main thread. I am a bit confused... class Thread { public: int mask; pthread_t thread; Thread( int ); void start(); static void * EntryPoint (void *); void Run(); }; Thread::Thread( int a) { mask =a; } void Thread::Run() { cout<<"thread begin to run" <<endl; cout <<" Thread Id is: "<< pthread_self() << endl; // the same thread Id. } void * Thread::EntryPoint(void * pthis) { cout << "entry" <<endl; Thread *pt = (Thread *) pthis; pt->Run(); } void Thread::start() { pthread_create(&thread, NULL, EntryPoint, (void *)ThreadId ); pthread_join(thread, NULL); } int main() { int input_array[8]={3,1,2,5,6,8,7,4}; Thread t1(1); Thread t2(2); t1.start(); t2.start() }

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  • PHP Object References in Frameworks

    - by bigstylee
    Before I dive into the disscusion part a quick question; Is there a method to determine if a variable is a reference to another variable/object? For example $foo = 'Hello World'; $bar = &$foo; echo (is_reference($bar) ? 'Is reference' : 'Is orginal'; I have been using PHP5 for a few years now (personal use only) and I would say I am moderately reversed on the topic of Object Orientated implementation. However the concept of Model View Controller Framework is fairly new to me. I have looked a number of tutorials and looked at some of the open source frameworks (mainly CodeIgnitor) to get a better understanding how everything fits together. I am starting to appreciate the real benefits of using this type of structure. I am used to implementing object referencing in the following technique. class Foo{ public $var = 'Hello World!'; } class Bar{ public function __construct(){ global $Foo; echo $Foo->var; } } $Foo = new Foo; $Bar = new Bar; I was surprised to see that CodeIgnitor and Yii pass referencs of objects and can be accessed via the following method: $this->load->view('argument') The immediate advantage I can see is a lot less code and more user friendly. But I do wonder if it is more efficient as these frameworks are presumably optimised? Or simply to make the code more user friendly? This was an interesting article Do not use PHP references.

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  • C# how to calculate hashcode from an object reference.

    - by Wayne
    Folks, here's a thorny problem for you! A part of the TickZoom system must collect instances of every type of object into a Dictionary< type. It is imperative that their equality and hash code be based on the instance of the object which means reference equality instead of value equality. The challenge is that some of the objects in the system have overridden Equals() and GetHashCode() for use as value equality and their internal values will change over time. That means that their Equals and GetHashCode are useless. How to solve this generically rather than intrusively? So far, We created a struct to wrap each object called ObjectHandle for hashing into the Dictionary. As you see below we implemented Equals() but the problem of how to calculate a hash code remains. public struct ObjectHandle : IEquatable<ObjectHandle>{ public object Object; public bool Equals(ObjectHandle other) { return object.ReferenceEquals(this.Object,other.Object); } } See? There is the method object.ReferenceEquals() which will compare reference equality without regard for any overridden Equals() implementation in the object. Now, how to calculate a matching GetHashCode() by only considering the reference without concern for any overridden GetHashCode() method? Ahh, I hope this give you an interesting puzzle. We're stuck over here. Sincerely, Wayne

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  • C++ interpreter conceptual problem

    - by Jan Wilkins
    I've built an interpreter in C++ for a language created by me. One main problem in the design was that I had two different types in the language: number and string. So I have to pass around a struct like: class myInterpreterValue { myInterpreterType type; int intValue; string strValue; } Objects of this class are passed around million times a second during e.g.: a countdown loop in my language. Profiling pointed out: 85% of the performance is eaten by the allocation function of the string template. This is pretty clear to me: My interpreter has bad design and doesn't use pointers enough. Yet, I don't have an option: I can't use pointers in most cases as I just have to make copies. How to do something against this? Is a class like this a better idea? vector<string> strTable; vector<int> intTable; class myInterpreterValue { myInterpreterType type; int locationInTable; } So the class only knows what type it represents and the position in the table This however again has disadvantages: I'd have to add temporary values to the string/int vector table and then remove them again, this would eat a lot of performance again. Help, how do interpreters of languages like Python or Ruby do that? They somehow need a struct that represents a value in the language like something that can either be int or string.

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  • How do you pass a BitmapImage from a background thread to the UI thread in WPF?

    - by DanM
    I have a background thread that generates a series of BitmapImage objects. Each time the background thread finishes generating a bitmap, I would like to show this bitmap to the user. The problem is figuring out how to pass the BitmapImage from the background thread to the UI thread. This is an MVVM project, so my view has an Image element: <Image Source="{Binding GeneratedImage}" /> My view-model has a property GeneratedImage: private BitmapImage _generatedImage; public BitmapImage GeneratedImage { get { return _generatedImage; } set { if (value == _generatedImage) return; _generatedImage= value; RaisePropertyChanged("GeneratedImage"); } } My view-model also has the code that creates the background thread: public void InitiateGenerateImages(List<Coordinate> coordinates) { ThreadStart generatorThreadStarter = delegate { GenerateImages(coordinates); }; var generatorThread = new Thread(generatorThreadStarter); generatorThread.ApartmentState = ApartmentState.STA; generatorThread.IsBackground = true; generatorThread.Start(); } private void GenerateImages(List<Coordinate> coordinates) { foreach (var coordinate in coordinates) { var backgroundThreadImage = GenerateImage(coordinate); // I'm stuck here...how do I pass this to the UI thread? } } I'd like to somehow pass backgroundThreadImage to the UI thread, where it will become uiThreadImage, then set GeneratedImage = uiThreadImage so the view can update. I've looked at some examples dealing with the WPF Dispatcher, but I can't seem to come up with an example that addresses this issue. Please advise.

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  • Issue calling superclass method in subclass constructor

    - by stormin986
    I get a NullPointerException calling a Superclass Method in Subclass Inner Class Constructor... What's the Deal? In my application's main class (subclass of Application), I have a public inner class that simply contains 3 public string objects. In the parent class I declare an object of that inner class. public class MainApplication extends Application { public class Data { public String x; public String y; public String z; } private Data data; MainApplication() { data = new Data() data.x = SuperClassMethod(); } } After I instantiate the object in the constructor, I get a runtime error when I try to assign a value in the inner class with a superclass method. Any idea what's up here?? Can you not call superclass methods in the subclass constructor? ** Edit ** Original question was about inner class member assignment in outer class constructor. Turned out the issue was with calling a superclass method in the class's constructor. It was giving me a null pointer exception. Thus, the question has changed.

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  • Persistant Http client connections in java

    - by Akusete
    I am trying to write a simple Http client application in Java and am a bit confused by the seemingly different ways to establish Http client connections, and efficiently re-use the objects. Current I am using the following steps (I have left out exception handling for simplicity) Iterator<URI> uriIterator = someURIs(); HttpClient client = new DefaultHttpClient(); while (uriIterator.hasNext()) { URI uri = uriIterator.next(); HttpGet request = new HttpGet(uri); HttpResponse response = client.execute(request); HttpEntity entity = response.getEntity(); InputStream s = entity.getContent(); processStream (); s.close(); } In regard to the code above, my questions is: Assuming all URI's are pointing to the same host (but different resources on that host). What is the recommended way to use a single http connection for all requests? And how do you close the connection after the last request? --edit: Also what is the difference between using uri.openConnection(), versus HttpClient? Which is preferable, and what other methods exist?

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  • Null Pointer Exception in Primavera P6 8.1

    - by gwrichard
    I am getting a null pointer exception in a Primavera P6 8.1 installation. The exception only occurs in one section of the web-client: Application settings.P6 web and the P6 API are deployed on the same WebLogic (10.3.5) node running on a Windows Server 2008 R2 installation. I have done this installation using this same software stack a dozen times and don't have this issue on any of the other installs. Exact error below: Match: beginTraversal Match: digest selected JREDesc: JREDesc[version 1.6.0_20+, heap=-1--1, args=null, href=http://java.sun.com/products/autodl/j2se, sel=false, null, null], JREInfo: JREInfo for index 0: platform is: 1.7 product is: 1.7.0_17 location is: http://java.sun.com/products/autodl/j2se path is: C:\Program Files (x86)\Java\jre7\bin\javaw.exe args is: null native platform is: Windows, x86 [ x86, 32bit ] JavaFX runtime is: JavaFX 2.2.7 found at C:\Program Files (x86)\Java\jre7\ enabled is: true registered is: true system is: true Match: ignoring maxHeap: -1 Match: ignoring InitHeap: -1 Match: digesting vmargs: null Match: digested vmargs: [JVMParameters: isSecure: true, args: ] Match: JVM args after accumulation: [JVMParameters: isSecure: true, args: ] Match: digest LaunchDesc: http://localhost:7001/p6/action/jnlp/appletsjnlp.jnlp?mainClass=com.primavera.pvapplets.adminpreferences.AdminPreferencesApplet&classPath=adminpreferences.jar,prm-applets-common.jar,forms-1.0.7.jar,prm-guisupport.jar,prm-to.jar,jide.jar,tablesupport.jar,formsupport.jar,applets-bo.jar,commons-lang.jar,prm-common.jar,resource_strings.jar,prm-img.jar,commons-logging.jar&name=AdminPreferences&version=8.1.2.0.0602 Match: digest properties: [] Match: JVM args: [JVMParameters: isSecure: true, args: ] Match: endTraversal .. Match: JVM args final: Match: Running JREInfo Version match: 1.7.0.17 == 1.7.0.17 Match: Running JVM args match: have:<> satisfy want:<> Java Plug-in 10.17.2.02 Using JRE version 1.7.0_17-b02 Java HotSpot(TM) Client VM User home directory = C:\Users\gwrichard ---------------------------------------------------- c: clear console window f: finalize objects on finalization queue g: garbage collect h: display this help message l: dump classloader list m: print memory usage o: trigger logging q: hide console r: reload policy configuration s: dump system and deployment properties t: dump thread list v: dump thread stack x: clear classloader cache 0-5: set trace level to <n> ----------------------------------------------------

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  • Return value from Object match

    - by Hito_kun
    I'm, by no means, JS fluent, so forgive me if im asking for some really basic stuff, but I've not being able to find a proper answer to my question. Im writting my first Node.js (plus Extra Framework and Socket.io) app and Im having some fun setting up the server side of a FB-like messenger (surprise!!!). So, let's say I have this data structure to store online users(This is a JSON Array, but I'm not sure it is the best way to do it or should I go with Javascript Objects): [ { "site": 45, "users": [ { "idUser": 5, "idSocket": "qwe87r7w8qwe", "name": "Carlos Ray Norris" }, { "idUser": 6, "idSocket": "v8d9d0fgfs7d", "name": "John Connor" } ] }, { "site": 48, "users": [ { "idUser": 22, "idSocket": "qwe87r7w8qwe", "name": "David Bowie" }, { "idUser": 23, "idSocket": "v8d9d0fgfs7d", "name": "Barack H. Obama" } ] } ] What I want to do is to search in the array for x value given y. In this case, retrieving the idSocket knowing the idUser WITHOUT having to run through the array values. So I have basically 2 questions: first, what would be the proper way to store users online? and secondly, how to find values matching with the values I already know (find the idSocket that has a given idUser). I would like a pure JS approach(or using some of the tools given by Node, Socket.io or Express), but if that's not possible then I can look for some JQuery.

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  • Nhibernate: Stop it from joining to a table that is not needed

    - by Aaron
    I have two tables (tbArea, tbPost) that relate to the following classes. class Area { int ID string Name ... } class Post { int ID string Title Area Area ... } These two classes map up with Fluent Nhibernate. Below is the post mapping. public class PostMapping : ClassMap<Post> { public PostMapping() { Cache.NonStrictReadWrite(); this.Table("tbPost"); Id(x => x.ID) .Column("PostID") .GeneratedBy .Identity(); References(x => x.Area) .ForeignKey("AreaID") .Column("AreaID"); ... } } Any time I perform a query on the Post table "where AreaID = 1(any AreaId)", nhibernate will join to the area table. (What Nhibernate generates for a query) SELECT post fields , area fields (automatically added) FROM tbPost p LEFT JOIN tbArea a on p.areaid = a.areaid where p.areaid = 1 I have tried setting Area to LazyLoad, to Fetch.Select, ReadOnly, and any other setting on the reference and still it will always join to Area. I am trying to optimize the backend database queries, and since I don't need the area object loaded just filtered I would like to eliminate the unnecessary join to Area each time I Query post. What configurations do I need to change or mappings to get area to still be related to post in my objects, but not query it when I filter on AreaID?

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  • Question on overview of C# OOP in business WinForms application - scope of Object

    - by TimR
    I may have all this OO completely wrong, but here goes: Ok the scenario is a classic order entry. Customer places an Order which has OrderLineItems of StockItems. Order is entered by Employee. 1) Application starts and asks for login/password 2) Employee selects 'Orders' from Mainmenu form 3) Orders forms opens.... 4) Employee selects Customer 5) Employee selects Stock adds to OrderLineItems 6) Selects second StockItem; add to OrderLineItems 7) Order is committed, [stock decremented, order posted to DB, Order printed] 8) Employee is returned to MainMenu Now with Object scope: 1) Application starts and asks for login/password Is this the best place to make objEmployee, to be kept whilst in this whole Sales application? 2) Employee selects 'Orders' from Mainmenu form 3) Orders forms opens.... *Make objOrderHeader, is objEmployee able to be passed in or is it created here, or re-created here.* 4) Employee selects Customer - adds/edits Customer details if required... Make objCustomer 5) Employee selects Stock adds to OrderLineItems... *Make objStockItem and objOrderLineItem - add to objOrderLineItems_collection* 6) Selects second StockItem; add to OrderLineItems... *Make objStockItem and objOrderLineItem - add to objOrderLineItems_collection* 7) Order is committed, [stock decremented, order posted to DB, Order printed, Order Entered By = EmployeeID] Once posted to Db, all objects now redundant/garbage [except objEmployee?] 8) Employee is returned to MainMenu is objEmployee still valid as an object?

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  • Question about WeakHashMap

    - by michael
    Hi, In the Javadoc of "http://java.sun.com/j2se/1.4.2/docs/api/java/util/WeakHashMap.html", it said "Each key object in a WeakHashMap is stored indirectly as the referent of a weak reference. Therefore a key will automatically be removed only after the weak references to it, both inside and outside of the map, have been cleared by the garbage collector." And then Note that a value object may refer indirectly to its key via the WeakHashMap itself; that is, a value object may strongly refer to some other key object whose associated value object, in turn, strongly refers to the key of the first value object. But should not both Key and Value should be used weak reference in WeakHashMap? i.e. if there is low on memory, GC will free the memory held by the value object (since the value object most likely take up more memory than key object in most cases)? And if GC free the Value object, the Key Object can be free as well? Basically, I am looking for a HashMap which will reduce memory usage when there is low memory (GC collects the value and key objects if necessary). Is it possible in Java? Thank you.

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  • What are the fastest-performing options for a read-only, unordered collection of unique strings?

    - by Dan Tao
    Disclaimer: I realize the totally obvious answer to this question is HashSet<string>. It is absurdly fast, it is unordered, and its values are unique. But I'm just wondering, because HashSet<T> is a mutable class, so it has Add, Remove, etc.; and so I am not sure if the underlying data structure that makes these operations possible makes certain performance sacrifices when it comes to read operations -- in particular, I'm concerned with Contains. Basically, I'm wondering what are the absolute fastest-performing data structures in existence that can supply a Contains method for objects of type string. Within or outside of the .NET framework itself. I'm interested in all kinds of answers, regardless of their limitations. For example I can imagine that some structure might be restricted to strings of a certain length, or may be optimized depending on the problem domain (e.g., range of possible input values), etc. If it exists, I want to hear about it. One last thing: I'm not restricting this to read-only data structures. Obviously any read-write data structure could be embedded inside a read-only wrapper. The only reason I even mentioned the word "read-only" is that I don't have any requirement for a data structure to allow adding, removing, etc. If it has those functions, though, I won't complain.

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  • Null reference exceptions in .net

    - by Carlo
    Hello, we're having this big problem with our application. It's a rather large application with several modules, and thousands and thousands lines of code. A lot of parts of the application are designed to exist only with a reference to another object, for example a Person object can never exists without a House object, so if you at any point in the app say: bool check = App.Person.House == null; check should always be false (by design), so, to keep using that example, while creating modules, testing, debugging, App.Person.House is never null, but once we shipped the application to our client, they started getting a bunch of NullReferenceException with the objects that by design, should never have a null reference. They tell us the bug, we try to reproduce it here, but 90% of the times we can't, because here it works fine. The app is being developed with C# and WPF, and by design, it only runs on Windows XP SP 3, and the .net framework v3.5, so we KNOW the user has the same operative system, service pack, and .net framework version as we do here, but they still get this weird NullReferenceExceptions that we can't reproduce. So, I'm just wondering if anyone has seen this before and how you fixed it, we have the app running here at least 8 hours a day in 5 different computers, and we never see those exceptions, this only happens to the client for some reason. ANY thought, any clue, any solution that could get us closer to fixing this problem will be greatly appreciated. Thanks!

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  • Problem importing Oracle .dmp file

    - by BitFiddler
    So I have looked at all the suggested ways of importing .dmp files and non of them seem to answer this question: where does the data go once you import it? Context: I created a user like so: SQL> create user IMPORTER identified by "12345"; SQL> grant connect, unlimited tablespace, resource to IMPORTER; I then ran the 'imp' command as follows: C:\>imp system/password FROMUSER=OVIEDOE TOUSER=IMPORTER file=c:\database1.dmp Now there were 9 .dmp files, after each one it asked me for the next one and then I received the message "Import terminated successfully with warnings." The warning was: Warning: the objects were exported by OVIEDOE, not by you import done in WE8MSWIN1252 character set and AL16UTF16 NCHAR character set export client uses WE8ISO8859P1 character set (possible charset conversion) IMP-00046: using FILESIZE value from export file of 2147483648 Now it says it was terminated successfully so my assumption (I am new to oracle so this may be wrong) is that the data was loaded. However, when I use SQL developer to connect to the database and look under the 'tables' node under the IMPORTER user, there is nothing there. What is going on? Did the data load? If so, where can I find it?

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  • Structuring input of data for localStorage

    - by WmasterJ
    It is nice when there isn't a DB to maintain and users to authenticate. My professor has asked me to convert a recent research project of his that uses Bespin and calculates errors made by users in a code editor as part of his research. The goal is to convert from MySQL to using HTML5 localStorage completely. Doesn't seem so hard to do, even though digging in his code might take some time. Question: I need to store files and state (last placement of cursor and active file). I have already done so by implementing the recommendations in another stackoverflow thread. But would like your input considering how to structure the content to use. My current solution Hashmap like solution with javascript objects: files = {}; // later, saving files[fileName] = data; And then storing in localStorage using some recommendations localStorage.setObject(files): Currently I'm also considering using some type of numeric id. So that names can be changed without any hassle renaming the key in the hashmap. What is your opinion on the way it is solved and would you do it any differently?

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  • Common NSNotification mistakes?

    - by Ben Packard
    A simplification... A building has an array of apartment objects. Each apartment has a single currentTenant. These tenants are of type Person. Note that currentTenant doesn't have a reference to the apartment, so can't send information back up the chain. When a tenant has a plumbing issue he raises an NSNotification: [nc postNotificationName:@"PlumbingIssue" object:self]; Each Apartment observes notifications ONLY FROM it's own current tenant (this is set up when the apartment is built, before there is a current tenant): [nc addObserver:self selector:@selector(alertBuildingManager:) name:@"PlumbingIssue" object:[self currentTenant]; When the apartment receives a notification from it's own currentTenant, it sends it's own notification, "PlumberRequired", along with the apartment number and the currentTenant in an NSDictionary. Apartment observes these notifications, which it will take from any apartment (or other object): [nc addObserver:self selector:@selector(callPlumber) name:@"PlumberRequired" object:nil]; Is there something I could be getting fundamentally wrong here? What's happening is that the apartment is receiving notifications from any and all currentTenants, rather than jus it's own. Sorry that the actual code is a bit too unwieldy to post. Was just wondering if there's a gap in my understanding about observing notifications from a particular sender?

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  • How to get more detail from an exception?

    - by cusimar9
    I have a .NET 4.0 web application which implements an error handler within the Application_Error event of Global.asax. When an exception occurs this intercepts it and sends me an email including a variety of information like the logged in user, the page the error occurred on, the contents of the session etc. This is all great but there is some fundamental detail missing which I seem unable to locate. For instance, this is a subset of an error I would receive and the associated stack trace: Source: Telerik.Web.UI Message: Selection out of range Parameter name: value Stack trace: at Telerik.Web.UI.RadComboBox.PerformDataBinding(IEnumerable dataSource) at Telerik.Web.UI.RadComboBox.OnDataSourceViewSelectCallback(IEnumerable data) at System.Web.UI.DataSourceView.Select(DataSourceSelectArguments arguments, DataSourceViewSelectCallback callback) at Telerik.Web.UI.RadComboBox.OnDataBinding(EventArgs e) at Telerik.Web.UI.RadComboBox.PerformSelect() at System.Web.UI.WebControls.BaseDataBoundControl.DataBind() at Telerik.Web.UI.RadComboBox.DataBind() at System.Web.UI.WebControls.BaseDataBoundControl.EnsureDataBound() at Telerik.Web.UI.RadComboBox.OnPreRender(EventArgs e) at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) Now as lovely as this is I could do with knowing a) the name of the control and b) the value which caused the control to be 'out of range'. Any suggestions about how I could get this sort of information? I've run this in debug mode and the objects passed to Global.asax don't seem to hold any more detail that I can see.

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