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• [Android] Putting Serializable Classes into SQL?

  - by CaseyB

  Here's the situation. I have a bunch of objects that implement Serializable that I want to store in a SQL database. I have two questions Is there a way to serialize the object directly into the database Is that the best way to do it or should I Write the object out to a formatting String and put it in the database that way and then parse it back out Write each member to the database with a field that is unique to each object

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• Controlling race condition at startup.

  - by Will Hartung

  I have some code that I want to have some one time initialisation performed. But this code doesn't have a definite lifecycle, so my logic can be potentially invoked by multiple threads before my initialisation is done. So, I want to basically ensure that my logic code "waits" until initialisation is done. This is my first cut. public class MyClass { private static final AtomicBoolean initialised = new AtomicBoolean(false); public void initialise() { synchronized(initialised) { initStuff(); initialised.getAndSet(true); initialised.notifyAll(); } } public void doStuff() { synchronized(initialised) { if (!initialised.get()) { try { initialised.wait(); } catch (InterruptedException ex) { throw new RuntimeException("Uh oh!", ex); } } } doOtherStuff(); } } I basically want to make sure this is going to do what I think it's going to do -- block doStuff until the initialised is true, and that I'm not missing a race condition where doStuff might get stuck on a Object.wait() that will never arrive. Edit: I have no control over the threads. And I want to be able to control when all of the initialisation is done, which is why doStuff() can't call initialise(). I used an AtomicBoolean as it was a combination of a value holder, and an object I could synchronize. I could have also simply had a "public static final Object lock = new Object();" and a simple boolean flag. AtomicBoolean conveniently gave me both. A Boolean can not be modified. The CountDownLatch is exactly what I was looking for. I also considered using a Sempahore with 0 permits. But the CountDownLatch is perfect for just this task.

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• Not seeing Sync Block in Object Layout

  - by bob-bedell

  It's my understanding the all .NET object instances begin with an 8 byte 'object header': a synch block (4 byte pointer into a SynchTableEntry table), and a type handle (4 byte pointer into the types method table). I'm not seeing this in VS 2010 RC's (CLR 4.0) debugger memory windows. Here's a simple class that will generate a 16 byte instance, less the object header. class Program { short myInt = 2; // 4 bytes long myLong = 3; // 8 bytes string myString = "aString"; // 4 byte object reference // 16 byte instance static void Main(string[] args) { new Program(); return; } } An SOS object dump tells me that the total object size is 24 bytes. That makes sense. My 16 byte instance plus an 8 byte object header. !DumpObj 0205b660 Name: Offset_Test.Program MethodTable: 000d383c EEClass: 000d13f8 Size: 24(0x18) bytes File: C:\Users\Bob\Desktop\Offset_Test\Offset_Test\bin\Debug\Offset_Test.exe Fields: MT Field Offset Type VT Attr Value Name 632020fc 4000001 10 System.Int16 1 instance 2 myInt 632050d8 4000002 4 System.Int64 1 instance 3 myLong 631fd2b8 4000003 c System.String 0 instance 0205b678 myString Here's the raw memory: 0x0205B660 000d383c 00000003 00000000 0205b678 00000002 ... And here are some annotations: offset 0 000d383c ;TypeHandle (pointer to MethodTable), 4 bytes offset 4 00000003 00000000 ;myLong, 8 bytes offset 12 0205b678 ;myString, 4 byte reference to address of "myString" on GC Heap offset 16 00000002 ;myInt, 4 bytes My object begins a address 0x0205B660. But I can only account for 20 bytes of it, the type handle and the instance fields. There is no sign of a synch block pointer. The object size is reported as 24 bytes, but the debugger is showing that it only occupies 20 bytes of memory. I'm reading Drill Into .NET Framework Internals to See How the CLR Creates Runtime Objects, and expected the first 4 bytes of my object to be a zeroed synch block pointer, as shown in Figure 8 of that article. Granted, this is an article about CLR 1.1. I'm just wondering if the difference between what I'm seeing and what this early article reports is a change in either the debugger's display of object layout, or in the way the CLR lays out objects in versions later than 1.1. Anyway, can anyone account for my 4 missing bytes?

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• Can you append a NSMutableArray to a file?

  - by Emil

  Hi. I am trying to write some data from an NSMutableArray to a plist, while keep the old plists content. The function writeToFile:atomically: overwrites the old contents with the new, I want to append the objects in the new array to the plist. How can this be done? Thank you.

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• Dynamically resizing CFWINDOW to fit content

  - by Ryan French

  Hi all, Am currently working on a site that uses a lot of cfwindow objects and I was wondering if anyone knows of a way to dynamically resize the window so that all the content fits in without the need for scroll bars. I have tried using the overflow=visible configuration but it doesnt seem to make a difference. Thanks in advance for any advice.

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• What will be the OOP approach? (or YOUR approach?)

  - by hsmit

  I'm having difficulties with some general OOP & Java approach. There are various ways to let classes/objects communicate with each other. To give a simple example: I need object A to perform action X. Object A needs P, Q and R to perform this action X. Will then Object A retrieve P, Q and R by itself (within action X), or must these values be parameters for action X?

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• How to check if a child-object is populated

  - by TheQ

  How can i check if a child-object of a linq-object is populated or not? Example code below. My model have two methods, one joins data, and the other does not: public static Member GetMemberWithPhoto(Guid memberId) { using (DataContext db = new DataContext()) { DataLoadOptions dataLoadOptions = new DataLoadOptions(); dataLoadOptions.LoadWith<Member>(x => x.UserPhoto); db.LoadOptions = dataLoadOptions; var query = from x in db.Members where x.MemberId == memberId select x; return query.FirstOrDefault(); } } public static Member GetMember(Guid memberId) { using (DataContext db = new DataContext()) { var query = from x in db.Members where x.MemberId == memberId select x; return query.FirstOrDefault(); } } Then my control have the following code: Member member1 = Member.GetMemberWithPhoto(memberId); Member member2 = Member.GetMember(memberId); Debug.WriteLine(member1.UserPhoto.ToString()); Debug.WriteLine(member2.UserPhoto.ToString()); The last line will generate a "Cannot access a disposed object" exception. I know that i can get rid of that exception just by not disposing the datacontext, but then the last line will generate a new query to the database, and i don't want that. What i would like is something like: Debug.WriteLine((member1.UserPhoto.IsPopulated()) ? member1.UserPhoto.ToString() : "none"); Debug.WriteLine((member2.UserPhoto.IsPopulated()) ? member2.UserPhoto.ToString() : "none"); Is it possible?

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• Does having more methods in a class mean that object uses more memory at runtime

  - by frinkz

  Say I have one class ClassBig with 100 methods inside, and a second with only 10 methods ClassSmall When I have objects at runtime ClassBig big = new ClassBig(); ClassSmall small = new ClassSmall(); Does the larger class take up more memory space? If both classes contained an identical method, does the larger class take longer to execute it?

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• Windsor OnCreated for all components

  - by jeffn825

  Hi, How would I go about globally intercepting the creation/resolution of all instances by my container? I know I can do this individually with OnCreated on a per-component basis, but I want to do this globally for all objects resolved by the container. Thanks.

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• When should I implement IDisposeable?

  - by Bobby

  What is the best practice for when to implement IDisposeable? Is the best rule of thumb to implement it if you have one managed object in the class, or does it depend if the object was created in the class or just passed in? Should I also do it for classes with no managed objects at all?

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• Java Detect Variable Change Using PropertyChangeSupport and PropertyChangeListener

  - by Sam

  I'm trying to print out debug statements when some third party code changes a variable. For example, consider the following: public final class MysteryClass { private int secretCounter; public synchronized int getCounter() { return secretCounter; } public synchronized void incrementCounter() { secretCounter++; } } public class MyClass { public static void main(String[] args) { MysteryClass mysteryClass = new MysteryClass(); // add code here to detect calls to incrementCounter and print a debug message } I don't have the ability to change the 3rd party MysteryClass, so I thought that I could use PropertyChangeSupport and PropertyChangeListener to detect changes to the secretCounter: public class MyClass implements PropertyChangeListener { private PropertyChangeSupport propertySupport = new PropertyChangeSupport(this); public MyClass() { propertySupport.addPropertyChangeListener(this); } public void propertyChange(PropertyChangeEvent evt) { System.out.println("property changing: " + evt.getPropertyName()); } public static void main(String[] args) { MysteryClass mysteryClass = new MysteryClass(); // do logic which involves increment and getting the value of MysteryClass } } Unfortunately, this did not work and I have no debug messages printed out. Does anyone see what is wrong with my implementation of the PropertyChangeSupport and Listener interfaces? I want to print a debug statement whenever incrementCounter is called or the value of secretCounter changes.

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• change sprite image cocos2d when collision between sprite and player occures.

  - by iPhone Fun

  hi friends, I want to change the sprite image while my application is running. I've taken 5 different sprite objects with different images. but when I use [self removeChild:Name of sprite cleanup:YES]; It is not removing the sprite. So is there any other way to perform such task?? Any help?? Thanks in advance.

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• Is it safe to make GL calls with multiple threads?

  - by user146780

  I was wondering if it was safe to make GL calls with multiple threads. Basically I'm using a GLUtesselator and was wondering if I could divide the objects to draw into 4 and assign a thread to each one. I'm just wondering if this would cause trouble since the tesselator uses callback functions. Can 2 threads run the same callback at the same time as long as that callback does not access ant global variables? Are there also other ways I could optimize OpenGL drawing using multithreading? Thanks

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• Building a decision-making game in jQuery? Where would I store data....

  - by redconservatory

  I built a slideshow/decision-making game in Flash but would like to try to redo it using jQuery. The slideshow part seems simple enough, however I have a series of user decisions that I'm not sure how to approach. In flash, if the user makes a decision, I would just store this in a variable or shared local objects, is this the same for jQuery? i.e. mix regular javascript variables with the jQuery?

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• Is it a good practice for a .js file to rely on variables declared in the including html

  - by Bozho

  In short: <script type="text/javascript"> var root = '${config.root}'; var userLanguage = '${config.language}'; var userTimezone = '${config.timezone}'; </script> <script type="text/javascript" src="js/scripts.js"></script> And then, in scripts.js, rely on these variables: if (userLanguage == 'en') { .. } The ${..} is simply a placeholder for a value in the script that generates the page. It can be php, jsp, asp, whatever. The point is - it is dynamic, and hence it can't be part of the .js file (which is static). So, is it OK for the static javascript file to rely on these externally defined configuration variables? (they are mainly configuration, of course). Or is it preferred to make the .js file be served dynamically as well (i.e. make it a .php / .jsp, with the proper Content-Type), and have these values defined in there.

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• How to save errors with the handleError in CakePHP 2.0?

  - by jags1988cr

  I have a big problem. Well, I'm trying to save the errors that happen in my web application. For example (only a example), if I make a division by zero, or happens an error in a query or something like that. So, I wanna catch that and save it in the database. But the handleError of CakePHP is static, so I can't use $this-MyModel-saveError(...). In my /app/Lib/AppError.php I have this: class AppError extends ErrorHandler { public $uses = array('Errors.Error'); public static function handleError($code, $description, $file = null, $line = null, $context = null) { //This print the error: echo "Code: ".$code." Description: ".$description." File: ".$file." Line: ".$line."<br>"; //I want to do this, (save to the database): $this->Error->saveError($code, $description, $file, $line); } } Without the $this-Error-saveError($code, $description, $file, $line); it works but I not only want to show the error. I think need an example or something like that. Please help me. Regards and thank you. Thanks... P.D.: Sorry for the English, I'm an english student...

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• Object Oriented vs Relational Databases

  - by Dan

  Objects oriented databases seem like a really cool idea to me, no need to worry about mapping your domain model to your database model, no messing around with sql or ORM tools. The way I understand it, relational DBs offer some advantages when there is massive amounts of data, and searching an indexing need to be done. To my mind 99% of websites are not massive, and enterprise issues never need to be thought about, so why arn't OO DBs more widely used?

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• How do I TRUNCATE TABLE using Django orm?

  - by Silver Light

  Hello! To empty database table, I use this SQL Query: TRUNCATE TABLE `books` How to I Truncate table using Django models and orm? I've tried this, but it doesn't work: Book.objects.truncate()

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• How to retrieve items from a django queryset?

  - by sharataka

  I'm trying to get the video element in a queryset but am having trouble retrieving it. user_channel = Everything.objects.filter(profile = request.user, playlist = 'Channel') print user_channel[0] #returns the first result without error print user_channel[0]['video'] #returns error Models.py: class Everything(models.Model): profile = models.ForeignKey(User) playlist = models.CharField('Playlist', max_length = 2000, null=True, blank=True) platform = models.CharField('Platform', max_length = 2000, null=True, blank=True) video = models.CharField('VideoID', max_length = 2000, null=True, blank=True) video_title = models.CharField('Title of Video', max_length = 2000, null=True, blank=True) def __unicode__(self): return u'%s %s %s %s %s' % (self.profile, self.playlist, self.platform, self.video, self.video_title)

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• When an active_record is saved, is it saved before or after its associated object(s)?

  - by SeeBees

  In rails, when saving an active_record object, its associated objects will be saved as well. But has_one and has_many association have different order in saving objects. I have three simplified models: class Team < ActiveRecord::Base has_many :players has_one :coach end class Player < ActiveRecord::Base belongs_to :team validates_presence_of :team_id end class Coach < ActiveRecord::Base belongs_to :team validates_presence_of :team_id end I use the following code to test these models: t = Team.new team.coach = Coach.new team.save! team.save! returns true. But in another test: t = Team.new team.players << Player.new team.save! team.save! gives the following error: > ActiveRecord::RecordInvalid: > Validation failed: Players is invalid I figured out that when team.save! is called, it first calls player.save!. player needs to validate the presence of the id of the associated team. But at the time player.save! is called, team hasn't been saved yet, and therefore, team_id doesn't yet exist for player. This fails the player's validation, so the error occurs. But on the other hand, team is saved before coach.save!, otherwise the first example will get the same error as the second one. So I've concluded that when a has_many bs, a.save! will save bs prior to a. When a has_one b, a.save! will save a prior to b. If I am right, why is this the case? It doesn't seem logical to me. Why do has_one and has_many association have different order in saving? Any ideas? And is there any way I can change the order? Say I want to have the same saving order for both has_one and has_many. Thanks.

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• Question regarding C++ Lists

  - by mousey

  Hi, list<Dog*> dog; ............. ............ So I added many dog objects to it. If I call dog.pop_front(); Does memory automatically gets deallocated ?

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• Retrieve POST data without knowing exact number of fields

  - by James

  Hi all! I'm creating an online poll from scratch which will be held in a database. I'm working on getting a system set up so someone can create a new poll. I will be having the user fill out a simple HTML form with the Questions and Answers (there may be several answers). The user will be able to add multiple questions and multiple answers for each question. As the total number of questions and answers will be decided by the user, I need to create some clever PHP to cater for this - however many there are. When dealing with a static number of questions, it's simple. But I'm having trouble thinking of a way to get all the POST data into individual PHP variables so I can process them. I was thinking of using a foreach loop, anyone got any ideas? Sorry for the long winded description! If anyone needs anything clarified, I'd be happy to do so. My problem is that I can't get my head around how to deal with the POST values when I don't know exactly which element of the array will contain what. If things were static with a set number of questions and answers, I'd know $_POST[0] was Question1, etc Thank you! =)

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• Thinking about using Bluej to learn Java

  - by lions_leash

  I would like to start learning Java, but there are so many resources out there... I am having a hard time deciding which path to take. I saw a neat book, Objects First with Java, and I tested out Bluej and some tutorials. Anyone use this and have comments?

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• Query Entity Framework 4

  - by nick

  Hi, Is it possible to run a query on an EF4.0 data context and get all objects of a certain type? Say the context has books, genres & authors but I only have a generic parameter, t. Is it possible to get all of type just by using this t? I don't think it is :(

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• Saving associated domain classes in Grails

  - by Cesar

  I'm struggling to get association right on Grails. Let's say I have two domain classes: class Engine { String name int numberOfCylinders = 4 static constraints = { name(blank:false, nullable:false) numberOfCylinders(range:4..8) } } class Car { int year String brand Engine engine = new Engine(name:"Default Engine") static constraints = { engine(nullable:false) brand(blank:false, nullable:false) year(nullable:false) } } The idea is that users can create cars without creating an engine first, and those cars get a default engine. In the CarController I have: def save = { def car = new Car(params) if(!car.hasErrors() && car.save()){ flash.message = "Car saved" redirect(action:index) }else{ render(view:'create', model:[car:car]) } } When trying to save, I get a null value exception on the Car.engine field, so obviously the default engine is not created and saved. I tried to manually create the engine: def save = { def car = new Car(params) car.engine = new Engine(name: "Default Engine") if(!car.hasErrors() && car.save()){ flash.message = "Car saved" redirect(action:index) }else{ render(view:'create', model:[car:car]) } } Didn't work either. Is Grails not able to save associated classes? How could I implement such feature?

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