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• How to set a __str__ method for all ctype Structure classes?

  - by Reuben Thomas

  [Since asking this question, I've found: http://www.cs.unc.edu/~gb/blog/2007/02/11/ctypes-tricks/ which gives a good answer.] I just wrote a __str__ method for a ctype-generated Structure class 'foo' thus: def foo_to_str(self): s = [] for i in foo._fields_: s.append('{}: {}'.format(i[0], foo.\_\_getattribute__(self, i[0]))) return '\n'.join(s) foo.\_\_str__ = foo_to_str But this is a fairly natural way to produce a __str__ method for any Structure class. How can I add this method directly to the Structure class, so that all Structure classes generated by ctypes get it? (I am using the h2xml and xml2py scripts to auto-generate ctypes code, and this offers no obvious way to change the names of the classes output, so simply subclassing Structure, Union &c. and adding my __str__ method there would involve post-processing the output of xml2py.)

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• iOS 5 - Coredata Sqlite DB losing data after killing app

  - by Brian Boyle

  I'm using coredata with a sqlite DB to persist data in my app. However, each time I kill my app I lose any data that was saved in the DB. I'm pretty sure its because the .sqlite file for my DB is just being replaced by a fresh one each time my app starts, but I can't seem to find any code that will just use the existing one thats there. It would be great if anyone could point me towards some code that could handle this for me. Cheers B - (NSPersistentStoreCoordinator *)persistentStoreCoordinator { if (__persistentStoreCoordinator != nil) { return __persistentStoreCoordinator; } NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption, [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil]; NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"FlickrCoreData.sqlite"]; NSError *error = nil; __persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]]; if (![__persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:options error:&error]) { NSLog(@"Unresolved error %@, %@", error, [error userInfo]); abort(); } return __persistentStoreCoordinator; }

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• Where is the help.py for Android's monkeyrunner

  - by Keyboardsurfer

  Hi, I just can't find the help.py file in order to create the API reference for the monkeyrunner. The command described at the Android references monkeyrunner <format> help.py <outfile> does not work when i call monkeyrunner html help.py /path/to/place/the/doc.html. It's quite obvious that the help.py file is not found and the monkeyrunner also tells me "Can't open specified script file". But a locate on my system doesn't bring me a help.py file that has anything to do with monkeyrunner or Android. So my question is: Where did they hide the help.py file for creating the API reference?

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• Is there a memory leak here?

  - by TheLearner

  Please see my comments in code: -(id)initWithCoordinate:(CLLocationCoordinate2D)c title:(NSString *)t { [super init]; coordinate = c; NSDate *today = [NSDate date]; NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init]; [dateFormatter setDateStyle:NSDateFormatterLongStyle]; NSString* formattedDate = [NSString stringWithFormat:@"%@ %@", [dateFormatter stringFromDate:today], t]; [self setTitle:formattedDate]; //Why does the app crash when I try and release formattedDate? I have after all passed its reference to the title property? [dateFormatter release]; //I need to release the dateformatter because I have finished using it and I have not passed on a reference to it return self; }

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• Replacing objects, handling clones, dealing with write logs

  - by Alix

  Hi everyone, I'm dealing with a problem I can't figure out how to solve, and I'd love to hear some suggestions. [NOTE: I realise I'm asking several questions; however, answers need to take into account all of the issues, so I cannot split this into several questions] Here's the deal: I'm implementing a system that underlies user applications and that protect shared objects from concurrent accesses. The application programmer (whose application will run on top of my system) defines such shared objects like this: public class MyAtomicObject { // These are just examples of fields you may want to have in your class. public virtual int x { get; set; } public virtual List<int> list { get; set; } public virtual MyClassA objA { get; set; } public virtual MyClassB objB { get; set; } } As you can see they declare the fields of their class as auto-generated properties (auto-generated means they don't need to implement get and set). This is so that I can go in and extend their class and implement each get and set myself in order to handle possible concurrent accesses, etc. This is all well and good, but now it starts to get ugly: the application threads run transactions, like this: The thread signals it's starting a transaction. This means we now need to monitor its accesses to the fields of the atomic objects. The thread runs its code, possibly accessing fields for reading or writing. If there are accesses for writing, we'll hide them from the other transactions (other threads), and only make them visible in step 3. This is because the transaction may fail and have to roll back (undo) its updates, and in that case we don't want other threads to see its "dirty" data. The thread signals it wants to commit the transaction. If the commit is successful, the updates it made will now become visible to everyone else. Otherwise, the transaction will abort, the updates will remain invisible, and no one will ever know the transaction was there. So basically the concept of transaction is a series of accesses that appear to have happened atomically, that is, all at the same time, in the same instant, which would be the moment of successful commit. (This is as opposed to its updates becoming visible as it makes them) In order to hide the write accesses in step 2, I clone the accessed field (let's say it's the field list) and put it in the transaction's write log. After that, any time the transaction accesses list, it will actually be accessing the clone in its write log, and not the global copy everyone else sees. Like this, any changes it makes will be done to the (invisible) clone, not to the global copy. If in step 3 the commit is successful, the transaction should replace the global copy with the updated list it has in its write log, and then the changes become visible for everyone else at once. It would be something like this: myAtomicObject.list = updatedCloneOfListInTheWriteLog; Problem #1: possible references to the list. Let's say someone puts a reference to the global list in a dictionary. When I do... myAtomicObject.list = updatedCloneOfListInTheWriteLog; ...I'm just replacing the reference in the field list, but not the real object (I'm not overwriting the data), so in the dictionary we'll still have a reference to the old version of the list. A possible solution would be to overwrite the data (in the case of a list, empty the global list and add all the elements of the clone). More generically, I would need to copy the fields of one list to the other. I can do this with reflection, but that's not very pretty. Is there any other way to do it? Problem #2: even if problem #1 is solved, I still have a similar problem with the clone: the application programmer doesn't know I'm giving him a clone and not the global copy. What if he puts the clone in a dictionary? Then at commit there will be some references to the global copy and some to the clone, when in truth they should all point to the same object. I thought about providing a wrapper object that contains both the cloned list and a pointer to the global copy, but the programmer doesn't know about this wrapper, so they're not going to use the pointer at all. The wrapper would be like this: public class Wrapper<T> : T { // This would be the pointer to the global copy. The local data is contained in whatever fields the wrapper inherits from T. private T thisPtr; } I do need this wrapper for comparisons: if I have a dictionary that has an entry with the global copy as key, if I look it up with the clone, like this: dictionary[updatedCloneOfListInTheWriteLog] I need it to return the entry, that is, to think that updatedCloneOfListInTheWriteLog and the global copy are the same thing. For this, I can just override Equals, GetHashCode, operator== and operator!=, no problem. However I still don't know how to solve the case in which the programmer unknowingly inserts a reference to the clone in a dictionary. Problem #3: the wrapper must extend the class of the object it wraps (if it's wrapping MyClassA, it must extend MyClassA) so that it's accepted wherever an object of that class (MyClass) would be accepted. However, that class (MyClassA) may be final. This is pretty horrible :$. Any suggestions? I don't need to use a wrapper, anything you can think of is fine. What I cannot change is the write log (I need to have a write log) and the fact that the programmer doesn't know about the clone. I hope I've made some sense. Feel free to ask for more info if something needs some clearing up. Thanks so much!

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• Access to nested methods when DSL

  - by Vyacheslav Loginov

  class Warcraft def initialize &block instance_eval &block end def method_missing name, *args, &block instance_variable_set("@#{name}".to_sym, args[0]) self.class.send(:define_method, name, proc { instance_variable_get("@#{name}")}) end def game &block @game = Game.new &block end class Game def initialize &block instance_eval &block end def method_missing name, *args, &block instance_variable_set("@#{name}".to_sym, args[0]) self.class.send(:define_method, name, proc { instance_variable_get("@#{name}")}) end end end warcraft = Warcraft.new do name "Warcraft III" battle_net :iccup game do side :sentinels hero "Furion" rune_appear_every 2 end end puts warcraft.inspect # => #<Warcraft:0x00000000be3e80 @name="Warcraft III", @battle_net=:iccup, @game=#<Warcraft::Game:0x000000009c6c38 @side=:sentinels, @hero="Furion", @rune_appear_every=2>> How to access nested methods? puts warcraft.battle_net # => iccup puts warcraft.side #=> #<Proc:[email protected]:9 (lambda)> puts warcraft.game #=> dsl.rb:18:in `instance_eval': block not supplied (ArgumentError) puts warcraft.game.side #=> dsl.rb:18:in `instance_eval': block not supplied (ArgumentError)

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• How does Sentry aggregate errors?

  - by Hugo Rodger-Brown

  I am using Sentry (in a django project), and I'd like to know how I can get the errors to aggregate properly. I am logging certain user actions as errors, so there is no underlying system exception, and am using the culprit attribute to set a friendly error name. The message is templated, and contains a common message ("User 'x' was unable to perform action because 'y'"), but is never exactly the same (different users, different conditions). Sentry clearly uses some set of attributes under the hood to determine whether to aggregate errors as the same exception, but despite having looked through the code, I can't work out how. Can anyone short-cut my having to dig further into the code and tell me what properties I need to set in order to manage aggregation as I would like? [UPDATE 1: event grouping] This line appears in sentry.models.Group: class Group(MessageBase): """ Aggregated message which summarizes a set of Events. """ ... class Meta: unique_together = (('project', 'logger', 'culprit', 'checksum'),) ... Which makes sense - project, logger and culprit I am setting at the moment - the problem is checksum. I will investigate further, however 'checksum' suggests that binary equivalence, which is never going to work - it must be possible to group instances of the same exception, with differenct attributes? [UPDATE 2: event checksums] The event checksum comes from the sentry.manager.get_checksum_from_event method: def get_checksum_from_event(event): for interface in event.interfaces.itervalues(): result = interface.get_hash() if result: hash = hashlib.md5() for r in result: hash.update(to_string(r)) return hash.hexdigest() return hashlib.md5(to_string(event.message)).hexdigest() Next stop - where do the event interfaces come from? [UPDATE 3: event interfaces] I have worked out that interfaces refer to the standard mechanism for describing data passed into sentry events, and that I am using the standard sentry.interfaces.Message and sentry.interfaces.User interfaces. Both of these will contain different data depending on the exception instance - and so a checksum will never match. Is there any way that I can exclude these from the checksum calculation? (Or at least the User interface value, as that has to be different - the Message interface value I could standardise.) [UPDATE 4: solution] Here are the two get_hash functions for the Message and User interfaces respectively: # sentry.interfaces.Message def get_hash(self): return [self.message] # sentry.interfaces.User def get_hash(self): return [] Looking at these two, only the Message.get_hash interface will return a value that is picked up by the get_checksum_for_event method, and so this is the one that will be returned (hashed etc.) The net effect of this is that the the checksum is evaluated on the message alone - which in theory means that I can standardise the message and keep the user definition unique. I've answered my own question here, but hopefully my investigation is of use to others having the same problem. (As an aside, I've also submitted a pull request against the Sentry documentation as part of this ;-)) (Note to anyone using / extending Sentry with custom interfaces - if you want to avoid your interface being use to group exceptions, return an empty list.)

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• How do you position a wx.MessageDialog (wxPython)?

  - by Jason

  Hi: Is there any reason why the position, pos, flag doesn't seem to work in the following example? dlg = wx.MessageDialog( parent=self, message='You must enter a URL', caption='Error', style=wx.OK | wx.ICON_ERROR | wx.STAY_ON_TOP, pos=(200,200) ) dlg.ShowModal() dlg.Destroy() The documentation is here: http://www.wxpython.org/docs/api/wx.MessageDialog-class.html 'self' is a reference to the frame. I'm running in Windows Vista, python26, wxpython28. The message dialog always appears to be in the middle of the screen. If for some reason it's not possible to position the dialog, is there anyway to at least restrict the dialog to be in the frame, rather than just the center of the screen? thanks!

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• Correct way to add "Tab Bar" in Navigation based tamplate in iPhon

  - by iPhoneDev

  I have added Tab Bar in Navigation based tamplate like this: [self.navigationController pushViewController:anotherViewController animated:YES]; And I think this is not the correct way to have Tab Bar in detail view in Navigation based tamplate. Please make me correct? UnsentView *unsent = [[UnsentView alloc] initWithNibName:@"UnsentView" bundle:nil]; unsent.title =@"Unsent"; UITabBarController *anotherViewController = [[UITabBarController alloc] init]; anotherViewController.viewControllers = [NSArray arrayWithObjects: unsent, setting, nil]; [self.navigationController pushViewController:anotherViewController animated:YES]; [anotherViewController release];

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• Ruby on Rails with_option cannot call class method

  - by Dmitri

  I have a problem calling class method from the with_option block with validations: Model: class Model < ActiveRecord::Base attr_accessible :field with_options :if => "<not important>" do |step| ... bunch of validations step.validates :field, :inclusion => {:within => Model.field} end private self.field (1..10) end end And it returns: undefined method `field' for #Class:0x5f394a8 self.class.field also doesn't work. What is wrong with it ? How to fix it ? Big big thanks!

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• Communicate multiple times with a process without breaking the pipe?

  - by Manux

  Hello, it's not the first time I'm having this problem and its really bugging me. Whenever I open a pipe using the Python subprocess module, I can only communicate with it once, as the documentation specifies: Read data from stdout and stderr, until end-of-file is reached proc = sub.Popen("psql -h darwin -d main_db".split(),stdin=sub.PIPE,stdout=sub.PIPE) print proc.communicate("select a,b,result from experiment_1412;\n")[0] print proc.communicate("select theta,zeta,result from experiment_2099\n")[0] The problem here is that the second time, Python isn't happy. Indeed, he decided to close the file after the first communicate: Traceback (most recent call last): File "a.py", line 30, in <module> print proc.communicate("select theta,zeta,result from experiment_2099\n")[0] File "/usr/lib64/python2.5/subprocess.py", line 667, in communicate return self._communicate(input) File "/usr/lib64/python2.5/subprocess.py", line 1124, in _communicate self.stdin.flush() ValueError: I/O operation on closed file So... multiple communications aren't allowed? I hope not ;) Please enlighten me.

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• Optimizing BeautifulSoup (Python) code

  - by user283405

  I have code that uses the BeautifulSoup library for parsing, but it is very slow. The code is written in such a way that threads cannot be used. Can anyone help me with this? I am using BeautifulSoup for parsing and than save into a DB. If I comment out the save statement, it still takes a long time, so there is no problem with the database. def parse(self,text): soup = BeautifulSoup(text) arr = soup.findAll('tbody') for i in range(0,len(arr)-1): data=Data() soup2 = BeautifulSoup(str(arr[i])) arr2 = soup2.findAll('td') c=0 for j in arr2: if str(j).find("<a href=") > 0: data.sourceURL = self.getAttributeValue(str(j),'<a href="') else: if c == 2: data.Hits=j.renderContents() #and few others... c = c+1 data.save() Any suggestions? Note: I already ask this question here but that was closed due to incomplete information.

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• How should I declare default values for instance variables in Python?

  - by int3

  Should I give my class members default values like this: class Foo: num = 1 or like this? class Foo: def __init__(self): self.num = 1 In this question I discovered that in both cases, bar = Foo() bar.num += 1 is a well-defined operation. I understand that the first method will give me a class variable while the second one will not. However, if I do not require a class variable, but only need to set a default value for my instance variables, are both methods equally good? Or one of them more 'pythonic' than the other? One thing I've noticed is that in the Django tutorial, they use the second method to declare Models. Personally I think the second method is more elegant, but I'd like to know what the 'standard' way is.

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• Hibernate object equality checking

  - by Sujee

  As far as I understand(correct me if I am wrong) Hibernate uses object reference to check the object equality. When Hibernate identifies that there are more than one objects attached to same DB record, it throws following exception. "a different object with the same identifier value was already associated with the session" My question is, does Hibernate use equal() method to check the object equality (The default equal method uses object reference)? If it is true, will overridden equal() method change the Hibernate behavior? Note: My question is not about the issues of implementing equal() or hashCode() methods in a Hibernate persisted object. Thank you.

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• Merge a hash with the key/values of a string in ruby

  - by LazyJason

  Hi there, I'm trying to merge a hash with the key/values of string in ruby. i.e. h = {:day => 4, :month => 8, :year => 2010} s = "/my/crazy/url/:day/:month/:year" puts s.interpolate(h) All I've found is to iterate the keys and replace the values. But I'm not sure if there's a better way doing this? :) class String  def interpolate(e)    self if e.each{|k, v| self.gsub!(":#{k}", "#{v}")}  end end Thanks

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• The pros and cons of use JSON for WCF service

  - by brz dot net

  What are the pros and cons of the following 2 cases: Case I: Traditional way: Add service reference in project. Create object and Get data from service on server side and bind to asp.net grid. Case II: Update Service for JSON behavior. Add service reference in project. Call service from javascript to get data. Bind data to jquery grid. Which one is the best approach and why?(Not developer point of view) If there is another approach which is more optimized, please explain it.

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• Modal View Does Not Appear in Center in Horizontal Orientation

  - by Sheehan Alam

  I have a UIPresentationFormSheet (contains a textview) that appears in the center of the screen when I am in vertical orientation. When I dismiss the modal view, it disappears fine. When I am in horizontal orientation my modal view does not appear in the center of the screen. I have to dismiss my keyboard for the modal view to appear in the center. [self presentModalViewController:composeTweetController animated:TRUE]; When I dismiss the modal view in horizontal orientation the app automatically switches to vertical orientation. -(void)dismissComposeTweetView{ [self dismissModalViewControllerAnimated:TRUE]; } I want the following to happen: Modal view should appear in the center in horizontal orientation Modal view should disappear without switching to vertical orientation

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• Eager load this rails association

  - by dombesz

  Hi, I have rails app which has a list of users. I have different relations between users, for example worked with, friend, preferred. When listing the users i have to decide if the current user can add a specific user to his friends. -if current_user.can_request_friendship_with(user) =add_to_friends(user) -else =remove_from_friends(user) -if current_user.can_request_worked_with(user) =add_to_worked_with(user) -else =remove_from_worked_with(user) The can_request_friendship_with(user) looks like: def can_request_friendship_with(user) !self.eql?(user) && !self.friendships.find_by_friend_id(user) end My problem is that this means in my case 4 query per user. Listing 10 users means 40 query. Could i somehow eager load this?

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• What garbage collection algorithms do all 5 major browsers use?

  - by Martin Wittemann

  I am currently rethinking the object dispose handling of the qooxdoo JavaScript framework. Have a look at the following diagram (A is currently in scope): Let's say we want to delete B. Generally, we cut all reference between all objects. This means we cut connection 1 to 5 in the example. Is this really necessary? As far as I have read hear 1, browsers use the mark-and-sweep algorithm. In that case, we just need to cut reference 1 (connection to the scope) and 5 (connection to the DOM) which could be much faster. But can I be sure that all browsers use the mark-and-sweep algorithm or something similar? 1 http://stackoverflow.com/questions/864516/what-is-javascript-garbage-collection

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• Python grab class in class definition.

  - by epochwolf

  I don't even know how to explain this, so here is the code I'm trying. class Test: type = self.__name__ #self doesn't work, how do I get a reference to Test? class Test2(Test): pass #Test2.type should return "Test2" The reason I'm even trying this is I'm working on creating a base class for an orm I'm using. I want to avoid defining the table name for every model I have. Also knowing what the limits of python is will help me avoid wasting time trying impossible things.

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• PG::Error: ERROR: operator does not exist: integer ~~ unknown

  - by rsvmrk

  I'm making a search-function in a Rails project with Postgres as db. Here's my code def self.search(search) if search find(:all, :conditions => ["LOWER(name) LIKE LOWER(?) OR LOWER(city) LIKE LOWER(?) OR LOWER(address) LIKE LOWER(?) OR (venue_type) LIKE (?)", "%#{search}%", "%#{search}%", "%#{search}%", "%#{search}%"]) else find(:all) end end But my problem is that "venue_type" is an integer. I've made a case switch for venue_type def venue_type_check case self.venue_type when 1 "Pub" when 2 "Nattklubb" end end Now to my question: How can I find something in my query when venue_type is an int?

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• Does SQL Server 2005 error message numbers back to the asp.net application?

  - by Duke

  I'd like to get the message number and severity level information from SQL Server upon execution of an erroneous query. For example, when a user attempts to delete a row being referenced by another record, and the cascade relationship is "no action", I'd like the application to be able to check for error message 547 ("The DELETE statement conflicted with the REFERENCE constraint...") and return a user friendly and localized message to the user. When running such a query directly on SQL Server, the following message is printed: Msg 547, Level 16, State 0, Line 1 <Error message...> In an Asp.Net app is this information available in an event handler parameter or elsewhere? Also, I don't suppose anyone knows where I can find a definitive reference of SQL Server message numbers?

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• NSOperationqueue i want to block main thread

  - by alexeyndru

  i want to block the main thread until something else is done in the background. i used: result=[self performSelectorInBackground:@selector(calculate:) withObject:expression]; just bellow this line I am using result: [self use:result]; i dont want to use result until it is available. to achieve this I implemented calculate: { [[(AppDelegate *)[[UIApplication sharedApplication] delegate] queue] waitUntilAllOperationsAreFinished]; calculating result... } and still, the result is used before it is calculated. so, i didnt block the main thread. pls help me do that. thanks

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• Custom accessor for array element

  - by memph1s

  I'm trying to create an accessor for one element from array with specific flag set to true: class EntranceObject < ActiveRecord::Base has_many :subscribers def customer self.subscribers.find(:first, :conditions => {:is_customer => true}) end def customer=(customer_params) self.subscribers << Subscriber.new(:name => customer_params[:name], :apartment => customer_params[:apartment], :phone_number => customer_params[:phone_number], :is_customer => true) end end class Subscriber < ActiveRecord::Base belongs_to :entrance_object validates_presence_of :name, :apartment end How do i need to validate this accessor in order to hightlight missing fields in a view? P.S. I'm newbie in RoR, maybe there is another approach to such work with one element from a collection? Thanks.

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• How to stop rotation of ABPersonViewController & ABNewPersonViewController in Landscape mode in ipho

  - by andy-iphone

  I am using a ABPersonViewController & ABNewPersonViewController class by pushview controller. ABPersonViewController *pvc = [[ABPersonViewController alloc] init]; [pvc setPersonViewDelegate:self]; [[self navigationController] pushViewController:pvc animated:YES]; In ABPersonViewController & ABNewPersonViewController page it is displaying in portrait mode. But when I rotate my iphone then it is perfectly rotating in landscape mode. But I want to stop this rotation. If I rotate my iphone in landscape mode it's view should be in portrait mode. Please help me ASAP. Any suggestion will be acepted.

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