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• Patterns and Libraries for working with raw UI values.

  - by ProfK

  By raw values, I mean the application level values provided by UI controls, such as the Text property on a TextBox. Too often I find myself writing code to check and parse such values before they get used as a business level value, e.g. PaymentTermsNumDays. I've mitigated a lot of the spade work with rough and ready extension methods like String.ToNullableInt, but we all know that just isn't right. We can't put the whole world on String's shoulders. Do I look at tasking my UI to provide business values, using a ruleset pushed out from the server app, or open my business objects up a bit to do the required sanitising etc. as they required? Neither of these approaches sits quite right with me; the first seems closer to ideal, but quite a bit of work, while the latter doesn't show much respect to the business objects' single responsibility. The responsibilities of the UI are a closer match. Between these extremes, I could also just implement another DTO layer, an IoC container with sanitising and parsing services, derive enhanced UI controls, or stick to copy and paste inline drudgery.

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• C++ traits question

  - by duli

  I have a templated class template <typename Data> class C { ..... } In most situations, I depend on the compiler to let me substitute types for Data. I call methods foo(), goo() on objects of type Data, so what I substitute needs to provide that. I now need to substitute int and string for my Data type. I do not want to specialize because the class is already too big and would require specializing each method (with only small code change). My options (please tell me if there are more) 1) I can provide wrapper classes around int and string which implement the methods foo(), goo() etc 2) provide a traits class traits that calls foo() or goo() on objects of classes that provide foo(),goo() (these are my present substitutable classes) and specialize these classes for int and string. Questions 1) what are the relative merits of 1 vs 2? 2) My traits classes will have static methods. Can a traits class have non-static methods as well? I see most traits classes define constants in the STL. 3) Do I make the traits classes global or should I pass them in as a template parameter for class C?

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• Are there any other ways to iterate through the attributes of a custom class, excluding the in-built ones?

  - by Ricardo Altamirano

  Is there another way to iterate through only the attributes of a custom class that are not in-built (e.g. __dict__, __module__, etc.)? For example, in this code: class Terrain: WATER = -1 GRASS = 0 HILL = 1 MOUNTAIN = 2 I can iterate through all of these attributes like this: for key, value in Terrain.__dict__.items(): print("{: <11}".format(key), " --> ", value) which outputs: MOUNTAIN --> 2 __module__ --> __main__ WATER --> -1 HILL --> 1 __dict__ --> <attribute '__dict__' of 'Terrain' objects> GRASS --> 0 __weakref__ --> <attribute '__weakref__' of 'Terrain' objects> __doc__ --> None If I just want the integer arguments (a rudimentary version of an enumerated type), I can use this: for key, value in Terrain.__dict__.items(): if type(value) is int: # type(value) == int print("{: <11}".format(key), " --> ", value) this gives the expected result: MOUNTAIN --> 2 WATER --> -1 HILL --> 1 GRASS --> 0 Is it possible to iterate through only the non-in-built attributes of a custom class independent of type, e.g. if the attributes are not all integral. Presumably I could expand the conditional to include more types, but I want to know if there are other ways I'm missing.

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• Boost shared_ptr use_count function

  - by photo_tom

  My application problem is the following - I have a large structure foo. Because these are large and for memory management reasons, we do not wish to delete them when processing on the data is complete. We are storing them in std::vector<boost::shared_ptr<foo>>. My question is related to knowing when all processing is complete. First decision is that we do not want any of the other application code to mark a complete flag in the structure because there are multiple execution paths in the program and we cannot predict which one is the last. So in our implementation, once processing is complete, we delete all copies of boost::shared_ptr<foo>> except for the one in the vector. This will drop the reference counter in the shared_ptr to 1. Is it practical to use shared_ptr.use_count() to see if it is equal to 1 to know when all other parts of my app are done with the data. One additional reason I'm asking the question is that the boost documentation on the shared pointer shared_ptr recommends not using "use_count" for production code.

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• How does git fetches commits associated to a file ?

  - by liadan

  I'm writing a simple parser of .git/* files. I covered almost everything, like objects, refs, pack files etc. But I have a problem. Let's say I have a big 300M repository (in a pack file) and I want to find out all the commits which changed /some/deep/inside/file file. What I'm doing now is: fetching last commit finding a file in it by: fetching parent tree finding out a tree inside recursively repeat until I get into the file additionally I'm checking hashes of each subfolders on my way to file. If one of them is the same as in commit before, I assume that file was not changed (because it's parent dir didn't change) then I store the hash of a file and fetch parent commit finding file again and check if hash change occurs if yes then original commit (i.e. one before parent) was changing a file And I repeat it over and over until I reach very first commit. This solution works, but it sucks. In worse case scenario, first search can take even 3 minutes (for 300M pack). Is there any way to speed it up ? I tried to avoid putting so large objects in memory, but right now I don't see any other way. And even that, initial memory load will take forever :( Greets and thanks for any help!

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• Top n items in a List ( including duplicates )

  - by Krishnan

  Trying to find an efficient way to obtain the top N items in a very large list, possibly containing duplicates. I first tried sorting & slicing, which works. But this seems unnnecessary. You shouldn't need to sort a very large list if you just want the top 20 members. So I wrote a recursive routine which builds the top-n list. This also works, but is very much slower than the non-recursive one! Question: Which is my second routine (elite2) so much slower than elite, and how do I make it faster ? My code is attached below. Thanks. import scala.collection.SeqView import scala.math.min object X { def elite(s: SeqView[Int, List[Int]], k:Int):List[Int] = { s.sorted.reverse.force.slice(0,min(k,s.size)) } def elite2(s: SeqView[Int, List[Int]], k:Int, s2:List[Int]=Nil):List[Int] = { if( k == 0 || s.size == 0) s2.reverse else { val m = s.max val parts = s.force.partition(_==m) val whole = if( parts._1.size > 1) parts._1.tail:::parts._2 else parts._2 elite2( whole.view, k-1, m::s2 ) } } def main(args:Array[String]) = { val N = 1000000/3 val x = List(N to 1 by -1).flatten.map(x=>List(x,x,x)).flatten.view println(elite2(x,20)) println(elite(x,20)) } }

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• Use `require()` with `node --eval`

  - by rentzsch

  When utilizing node.js's newish support for --eval, I get an error (ReferenceError: require is not defined) when I attempt to use require(). Here's an example of the failure: $ node --eval 'require("http");' undefined:1 ^ ReferenceError: require is not defined at eval at <anonymous> (node.js:762:36) at eval (native) at node.js:762:36 $ Here's a working example of using require() typed into the REPL: $ node > require("http"); { STATUS_CODES: { '100': 'Continue' , '101': 'Switching Protocols' , '102': 'Processing' , '200': 'OK' , '201': 'Created' , '202': 'Accepted' , '203': 'Non-Authoritative Information' , '204': 'No Content' , '205': 'Reset Content' , '206': 'Partial Content' , '207': 'Multi-Status' , '300': 'Multiple Choices' , '301': 'Moved Permanently' , '302': 'Moved Temporarily' , '303': 'See Other' , '304': 'Not Modified' , '305': 'Use Proxy' , '307': 'Temporary Redirect' , '400': 'Bad Request' , '401': 'Unauthorized' , '402': 'Payment Required' , '403': 'Forbidden' , '404': 'Not Found' , '405': 'Method Not Allowed' , '406': 'Not Acceptable' , '407': 'Proxy Authentication Required' , '408': 'Request Time-out' , '409': 'Conflict' , '410': 'Gone' , '411': 'Length Required' , '412': 'Precondition Failed' , '413': 'Request Entity Too Large' , '414': 'Request-URI Too Large' , '415': 'Unsupported Media Type' , '416': 'Requested Range Not Satisfiable' , '417': 'Expectation Failed' , '418': 'I\'m a teapot' , '422': 'Unprocessable Entity' , '423': 'Locked' , '424': 'Failed Dependency' , '425': 'Unordered Collection' , '426': 'Upgrade Required' , '500': 'Internal Server Error' , '501': 'Not Implemented' , '502': 'Bad Gateway' , '503': 'Service Unavailable' , '504': 'Gateway Time-out' , '505': 'HTTP Version not supported' , '506': 'Variant Also Negotiates' , '507': 'Insufficient Storage' , '509': 'Bandwidth Limit Exceeded' , '510': 'Not Extended' } , IncomingMessage: { [Function: IncomingMessage] super_: [Function: EventEmitter] } , OutgoingMessage: { [Function: OutgoingMessage] super_: [Function: EventEmitter] } , ServerResponse: { [Function: ServerResponse] super_: [Circular] } , ClientRequest: { [Function: ClientRequest] super_: [Circular] } , Server: { [Function: Server] super_: { [Function: Server] super_: [Function: EventEmitter] } } , createServer: [Function] , Client: { [Function: Client] super_: { [Function: Stream] super_: [Function: EventEmitter] } } , createClient: [Function] , cat: [Function] } > Is there a way to use require() with node's --eval? I'm on node 0.2.6 on Mac OS X 10.6.5.

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• Force calling the derived class implementation within a generic function in C#?

  - by Adam Hardy

  Ok so I'm currently working with a set of classes that I don't have control over in some pretty generic functions using these objects. Instead of writing literally tens of functions that essentially do the same thing for each class I decided to use a generic function instead. Now the classes I'm dealing with are a little weird in that the derived classes share many of the same properties but the base class that they are derived from doesn't. One such property example is .Parent which exists on a huge number of derived classes but not on the base class and it is this property that I need to use. For ease of understanding I've created a small example as follows: class StandardBaseClass {} // These are simulating the SMO objects class StandardDerivedClass : StandardBaseClass { public object Parent { get; set; } } static class Extensions { public static object GetParent(this StandardDerivedClass sdc) { return sdc.Parent; } public static object GetParent(this StandardBaseClass sbc) { throw new NotImplementedException("StandardBaseClass does not contain a property Parent"); } // This is the Generic function I'm trying to write and need the Parent property. public static void DoSomething<T>(T foo) where T : StandardBaseClass { object Parent = ((T)foo).GetParent(); } } In the above example calling DoSomething() will throw the NotImplemented Exception in the base class's implementation of GetParent(), even though I'm forcing the cast to T which is a StandardDerivedClass. This is contrary to other casting behaviour where by downcasting will force the use of the base class's implementation. I see this behaviour as a bug. Has anyone else out there encountered this?

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• Designing a database for a user/points system? (in Django)

  - by AP257

  First of all, sorry if this isn't an appropriate question for StackOverflow. I've tried to make it as generalisable as possible. I want to create a database (MySQL, site running Django) that has users, who can be allocated a certain number of points for various types of action - it's a collaborative game. My requirements are to obtain: the number of points a user has the user's ranking compared to all other users and the overall leaderboard (i.e. all users ranked in order of points) This is what I have so far, in my Django models.py file: class SiteUser(models.Model): name = models.CharField(max_length=250 ) email = models.EmailField(max_length=250 ) date_added = models.DateTimeField(auto_now_add=True) def points_total(self): points_added = PointsAdded.objects.filter(user=self) points_total = 0 for point in points_added: points_total += point.points return points_total class PointsAdded(models.Model): user = models.ForeignKey('SiteUser') action = models.ForeignKey('Action') date_added = models.DateTimeField(auto_now_add=True) def points(self): points = Action.objects.filter(action=self.action) return points class Action(models.Model): points = models.IntegerField() action = models.CharField(max_length=36) However it's rapidly becoming clear to me that it's actually quite complex (in Django query terms at least) to figure out the user's ranking and return the leaderboard of users. At least, I'm finding it tough. Is there a more elegant way to do something like this? This question seems to suggest that I shouldn't even have a separate points table - what do people think? It feels more robust to have separate tables, but I don't have much experience of database design.

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• In sync query calls, one query causing other query to run slower. Why?

  - by Irchi

  Sorry for the long question, but I think this is an interesting situation and I couldn't find any explanations for it: I was involved in optimization of an application that performed a large number of sequential SELECT and INSERT statements on a single dedicated SQL Server database. The process needs to INSERT a large number of records into a table, but for each of them there should be some value mappings, which performed using SELECT statements on another table in the same database. For a specific execution, it took 90 minutes to run. I used a profiler (JProfiler - the application is Java-based) to determine how much time does each part of the application take. It yields that 60% of the time was spent on INSERT method calls, and almost 20% on SELECT calls (the rest distributed in other parts). After some trials, I came to this situation: I commented out the INSERT query that took 60% of the time. I was expecting for the total run time to be around 35 minutes, as I have removed 60% of the 90 minutes. But the whole process took the same 90 minutes (doing only SELECTs and nothing else), but each SELECT took longer this time! Everything was running sync, there were no async calls. And there was only one single thread of execution. SELECT and INSERT queries are very simple, and don't have anything special, and they are on different tables, but on the same DB. I tested with both the DB on the application machine, and on a remote network machine. I can't think of any explanation for this, as the Profiler (Application profiler, not SQL Profiler) reported the changes in the method call times, and by removing INSERT statements SELECT statements took longer to run. Can anyone give me some kind of explanation of what could have happened? (there can't be cache / query optimization stuff, because the queries were run in sync, and in a single thread, and it was far from affecting the cache this much) I should note that the bottleneck of the speed was in SQL server, using most of the CPU time.

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• Strange behavior when overloading methods in Java

  - by Sep

  I came across this weird (in my opinion) behavior today. Take this simple Test class: public class Test { public static void main(String[] args) { Test t = new Test(); t.run(); } private void run() { List<Object> list = new ArrayList<Object>(); list.add(new Object()); list.add(new Object()); method(list); } public void method(Object o) { System.out.println("Object"); } public void method(List<Object> o) { System.out.println("List of Objects"); } } It behaves the way you expect, printing "List of Objects". But if you change the following three lines: List<String> list = new ArrayList<String>(); list.add(""); list.add(""); you will get "Object" instead. I tried this a few other ways and got the same result. Is this a bug or is it a normal behavior? And if it is normal, can someone explain why? Thanks.

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• Saving Data to Relational Database (Entity Framework)

  - by sheefy

  I'm having a little bit of trouble saving data to a database. Basically, I have a main table that has associations to other tables (Example Below). Tbl_Listing ID UserID - Associated to ID in User Table CategoryID - Associated to ID in Category Table LevelID - Associated to ID in Level Table. Name Address Normally, it's easy for me to add data to the DB (using Entity Framework). However, I'm not sure how to add data to the fields with associations. The numerous ID fields just need to hold an int value that corresponds with the ID in the associated table. For example; when I try to access the column in the following manner I get a "Object reference not set to an instance of an object." error. Listing NewListing = new Listing(); NewListing.Tbl_User.ID = 1; NewListing.Tbl_Category.ID = 2; ... DBEntities.AddToListingSet(NewListing); DBEntities.SaveChanges(); I am using NewListing.Tbl_User.ID instead of NewListing.UserID because the UserID field is not available through intellisense. If I try and create an object for each related field I get a "The relationship between the two objects cannot be defined because they are attached to different ObjectContext objects." error. With this method, I am trying to add the object without the .ID shown above - example NewListing.User = UserObject. I know this should be simple as I just want to reference the ID from the associated table in the main Listing's table. Any help would be greatly appreciated. Thanks in advance, -S

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• Change object on client side or on server side

  - by Polina Feterman

  I'm not sure what is the best practice. I have some big and complex objects (NOT flat). In that object I have many related objects - for example Invoice is the main class and one of it's properties is invoiceSupervisor - a big class by it's own called User. User can also be not flat and have department property - also an object called Department. For example I want create new Invoice. First way: I can present to client several fields to fill in. Some of them will be combos that I will need to fill with available values. For example available invoiceSupervisors. Then all the chosen values I can send to server and on server I can create new Invoice and assign all chosen values to that new Invoice. Then I will need to assign new supervisor I will pull the chosen User by id that user picked up on server from combobox. I might do some verification on the User such as does the user applicable to be invoice supervisor. Then I will assign the User object to invoiceSupervisor. Then after filling all properties I will save the new invoice. Second way: In the beginning I can call to server to get a new Invoice. Then on client I can fill all chosen values , for example I can call to server to get new User object and then fill it's id from combobox and assign the User as invoiceSupervisor. After filling the Invoice object on client I can send it to server and then the server will save the new invoice. Before saving server can run some validations as well. So what is the best approach - to make the object on client and send it to server or to collect all values from client and to make a new object on server using those values ?

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• Forcing size of a complex Flash object.

  - by John

  As I've found recently, setting width/height properties on a Sprite only forces the Sprite to fit the given dimensions by scaling the actual size, which is calculated by Flash based on the rendered content. This leaves me confused. If I have a custom Sprite subclass which draws using Graphics, how can I do layout before an initial render - the size will be zero until it is first drawn? For a more complex issue, let's say I have a 2D game world with objects spread over a wide area with world coordinates from (0,0) to (5000,5000), where each object has a size of maybe up to 100x100. I want to have a Flash component which is the "game window", and has a fixed size like 400x300, rendering part of the game world. So how do I force the game window size to 400x300 pixels? I can draw a 400x300 rectangle to get the size correct but then if I draw any objects which are partly in-view, they can screw this up. Is the right approach to provide a custom setSize(w,h) method which is used rather than width & height setters? But even so, is there no way to make a Sprite force to the size I want? Do you really have to catch it every render and re-scale it?

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• Building a calendar navigation in Rails (controller and view links)

  - by user532339

  Trying to get the next month when clicking the link_to. I've done the following in the view. <%= form_tag rota_days_path, :method => 'get' do %> <p> <%= hidden_field_tag(:next_month, @t1) %> <%= link_to 'Next Month', rota_days_path(:next_month => @next_month)%> </p> <% end %> class RotaDaysController < ApplicationController # GET /rota_days # GET /rota_days.json # load_and_authorize_resource respond_to :json, :html def index @rota_days = RotaDay.all @hospitals = Hospital.all @t1 = Date.today.at_beginning_of_month @t2 = Date.today.end_of_month @dates = (@t1..@t2) #Concat variable t1 + t2 together # @next_month = Date.today + 1.month(params[: ??? ] #Old if params[:next_month] # @next_month = Date.today >> 1 @next_month = params[:next_month] + 1.month @t1 = @next_month.at_beginning_of_month @t2 = @next_month.end_of_month @dates = (@t1..@t2) end @title = "Rota" respond_to do |format| format.html # index.html.erb format.json { render json: @rota_days } end end I have identified that the reason why this may not be working is in because of the following in my controller @next_month = params[:next_month] + 1.month the last two called methods is defined only on time/date objects. but not on fixnum/string objects. I understand I am missing something from this Update I have found that the actual issue is that the `params[:next_month] is a string and I am trying to add a date to to it. Which means I need to convert the string to a date/time object. Console output: Started GET "/rota_days" for 127.0.0.1 at 2012-12-14 22:14:36 +0000 Processing by RotaDaysController#index as HTML User Load (0.0ms) SELECT `users`.* FROM `users` WHERE `users`.`id` = 1 LIMIT 1 RotaDay Load (0.0ms) SELECT `rota_days`.* FROM `rota_days` Hospital Load (1.0ms) SELECT `hospitals`.* FROM `hospitals` Rendered rota_days/index.html.erb within layouts/application (23.0ms) Role Load (0.0ms) SELECT `roles`.* FROM `roles` INNER JOIN `roles_users` ON `roles`.`id` = `roles_users`.`role_id` WHERE `roles_users`.`user_id` = 1 AND `roles`.`name` = 'Administrator' LIMIT 1 Completed 200 OK in 42ms (Views: 39.0ms | ActiveRecord: 1.0ms)

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• Django - Problem with models/manager to organise a query...

  - by user296644

  Hi, I have an application to count the number of access to an object for each website in a same database. class SimpleHit(models.Model): """ Hit is the hit counter of a given object """ content_type = models.ForeignKey(ContentType) object_id = models.PositiveIntegerField() content_object = generic.GenericForeignKey('content_type', 'object_id') site = models.ForeignKey(Site) hits_total = models.PositiveIntegerField(default=0, blank=True) [...] class SimpleHitManager(models.Manager): def get_query_set(self): print self.model._meta.fields qset = super(SimpleHitManager, self).get_query_set() qset = qset.filter(hits__site=settings.SITE_ID) return qset class SimpleHitBase(models.Model): hits = generic.GenericRelation(SimpleHit) objects = SimpleHitManager() _hits = None def _db_get_hits(self, only=None): if self._hits == None: try: self._hits = self.hits.get(site=settings.SITE_ID) except SimpleHit.DoesNotExist: self._hits = SimpleHit() return self._hits @property def hits_total(self): return self._db_get_hits().hits_total [...] class Meta: abstract = True And I have a model like: class Model(SimpleHitBase): name = models.CharField(max_length=255) url = models.CharField(max_length=255) rss = models.CharField(max_length=255) creation = AutoNowAddDateTimeField() update = AutoNowDateTimeField() So, my problem is this one: when I call Model.objects.all(), I would like to have one request for the SQL (not two). In this case: one for Model in order to have information and one for the hits in order to have the counter (hits_total). This is because I cannot call directly hits.hits_total (due to SITE_ID?). I have tried select_related, but it seems to do not work... Question: - How can I add column automatically like (SELECT hits.hits_total, model.* FROM [...]) to the queryset? - Or use a functional select_related with my models? I want this model could be plugable on all other existing model. Thank you, Best regards.

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• Why is it possible to enumerate a LinqToSql query after calling Dispose() on the DataContext?

  - by DanM

  I'm using the Repository Pattern with some LinqToSql objects. My repository objects all implement IDisposable, and the Dispose() method does only thing--calls Dispose() on the DataContext. Whenever I use a repository, I wrap it in a using person, like this: public IEnumerable<Person> SelectPersons() { using (var repository = _repositorySource.GetNew<Person>(dc => dc.Person)) { return repository.GetAll(); } } This method returns an IEnumerable<Person>, so if my understanding is correct, no querying of the database actually takes place until Enumerable<Person> is traversed (e.g., by converting it to a list or array or by using it in a foreach loop), as in this example: var persons = gateway.SelectPersons(); // Dispose() is fired here var personViewModels = ( from b in persons select new PersonViewModel { Id = b.Id, Name = b.Name, Age = b.Age, OrdersCount = b.Order.Count() }).ToList(); // executes queries In this example, Dispose() gets called immediately after setting persons, which is an IEnumerable<Person>, and that's the only time it gets called. So, a couple questions: How does this work? How can a disposed DataContext still query the database for results when I walk the IEnumerable<Person>? What does Dispose() actually do? I've heard that it is not necessary (e.g., see this question) to dispose of a DataContext, but my impression was that it's not a bad idea. Is there any reason not to dispose of it?

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• ANDROID SAX Parser issue

  - by Chris Watson

  Since I am new to java programming, I need a bit of help with this. I stuck on this one issue and can't continue until I get this to work. I am trying to make a string from that includes a preference int. I saved the data and can display the int (just sample code): SharedPreferences prefs=PreferenceManager .getDefaultSharedPreferences(this); list.setText(prefs.getString("list", "22")); now, I have a xml parser that is pulling a url correctly as a static string: public static String feedUrl = String.format("http://www.freshpointmarketing.com/iphone/objects/XML/AND.php?ID=%d", 22); Works great... now my issue...... I need to have the preference "int" become the variable in the string, thus making it not static. static SharedPreferences prefs=PreferenceManager.getDefaultSharedPreferences(this); static int myVariable = prefs.getInt("list1", 22); public static String feedUrl = String.format("http://www.freshpointmarketing.com/iphone/objects/XML/AND.php?ID=%d", myVariable); If I take out all static references, I get an error on this: private void loadFeed(ParserType type){ try{ FeedParser parser = FeedParserFactory.getParser(type); long start = System.currentTimeMillis(); messages = parser.parse(); long duration = System.currentTimeMillis() - start; Log.i("AndroidNews", "Parser duration=" + duration); String xml = writeXml(); Log.i("AndroidNews", xml); List<String> titles = new ArrayList<String>(messages.size()); for (Message msg : messages){ titles.add(msg.getTitle()); } ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, R.layout.row,titles); this.setListAdapter(adapter); } catch (Throwable t){ Log.e("AndroidNews",t.getMessage(),t); } } thanks

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• c# How to implement a collection of generics

  - by Amy

  I have a worker class that does stuff with a collection of objects. I need each of those objects to have two properties, one has an unknown type and one has to be a number. I wanted to use an interface so that I could have multiple item classes that allowed for other properties but were forced to have the PropA and PropB that the worker class requires. This is the code I have so far, which seemed to be OK until I tried to use it. A list of MyItem is not allowed to be passed as a list of IItem even though MyItem implements IItem. This is where I got confused. Also, if possible, it would be great if when instantiating the worker class I don't need to pass in the T, instead it would know what T is based on the type of PropA. Can someone help get me sorted out? Thanks! public interface IItem<T> { T PropA { get; set; } decimal PropB { get; set; } } public class MyItem : IItem<string> { public string PropA { get; set; } public decimal PropB { get; set; } } public class WorkerClass<T> { private List<T> _list; public WorkerClass(IEnumerable<IItem<T>> items) { doStuff(items); } public T ReturnAnItem() { return _list[0]; } private void doStuff(IEnumerable<IItem<T>> items) { foreach (IItem<T> item in items) { _list.Add(item.PropA); } } } public void usage() { IEnumerable<MyItem> list= GetItems(); var worker = new WorkerClass<string>(list);//Not Allowed }

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• Hibernate Relationship Mapping/Speed up batch inserts

  - by manyxcxi

  I have 5 MySQL InnoDB tables: Test,InputInvoice,InputLine,OutputInvoice,OutputLine and each is mapped and functioning in Hibernate. I have played with using StatelessSession/Session, and JDBC batch size. I have removed any generator classes to let MySQL handle the id generation- but it is still performing quite slow. Each of those tables is represented in a java class, and mapped in hibernate accordingly. Currently when it comes time to write the data out, I loop through the objects and do a session.save(Object) or session.insert(Object) if I'm using StatelessSession. I also do a flush and clear (when using Session) when my line count reaches the max jdbc batch size (50). Would it be faster if I had these in a 'parent' class that held the objects and did a session.save(master) instead of each one? If I had them in a master/container class, how would I map that in hibernate to reflect the relationship? The container class wouldn't actually be a table of it's own, but a relationship all based on two indexes run_id (int) and line (int). Another direction would be: How do I get Hibernate to do a multi-row insert?

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• reverse many to many fields in Django + count them

  - by cleliodpaula

  I'm trying to figure out how to solve this class Item(models.Model): type = models.ForeignKey(Type) name = models.CharField(max_lenght = 10) ... class List(models.Model): items = models.ManyToManyField(Item) ... I want to count how many an Item appears in another Lists, and show on template. view def items_by_list(request, id_): list = List.objects.get(id = id_) qr = list.items.all() #NOT TESTED num = [] i = 0 for item in qr: num[i] = List.objects.filter(items__id = item__id ).count() #FINISH NOT TESTED c = {} c.update(csrf(request)) c = {'request':request, 'list' : qr, 'num' : num} return render_to_response('items_by_list.html', c, context_instance=RequestContext(request)) template {% for dia in list %} <div class="span4" > <div> <h6 style="color: #9937d8">{{item.type.description}}</h6> <small style="color: #b2e300">{{ item.name }}</small> <small style="color: #b2e300">{{COUNT HOW MANY TIMES THE ITEM APPEAR ON OTHER LISTS}}</small> </div> {% endfor %} This seems to be easy, but I could not implement yet. If anyone has some glue to me, please help me. Thanks in advance.

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• How to get a specific attribute from an object list?

  - by anarhikos

  I've an array keeping a list of Group objects. I want to set this list to the DropDownChoice component. However I want to show the end user only the name attribute of Group objects, and then get the selected values' id attribute to add database. What to do? private List<Group> groupTypes; DatabaseApp db = new DatabaseApp(); groupTypes = db.getGroups(); groupDropDownChoice = new DropDownChoice("type", groupTypes); ... ... addUserForm.add(new Button("submit"){ @Override public void onSubmit(){ Group group = (Group) groupDropDownChoice.getModelObject(); ... ... db.addUser(group.getId(), den, name, login, email, password1); DatabaseApp.java public List<Group> getGroups() throws SQLException{ List<Group> groups = new ArrayList<Group>(); try { String query = "SELECT * FROM [GROUP]"; Statement statement = db.createStatement(); ResultSet result = statement.executeQuery(query); while(result.next()){ int id = result.getInt("ID"); String name = result.getString("NAME"); groups.add(new Group(id, name)); } result.close(); } catch (SQLException ex) { throw new SQLException(ex.getMessage()); } return groups; }

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• Could git do not store history of specific folders when working with git-svn?

  - by Timofey Basanov

  In short: Is there a way to disable storing full history for specific folders in git-svn repo? We have pretty large SVN repo with big checkout. I would like to migrate it to Git for my local development, because Git speeds up update and status commands orders of magnitude. When I simply do git svn clone it creates very big repo. Big enough to be bigger then my whole HDD. The problem lies in binary directories for which history is too large. Latest binaries are required for proper local build, but history is not required at all for my development process. I will never change them myself. I would like to store only latest versions for specific folders, or may be a history, but for no more than a week. I could only found filter for git svn fetch, which excludes specific folders at all. This is not exactly what I need. It's OK with me to have Cron task which deletes history from specific folders, but I do not know how to make one. Also Cron does not solve problem of first git svn clone. P.S. SVN repository structure could not be changed by any means.

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• C# / this. and List<T>

  - by user3533030

  I am having trouble understanding how to initialize a List of objects and use it with methods inside of a class. I understand the mechanics of the List, but not how to initialize it inside a method and use it later. For example, I want to have a class that creates the List when it is constructed. Then, I want to use a method of that class to add elements to the list. The elements in the list are objects defined by the SolidWorks API. So, to construct the List, I used... public class ExportPoints : Exporter { public List<SldWorks.SketchPoint> listOfSketchPoints; public ExportPoints(SldWorks.SldWorks swApp, string nameSuffix) : base(swApp, nameSuffix) { List<SldWorks.SketchPoint> listOfSketchPoints = new List<SldWorks.SketchPoint>(); } public void createListOfFreePoints() { try { [imagine more code here] this.listOfSketchPoints.Add(pointTest); } catch (Exception e) { Debug.Print(e.ToString()); return; } } This fails during execution as if the listOfSketchPoints was never initialized as a List. So, I tried a hack and this worked: public ExportPoints(SldWorks.SldWorks swApp, string nameSuffix) : base(swApp, nameSuffix) { List<SldWorks.SketchPoint> listOfSketchPoints = new List<SldWorks.SketchPoint>(); this.listOfSketchPoints = listOfSketchPoints; } This approach creates the behavior that I want. However, it seems that I lack some understanding as to why this is necessary. Shouldn't it be possible to "initialize" a List that is a property of your object with a constructor? Why would you need to create the list, then assign the pointer of that new List to your property?

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• Replacing text with variables

  - by Steve

  I have to send out letters to certain clients and I have a standard letter that I need to use. I want to replace some of the text inside the body of the message with variables. Here is my maturity_letter models.py class MaturityLetter(models.Model): default = models.BooleanField(default=False, blank=True) body = models.TextField(blank=True) footer = models.TextField(blank=True) Now the body has a value of this: Dear [primary-firstname], AN IMPORTANT REMINDER… You have a [product] that is maturing on [maturity_date] with [financial institution]. etc Now I would like to replace everything in brackets with my template variables. This is what I have in my views.py so far: context = {} if request.POST: start_form = MaturityLetterSetupForm(request.POST) if start_form.is_valid(): agent = request.session['agent'] start_date = start_form.cleaned_data['start_date'] end_date = start_form.cleaned_data['end_date'] investments = Investment.objects.all().filter(maturity_date__range=(start_date, end_date), plan__profile__agent=agent).order_by('maturity_date') inv_form = MaturityLetterInvestments(investments, request.POST) if inv_form.is_valid(): sel_inv = inv_form.cleaned_data['investments'] context['sel_inv'] = sel_inv maturity_letter = MaturityLetter.objects.get(id=1) context['mat_letter'] = maturity_letter context['inv_form'] = inv_form context['agent'] = agent context['show_report'] = True Now if I loop through the sel_inv I get access to sel_inv.maturity_date, etc but I am lost in how to replace the text. On my template, all I have so far is: {% if show_letter %} {{ mat_letter.body }} <br/> {{ mat_letter.footer }} {% endif %} Much appreciated.

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