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• Unit Testing in the real world

  - by Malfist

  I manage a rather large application (50k+ lines of code) by myself, and it manages some rather critical business actions. To describe the program simple, I would say it's a fancy UI with the ability to display and change data from the database, and it's managing around 1,000 rental units, and about 3k tenants and all the finances. When I make changes, because it's so large of a code base, I sometimes break something somewhere else. I typically test it by going though the stuff I changed at the functional level (i.e. I run the program and work through the UI), but I can't test for every situation. That is why I want to get started with unit testing. However, this isn't a true, three tier program with a database tier, a business tier, and a UI tier. A lot of the business logic is performed in the UI classes, and many things are done on events. To complicate things, everything is database driven, and I've not seen (so far) good suggestions on how to unit test database interactions. How would be a good way to get started with unit testing for this application. Keep in mind. I've never done unit testing or TDD before. Should I rewrite it to remove the business logic from the UI classes (a lot of work)? Or is there a better way?

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• Types issue in F#

  - by Andry

  Hello! In my ongoing adventure deep diving into f# I am understanding a lot of this powerful language but there are things that I still do not understand so clearly. One of the most important issues I need to master is types. Well the book I am reading is very straight forward and introduces entities and main functionalities with a direct approach. The first thing I could get start with is types. It introduces the main types as list, option, tuples, and so on... It is clearly underlined that all these types are IMMUTABLE for many reasons regarding functional programming and data consistance in functional programing. Well, no problems until now... But now I am getting started with Concrete Types... Well... I have problems in managing with types like list, option, tuples, types created through new operator and concrete types created using type keyword (for abbreviations, concrete types...). So my question is: how can I efficently catalogue/distinguish all types of data in f#???? I can create a perfect separation among types in C#, VB.NET... FOr example in VB.NET there are value and reference types while in C# there are only references and also int, double are treated as objects (they are objects while in VB.NET a value type is not a object and there is a split in types for this reason). Well in F# I cannot create such differences among types in the language. Can you help me? I hope I was clear.

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• Yaml::load_file acting different between development and production (Rails)

  - by James

  Hi, I am completely stumped at the nature of this problem. We export data from our application into a 'cleaned' YAML file (stripping out IDs, created_at etc). Then we (will) allow users to import these files back into the application - it is the import that is completely bugging me out. In development, YAML::load_file(params[:uploaded_data].local_path) returns an array of YAML::Objects's (and it doesn't matter which of the number of different ways the file could be loaded): [#{"exception_count"="0", "title"="Start", "amount"="70.00", "colour"=nil, "repeat_type_id"="0", "repeat_interval"="1"}}, etc etc] Which is very nice, as the attributes also include the (associated model) exceptions that you see an exception_count for. However on production (rails 2.3.2, running REE 1.8.7 and 1.8.6 for testing, tested on two different production env's, and running production locally) it returns an array of the Objects within the YAML - in this case, Event: [#, repeat_type_id: 0, colour: nil, repeat_interval: 1, exception_count: 0, etc etc] Now this would be just perplexing if it also included the associated model Exception with it - however it doesn't. Can anyone at all shed some light on why the Yaml parser would behave so differently between production and development? I'm on rails 2.3.2, running REE 1.8.7; however I've also tested running Ruby 1.8.6 with exactly the same results. Thanks for any help!

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• [Cocoa] Can't find leak in my code.

  - by ryyst

  Hi, I've been spending the last few hours trying to find the memory leak in my code. Here it is: NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; expression = [expression stringByTrimmingCharactersInSet: [NSCharacterSet whitespaceAndNewlineCharacterSet]]; // expression is an NSString object. NSArray *arguments = [NSArray arrayWithObjects:expression, [@"~/Desktop/file.txt" stringByExpandingTildeInPath], @"-n", @"--line-number", nil]; NSPipe *outPipe = [[NSPipe alloc] init]; NSTask *task = [[NSTask alloc] init]; [task setLaunchPath:@"/usr/bin/grep"]; [task setArguments:arguments]; [task setStandardOutput:outPipe]; [outPipe release]; [task launch]; NSData *data = [[outPipe fileHandleForReading] readDataToEndOfFile]; [task waitUntilExit]; [task release]; NSString *string = [[NSString alloc] initWithBytes:[data bytes] length:[data length] encoding:NSUTF8StringEncoding]; string = [string stringByReplacingOccurrencesOfString:@"\r" withString:@""]; int linesNum = 0; NSMutableArray *possibleMatches = [[NSMutableArray alloc] init]; if ([string length] > 0) { NSArray *lines = [string componentsSeparatedByString:@"\n"]; linesNum = [lines count]; for (int i = 0; i < [lines count]; i++) { NSString *currentLine = [lines objectAtIndex:i]; NSArray *values = [currentLine componentsSeparatedByString:@"\t"]; if ([values count] == 20) [possibleMatches addObject:currentLine]; } } [string release]; [pool release]; return [possibleMatches autorelease]; I tried to follow the few basic rules of Cocoa memory management, but somehow there still seems to be a leak, I believe it's an array that's leaking. It's noticeable if possibleMatches is large. You can try the code by using any large file as "~/Desktop/file.txt" and as expression something that yields many results when grep-ing. What's the mistake I'm making? Thanks for any help! -- Ry

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• Getter and Setter vs. Builder strategy

  - by Extrakun

  I was reading a JavaWorld's article on Getter and Setter where the basic premise is that getters expose internal content of an object, hence tightening coupling, and go on to provide examples using builder objects. I was rather leery of abolishing getter/setter but on second reading of the article, see to quite like the idea. However, sometimes I just need one cruical element of an entity class, such as the user's id and writing one whole class just to extract that cruical element seems like overkill. It also implies that for different view, a different type of importer/exporter must be implemented (or the whole data of the class to be exported out, thus resulting in waste). Usually I tend towards filtering the result of a getter - for example, if I need to output the price of a product in different currency, I would code it as: return CurrencyOutput::convertTo($product->price(), 'USD'); This is with the understanding that the raw output of a getter is not necessary the final result to be pushed onto a screen or a database. Is getter/setter really as bad as it is protrayed to be? When should one adopt a builder strategy, or a 'get the result and filter it' approach? How do you avoid having a class needing to know about every other objects if you are not using getter/setter?

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• Good patterns for loose coupling in Java?

  - by Eye of Hell

  Hello. I'm new to java, and while reading documentation so far i can't find any good ways for programming with loose coupling between objects. For majority of languages i know (C++, C#, python, javascript) i can manage objects as having 'signals' (notification about something happens/something needed) and 'slots' (method that can be connected to signal and process notification/do some work). In all mentioned languages i can write something like this: Object1 = new Object1Class(); Object2 = new Object2Class(); Connect( Object1.ItemAdded, Object2.OnItemAdded ); Now if object1 calls/emits ItemAdded, the OnItemAdded method of Object2 will be called. Such loose coupling technique is often referred as 'delegates', 'signal-slot' or 'inversion of control'. Compared to interface pattern, technique mentioned don't need to group signals into some interfaces. Any object's methods can be connected to any delegate as long as signatures match ( C++Qt even extends this by allowing only partial signature match ). So i don't need to write additional interface code for each methods / groups of methods, provide default implementation for interface methods not used etc. And i can't see anything like this in Java :(. Maybe i'm looking a wrong way?

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• unable to find a MessageBodyReader

  - by Cristian Boariu

  Hi guys, I have this interface: @Path("inbox") public interface InboxQueryResourceTest { @POST @Path("{membershipExternalId}/query") @Consumes(MediaType.APPLICATION_XML) @Produces("multipart/mixed") public MultipartOutput query(@PathParam("membershipExternalId") final String membershipExternalId, @QueryParam("page") @DefaultValue("0") final int page, @QueryParam("pageSize") @DefaultValue("10") final int pageSize, @QueryParam("sortProperty") final List<String> sortPropertyList, @QueryParam("sortReversed") final List<Boolean> sortReversed, @QueryParam("sortType") final List<String> sortTypeString, final InstanceQuery instanceQuery) throws IOException; } I have implemented the method to return a MultipartOutput. I am posting an xml query from Fiddler and i receive the result without any problem. BUT i have done an integration test for the same interface, i send the same objects and i put the response like: final MultipartOutput multiPartOutput = getClient().query(getUserRestAuth(), 0, 25, null, null, null, instanceQuery); But here, so from integration tests, i receive a strange error: Unable to find a MessageBodyReader of content-type multipart/mixed;boundary="74c5b6b4-e820-452d-abea-4c56ffb514bb" and type class org.jboss.resteasy.plugins.providers.multipart.MultipartOutput Anyone has any ideea why only in integration tests i receive this error? PS: Some of you will say that i do not send application/xml as ContentType but multipart, which of course is false because the objects are annotated with the required @XmlRootElement etc, otherways neither the POST from Fiddler would work.

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• How to mimic built-in .NET serialization idioms?

  - by Matt Enright

  I have a library (written in C#) for which I need to read/write representations of my objects to disk (or to any Stream) in a particular binary format (to ensure compatibility with C/Java library implementations). The format requires a fair amount of bit-packing and some DEFLATE'd bytestreams. I would like my library, however, to be as idiomatic .NET as possible, however, and so would like to provide an API as close as possible to the normal binary serialization process. I'm aware of the ability to implement the IFormatter interface, but being that I really am unable to reuse any part of the built-in serialization stack, is it worth doing this, or will it just bring unnecessary overhead. In other words: Implement IFormatter and co. OR Just provide "Serialize"/"Deserialize" methods that act on a Stream? A good point brought up below about needing the serialization semantics for any case involving Remoting. In a case where using MarshalByRef objects is feasible, I'm pretty sure that this won't be an issue, so leaving that aside are there any benefits or drawbacks to using the ISerializable/IFormatter versus a custom stack (or, is my understanding remoting incorrectly)?

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• Sorting an XML in Java

  - by Java Guy

  Hello I have an XML similiar to below, which needed to be sorted using the date field. <root> <Node1><date></date></Node1> <Node1><date></date></Node1> <Node1> <date></date></Node1> <Node1> <date></date></Node1> <Node2> <date></date></Node2> <Node2> <date></date></Node2> <Node2> <date></date></Node2> <Node2> <date></date> </Node2> </root> I would like to sort the XML based on the date(say asc order), irrespective of whether the date is under Node1 or Node2. Actually in Java code I have two seperate lists, one with Node1 objects and other with Node2 obects. I can sort the list in any order sperately inside java. But I need to have the dates sorted irrespective of the nodes it is apperaing on the XML. What is the best approach to sort this way in Java? Actaully I am using Castor for marshalling the java objects to XML. If you know this can be done with Castor, that will be great!

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• How to maintain an ordered table with Core Data (or SQL) with insertions/deletions?

  - by Jean-Denis Muys

  This question is in the context of Core Data, but if I am not mistaken, it applies equally well to a more general SQL case. I want to maintain an ordered table using Core Data, with the possibility for the user to: reorder rows insert new lines anywhere delete any existing line What's the best data model to do that? I can see two ways: 1) Model it as an array: I add an int position property to my entity 2) Model it as a linked list: I add two one-to-one relations, next and previous from my entity to itself 1) makes it easy to sort, but painful to insert or delete as you then have to update the position of all objects that come after 2) makes it easy to insert or delete, but very difficult to sort. In fact, I don't think I know how to express a Sort Descriptor (SQL ORDER BY clause) for that case. Now I can imagine a variation on 1): 3) add an int ordering property to the entity, but instead of having it count one-by-one, have it count 100 by 100 (for example). Then inserting is as simple as finding any number between the ordering of the previous and next existing objects. The expensive renumbering only has to occur when the 100 holes have been filled. Making that property a float rather than an int makes it even better: it's almost always possible to find a new float midway between two floats. Am I on the right track with solution 3), or is there something smarter?

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• Android Hashtable Serialization

  - by Nsyed

  Hi All, I am having a weird issue with serialization of a Hashtable. I have made a Server, Client app. Where server(PC/MAC) is serializing a Hashtable and sending it to Client(Android) through UDP. The data is sent/read correctly but I get a bunch of these messages below on LogCat. 04-12 11:19:43.059: DEBUG/dalvikvm(407): GetFieldID: unable to find field Ljava/util/Hashtable;.loadFactor:F Occasionally, I would see these 04-12 11:21:19.150: DEBUG/dalvikvm(407): GC freed 10814 objects / 447184 bytes in 97ms The app would run for 2-3 mins and then crash. Interestingly enough I do not see the Loadfactor errors on SDK 1.5. But I do see the GC Free xxxx objects, quiet often. After debugging I have found that the issue is with de-serialization and the error/warning are coming from following code Code: ByteArrayInputStream bis = new ByteArrayInputStream(bytes); ObjectInputStream ois = new ObjectInputStream(bis); object = ois.readObject(); at Code: object = ois.readObject(); on the client. My server is serializing code is the following. Code: ByteArrayOutputStream bos = new ByteArrayOutputStream(); ObjectOutputStream oos = new ObjectOutputStream(bos); oos.writeObject(obj); Any idea what is going on? Thanks for the Help!

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• How to avoid loading a LINQ to SQL object twice when editting it on a website.

  - by emzero

  Hi guys I know you are all tired of this Linq-to-Sql questions, but I'm barely starting to use it (never used an ORM before) and I've already find some "ugly" things. I'm pretty used to ASP.NET Webforms old school developing, but I want to leave that behind and learn the new stuff (I've just started to read a ASP.NET MVC book and a .NET 3.5/4.0 one). So here's is one thing I didn't like and I couldn't find a good alternative to it. In most examples of editing a LINQ object I've seen the object is loaded (hitting the db) at first to fill the current values on the form page. Then, the user modify some fields and when the "Save" button is clicked, the object is loaded for second time and then updated. Here's a simplified example of ScottGu NerdDinner site. // // GET: /Dinners/Edit/5 [Authorize] public ActionResult Edit(int id) { Dinner dinner = dinnerRepository.GetDinner(id); return View(new DinnerFormViewModel(dinner)); } // // POST: /Dinners/Edit/5 [AcceptVerbs(HttpVerbs.Post), Authorize] public ActionResult Edit(int id, FormCollection collection) { Dinner dinner = dinnerRepository.GetDinner(id); UpdateModel(dinner); dinnerRepository.Save(); return RedirectToAction("Details", new { id=dinner.DinnerID }); } As you can see the dinner object is loaded two times for every modification. Unless I'm missing something about LINQ to SQL caching the last queried objects or something like that I don't like getting it twice when it should be retrieved only one time, modified and then comitted back to the database. So again, am I really missing something? Or is it really hitting the database twice (in the example above it won't harm, but there could be cases that getting an object or set of objects could be heavy stuff). If so, what alternative do you think is the best to avoid double-loading the object? Thank you so much, Greetings!

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• DataTable vs. Collection in .Net

  - by B Pete

  I am writing a program that needs to read a set of records that describe the register map of a device I need to communicate with. Each record will have a handfull of fields that describe the properties of each register. I don't really need to edit or modify the data in my VB or C# program, though I would like to be able to display the data on a grid. I would like to store the data in a CSV file, or perhaps an XML file. I need to enable users to edit the data off-line, preferably in excel. I am considering using a DataTable or a Collection of "Register" objects (which I would define). I prototyped a DataTable, and found I can read/write XML easily using the built in methods and I can easily bind to a DataGridView. I was not able to find a way to retreive info on a single register without using a query that returns a collection of rows, even though I defined a unique primaty key column. The syntax to get a value from a column is also complex, though I could be missing something on both counts. I'm tempted to use a collection of "Register" objects that I can access via a unique key. It would be a little more coding up front, but seems like a cleaner solution overall. I should still be able to use LINQ to dataset to query subsets of registers when I need them, but would also be able to grab a single field using a the key value, something like this: Registers(keyValue).fieldName). Which would be a cleaner approach to the problem? Is there a way to read/write XML into a Collection without needing custom code? Could this be accomplished using String for a key?

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• Problem with JMX query of Coherence node MBeans visible in JConsole

  - by Quinn Taylor

  I'm using JMX to build a custom tool for monitoring remote Coherence clusters at work. I'm able to connect just fine and query MBeans directly, and I've acquired nearly all the information I need. However, I've run into a snag when trying to query MBeans for specific caches within a cluster, which is where I can find stats about total number of gets/puts, average time for each, etc. The MBeans I'm trying to access programatically are visible when I connect to the remote process using JConsole, and have names like this: Coherence:type=Cache,service=SequenceQueue,name=SEQ%GENERATOR,nodeId=1,tier=back It would make it more flexible if I can dynamically grab all type=Cache MBeans for a particular node ID without specifying all the caches. I'm trying to query them like this: QueryExp specifiedNodeId = Query.eq(Query.attr("nodeId"), Query.value(nodeId)); QueryExp typeIsCache = Query.eq(Query.attr("type"), Query.value("Cache")); QueryExp cacheNodes = Query.and(specifiedNodeId, typeIsCache); ObjectName coherence = new ObjectName("Coherence:*"); Set<ObjectName> cacheMBeans = mBeanServer.queryMBeans(coherence, cacheNodes); However, regardless of whether I use queryMBeans() or queryNames(), the query returns a Set containing... ...0 objects if I pass the arguments shown above ...0 objects if I pass null for the first argument ...all MBeans in the Coherence:* domain (112) if I pass null for the second argument ...every single MBean (128) if I pass null for both arguments The first two results are the unexpected ones, and suggest a problem in the QueryExp I'm passing, but I can't figure out what the problem is. I even tried just passing typeIsCache or specifiedNodeId for the second parameter (with either coherence or null as the first parameter) and I always get 0 results. I'm pretty green with JMX — any insight on what the problem is? (FYI, the monitoring tool will be run on Java 5, so things like JMX 2.0 won't help me at this point.)

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• Can a function return an object? Objective-C and NSMutableArray

  - by seaworthy

  I have an NSMutableArray. It's members eventually become members of an array instance in a class. I want to put the instantiantion of NSMutable into a function and to return an array object. If I can do this, I can make some of my code easier to read. Is this possible? Here is what I am trying to figure out. //Definition: > function Objects (float a, float b) { > NSMutableArray *array = [[NSMutableArray alloc] init]; > [array addObject:[NSNumber numberWithFloat:a]]; > [array addObject:[NSNumber numberWithFloat:b]]; > //[release array]; ???????? return array; > } //Declaration: Math *operator = [[Math alloc] init]; [operator findSum:Objects(20.0,30.0)]; My code compiles if I instantiate NSMutableArray right before I send the message to the receiver. I know I can have an array argument along with the method. What I have problem seeing is how to use a function and to replace the argument with a function call. Any help is appreciated. I am interested in the concept not in suggestions to replace the findSum method.

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• can a OOM be caused by not finding enough contiguous memory?

  - by raticulin

  I start some java code with -Xmx1024m, and at some point I get an hprof due to OOM. The hprof shows just 320mb, and give me a stack trace: at java.util.Arrays.copyOfRange([CII)[C (Arrays.java:3209) at java.lang.String.<init>([CII)V (String.java:215) at java.lang.StringBuilder.toString()Ljava/lang/String; (StringBuilder.java:430) ... This comes from a large string I am copying. I remember reading somewhere (cannot find where) what happened is these cases is: process still has not consumed 1gb of memory, is way below even if heap still below 1gb, it needs some amount of memory, and for copyOfRange() it has to be continuous memory, so even if it is not over the limit yet, it cannot find a large enough piece of memory on the host, it fails with an OOM. I have tried to look for doc on this (copyOfRange() needs a block of continuous memory), but could not find any. The other possible culprit would be not enough permgen memory. Can someone confirm or refute the continuous memory hypothesis? Any pointer to some doc would help too.

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• What's the purpose of "import package"?

  - by codethief

  As I just found out import package does not make the package's modules available through package.module. The same obviously holds true for from package import subpackage as well as from package import * What's the purpose of importing a package at all then if I can't access its submodules but only the objects defined in __init__.py? It makes sense to me that from package import * would bloat the namespace, which, however, doesn't apply in case of the other two ways! I also understand that loading all submodules might take a long time. But I don't know what these unwanted side-effects, "that should only happen when the sub-module is explicitly imported", are which the author of the previous link mentions. To me it looks like doing an import package[.subpackage] (or from package import subpackage) makes absolutely no sense if I don't exactly want to access objects provided in __init__.py. Are those unwanted side effects really that serious that the language actually has to protect the programmer from causing them? Actually, I thought that Python was a little bit more about "If the programmer wants to do it, let him do it." In my case, I really do want to import all submodules with the single statement from package import subpackage, because I need all of them! Telling Python in the init.py file which submodules I'm exactly talking about (all of them!) is quite cumbersome from my point of view. Please enlighten me. :)

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• E_ACCESSDENIED on CoCreateInstance

  - by vucetica

  Here is a code snippet #include "stdafx.h" #include <tchar.h> #include <windows.h> #include <dshow.h> #include <ExDisp.h> int _tmain(int argc, _TCHAR* argv[]) { CoInitialize(NULL); HRESULT hr = S_OK; DWORD err = 0; // Try to create graph builder IGraphBuilder* pGraph = 0; hr = CoCreateInstance(CLSID_FilterGraph, NULL, CLSCTX_INPROC_SERVER, IID_IGraphBuilder, (void**)&pGraph ); err = GetLastError(); // Here, hr is E_ACCESSDENIED // err is 5 (ERROR_ACCESS_DENIED) // Try to create capture graph builder (succeeds) ICaptureGraphBuilder2* pBuild = 0; hr = CoCreateInstance(CLSID_CaptureGraphBuilder2, NULL, CLSCTX_INPROC_SERVER, IID_ICaptureGraphBuilder2, (void **)&pBuild ); err = GetLastError(); // Here, hr is S_OK // err is 0 (ERROR_SUCCESS) // Try to create IWebBrowser (succeeds) IWebBrowser2* pBrowser = 0; hr = CoCreateInstance (CLSID_InternetExplorer, NULL, CLSCTX_LOCAL_SERVER, IID_IWebBrowser2, (LPVOID *)&pBrowser); err = GetLastError(); // Here, hr is S_OK // err is 0 (ERROR_SUCCESS) return 0; } I'm trying to create IFilterGraph, which fails with E_ACCESSDENIED. On the other hand, creating other directshow objects works ok. The same with some other COM objects (tried with IWebBrowser2 as an example). Any idea what can be the problem? Thanks!

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• Query MySQL data from Excel (or vice-versa)

  - by Charles

  I'm trying to automate a tedious problem. I get large Excel (.xls or .csv, whatever's more convenient) files with lists of people. I want to compare these against my MySQL database.* At the moment I'm exporting MySQL tables and reading them from an Excel spreadsheet. At that point it's not difficult to use =LOOKUP() and such commands to do the work I need, and of course the various text processing I need to do is easy enough to do in Excel. But I can't help but think that this is more work than it needs to be. Is there some way to get at the MySQL data directly from Excel? Alternately, is there a way I could access a reasonably large (~10k records) csv file in a sql script? This seems to be rather basic, but I haven't managed to make it work so far. I found an ODBC connection for MySQL but that doesn't seem to do what I need. In particular, I'm testing whether the name matches or whether any of four email addresses match. I also return information on what matched for the benefit of the next person to use the data, something like "Name 'Bob Smith' not found, but 'Robert Smith' matches on email address robert.smith@foo".

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• Adding a JLabel to JLayeredPane from event listener not dragging.

  - by Cody

  Ok, So for some reason When I add components to a JLayeredPane in its constructor: JLabel label = new JLabel(); label.setSize(100,100); label.setText("This works"); add(label); It works perfectly fine, but If a add it later in the JLayeredPane's parent EDT it doesnt let me move the objects around but they let me see the objects. Adding from EDT: JLabel label = new JLabel(); label.setToolTipText(url.getHost()); label.setIcon(icon); label.setBorder(new LineBorder(null)); label.setSize(icon.getIconWidth(), icon.getIconHeight()); dressFrame.layeredPane.add(label, JLayeredPane.DRAG_LAYER); Dragging method: Component c = findComponentAt(e.getX(), e.getY()); if (c instanceof JLayeredPane) { pieceSelected = false; return; } Point parentLocation = c.getLocation(); xAdjustment = parentLocation.x - e.getX(); yAdjustment = parentLocation.y - e.getY(); movingPiece = c; movingPiece.setLocation(e.getX() + xAdjustment, e.getY() + yAdjustment); pieceSelected = true;

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• Is it approproate it use django signals withing the same app

  - by Alex Lebedev

  Trying to add email notification to my app in the cleanest way possible. When certain fields of a model change, app should send a notification to a user. Here's my old solution: from django.contrib.auth import User class MyModel(models.Model): user = models.ForeignKey(User) field_a = models.CharField() field_b = models.CharField() def save(self, *args, **kwargs): old = self.__class__.objects.get(pk=self.pk) if self.pk else None super(MyModel, self).save(*args, **kwargs) if old and old.field_b != self.field_b: self.notify("b-changed") # Sevelar more events here # ... def notify(self, event) subj, text = self._prepare_notification(event) send_mail(subj, body, settings.DEFAULT_FROM_EMAIL, [self.user.email], fail_silently=True) This worked fine while I had one or two notification types, but after that just felt wrong to have so much code in my save() method. So, I changed code to signal-based: from django.db.models import signals def remember_old(sender, instance, **kwargs): """pre_save hanlder to save clean copy of original record into `old` attribute """ instance.old = None if instance.pk: try: instance.old = sender.objects.get(pk=instance.pk) except ObjectDoesNotExist: pass def on_mymodel_save(sender, instance, created, **kwargs): old = instance.old if old and old.field_b != instance.field_b: self.notify("b-changed") # Sevelar more events here # ... signals.pre_save.connect(remember_old, sender=MyModel, dispatch_uid="mymodel-remember-old") signals.post_save.connect(on_mymodel_save, sender=MyModel, dispatch_uid="mymodel-on-save") The benefit is that I can separate event handlers into different module, reducing size of models.py and I can enable/disable them individually. The downside is that this solution is more code and signal handlers are separated from model itself and unknowing reader can miss them altogether. So, colleagues, do you think it's worth it?

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• Practices for keeping JavaScript and CSS in sync?

  - by Rene Saarsoo

  I'm working on a large JavaScript-heavy app. Several pieces of JavaScript have some related CSS rules. Our current practice is for each JavaScript file to have an optional related CSS file, like so: MyComponent.js // Adds CSS class "my-comp" to div MyComponent.css // Defines .my-comp { color: green } This way I know that all CSS related to MyComponent.js will be in MyComponent.css. But the thing is, I all too often have very little CSS in those files. And all too often I feel that it's too much effort to create a whole file to just contain few lines of CSS - it would be easier to just hardcode the styles inside JavaScript. But this would be the path to the dark side... Lately I've been thinking of embedding the CSS directly inside JavaScript - so it could still be extracted in the build process and merged into one large CSS file. This way I wouldn't have to create a new file for every little CSS-piece. Additionally when I move/rename/delete the JavaScript file I don't have to additionally move/rename/delete the CSS file. But how to embed CSS inside JavaScript? In most other languages I would just use string, but JavaScript has some issues with multiline strings. The following looks IMHO quite ugly: Page.addCSS("\ .my-comp > p {\ font-weight: bold;\ color: green;\ }\ "); What other practices have you for keeping your JavaScript and CSS in sync?

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• Reformat SQLGeography polygons to JSON

  - by James

  I am building a web service that serves geographic boundary data in JSON format. The geographic data is stored in an SQL Server 2008 R2 database using the geography type in a table. I use [ColumnName].ToString() method to return the polygon data as text. Example output: POLYGON ((-6.1646509904325884 56.435153006374627, ... -6.1606079906751 56.4338050060666)) MULTIPOLYGON (((-6.1646509904325884 56.435153006374627 0 0, ... -6.1606079906751 56.4338050060666 0 0))) Geographic definitions can take the form of either an array of lat/long pairs defining a polygon or in the case of multiple definitions, an array or polygons (multipolygon). I have the following regex that converts the output to JSON objects contained in multi-dimensional arrays depending on the output. Regex latlngMatch = new Regex(@"(-?[0-9]{1}\.\d*)\s(\d{2}.\d*)(?:\s0\s0,?)?", RegexOptions.Compiled); private string ConvertPolysToJson(string polysIn) { return this.latlngMatch.Replace(polysIn.Remove(0, polysIn.IndexOf("(")) // remove POLYGON or MULTIPOLYGON .Replace("(", "[") // convert to JSON array syntax .Replace(")", "]"), // same as above "{lng:$1,lat:$2},"); // reformat lat/lng pairs to JSON objects } This is actually working pretty well and converts the DB output to JSON on the fly in response to an operation call. However I am no regex master and the calls to String.Replace() also seem inefficient to me. Does anyone have any suggestions/comments about performance of this?

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• Opengl Iphone SDK: How to tell if you're touching an object on screen?

  - by TheGambler

  First is my touchesBegan function and then the struct that stores the values for my object. I have an array of these objects and I'm trying to figure out when I touch the screen if I'm touching an object on the screen. I don't know if I need to do this by iterating through all my objects and figure out if I'm touching an object that way or maybe there is an easier more efficient way. How is this usually handled? -(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{ [super touchesEnded:touches withEvent:event]; UITouch* touch = ([touches count] == 1 ? [touches anyObject] : nil); CGRect bounds = [self bounds]; CGPoint location = [touch locationInView:self]; location.y = bounds.size.height - location.y; float xTouched = location.x/20 - 8 + ((int)location.x % 20)/20; float yTouched = location.y/20 - 12 + ((int)location.y % 20)/20; } typedef struct object_tag // Create A Structure Called Object { int tex; // Integer Used To Select Our Texture float x; // X Position float y; // Y Position float z; // Z Position float yi; // Y Increase Speed (Fall Speed) float spinz; // Z Axis Spin float spinzi; // Z Axis Spin Speed float flap; // Flapping Triangles :) float fi; // Flap Direction (Increase Value) } object;

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• OutOfMemoryException

  - by Andrew

  I have an application that is pretty memory hungry. It holds a large amount of data in some big arrays. I have recently been noticing the occasional OutOfMemoryException. These OutOfMemoryExceptions are occurring long before my application (ASP.Net) has used up the 800mb available to it. I have track the issue down to the area of code where the array is resized. The array contains a structure that is 74bytes in size. (I know that you shouldn't create struct's that are bigger than 16bytes), but this application is a port from a Vb6 application). I have tried changing the struct to a class and this appears to have fixed the problem for now. I think the reason that changing to a class solves the problem has to do with the fact that when using a struct and the array is resized, a segment of memory that is large enough to store the new array needs to be reserved (e.g. (currentArraySize + increaseBySize)*74) cannot be found. This leads to the OutOfMemoryException. This isn't the case with a class as each element of the array only needs 8bytes to store a pointer to the new object. Is my thinking correct here?

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