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  • Is there a good design pattern for this messaging class?

    - by salonMonsters
    Is there a good design pattern for this? I want to create a messaging class. The class will be passed: the type of message (eg. signup, signup confirmation, password reminder etc) the client's id The class needs to then look up the client's messaging preferences in the db (whether they want communication by email, sms or both) Then depending on the client's preference it will format the message for the medium (short version for sms, long form for email) and send it through our mail or sms provider's API. Because the fact that we want to be able to change out email and sms providers if need be I wondered if the Command Pattern would be a good choice.

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  • Where can I find design exercises to work on?

    - by Oak
    I feel it's important to continue practicing my problem-solving skills. Writing my own mini-projects is one way, but another is to try and solve problems posted online. It's easy to find interesting programming quizzes online that require applying clever algorithms to solve - Project Euler is one well-known example. However, in a lot of real-life projects the design of the software - especially in the initial phases - has a large impact and at later stages it cannot be tweaked as easily as plain algorithms. In order to improve these skills, I'm looking for any collection of design problems. When I say "design", I mean the abstract design of a software solution - for example what modules will there be and what are the dependencies between them, how data will flow in the program, what sort of data needs to be saved in the database, etc. Design problems are those problems that are critical to solve in the early stages of any project, but their solution is a whiteboard diagram without a single line of code. Of course these sort of problems do not have a single correct solution, but I'll be especially happy with any place that also displays pros and cons of the typical solutions that might be used to approach the problem.

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  • What modelling technique do you use for your continuous design?

    - by d3prok
    Together with my teammates, I'm trying to self-learn XP and apply its principles. We're successfully working in TDD and happily refactoring our code and design. However we're having problems with the overall view of the design of the project. Lately we were wondering what would be the "good" practices for an effective continuous design of the code. We're not strictly seeking the right model, like CRC cards, communication diagrams, etc., instead we're looking for a technique to constantly collaborate on the high level view of the system (not too high though). I'll try to explain myself better: I'm actually interested in the way CRC cards are used to brainstorm a model and I would mix them with some very rough UML diagrams (that we already use). However, what we're looking for are some principles for deciding when, how and how much to model during our iterations. Have you any suggestion on this matter? For example, when your teammates and you know you need a design session and how your meetings work?

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  • What design pattern do you use to support graceful fallback on old platforms?

    - by JoJo
    Let's say I need to add a drop shadow behind a box. Some old platforms do not support drop shadows, so I have to fake it by putting an image behind the box. Here's the pseudo code of how I'm currently handling this fallback: if (dropShadowsAreSupported) { box.addDropShadow("black"); } else { box.putImageBehindIt("gaussianBlur.png"); } Is this the right way to handle it? It seems too amateur to me. Is there a better design pattern?

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  • Is there a name for this use of the State design pattern?

    - by Chris C
    I'm looking to see if there is a particular name for this style of programming a certain kind of behavior into a program. Said program runs in real time, in an update loop, and the program uses the State design pattern to do some work, but it's the specific way it does the work that I want to know about. Here's how it's used. - Object Foo constructed, with concrete StateA object in it - First loop runs --- Foo.Run function calls StateA.Bar --- in StateA.Bar replace Foo's state to StateB - Second loop runs --- Foo.Run calls StateB.Bar - Third loop runs --- Foo.Run calls StateB.Bar - Fourth loop --- etc. So in short, Foo doesn't have an explicit Initialize function. It will just have Run, but Run will do something unique in the first frame to initialize something for Foo and then replace it with a different action that will repeat in all the frames following it- thus not needing to check if Foo's already initialized. It's just a "press start and go" action. What would you call implementing this type of behavior?

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  • Main class passes dbConn obj to all its services, I need to change the dbConn for one of its services. - suggestion for design pattern

    - by tech_learner
    There is this main class and there are several services ( which uses db connection to retrieve data ) These services are initialized in the main class db properties are obtained from the property file and then dbconnection is opened by calling a method dbOpen() written in the main class and the resultant connection object is set to the service objects by iterating through the list of services and by calling setConnection method on the service note: that the services are instantiated in the main class and the main class is not a superclass for services. I also need to mention that there is this recycle db connection scenario only main class is aware of. /** connects to DB, optionally recycling existing connection), * throws RuntimeException if unable to connect */ private void connectDb(boolean recycle) { try { if (recycle) { log.status( log.getSB().append("Recycling DB Connection") ); closeDb(); } openDb(); for ( int i = 0 ; i < service.length ; i++ ) { service[i].setConnection(db); } } One of the service needs to use a different database, what is the best design pattern to use?

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  • "Never do in code what you can get the SQL server to do well for you" - Is this a recipe for a bad design?

    - by PhonicUK
    It's an idea I've heard repeated in a handful of places. Some more or less acknowledging that once trying to solve a problem purely in SQL exceeds a certain level of complexity you should indeed be handling it in code. The logic behind the idea is that for the large majority of cases, the database engine will do a better job at finding the most efficient way of completing your task than you could in code. Especially when it comes to things like making the results conditional on operations performed on the data. Arguably with modern engines effectively JIT'ing + caching the compiled version of your query it'd make sense on the surface. The question is whether or not leveraging your database engine in this way is inherently bad design practice (and why). The lines become blurred further when all the logic exists inside the database and you're just hitting it via an ORM.

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  • Are there any well known anti-patterns in the field of system administration?

    - by ojblass
    I know a few common patterns that seem to bedevil nearly every project at some point in its life cycle: Inability to take outages Third party components locking out upgrades Non uniform environments Lack of monitoring and alerting Missing redundancy Lack of Capacity Poor Change Management Too liberal or tight access policies Organizational changes adversely blur infrastructure ownership I was hoping there is some well articulated library of these anti-patterns summarized in a book or web site. I am almost positive that many organizations are learning through trial by fire methods. If not let's start one.

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  • Comparison of Architecture presentation patterns MVP(SC),MVP(PV),PM,MVVM and MVC

    This article will compare four important architecture presentation patterns i.e. MVP(SC),MVP(PV),PM,MVVM and MVC. Many developers are confused around what is the difference between these patterns and when should we use what. This article will first kick start with a background and explain different...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Comparison of Architecture presentation patterns MVP(SC),MVP(PV),PM,MVVM and MVC

    This article will compare four important architecture presentation patterns i.e. MVP(SC),MVP(PV),PM,MVVM and MVC. Many developers are confused around what is the difference between these patterns and when should we use what. This article will first kick start with a background and explain different...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Vermeidung von SOA Anti-Patterns mittels AIA

    - by Hans Viehmann
    Gerade ist mir ein White Paper des Enterprise Architecture Teams in die Hände gefallen, das sich mit SOA Anti-Patterns befasst. Es ist zwar kein AIA Paper im eigentlichen Sinne, aber mit AIA hat man natürlich eine gute Unterstützung darin, die dort beschriebenen Fehler zu vermeiden. Das White Paper behandelt Themen wie: Vermeidung von SOA Silos SOA Reifegrad und Projekt-Management Ausuferndes Service Portfolio Umgang mit Referenz-Architekturen EAI 2.0 - Punkt-zu-Punkt Integration auf offenen Standards Ein Link auf das Dokument ist unten angefügt - viel Vergnügen bei der Lektüre ... Oracle White Paper: SOA Anti-Patterns.

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  • Google I/O 2012 - Playing with Patterns

    Google I/O 2012 - Playing with Patterns "Marco Paglia Best-in-class application designers and developers will talk about their experience in developing for Android, showing screenshots from their app, exploring the challenges they faced, and offering creative solutions congruent with the Android Design guide. Guests will be invited to show examples of visual and interaction patterns in their application that manage to keep it simultaneously consistent and personal. For all I/O 2012 sessions, go to developers.google.com From: GoogleDevelopers Views: 1 0 ratings Time: 02:13:20 More in Science & Technology

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  • Google I/O 2012 - Knowledge-Based Application Design Patterns

    Google I/O 2012 - Knowledge-Based Application Design Patterns Shawn Simister In this talk we'll look at emerging design patterns for building web applications that take advantage of large-scale, structured data. We'll look at open datasets like Wikipedia and Freebase as well as structured markup like Schema.org and RDFa to see what new types of applications these technologies open up for developers. For all I/O 2012 sessions, go to developers.google.com From: GoogleDevelopers Views: 1 0 ratings Time: 56:55 More in Science & Technology

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  • Protobuf design patterns

    - by Monster Truck
    I am evaluating Google Protocol Buffers for a Java based service (but am expecting language agnostic patterns). I have two questions: The first is a broad general question: What patterns are we seeing people use? Said patterns being related to class organization (e.g., messages per .proto file, packaging, and distribution) and message definition (e.g., repeated fields vs. repeated encapsulated fields*) etc. There is very little information of this sort on the Google Protobuf Help pages and public blogs while there is a ton of information for established protocols such as XML. I also have specific questions over the following two different patterns: Represent messages in .proto files, package them as a separate jar, and ship it to target consumers of the service --which is basically the default approach I guess. Do the same but also include hand crafted wrappers (not sub-classes!) around each message that implement a contract supporting at least these two methods (T is the wrapper class, V is the message class (using generics but simplified syntax for brevity): public V toProtobufMessage() { V.Builder builder = V.newBuilder(); for (Item item : getItemList()) { builder.addItem(item); } return builder.setAmountPayable(getAmountPayable()). setShippingAddress(getShippingAddress()). build(); } public static T fromProtobufMessage(V message_) { return new T(message_.getShippingAddress(), message_.getItemList(), message_.getAmountPayable()); } One advantage I see with (2) is that I can hide away the complexities introduced by V.newBuilder().addField().build() and add some meaningful methods such as isOpenForTrade() or isAddressInFreeDeliveryZone() etc. in my wrappers. The second advantage I see with (2) is that my clients deal with immutable objects (something I can enforce in the wrapper class). One disadvantage I see with (2) is that I duplicate code and have to sync up my wrapper classes with .proto files. Does anyone have better techniques or further critiques on any of the two approaches? *By encapsulating a repeated field I mean messages such as this one: message ItemList { repeated item = 1; } message CustomerInvoice { required ShippingAddress address = 1; required ItemList = 2; required double amountPayable = 3; } instead of messages such as this one: message CustomerInvoice { required ShippingAddress address = 1; repeated Item item = 2; required double amountPayable = 3; } I like the latter but am happy to hear arguments against it.

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  • Add an objective @property attribute in objective-c

    - by morticae
    Does anyone know of a way to add additional attribute types to the @property keyword without modifying the compiler? Or can anyone think of another way to genericize getter/setter creation? Basically, I have a lot of cases in a recent project where it's handy for objects to lazily instantiate their array properties. This is because we have "event" objects that can have a wide variety of collections as properties. Subclassing for particular events is undesirable because many properties are shared, and it would become a usability nightmare. For example, if I had an object with an array of songs, I'd write a getter like the following: - (NSMutableArray *)songs { if (!songs) { songs = [[NSMutableArray alloc] init]; } return songs; } Rather than writing dozens of these getters, it would be really nice to get the behavior via... @property (nonatomic, retain, lazyGetter) NSMutableArray *songs; Maybe some fancy tricks via #defines or something? Other ideas?

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  • UIModalPresentationFormSheet on iPad in landscape mode

    - by Ivan
    I created a UIViewController view from XIB with modalPresentationStyle set to UIModalPresentationFormSheet and everything works great in portrait mode. When I switch to landscape the view gets moved upperleft (it's not centered as it should be) and most part of it is clipped. Any ideas why this is happening and how to solve it? Thanks

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  • iphone development-leopard or snow leopard?

    - by ying
    i am planning start my iphone development, and i have a iMac with tiger 10.4 OS version, planning to upgrade to Leopard 10.5.6 OS X, but i heard apple going to release the Snow Leopard in september, will development environment shift to snow leopard instead of leopard,and Leopard 10.5.7 no longer be used to development?is now a good timing to upgrade?

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  • Problem with Rotating a UIScrollview

    - by leachianus.gecko
    Hey guys, I am having issues trying to get the pageControl sample code to work with rotation. I managed to get it to rotate but it does not visually loads correctly until I start to scroll (then it works fine). Any Idea on how I can fix this problem? Here is a link to the project if you want to see it in action. This code is based off the PageControl example apple has provided. here is the code: #import "ScrollingViewController.h" #import "MyViewController.h" @interface ScrollingViewController (PrivateMethods) - (void)loadScrollViewWithPage:(int)page; @end @implementation ScrollingViewController @synthesize scrollView; @synthesize viewControllers; - (void)viewDidLoad { amount = 5; [super viewDidLoad]; [self setupPage]; } - (void)didReceiveMemoryWarning { [super didReceiveMemoryWarning]; } - (void)viewDidUnload { [scrollView release]; } - (void)dealloc { [super dealloc]; } - (void)setupPage { NSMutableArray *controllers = [[NSMutableArray alloc] init]; for (unsigned i = 0; i < amount; i++) { [controllers addObject:[NSNull null]]; } self.viewControllers = controllers; [controllers release]; // a page is the width of the scroll view scrollView.pagingEnabled = YES; scrollView.contentSize = CGSizeMake(scrollView.frame.size.width * amount, 200); scrollView.showsHorizontalScrollIndicator = NO; scrollView.showsVerticalScrollIndicator = NO; scrollView.scrollsToTop = NO; scrollView.delegate = self; [self loadScrollViewWithPage:0]; [self loadScrollViewWithPage:1]; } #pragma mark - #pragma mark UIScrollViewDelegate stuff - (void)scrollViewDidScroll:(UIScrollView *)_scrollView { if (pageControlIsChangingPage) { return; } /* * We switch page at 50% across */ CGFloat pageWidth = _scrollView.frame.size.width; int dog = floor((_scrollView.contentOffset.x - pageWidth / 2) / pageWidth) + 1; // pageControl.currentPage = page; [self loadScrollViewWithPage:dog - 1]; [self loadScrollViewWithPage:dog]; [self loadScrollViewWithPage:dog + 1]; } - (void)loadScrollViewWithPage:(int)page { if (page < 0) return; if (page >= amount) return; MyViewController *controller = [viewControllers objectAtIndex:page]; if ((NSNull *)controller == [NSNull null]) { controller = [[MyViewController alloc] initWithPageNumber:page]; [viewControllers replaceObjectAtIndex:page withObject:controller]; [controller release]; } if (nil == controller.view.superview) { CGRect frame = scrollView.frame; frame.origin.x = frame.size.width * page; frame.origin.y = 0; controller.view.frame = frame; [scrollView addSubview:controller.view]; } } - (void)didRotateFromInterfaceOrientation:(UIInterfaceOrientation)fromInterfaceOrientation { [self setupPage]; } - (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation { // Return YES for supported orientations return YES; } #pragma mark - #pragma mark PageControl stuff @end

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  • iphone - Programmatically set (System-wide) proxy settings?

    - by Andrew
    I am new to iPhone development, so I'm sorry if this is a stupid question. I am developing an application whose purpose will be to route all iPhone activity through my company's proxy. Is there a way to programmatically set system-wide proxy settings in the iPhone (which will also take effect on the 3G connection)? I know there is a way to manually set proxy settings for each wifi connection. Detecting new networks and setting the proxy on them would be acceptable. However, I need to also be able to set the proxy on the 3G connection. Also, bonus: Is there a way to programmatically change the "Restrictions" settings? If anyone has any tips or can point me in the right direction, I would appreciate it. Thanks. EDIT: Please understand that this is for a legitimate purpose. Apple has to approve app store additions, so it's not like I'm trying to spread a virus. Please, constructive answers only.

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  • CGBitmapContextCreate issue while trying to resize images

    - by Jeff
    Hello! I'm running into an issue when I try to create a CGContextRef while attempting to resize some images: There are the errors Sun May 16 20:07:18 new-host.home app [7406] <Error>: Unable to create bitmap delegate device Sun May 16 20:07:18 new-host.home app [7406] <Error>: createBitmapContext: failed to create delegate. My code looks like this - (UIImage*) resizeImage:(UIImage*)originalImage withSize:(CGSize)newSize { CGSize originalSize = originalImage.size; CGFloat originalAspectRatio = originalSize.width / originalSize.height; CGImageRef cgImage = nil; int bitmapWidth = newSize.width; int bitmapHeight = newSize.height; CGColorSpaceRef colorspace = CGColorSpaceCreateDeviceRGB(); CGContextRef context = CGBitmapContextCreate(nil, bitmapWidth, bitmapHeight, 8, bitmapWidth * 4, colorspace, kCGImageAlphaPremultipliedLast); if (context != nil) { // Flip the coordinate system //CGContextScaleCTM(context, 1.0, -1.0); //CGContextTranslateCTM(context, 0.0, -bitmapHeight); // Black background CGRect rect = CGRectMake(0, 0, bitmapWidth, bitmapHeight); CGContextSetRGBFillColor (context, 0, 0, 0, 1); CGContextFillRect (context, rect); // Resize box to maintain aspect ratio if (originalAspectRatio < 1.0) { rect.origin.y += (rect.size.height - rect.size.width / originalAspectRatio) * 0.5; rect.size.height = rect.size.width / originalAspectRatio; } else { rect.origin.x += (rect.size.width - rect.size.height * originalAspectRatio) * 0.5; rect.size.width = rect.size.height * originalAspectRatio; } CGContextSetInterpolationQuality(context, kCGInterpolationHigh); // Draw image CGContextDrawImage (context, rect, [originalImage CGImage]); // Get image cgImage = CGBitmapContextCreateImage (context); // Release context CGContextRelease(context); } CGColorSpaceRelease(colorspace); UIImage *result = [UIImage imageWithCGImage:cgImage]; CGImageRelease (cgImage); return result; }

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  • Core Data NSPredicate for relationships.

    - by Mugunth Kumar
    My object graph is simple. I've a feedentry object that stores info about RSS feeds and a relationship called Tag that links to "TagValues" object. Both the relation (to and inverse) are to-many. i.e, a feed can have multiple tags and a tag can be associated to multiple feeds. I referred to http://stackoverflow.com/questions/844162/how-to-do-core-data-queries-through-a-relationship and created a NSFetchRequest. But when fetch data, I get an exception stating, NSInvalidArgumentException unimplemented SQL generation for predicate What should I do? I'm a newbie to core data :( I know I've done something terribly wrong... Please help... Thanks -- NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; // Edit the entity name as appropriate. NSEntityDescription *entity = [NSEntityDescription entityForName:@"FeedEntry" inManagedObjectContext:managedObjectContext]; [fetchRequest setEntity:entity]; // Edit the sort key as appropriate. NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"authorname" ascending:NO]; NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil]; [fetchRequest setSortDescriptors:sortDescriptors]; NSEntityDescription *tagEntity = [NSEntityDescription entityForName:@"TagValues" inManagedObjectContext:self.managedObjectContext]; NSPredicate *tagPredicate = [NSPredicate predicateWithFormat:@"tagName LIKE[c] 'nyt'"]; NSFetchRequest *tagRequest = [[NSFetchRequest alloc] init]; [tagRequest setEntity:tagEntity]; [tagRequest setPredicate:tagPredicate]; NSError *error = nil; NSArray* predicates = [self.managedObjectContext executeFetchRequest:tagRequest error:&error]; TagValues *tv = (TagValues*) [predicates objectAtIndex:0]; NSLog(tv.tagName); // it is nyt here... NSPredicate *predicate = [NSPredicate predicateWithFormat:@"tag IN %@", predicates]; [fetchRequest setPredicate:predicate]; // Edit the section name key path and cache name if appropriate. // nil for section name key path means "no sections". NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:managedObjectContext sectionNameKeyPath:nil cacheName:@"Root"]; aFetchedResultsController.delegate = self; self.fetchedResultsController = aFetchedResultsController; --

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  • UIDatePicker locale does nothing?

    - by morticae
    I'm creating a UIDatePicker programmatically, and setting its locale with the following code: datePicker.locale = [[[NSLocale alloc] initWithLocaleIdentifier:@"es_ES"] autorelease]; The datepicker still appears in English (or whatever language I've set the phone to). Anyone have any idea why this does nothing, or how to fix it?

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