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• Help Me Understand C++ Header files and Classes

  - by JamesW

  OK, So I am trying to transition from intermediate Delphi to C++ Object Oriented programing. I have read Ivar Horton's book on visual C++ 2010. I can pull off the simple console applications no problem. I get the language itself (kinda). Where I am struggling is with headers and classes. I also understand what header files and classes do in general. What I am not getting is the implementation when do I use a header or a class? Do I need to create classes for everything I do? Do my actual work functions need to be in header files or in CPP files? I'm lost on the proper uses of these and could use some real world guidance from more experienced programmers. I am trying to transition to windows applications using the MFC if that is helpful.

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• Why prefix sql function names?

  - by AaronLS

  What is a scenario that exemplifies a good reason to use prefixes, such as fn_GetName, on function names in SQL Server? It would seem that it would be unnecessary since usually the context of its usage would make it clear that it's a function. I have not used any other language that has ever needed prefixes on functions, and I can't think of a good scenario that would show why SQL is any different. My only thinking is that perhaps in older IDE's it was useful for grouping functions together when the database objects were all listed together, but modern IDE's already make it clear what is a function.

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• Mapping US zip code to time zone

  - by Doug Kavendek

  When users register with our app, we are able to infer their zip code when we validate them against a national database. What would be the best way to determine a good potential guess of their time zone from this zip code? We are trying to minimize the amount of data we explicitly have to ask them for. They will be able to manually set the time zone later if our best guess is wrong. I realize zip codes won't help with figuring out the time zone outside the US, but in that case we'd have to manually ask anyway, and we deal predominantly with the US regardless. I've found a lot of zip code databases, and so far only a few contain time zone information, but those that do are not free, such as this one. If it's absolutely necessary to pay a subscription to a service in order to do this, then it will not be worth it and we will just have to ask users explicitly. Although language isn't particularly relevant as I can probably convert things however needed, we're using PHP and MySQL.

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• Working with OAuth on Google with Python

  - by Dan Loewenherz

  I'm having a very frustrating time creating a valid signature for Google's OAuth implementation. I have narrowed it all down to the fact that my signature-generation code has an error of some sort; what it is I have no idea. This is the signature base string in its entirety: GET&https%3A%2F%2Fwww.google.com%2Faccounts%2FOAuthGetAccessToken&oauth_consumer_key%3Ddlosplayground.appspot.com%26oauth_nonce%3D72815d55697cb24301fab03e1f7f1d66%26oauth_signature_method%3DHMAC-SHA1%26oauth_timestamp%3D1274327867%26oauth_token%3D4%252FX2cZ54JuseQbgRwzTBzZ7lqIwqof%26oauth_verifier%3Dihf0F2Fx%252FpnCmwbVQnk2xMre%26oauth_version%3D1.0 The OAuth Playground returns an oauth_signature of gF8qAfWjpdKjKb4KR%2FvA2Gy0vhU%3D. My code gives me ikMpIKJQJ58jseg%2BKPBTecjmYPE%3D, so obviously I'm doing something wrong. Here's my signature generation code (equivalent to that of the standard oauth.py library): binascii.b2a_base64(hmac.new(CONSUMER_SECRET, BASE_STRING, hashlib.sha1).digest())[:-1] Any thoughts?

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• Does "Value Restriction" mean that there is no higher order functional programming?

  - by Sadache

  Does "Value Restriction" mean that there is no higher order functional programming? I have a problem that each time I try to do a bit of HOP I get caught by a VR error. Example: let simple (s:string)= fun rq->1 let oops= simple "" type 'a SimpleType= F of (int ->'a-> 'a) let get a = F(fun req -> id) let oops2= get "" and I would like to know whether it is a problem of a prticular implementation of VR or it is a general problem that has no solution in a mutable type-infered language that doesn't include mutation in the type system.

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• Are any of these quad-tree libraries any good?

  - by Noctis Skytower

  It appears that a certain project of mine will require the use of quad-trees, something that I have never worked with before. From what I have read they should allow substantial performance enhancements than a brute-force attempt at the problem would yield. Are any of these python modules any good? Quadtree 0.1.2 <= No: unable to execute in Python 3.1 QuadTree <= Yes: simple while working with rectangles quadtree.py <= No: no support for needed operations EDIT: Does anyone know of a better implementation that the one presented on the pygame wiki article?

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• Java generics: Illegal forward reference

  - by Arian

  Given a generic interface interface Foo<A, B> { } I want to write an implementation that requires A to be a subclass of B. So I want to do class Bar<A, B super A> implements Foo<A, B> { } // --> Syntax error or class Bar<A extends B, B> implements Foo<A, B> { } // --> illegal forward reference But the only solution that seems to work is this: class Bar<B, A extends B> implements Foo<A, B> { } which is kind of ugly, because it reverses the order of the generic parameters. Are there any solutions or workarounds to this problem?

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• PHP - Frameworks, ORM, Encapsulation.

  - by Ian

  Programming languages/environments aside, are there many developers who are using a framework in PHP, ORM and still abide by encapsulation for the DAL/BLL? I'm managing a team of a few developers and am finding that most of the frameworks require me to do daily code inspection because my developers are using the built in ORM. Right now, I've been using a tool to generate the classes and CRUD myself, with an area for them to write additional queries/functions. What's been happening though, is they are creating vulnerabilities by not doing proper checks on data permission, or allowing the key fields to be manipulated in the form. Any suggestions, other than get a new team and a new language (I've seen Python/Ruby frameworks have the same issues).

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• How to find control points for a BezierSegment given Start, End, and 2 Intersection Pts in C# - AKA

  - by softwarequestioneer

  Hi, I've been struggling looking for an understandable way to do this. I have four points, a StartPt, EndPoint, and Intersection points to represent the peak and valley in the bezier. The BezierSegment in C# requires start, controlPoint 1, controlPoint 2, endpoint - however I don't have any control points I only have these two points that lie along the bezier curves (i'm calling them intersection points above)... how can I calculate the two control points? Thanks in advance, this has been driving me crazy. There's some kind of explanation here: http://www.tinaja.com/glib/nubz4pts1.pdf but it's written in postscript and that language makes no sense to me at all - it's over my head.

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• PHP or C# script to parse CSV table values to fill in one-to-many table

  - by Yaaqov

  I'm looking for an example of how to split-out comma-delimited data in a field of one table, and fill in a second table with those individual elements, in order to make a one-to-many relational database schema. This is probably really simple, but let me give an example: I'll start with everything in one table, Widgets, which has a "state" field to contain states that have that widget: Table: WIDGET =============================== | id | unit | states | =============================== |1 | abc | AL,AK,CA | ------------------------------- |2 | lmn | VA,NC,SC,GA,FL | ------------------------------- |3 | xyz | KY | =============================== Now, what I'd like to create via code is a second table to be joined to WIDGET called *Widget_ST* that has widget id, widget state id, and widget state name fields, for example Table: WIDGET_ST ============================== | w_id | w_st_id | w_st_name | ------------------------------ |1 | 1 | AL | |1 | 2 | AK | |1 | 3 | CA | |2 | 1 | VA | |2 | 2 | NC | |2 | 1 | SC | |2 | 2 | GA | |2 | 1 | FL | |3 | 1 | KY | ============================== I am learning C# and PHP, so responses in either language would be great. Thanks.

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• How to learn to program C the right way

  - by sfactor

  i have been programming in C/C++ for my academic courses a lot and was under the impression i had a pretty good grasp of it. but lately i had to work in a bluetooth application that had a server and client implementation in a Linux box and an embedded system. i learned bluez bluetooth API, socket/network programming and coded it. however i ran into a lot of problems with memory leaks and segmentation faults and other memory related errors along the way.as the code grew more complex i all but lost control of the pointers and threads and sockets. this got me wondering that i had a lot to learn that they didn't say in the basic C/C++ books. so i wanted to ask for the resources that are available that'll help be code better in a professional way in C/C++ .especially for the Linux/Mac environment (gcc compiler).

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• Simple ViewController / View, remove white bar?

  - by fuzzygoat

  I am just looking at setting up a simple viewController programatically, I have a ViewController.xib file that I have set the background color to RED in interface builder. I have also added the following to my AppDelegate.m @implementation syntax_MapViewAppDelegate @synthesize window; -(BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions { viewController = [[MapViewController alloc] init]; [window addSubview:[viewController view]]; [window makeKeyAndVisible]; return YES; } -(void)dealloc { [viewController release]; [window release]; [super dealloc]; } @end When I run the code it does what I expect apart from the white bar at the bottom of the screen, can anyone give me any pointers in how to remove this? I have a feeling I might need to position the view within the window, but I am not sure how? cheers Gary

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• [Python] How can I speed up unpickling large objects if I have plenty of RAM?

  - by conradlee

  It's taking me up to an hour to read a 1-gigabyte NetworkX graph data structure using cPickle (its 1-GB when stored on disk as a binary pickle file). Note that the file quickly loads into memory. In other words, if I run: import cPickle as pickle f = open("bigNetworkXGraph.pickle","rb") binary_data = f.read() # This part doesn't take long graph = pickle.loads(binary_data) # This takes ages How can I speed this last operation up? Note that I have tried pickling the data both in using both binary protocols (1 and 2), and it doesn't seem to make much difference which protocol I use. Also note that although I am using the "loads" (meaning "load string") function above, it is loading binary data, not ascii-data. I have 128gb of RAM on the system I'm using, so I'm hoping that somebody will tell me how to increase some read buffer buried in the pickle implementation.

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• Type problem when including tuple

  - by Person

  I'm using Visual Studio 2008 with Feature Pack 1. I have a typedef like this typedef std::tr1::tuple<std::string, std::string, int> tileInfo with a function like this const tileInfo& GetTile( int x, int y ) const. In the implementation file the function has the exact same signature (with the added class name qualifier) and I am getting a redefinition: different type modifiers error. It seems to be looking for an int& instead of a tileInfo& When I mouse over the type of the function in the header, i.e. tileInfo& it brings up a little bar saying static const int tileInfo. I think this may be the problem, but I'm not sure what to do. Any help is appreciated, thanks.

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• Suggestions: Anti-Pattern counter-examples

  - by Tom W

  It doesn't seem that this exact question has been asked before, so I'll fire away: Most of us are familiar with the concept of an anti-pattern. However, avoiding implementation of anti-patterns can in principle swing too far the other way and cause problems itself. As an example, "Design by Committee" has a counter-example that I'd call "Design by Maverick" - wherein the design of an important feature is handed off to an individual to do what they think best, with the intention of reviewing their work later and deciding whether it should be finalised or go through another iteration. This takes much longer in practice as the rest of the team are occupied by other things, and can end up with a feature that's useful to nobody, particularly if the Maverick is not themselves an experienced end-user. Does anyone have any more examples of anti-pattern counter-examples?

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• Erlang on a JVM/CLR

  - by Fortyrunner

  I've just started reading Joe Armstrongs book on Erlang and listened to his excellent talk on Software Engineering Radio. Its an interesting language/system and one whose time seems to have come around with the advent of multi-core machines. My question is: what is there to stop it being ported to the JVM or CLR? I realise that both virtual machines aren't setup to run the lightweight processes that Erlang calls for - but couldn't these be simulated by threads? Could we see a lightweight or cutdown version of Erlang on a non Erlang VM?

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• CUDA small kernel 2d convolution - how to do it

  - by paulAl

  I've been experimenting with CUDA kernels for days to perform a fast 2D convolution between a 500x500 image (but I could also vary the dimensions) and a very small 2D kernel (a laplacian 2d kernel, so it's a 3x3 kernel.. too small to take a huge advantage with all the cuda threads). I created a CPU classic implementation (two for loops, as easy as you would think) and then I started creating CUDA kernels. After a few disappointing attempts to perform a faster convolution I ended up with this code: http://www.evl.uic.edu/sjames/cs525/final.html (see the Shared Memory section), it basically lets a 16x16 threads block load all the convolution data he needs in the shared memory and then performs the convolution. Nothing, the CPU is still a lot faster. I didn't try the FFT approach because the CUDA SDK states that it is efficient with large kernel sizes. Whether or not you read everything I wrote, my question is: how can I perform a fast 2D convolution between a relatively large image and a very small kernel (3x3) with CUDA?

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• Loose Coupling of Components

  - by David

  I have created a class library (assembly) that provides messaging, email and sms. This class library defines an interface IMessenger which the classes EmailMessage and SmsMessage both implement. I see this is a general library that would be part of my infrastructure layer and would / can be used across any development. Now, in my application layer I have a class that requires to use a messaging component, I obviously want to use the messaging library that I have created. Additionally, I will be using an IoC container (Spring.net) to allow me to inject my implementation i.e. either email or sms. Therefore, I want to program against an interface in my application layer class, do I then need to reference my message class library from my application layer class? Is this tightly coupling my application layer class to my message class library? Should I be defining the interface - IMessenger in a seperate library? Or should I be doing something else?

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• c99 goto past initialization

  - by R Samuel Klatchko

  While debugging a crash, I came across this issue in some code: int func() { char *p1 = malloc(...); if (p1 == NULL) goto err_exit; char *p2 = malloc(...); if (p2 == NULL) goto err_exit; ... err_exit: free(p2); free(p1); return -1; } The problem occurs when the first malloc fails. Because we jump across the initialization of p2, it contains random data and the call to free(p2) can crash. I would expect/hope that this would be treated the same way as in C++ where the compiler does not allow a goto to jump across an initialization. My question: is jumping across an initialization allowed by the standard or is this a bug in gcc's implementation of c99?

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• PHP complete sample website source

  - by MarceloRamires

  I'm new to PHP, and it appears that the way I learn the fastest is to study a new language a well developed complete program (or website, in this case) changing stuff seeing what happens and consulting books. There are lots of recommendations of books all around, and that's pretty much covered. I'd like to find the sourcecode of a website. Either a well known, well developed open-source website, or a sample sourcecode of a complete website (maybe one used in a book or something). Everyone says they should find the way they learn better.. Well, that's mine. PS.: By complete I mean having several common functionalities (such as login), database connection, use of security conventions, maybe a popular framework, and being up-to-date.

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• PostgreSQL: keep a certain number of records in a table

  - by Alexander Farber

  Hello, I have an SQL-table holding the last hands received by a player in card game. The hand is represented by an integer (32 bits == 32 cards): create table pref_hand ( id varchar(32) references pref_users, hand integer not NULL check (hand > 0), stamp timestamp default current_timestamp ); As the players are playing constantly and that data isn't important (just a gimmick to be displayed at player profile pages) and I don't want my database to grow too quickly, I'd like to keep only up to 10 records per player id. So I'm trying to declare this PL/PgSQL procedure: create or replace function pref_update_game(_id varchar, _hand integer) returns void as $BODY$ begin delete from pref_hand offset 10 where id=_id order by stamp; insert into pref_hand (id, hand) values (_id, _hand); end; $BODY$ language plpgsql; but unfortunately this fails with: ERROR: syntax error at or near "offset" because delete doesn't support offset. Does anybody please have a better idea here? Thank you! Alex

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• Is Boost.Tuple compatible with C++0x variadic templates ?

  - by Thomas Petit

  Hi, I was playing around with variadic templates (gcc 4.5) and hit this problem : template <typename... Args> boost::tuple<Args...> my_make_tuple(Args... args) { return boost::tuple<Args...>(args...); } int main (void) { boost::tuple<int, char> t = my_make_tuple(8, 'c'); } GCC error message : sorry, unimplemented: cannot expand 'Arg ...' into a fixed-length argument list In function 'int my_make_tuple(Arg ...)' If I replace every occurrence of boost::tuple by std::tuple, it compiles fine. Is there a problem in boost tuple implementation ? Or is this a gcc bug ? I must stick with Boost.Tuple for now. Do you know any workaround ? Thanks.

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• How can I implement incremental (find-as-you-type) search on command line?

  - by florianbw

  I'd like to write small scripts which feature incremental search (find-as-you-type) on the command line. Use case: I have my mobile phone connected via USB, Using gammu --sendsms TEXT I can write text messages. I have the phonebook as CSV, and want to search-as-i-type on that. What's the easiest/best way to do it? It might be in bash/zsh/Perl/Python or any other scripting language. Edit: Solution: Modifying Term::Complete (http://search.cpan.org/~jesse/perl-5.12.0/lib/Term/Complete.pm) did what I want. See below for the answer.

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• EXC_BAD_ACCESS at UITableView on IOS

  - by Suprie

  Hi all, When scrolling through table, my application crash and console said it was EXC_BAD_ACCESS. I've look everywhere, and people suggest me to use NSZombieEnabled on my executables environment variables. I've set NSZombieEnabled, NSDebugEnabled, MallocStackLogging and MallocStackLoggingNoCompact to YES on my executables. But apparently i still can't figure out which part of my program that cause EXC_BAD_ACCESS. This is what my console said [Session started at 2010-12-21 21:11:21 +0700.] GNU gdb 6.3.50-20050815 (Apple version gdb-1510) (Wed Sep 22 02:45:02 UTC 2010) Copyright 2004 Free Software Foundation, Inc. GDB is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions. Type "show copying" to see the conditions. There is absolutely no warranty for GDB. Type "show warranty" for details. This GDB was configured as "x86_64-apple-darwin".sharedlibrary apply-load-rules all Attaching to process 9335. TwitterSearch(9335) malloc: recording malloc stacks to disk using standard recorder TwitterSearch(9335) malloc: process 9300 no longer exists, stack logs deleted from /tmp/stack-logs.9300.TwitterSearch.suirlR.index TwitterSearch(9335) malloc: stack logs being written into /tmp/stack- logs.9335.TwitterSearch.tQJAXk.index 2010-12-21 21:11:25.446 TwitterSearch[9335:207] View Did Load Program received signal: “EXC_BAD_ACCESS”. And this is when i tried to type backtrace on gdb : Program received signal: “EXC_BAD_ACCESS”. (gdb) backtrace #0 0x00f20a67 in objc_msgSend () #1 0x0565cd80 in ?? () #2 0x0033b7fa in -[UITableView(UITableViewInternal) _createPreparedCellForGlobalRow:withIndexPath:] () #3 0x0033177f in -[UITableView(UITableViewInternal) _createPreparedCellForGlobalRow:] () #4 0x00346450 in -[UITableView(_UITableViewPrivate) _updateVisibleCellsNow:] () #5 0x0033e538 in -[UITableView layoutSubviews] () #6 0x01ffc451 in -[CALayer layoutSublayers] () #7 0x01ffc17c in CALayerLayoutIfNeeded () #8 0x01ff537c in CA::Context::commit_transaction () #9 0x01ff50d0 in CA::Transaction::commit () #10 0x020257d5 in CA::Transaction::observer_callback () #11 0x00d9ffbb in __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ () #12 0x00d350e7 in __CFRunLoopDoObservers () #13 0x00cfdbd7 in __CFRunLoopRun () #14 0x00cfd240 in CFRunLoopRunSpecific () #15 0x00cfd161 in CFRunLoopRunInMode () #16 0x01a73268 in GSEventRunModal () #17 0x01a7332d in GSEventRun () #18 0x002d642e in UIApplicationMain () #19 0x00001d4e in main (argc=1, argv=0xbfffee34) at /Users/suprie/Documents/Projects/Self/cocoa/TwitterSearch/main.m:14 I really appreciate for any clue to help me debug my application. EDIT this is the Header file of table #import <UIKit/UIKit.h> @interface TwitterTableViewController : UITableViewController { NSMutableArray *twitters; } @property(nonatomic,retain) NSMutableArray *twitters; @end and the implementation file #import "TwitterTableViewController.h" @implementation TwitterTableViewController @synthesize twitters; #pragma mark - #pragma mark Table view data source - (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView { // Return the number of sections. return 1; } - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { // Return the number of rows in the section. return [twitters count]; } - (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath { return 90.0f; } - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { const NSInteger TAG_IMAGE_VIEW = 1001; const NSInteger TAG_TWEET_VIEW = 1002; const NSInteger TAG_FROM_VIEW = 1003; static NSString *CellIdentifier = @"Cell"; UIImageView *imageView; UILabel *tweet; UILabel *from; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease]; // Image imageView = [[[[UIImageView alloc] initWithFrame:CGRectMake(5.0f, 5.0f, 60.0f, 60.0f)] autorelease] retain]; [cell.contentView addSubview:imageView]; imageView.tag = TAG_IMAGE_VIEW; // Tweet tweet = [[[UILabel alloc] initWithFrame:CGRectMake(105.0f, 5.0f, 200.0f, 50.0f)] autorelease]; [cell.contentView addSubview:tweet]; tweet.tag = TAG_TWEET_VIEW; tweet.numberOfLines = 2; tweet.font = [UIFont fontWithName:@"Helvetica" size:12]; tweet.textColor = [UIColor blackColor]; tweet.backgroundColor = [UIColor clearColor]; // From from = [[[UILabel alloc] initWithFrame:CGRectMake(105.0f, 55.0, 200.0f, 35.0f)] autorelease]; [cell.contentView addSubview:from]; from.tag = TAG_FROM_VIEW; from.numberOfLines = 1; from.font = [UIFont fontWithName:@"Helvetica" size:10]; from.textColor = [UIColor blackColor]; from.backgroundColor = [UIColor clearColor]; } // Configure the cell... NSMutableDictionary *twitter = [twitters objectAtIndex:(NSInteger) indexPath.row]; // cell.text = [twitter objectForKey:@"text"]; tweet.text = (NSString *) [twitter objectForKey:@"text"]; tweet.hidden = NO; from.text = (NSString *) [twitter objectForKey:@"from_user"]; from.hidden = NO; NSString *avatar_url = (NSString *)[twitter objectForKey:@"profile_image_url"]; NSData * imageData = [[NSData alloc] initWithContentsOfURL: [NSURL URLWithString: avatar_url]]; imageView.image = [UIImage imageWithData: imageData]; imageView.hidden = NO; return cell; } #pragma mark - #pragma mark Table view delegate - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { NSMutableDictionary *twitter = [twitters objectAtIndex:(NSInteger)indexPath.row]; NSLog(@"Twit ini kepilih :%@", [twitter objectForKey:@"text"]); } #pragma mark - #pragma mark Memory management - (void)didReceiveMemoryWarning { // Releases the view if it doesn't have a superview. [super didReceiveMemoryWarning]; } - (void)viewDidUnload { } - (void)dealloc { [super dealloc]; } @end

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• Complain about jQuery Tag's

  - by jAndy

  Hi Folks, I'm complaining about the growth of jQuery tagged questions at stackoverflow. There are so many people who ask, 'How to implement a specific plugin?' or 'How to use that plugin?' which makes me kinda sick. IMO: If you Tag a question to jQuery, javascript or C, it should be a question about the language itself and not some 'goofy' little plugin. Best case scenario, Tag those questions with jquery-plugins. I know I'm breaking my own rule along with this post, but I just realized that trend and I'm really interested in other opinions about that. Kind Regards --Andy

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