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• Learn C first before learning Objective-C

  - by Lark

  Being an aspiring Apple developer, I want to get the opinions of the community if it is better to learn C first before moving into Objective-C and ultimately the Cocoa Framework? My gut says learn C, which will give me a good foundation.

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• Optimising RSS parsing on App Engine to avoid high CPU warnings

  - by Danny Tuppeny

  I'm pulling some RSS feeds into a datastore in App Engine to serve up to an iPhone app. I use cron to schedule updating the RSS every x minutes. Each task only parses one RSS feed (which has 15-20 items). I frequently get warnings about high CPU usage in the App Engine dashboard, so I'm looking for ways to optimise my code. Currently, I use minidom (since it's already there on App Engine), but I suspect it's not very efficient! Here's the code: dom = minidom.parseString(urlfetch.fetch(url).content) if dom: items = [] for node in dom.getElementsByTagName('item'): item = RssItem( key_name = self.getText(node.getElementsByTagName('guid')[0].childNodes), title = self.getText(node.getElementsByTagName('title')[0].childNodes), description = self.getText(node.getElementsByTagName('description')[0].childNodes), modified = datetime.now(), link = self.getText(node.getElementsByTagName('link')[0].childNodes), categories = [self.getText(category.childNodes) for category in node.getElementsByTagName('category')] ); items.append(item); db.put(items); def getText(self, nodelist): rc = '' for node in nodelist: if node.nodeType == node.TEXT_NODE: rc = rc + node.data return rc There isn't much going on, but the scripts often take 2-6 seconds CPU time, which seems a bit excessive for looping through 20ish items and reading a few attributes. What can I do to make this faster? Is there anything particularly bad in the above code, or should I change to another way of parsing? Are there are any libraries (that work on App Engine) that would be better, or would I be better parsing the RSS myself?

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• Learning about tests for junior programmers

  - by RHaguiuda

  I`m not sure if its okay to ask it on stackoverflow. Ive been reading a log about tests, unit tests, tests frameworks, mocks and so on, but as a junior programmer I dont know anything about tests, not even where to start! Can anyone explain to young programmers about tests, how they`re run, where and what to test, what is unit testing, integration testing, automated tests? How much to test? And more important: how much test is enough? I belive this would be very helpfull. If possible indicate a few books too about these subjects. Thanks

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• Datamodel for a MVC learning project

  - by Dofs

  Hi, I am trying to learn Microsoft MVC 2, and have in that case found a small project I wanted to deploy it on. My idea was to simulate a restaurant where you can order a table. Basics: A user can only reserve a full table, so I don't have the trouble of merging people on different tables. A person can order a table for a certain amount of hours. My question was how I could make the data model the smartest way. I thought of just having a my database like this: Table { Id, TableName } Reservations { Id TableId ReservedFrom ReservedTo UserId } User { UserId UserName ... } By doing it this way I would have to program a lot of the logic in e.g. the business layer, to support which tables are occupied at what time, instead of having the data model handle it. Therefore do you guys have a better way to do this?

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• Learning OOP Design

  - by waiwai933

  I've read Head First Java, and I understand how OOP works. Here's my problem: I'm a PHP programmer, and while I've used OOP in PHP, I'm having trouble figuring out what should be an object and what methods to give it. For example, let's say I have a app that allows people to log in and edit a document. Why should the document be an object if there will ever only be one instance? Should I give the deleteDocument() method to the document object or the admin object? The document is the one being deleted, but the admin is the one performing the action. So my real question is, coming from a procedural background, how do I figure out what should be objects and what should have what methods?

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• Explaining the need to avoid horizontal scroll

  - by Bradley Herman

  I need help explaining to my boss why her design is poor on a client's website. She has no knowledge of the web, and it can be difficult as a web developer working with a woman who is a graphic designer (not even a web designer really). On a current site she has designed, an image bar "needs" to be ~1200px according to her, though it isn't necessary with the content. A quick sketch to illustrate what's going on: As you see, the banner spills out past the 960px of the content and as wide as 1200px. This creates a horizontal scroll when all the content is viewable within the 960px wide viewport. I need to make this an <img and not a CSS background because it's a jQuery slideshow that fades from image to image. I think this is a big problem because a lot of people are going to get a horizontal scroll bar imposed in their browser when they're still able to see all the relevant content. She thinks no one will notice and it'll be fine; I think it's very bad practice and confusing to the end user. How do I explain the problem to her?

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• Efficient code to avoid circular references in c# object model

  - by Kumar

  I have an excel like grid where values can be typed referencing other rows To check for circular references when a new value is entered, i traverse the tree and create a list of values referenced thus far, if the current value is found in this list, i return an error thus avoiding a circular reference. This is infrequent enough where extreme performance is not an issue but... Question - is there a better way ? I'm told it's not the most optimal but no answer was provided so on to the experts @ SO :)

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• Resources for learning Monads, Functors, Monoids, Arrows etc

  - by Dony Borris

  Can you people please suggest some good books / weblinks from where I can get to learn about above mentioned concepts? (Please note that I am a Java programmer and have NO prior experience with functional programming. I have been studying Scala since last one month and would appreciate the resources that try to teach the above mentioned concepts with Scala. (or even Java, if posible))

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• Two-phase lookup: can I avoid "code bloat"?

  - by Pietro

  Two-phase lookup question: Is there a more synthetic way to write this code, i.e. avoiding all those "using" directives? I tried with "using CBase<T>;", but it is not accepted. #include <iostream> template <typename T> class CBase { protected: int a, b, c, d; // many more... public: CBase() { a = 123; } }; template <typename T> class CDer : public CBase<T> { // using CBase<T>; // error, but this is what I would like using CBase<T>::a; using CBase<T>::b; using CBase<T>::c; //... public: CDer() { std::cout << a; } }; int main() { CDer<int> cd; } In my real code there are many more member variables/functions, and I was wondering if it is possible to write shorter code in some way. Of course, using the CBase::a syntax does not solve the problem... Thank's! gcc 4.1 MacOS X 10.6

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• How to avoid game rendering component circular references?

  - by CodexArcanum

  I'm working on a simple game design, and I wanted to break up my game objects into more reusable components. But I'm getting stuck on how exactly to implement the design I have in mind. Here's an example: I have a Logger object, whose job is simply to store a list of messages and render them to screen. You know, logging. Originally the Logger just held the list, and the game loop rendered it's contents. Then I moved the rendering logic into the Logger.Draw() method, and now I want to move it further into a LoggerRenderer object. In effect, I want to have the game loop call RenderAll, which will then call Logger.Render, which will in turn call the LoggerRenderer.Render and finally output the text. So the Logger needs to contain a Renderer object, but the Renderer needs access to the Logger's state (the message queue) in order to render. How do I resolve that? Should I be passing in the message queue and other state information explicitly to the Render method? Or should the game loop be calling the Renderer directly and it links back to the logger, but the RenderAll method never actually sees the logger object itself? This feels kind of like Command pattern, but I'm botching it up terribly.

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• Avoid trailing zeroes in printf()

  - by Gorpik

  I keep stumbling on the format specifiers for the printf() family of functions. What I want is to be able to print a double (or float) with a maximum given number of digits after the decimal point. If I use: printf("%1.3f", 359.01335); printf("%1.3f", 359.00999); I get 359.013 359.010 Instead of the desired 359.013 359.01 Can anybody help me?

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• Learning to create beautiful /next-generation GUI

  - by ShaChris23

  I really want to create a stunning-looking GUI desktop application that looks like, for example: Mac OS X interface Picasa desktop client on windows IPhone apps Office 2007 I've mostly been programming GUI using Qt/Swing/WinForm and I'm tired of creating so plain looking GUI, lol. So I was thinking about diving into stuff like: jQuery WPF/C# iPhone SDK Silverlight Adobe Air/Flex Just to get some ideas on how to create really cool looking UI. Does that sound like a good list? Any developers here that could share what platform they use to create very cool looking desktop app? On a sidenote, I really wonder what developers at Apple / Microsoft use to develop their own cool-looking software. EDIT A lot of responses talk about the importance of usability over "cool-looking".. I totally agree that usability and simplicity are the most important aspects of user interface design. I've been doing GUI development for a while now ( 3 years), so that I understand. But using cool-looking UI also improves user experience + it could make big difference on whether or not your software sells. I mean, otherwise why would Microsoft/Apple try to make their OS UI look "cooler" everytime there's a new version? Why would websites like pragprog.com, or versionsapp.com. make their websites look like that? Basically you kill 2 birds with one stone: stunnning-looking UI + super usability (because it looks simple and intuitive). That is what I'm striving for. And as far as I know, I cannot achieve that using Qt/Winform. Most of the books I have read just show you how to make average-looking (read: 1990's) UI. I want to learn how to create cool-looking UI. And the only place I see cool-looking UIs these days are the technology I list above. I'm not enamored with any technology; but I just want to know how things are done in other technology to see if I could apply them to the technology I'm using, or see if I could use those technology in my line of work. An example: if I were to pick between this UI and this UI, I probably would pick the latter, if just based on looks alone. Functionally, they are just the same UI; they both allow you to keep track of your time. They both contain buttons and textboxes, etc. But the fact that they look different, also differentiate them in terms of attractiveness. So in all, I think the "ice on the cake" is very important. I would say it's the thing you strive for after you are certain you have a totally intuitive, usable UI.

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• How to cast sockaddr_storage and avoid breaking strict-aliasing rules

  - by sinoth

  I'm using Beej's Guide to Networking and came across an aliasing issue. He proposes a function to return either the IPv4 or IPv6 address of a particular struct: 1 void *get_in_addr( struct sockaddr *sa ) 2 { 3 if (sa->sa_family == AF_INET) 4 return &(((struct sockaddr_in*)sa)->sin_addr); 5 else 6 return &(((struct sockaddr_in6*)sa)->sin6_addr); 7 } This causes GCC to spit out a strict-aliasing error for sa on line 3. As I understand it, it is because I call this function like so: struct sockaddr_storage their_addr; ... inet_ntop(their_addr.ss_family, get_in_addr((struct sockaddr *)&their_addr), connection_name, sizeof connection_name); I'm guessing the aliasing has to do with the fact that the their_addr variable is of type sockaddr_storage and another pointer of a differing type points to the same memory. Is the best way to get around this sticking sockaddr_storage, sockaddr_in, and sockaddr_in6 into a union? It seems like this should be well worn territory in networking, I just can't find any good examples with best practices. Also, if anyone can explain exactly where the aliasing issue takes place, I'd much appreciate it.

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• How to avoid namespace content indentation in vim?

  - by freitass

  How to set vim to not indent namespace content in C++? namespace { < statement_list > // Unwanted indentation } Surprisingly, 'cinoptions' doesn't provide a way to edit namespace content indentation.

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• Avoid generating empty STDOUT and STDERR files with Sun Grid Engine (SGE) and array jobs

  - by vy32

  I am running array jobs with Sun Grid Engine (SGE). My carefully scripted array job workers generate no stdout and no stderr when they function properly. Unfortunately, SGE insists on creating an empty stdout and stderr file for each run. Sun's manual states: STDOUT and STDERR of array job tasks will be written into dif- ferent files with the default location .['e'|'o']'.' In order to change this default, the -e and -o options (see above) can be used together with the pseudo-environment-vari- ables $HOME, $USER, $JOB_ID, $JOB_NAME, $HOSTNAME, and $SGE_TASK_ID. Note, that you can use the output redirection to divert the out- put of all tasks into the same file, but the result of this is undefined. I would like to have the output files suppressed if they are empty. Is there any way to do this?

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• Any specifications/docs around optimization of Google Apps Script, to avoid timeouts and "hangs"

  - by BruceM

  From my experience so far, it seems that if you write a script that makes lots of expensive calls close together, the functionality just "hangs", or you get inconsistent responses, and have to refresh the browser because sheets stop updating etc. Are there any docs or specs that clarify this, as releasing an app fr real-world use is not possible if users can expect it to work most of the time, and produce random results every now and then...

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• How to avoid mixed eol-styles in a svn repository

  - by Ken

  Is there a best practice for preventing mixed eol-styles in a subversion repository. I know that svn:eol-style=native can be set as an auto-prop, but I would have to ensure that it was set for all committers. I'm also reluctant to do a retrospective, repository-wide change of svn:eol-style if there is a less invasive solution.

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• How to avoid serializing zero values with Simple Xml

  - by Bram Vandenbussche

  I'm trying to serialise an object using simple xml (http://simple.sourceforge.net/). The object setup is pretty simple: @Root(name = "order_history") public class OrderHistory { @Element(name = "id", required = false) public int ID; @Element(name = "id_order_state") public int StateID; @Element(name = "id_order") public int OrderID; } The problem is when I create a new instance of this class without an ID: OrderHistory newhistory = new OrderHistory(); newhistory.OrderID = _orderid; newhistory.StateID = _stateid; and I serialize it via simple xml: StringWriter xml = new StringWriter(); Serializer serializer = new Persister(); serializer.write(newhistory, xml); it still reads 0 in the resulting xml: <?xml version='1.0' encoding='UTF-8'?> <order_history> <id>0</id> <id_order>2</id_order> <id_order_state>8</id_order_state> </order_history> I'm guessing the reason for this is that the ID property is not null, since integers can't be null. But I really need to get rid of this node, and I'd rather not remove it manually. Any clues anyone?

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• How to avoid "message superview sent to freed object" iphone

  - by Giovanni

  I have this code: CardView *aCardView = [self prendiCartaDalMazzo]; [aCardView removeFromSuperview]; [self.mieCarte addSubview:aCardView]; when i try to add aCardView as as subview of mieCarte then i get this error: objc[4800]: FREED(id): message superview sent to freed object=0x393f130 Program received signal: “EXC_BAD_INSTRUCTION”. Thanks at all can help.

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• Learning Hibernate: too many connections

  - by stivlo

  I'm trying to learn Hibernate and I wrote the simplest Person Entity and I was trying to insert 2000 of them. I know I'm using deprecated methods, I will try to figure out what are the new ones later. First, here is the class Person: @Entity public class Person { private int id; private String name; @Id @GeneratedValue(strategy = GenerationType.TABLE, generator = "person") @TableGenerator(name = "person", table = "sequences", allocationSize = 1) public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } } Then I wrote a small App class that insert 2000 entities with a loop: public class App { private static AnnotationConfiguration config; public static void insertPerson() { SessionFactory factory = config.buildSessionFactory(); Session session = factory.getCurrentSession(); session.beginTransaction(); Person aPerson = new Person(); aPerson.setName("John"); session.save(aPerson); session.getTransaction().commit(); } public static void main(String[] args) { config = new AnnotationConfiguration(); config.addAnnotatedClass(Person.class); config.configure("hibernate.cfg.xml"); //is the default already new SchemaExport(config).create(true, true); //print and execute for (int i = 0; i < 2000; i++) { insertPerson(); } } } What I get after a while is: Exception in thread "main" org.hibernate.exception.JDBCConnectionException: Cannot open connection Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Too many connections Now I know that probably if I put the transaction outside the loop it would work, but mine was a test to see what happens when executing multiple transactions. And since there is only one open at each time, it should work. I tried to add session.close() after the commit, but I got Exception in thread "main" org.hibernate.SessionException: Session was already closed So how to solve the problem?

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• Why avoid increment ("++") and decrement ("--") operators in JavaScript?

  - by artlung

  I'm a big fan of Douglas Crockford's writing on JavaScript, particularly his book JavaScript: The Good Parts. It's made me a better JavaScript programmer and a better programmer in general. One of his tips for his jslint tool is this : ++ and -- The ++ (increment) and -- (decrement) operators have been known to contribute to bad code by encouraging excessive trickiness. They are second only to faulty architecture in enabling to viruses and other security menaces. There is a plusplus option that prohibits the use of these operators. This has always struck my gut as "yes, that makes sense," but has annoyed me when I've needed a looping condition and can't figure out a better way to control the loop than a while( a < 10 )do { a++ } or for (var i=0;i<10;i++) { } and use jslint. It's challenged me to write it differently. I also know in the distant past using things, in say PHP like $foo[$bar++] has gotten me in trouble with off-by-one errors. Are there C-like languages or other languages with similarities that that lack the "++" and "--" syntax or handle it differently? Are there other rationales for avoiding "++" and "--" that I might be missing? UPDATE -- April 9, 2010: In the video Crockford on JavaScript -- Part 5: The End of All Things, Douglas Crockford addresses the ++ issue more directly and with more detail. It appears at 1:09:00 in the timeline. Worth a watch.

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• Explaining to boss why we need to avoid horizontal scroll

  - by Bradley Herman

  I need help explaining to my boss why her design is poor on a clients website. She has no knowledge of web and it can be difficult as a web developer working with a woman who is a graphic designer (not even a web designer really). On a current site she has designed, an image bar "needs" to be like 1200px according to her, though it isn't necessary with the content. I'll show a quick sketch to illustrate what's going on: http://imgur.com/MNGOT.jpg As you see, the banner spills out past the 960px of the content and as wide as 1200px. This creates a horizontal scroll when all the content is viewable within the 960px wide viewport. I need to make this an img and not a css background because it's a jquery slideshow that fades from image to image. I think this is a big problem because a lot of people are going to get a horizontal scroll bar imposed in their browser when they're still able to see all the relevant content. How do I help her explain it. She thinks no one will notice and it'll be fine, I think it's very bad practice and confusing to the end user. Any help?

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• Summer Learning Opportunities for an upcoming College Freshman

  - by SteveStifler

  I'm currently a senior in high school, about to matriculate and pursue a major in Computer Science (possibly dual-major with electrical engineering. Comments?). I already program regularly as a hobby, but I would like to get a jump start this summer by perhaps attending a seminar, helping out on an open source project...you know, something legitimate that will bolster my knowledge of the computer science field. Any ideas?

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• Newbie: UINavigationController is pulling me back from further learning :(

  - by nithin

  I have created a window-based application and my problem is I am unable to create UINavigationController on the go. InFact I don't know how to do that. My AppDelegeate - (void)applicationDidFinishLaunching:(UIApplication *)application { // Override point for customization after application launch [window addSubview:logInView.view]; [window makeKeyAndVisible]; } here the logInView is an object of @interface LogInViewController : UIViewController { IBOutlet UITextField *usernameField; IBOutlet UITextField *passwordField; IBOutlet UIButton *logInButton; } -(IBAction) logInClick:(id) sender; from the click action of this loginviewcontroller It should be showing the home screen with navigation controller. and I have to add many subviews. My question is where should I init the UINavigationController and where could I write the codes for adding subviews? how to map it with interfacebuilder?

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• Learning web development as I go

  - by Matt Luongo

  Hey everybody, I've been seriously preparing to take the entrepreneurship leap. I've got a great partner, and we're going to take on some minor funding, and do the thing. Our product is web-based- I'll deem it YAWA (Yet Another Web Application). Both my partner and I have database and web development experience, and I've had a front-end developer in mind for a while. Except, well- he just bowed out. I know a fair amount about the associated technologies (XHTML, CSS, Javascript and some JQuery) interface-side, but I've never had to deal with real-world scenarios, eg cross-browser design. Am I going to be able to survive without this guy? Is it realistic to believe that I can learn the details as I go?

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