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  • Objective C instance variables - Newbie

    - by Dwayne King
    OK - so I'm sure my confusion here is just a result of being stuck in a "Java mindset" and not understanding how Obj C differs in this case. In Java, I can declare a variable in a class, like this, and each instance of that class will have it's own: MyClass { String myVar; MyClass() { // constructor } } In Obj C I tried to do the same thing by declaring a variable only in the .m file like this: #import "MyClass.h" @implementation MyClass NSString *testVar; @end My expectation here was that this variable has a scope limited to this class. So I created a second class (identical): #import "MySecondClass.h" @implementation MySecondClass NSString *testVar; @end What I'm seeing (and has me baffled) is that changing the variable in one class, affects the value seen in the other class. In fact, if I set a breakpoint, and then "Jump to Definition" of the variable, it takes me to th I've created an extremely small XCode project that demonstrates the problem here Nothing more humbling than moving to a new language :) Thanks in advance.

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  • WPF UserControl event called only once?

    - by 742
    Hi Everyone, I need to bind two-way a property of a user control to a property of a containing user control. I also need to set a default value to the property from code in the child (cannot be done easily from XAML tags). If I call my code from the child constructor, the value is set in the parent but the change callback routine is not triggered (my understanding is that the parent doesn't yet exist at the time the child is created). My current workaround is to catch the Loaded event of the child and to call the code from the handler. Howver as Loaded is called more than once, I need to set a flag to set the property only the first time. I don't like this way, but I don't know if there is a single shot event that could be used, or if this can be done otherwise. Any feedback based on your experience?

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  • Is the offical Sun Java EE tutorial the best way to learn how to make Java web apps?

    - by Nick
    I've been a web developer for almost a decade. I've mostly used classic ASP/JavaScript and I'd like to move into Java based apps. I have a decent understanding of Java itself (enough to know how to lookup what I don't know) and I spent some time doing minor work on a JSF/Spring/Hibernate app, but from what a trusted coworker told me, this application is the example of what not to do. I want to learn the really hardcore stuff (EJBs, HA Clustering, etc), but I know I have to walk before I can run. Is the Sun Tutorial the best place to start? Or is there an definitive book (like K&R for C or Gang of Four for design patterns) that I should buy?

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  • what the java command's -jar option really does

    - by JBoy
    Does the -jar option of the java command also compile the sources before running the main method? I believe so but i would like to have a better understanding of the internal process, from the man page you can clearly see a small workflow sequence: -jar Execute a program encapsulated in a JAR file. The first argument is the name of a JAR file instead of a startup class name. In order for this option to work, the manifest of the JAR file must contain a line of the form Main-Class: classname. Here, classname identifies the class having the public static void main(String[] args) method that serves as your application's starting point. See the Jar tool reference page and the Jar trail of the Java Tutorial @ But it does not mention that it compiles the sources.

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  • slow android emulator

    - by Andrie
    I have a 2.67GHz Celeron Processor, 1.21GBs of RAM on a x86 Windows XP Pro machine. My understanding is that the emulator should start fairly quickly on such a machine, but for me it does not. I have followed all instructions in setting up the IDE, SDKs, JDKs and such and have had some success in staring the emulator quickly but is very particulary. How can I if possible fix this problem. Even if it starts and loads home screen it is very sluggish. Any help would be appreciated guys thanks. I have tried the Eclipse IDE in Galileos, and Ganymede.

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  • How can I (is there a way to) convert an HRESULT into a system specific error message?

    - by Billy ONeal
    According to this, there's no way to convert a HRESULT error code into a Win32 error code. Therefore (at least to my understanding), my use of FormatMessage in order to generate error messages (i.e. std::wstring Exception::GetWideMessage() const { using std::tr1::shared_ptr; shared_ptr<void> buff; LPWSTR buffPtr; DWORD bufferLength = FormatMessageW( FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_IGNORE_INSERTS, NULL, GetErrorCode(), 0, reinterpret_cast<LPWSTR>(&buffPtr), 0, NULL); buff.reset(buffPtr, LocalFreeHelper()); return std::wstring(buffPtr, bufferLength); } ) does not work for HRESULTs. How do I generate these kinds of system-specific error strings for HRESULTs?

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  • Cocoa Interface Builder object initialization

    - by Stanley
    Base on the documentation and sample code that I have gone through, I got an impression that when a class defined in xcode is read into and configured in Interface Builder, an object based on the class is effectively created and stored in an xib or nib file. So the object is ready to be used when the corresponding application is launched. Alternatively, for classes that have not been handled by Interface Builder, code such as the "new" statements have to be written in xcode explicitly in order for the associated objects to be created and used. It will be very nice to have people who are more knowledgable than me to confirm or to correct my very naive understanding of Interface Builder ...

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  • Response.Redirect causes System.Threading.ThreadAbortException

    - by RandomBen
    When I use Response.Redirect(...) to redirect my form to a new page I get the error: A first chance exception of type 'System.Threading.ThreadAbortException' occurred in mscorlib.dll An exception of type 'System.Threading.ThreadAbortException' occurred in mscorlib.dll but was not handled in user code My understanding of this is that the error is being caused by the webserver aborting the remainder of the page the response.redirect was called on. I know I can add a second parameter to Response.Redirect that is called endResponse. If I set endResponse to True I still get the error but if I set it to False then I do not. I am pretty sure though that that means the webserver is running the rest of the page I redirected away from. Which would seem to be inefficient to say the least. Is there a better way to do this? Something other than Response.Redirect or is there a way to force the old page to stop loading where I will not get a ThreadAbortException?

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  • Display values and how many times they occured using a Dictionary

    - by user1730056
    I've been told to By using a dictionary (or your solution to Part 4), write a method at_least(a, n) that takes a list, a, and an integer, n, as arguments and returns a list containing only the elements of a that occur at least n times. For complete marks, the list should contain the elements in order of their first occurrence in a. I was able to figure this without using a dictionary, with def at_least2(a, n): return [x for x in a if a.count(x) is n] I was wondering how I can write this using a dictionary? The input is: a = [-6, 8, 7, 3, 2, -9, 1, -3, 2, -4, 4, -8, 7, 8, 2, -2, -7, 0, 1, -9, -3, -7, -3, -5, 6, -3, 6, -3, -10, -8] def at_least(a, 2): and the output: [8, 7, 2, -9, 1, -3, 2, -8, 7, 8, 2, -7, 1, -9, -3, -7, -3, 6, -3, 6, -3, -8] Edit: I don't understand how a dictionary is being used, yet the output isn't in dictionary form? My understanding is that dictionaries have values for each object. I'm not sure if I'm using the right terms.

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  • How to Vertically Center Images on a Line?

    - by jeremy
    What's the best way to center icons on a line when the images are smaller than the line height? For example (styles inline for easier reading): <div style="line-height: 20px"> <img style="width: 12px; height: 12px;"/> Blah blah blah </div> Here's a jsFiddle example. This example also shows why vertical-align: middle does not work. I want the img to be centered against the text of the div. That is, even if the text wrapped to multiple lines, the image would be centered against a single line. Ideally, the solution would not involve setting margings/paddings on the image and would work even if I didn't know the line-height. Things I've read: How do I vertically align text next to an image with CSS? (deals with case where image is larger, doesn't seem to apply here) Understanding vertical-align

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  • Which is the future of web development: HTML5 or Silverlight(or other RIA framework)?

    - by Morgan Cheng
    My colleagues have a heated debate on what is the future of web development. One side is supporting HTML5 and the other is supporting Silverlight. There is no conclusion of the debate yet. In my humble opinion as a programmer, HTML5 will not improve programming productivity, while Silverlight will. In my understanding, programmers still need to program in JavaScript to take advantage of HTML5. For Silverlight, we can use C# which is static-type language. A lot of coding defects can be found in compilation time. For HTML5, different browsers might still have different behavior even though there is spec. For Silverlight, generally what works in IE will work the same way in other browsers. Just my thoughts. Any idea on how to choose future direction of web development?

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  • PHP no wait sem_acquire?

    - by SerEnder
    Not a specific code question, but more of a general coding question. I'm trying to use a semaphore in a work project to limit the number of users that can access certain processes at a concurrent time. From my understanding the following: $iKey = ftock($sSomeFileLocation,'sOneCharacterString'); //Generate the key if($sem_id = sem_get($iKey){ //1 user allowed if(sem_acquire($sem_id)){ //Do the limited process here sem_release($sem_id); } } The problem that I see here is that if there is already one user who has the semaphore key, then the next user just waits until the first user is done rather than just faulting out. Anyone know of a way that if the max_acquire number has been reached, sem_acquire (or similar) will just return false? Thanks

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  • geom_rect and NULL

    - by csgillespie
    I've been looking at the geom_rect example in section 5.10 of the ggplot2 book and don't understand the purpose of the NULL's in the aes function. For example, using the mpg data: g = ggplot(data=mpg, aes(x=displ, y=hwy)) + geom_point() #Produces a plot with a transparent filled region g + geom_rect(aes(NULL, NULL), alpha=0.1,xmin=5, xmax=7, ymin=10, ymax=45, fill="blue") #Solid filled region (v0.9) or nothing in v0.8 g + geom_rect(alpha=0.1,xmin=5, xmax=7, ymin=10, ymax=45, fill="blue") My understanding is that the NULL's are resetting the x & y mapping, but I don't see why this should affect the transparency.

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  • Casting to specific asp.net page type

    - by DEH
    I have an asp.net page with a code-behind class definition as follows: public partial class examplepage : System.Web.UI.Page I'd like to set a public property within the page that I can reference from other classes. My understanding is that if I cast to examplepage then I should be able to get at the public property that is specific to example page, as in: string test=((examplepage)HttpContext.Current.Handler).propertyX; However, when I try casting as above the compiler does not recognise examplepage. Can anyone tell me how I can cast? I have no specific namespaces defined. Thanks

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  • Is Learning the win32 API Worthwhile?

    - by kronoz
    I was certain that somebody would have specifically asked this question, but from what I can see no-one has (there's been a question about learning win32 but that doesn't cover whether it's worthwhile doing so). I am very interested in gaining a deeper understanding of all the systems I use (I mostly program in C#, at least professionally), so I wondered, very simply - is learning win32 worthwhile, or is it overkill? Am I wasting my time? Is the knowledge I'd gain worth the effort? Similar / related questions on StackOverflow: Does it still make sense to learn low level WinAPI programming? How relevant is Win32 programming to modern professionals?

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  • How To: Call a web service from ajax

    - by Kolten
    I have a simple Web Service that send email and is called via: public bool SendMail(string format, string from, string to, string cc, string bcc, string subject, string body, string replyTo) I have never used ajax before, and find I need to call this service and pass form contents to it from a simple html page (I cannot use asp or asp.net unfortunately). Can I get a quick rundown of what is required? I have searched for simple examples, but find I am having difficulty understanding how to call it and pass the parameters required of the Web Service. Thanks all!

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  • Why are Asynchronous processes not called Synchronous?

    - by Balk
    So I'm a little confused by this terminology. Everyone refers to "Asynchronous" computing as running different processes on seperate threads, which gives the illusion that these processes are running at the same time. This is not the definition of the word asynchronous. a·syn·chro·nous –adjective 1. not occurring at the same time. 2. (of a computer or other electrical machine) having each operation started only after the preceding operation is completed. What am I not understanding here?

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  • How to remove thie ".svc" extension in RESTful WCF service?

    - by Morgan Cheng
    In my knowledge, the RESTful WCF still has ".svc" in its URL. For example, if the service interface is like [OperationContract] [WebGet(UriTemplate = "/Value/{value}")] string GetDataStr(string value); The access URI is like "http://machinename/Service.svc/Value/2". In my understanding, part of REST advantage is that it can hide the implementation details. A RESTful URI like "http://machinename/Service/value/2" can be implemented by any RESTful framework, but a "http://machinename/Service.svc/value/2" exposes its implementation is WCF. How can I remove this ".svc" host in the access URI?

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  • Logical Programming Problem

    - by user353060
    Hello, I've been trying to solve this problem for quite sometime but I am having trouble with it. Let's say on a trigger, you receive values. First trigger: You get 1 Second trigger: You get 1, 2 Third trigger: You get 1, 2, 3 So, I store 1. For 2nd trigger, I store 2 since 1 already exist. For 3rd trigger, I store 3 since 1,2 already exist so in total I have stored 1,2,3 As you can see, we can easily check for new values, if old != new. Here's come the problem: Fourth trigger: You get 1, 2, 4 For 4th trigger, I store 1, 2 because it exists but how do I check against 3 and remove 3 from store and check if 4 is new? If you are having problems understanding this, feel free to clarify. Thanks!

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  • Hibernate entities stored as HttpSession attribute values

    - by njudge
    I'm dealing with a legacy Java application with a large, fairly messy codebase. There's a fairly standard 'User' object that gets stored in the HttpSession between requests, so the servlets do stuff like this at the top: HttpSession session = request.getSession(true); User user = (User)session.getAttribute("User"); The old user authentication layer (which I won't describe; suffice to say, it did not use a database) is being replaced with code mapped to the DB with Hibernate. So 'User' is now a Hibernate entity. My understanding of Hibernate object life cycles is a little fuzzy, but it seems like storing 'User' in the HttpSession now becomes a problem, because it will be retrieved in a different transaction during the next request. What is the right thing to be doing here? Can I just use the Hibernate Session object's update() method to reattach the User instance the next time around? Do I need to?

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  • problems with Haskell's Number Types

    - by mindeavor.
    I have the following haskell code: fac n = product [1..n] taylor3s w0 f f' f'' t h = w1 : taylor3s w1 f f' f'' (t+h) h where hp i = h^i / fac i w1 = w0 + (hp 1) * f t w0 + (hp 2) * f' t w0 + (hp 3) * f'' t w0 taylor_results = take 4 $ taylor3s 1 f f' f'' 1 0.25 where f t x = t^4 - 4*x/t f' t x = 4*t^3 - 4*(f t x)/t + 4*x/t^2 f'' t x = 12*t^2 - 4*(f' t x)/t + 8*(f t x)/t^2 - 8*x/t^3 taylor_results is supposed to be a use case of taylor3s. However, there is something wrong with the number type inferencing. When I try to compile, this is the error I get: practice.hs:93:26: Ambiguous type variable `a' in the constraints: `Integral a' arising from a use of `taylor3s' at practice.hs:93:26-51 `Fractional a' arising from a use of `f' at practice.hs:93:37 Possible cause: the monomorphism restriction applied to the following: taylor_results :: [a] (bound at practice.hs:93:0) Probable fix: give these definition(s) an explicit type signature or use -XNoMonomorphismRestriction Can someone help me with understanding what the problem is?

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  • Rails routes looking for show action

    - by user1334345
    I am pretty new to rails and basically I want to make a user registration form. I am currently using rails 3.2.3 Basically I want to make basic routes like user/register on top of basic REST route for user. Here are my routes.rb resources :user do collection do get 'register' end end And here are my rake routes: register_user_index GET /user/register(.:format) user#register user_index GET /user(.:format) user#index POST /user(.:format) user#create new_user GET /user/new(.:format) user#new edit_user GET /user/:id/edit(.:format) user#edit user GET /user/:id(.:format) user#show PUT /user/:id(.:format) user#update DELETE /user/:id(.:format) user#destroy From my understanding, since register user is on top of show, it should match with register first before going to show. However, when I try to do localhost:3000/user/register, it gives me this error: No route matches {:action="show", :controller="user"} Can somebody help me with this? Thanks!!

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  • How messages flows between computers connected with Internet or LAN ?

    - by Praveen
    Hi All, I have been doing Windows programming in .Net since last two years. Now I am shifting to web programming so I just stuck in understanding the fundamentals of web programming, after googling I came to StackOverflow to learn from all of you great guys. My confusion is about how messages flow between systems in distributed enviornment ? I mean suppose I want to send a message "Hello" to a system connected to LAN or Internet, then what will be the steps taken to send the message. Second thing is suppose my system is "A" and I wana send message to system "B" which is connected via a wire, so how the message flows on wire and how system "B" reads it from the wire ? Please someone explain me in a layman terms. Thank you all in advance.

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  • How to Vertically Center Icons on a Line?

    - by jeremy
    What's the best way to center icons on a line when the icons are smaller than the line height? For example (styles inline for easier reading): <div style="line-height: 20px"> <img style="width: 12px; height: 12px;"/> Blah blah blah </div> I want the img to be centered on a single line of the div, above. That is, even if the text wrapped to multiple lines, the image would be centered against a single line. Ideally, the solution would not involve setting margings/paddings on the image and would work even if I didn't know the line-height. Things I've read: How do I vertically align text next to an image with CSS? (deals with case where image is larger, doesn't seem to apply here) Understanding vertical-align

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  • How to start coding the "Dining Philosophers" simulation?

    - by GrizzlyGuru
    I'm not a beginner at C# but I really need to increase my understanding, so I've picked a classic deadlock problem to code to help teach myself some of the more advanced concepts of C#. The Dining Philosophers Problem seems like a good one, but I need a little help to get started. I know I need to approach the "diners" as objects, but to simulate the random delays between eating, should I look to threading with each diner in a separate thread? Do I need some kind of "master" to monitor all the actions? Any general design concept advice is welcome, but I'd like to do the grunt programming as an exercise. Thanks!

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