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  • Why is the Objective-C Boolean data type defined as a signed char?

    - by EddieCatflap
    Something that has piqued my interest is Objective-C's BOOL type definition. Why is it defined as a signed char (which could cause unexpected behaviour if a value greater than 1 byte in length is assigned to it) rather than as an int, as C does (much less margin for error: a zero value is false, a non-zero value is true)? The only reason I can think of is the Objective-C designers micro-optimising storage because the char will use less memory than the int. Please can someone enlighten me?

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  • Would knowing Python help with creating iPhone applications?

    - by Josh
    Here is what the apple site says: With Snow Leopard, Mac OS X makes it easy to use scripting languages as full application development tools. Snow Leopard ships with support for the RubyCocoa Bridge and the PyObjC bridge. These two bridges give developers access not only to system APIs, but to Cocoa frameworks such as AppKit and Core Data, enabling you to build fully native Mac OS X applications in Ruby or Python. The RubyCocoa and PyObjC bridges allow you to freely mix code written in Objective-C with code written in the scripting language. You can quickly build prototypes and then optimise by implementing performance-critical pieces in Objective-C. How could Python help in this case?

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  • What is the convention for the star location in reference variables?

    - by Brett Ryan
    Have been learning Objective-C and different books and examples use differing conventions for the location of the star (*) when naming reference variables. MyType* x; MyType *y; MyType*z; // this also works Personally I prefer the first option as it illustrates that x is a "pointer type of MyType". I see the first two used interchangeably, and sometimes in the same code I've seen differing uses of both. I want to know what is the most common convention It's been a very long time since I've programmed in C (15 years) so I can't remember if all variants are legal for C also or if this is Objective-C specific. I'd prefer answers which state why one is better than the other, as how I explained how I read it above.

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  • When should one use "out" parameters?

    - by qegal
    In Objective-C, there are several methods like initWithContentsOfFile:encoding:error: where one passes in a reference to an NSError object for the error: parameter. In this example, the value of the NSError object passed in can change based on what goes on at runtime when the method is being called and whether the body of the method was executed in a certain way successfully. In a way I think of this NSError object as sort of like a second return value from the method, and only differs from an object anObject in the statement return anObject; in that when this statement is called, execution leaves the method. So my question is, not only in the context of error handling in Objective-C, but in general, when should one use an "out" parameter in place of returning said value in a return statement?

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  • Learning C++ but wanting to develop iOS Apps

    - by DiscreteGenius
    I'm a computer engineering student and taking my second programming class. I'm learning C++ using "C++ Primer Plus" 5th edition by Prata. I want to develop for iOS. I understand the main language for Xcode is Objective-C. Am I hurting myself by learning C++ before any other language (notably before my desired lang Objective-C)? There's got to be a reason the university requires C++ to learn as a basis language. Please offer any helpful guidance or how I should go about this. Thanks//

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  • Switching domains in one's career?

    - by rocknroll
    I have been a C++,Qt programmer for the last 3.5 years and have hit a plateau in terms of doing something new. Work has been repetitive and routine. I personally believe it is time to move on but off late I am getting more offers in mobile development like Android,Iphone etc. The latest offer I have is for objective-C based profile. I do not have the slightest idea about objective-C apart from that it is Object oriented C resembling C++ but not exactly a clone. Questions in my mind are --what are the pros/cons of this careers switch or for any such switch? --Is it good for one's career to change domains after sometime? --How difficult it is to get back to one's previous area of proficiency? Thanks

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  • I'm looking for websites with programming problems that I can practice [on hold]

    - by Spentak
    I want to become a more skilled programmer. I also want to do it through Objective-C and iOS. What websites or programs that you know of have problems that I can solve (with the answers)? I have failed some programming tests for jobs (such as "Given 2 values in a Binary Tree - how do you find the lowest common ancestor?) and I want to become a better engineer. I have developed 54 iOS/Android apps to date, but my core CS Skills apparently are rusty/bad. I have looked at TopCoder - but there aren't very many competitions going on, the website is terrible, and there does not appear to be anything that really supports Objective-C/iOS Websites?

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  • How can I add forward class references used in the -Swift.h header?

    - by Bill
    I'm integrating Swift code into a large Objective-C project, but I'm running into problems when my Swift code refers to Objective-C classes. For example, suppose I have: An Objective-C class called MyTableViewController An Objective-C class called DeletionWorkflow I declared a Swift class as follows: class DeletionVC: MyTableViewController { let deleteWorkflow: DeletionWorkflow ... } If I now try to use this class by importing ProjectName-Swift.h into Objective-C code, I get undefined symbol errors for both MyTableViewController and DeletionWorkflow. I can fix the problem in that individual source file by importing DeletionWorkflow.h and MyTableViewController.h before I import ProjectName-Swift.h but this doesn't scale up to a large project where I want my Swift and Objective-C to interact often. Is there a way to add forward class references to ProjectName-Swift.h so that these errors don't occur when I try to use Swift classes from Objective-C code in my app?

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  • Convert C function to Objective C or alternative way to include C library?

    - by Moshe
    Background: I'm new to Objective-C and I've never touched C before. I'm trying to include a C library in my iPhone/iPod Touch project and I could not successfully compile the library's source code using the included instructions, so I've resorted to including the .h and .c files in Xcode. The library is for Hebrew Dates and corresponding Jewish Holidays. It can be found here: http://sourceforge.net/projects/libhdate/ I cannot seem to import the .c files into my implementation files. I can import the .h files though. When I try to use #import "file.c", where file.c is a file that is in XCode, it doesn't work. Why not? I've considered just writing the functions over in Objective-C, albeit only my needed functions and not the whole library. How can I make the following C function work in Objective-C? Are there other things that need to be included/re-coded/compiled? How so? I am almost certain something is missing, but I'm not sure what. Code: int hdate_get_omer_day(hdate_struct const * h) { int omer_day; hdate_struct sixteen_nissan; hdate_set_hdate(&sixteen_nissan, 16, 7, h->hd_year); omer_day = h->hd_jd - sixteen_nissan.hd_jd + 1; if ((omer_day > 49) || (omer_day < 0)) omer_day = 0; return omer_day; } So... should I be converting it, or trying somehow to compile to an appropriate format and how so? (I don't know what format a static library should be in, by the way, or if it should be static... - I'm so lost here....) I appreciate the help!

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  • Help needed with AES between Java and Objective-C (iPhone)....

    - by Simon Lee
    I am encrypting a string in objective-c and also encrypting the same string in Java using AES and am seeing some strange issues. The first part of the result matches up to a certain point but then it is different, hence when i go to decode the result from Java onto the iPhone it cant decrypt it. I am using a source string of "Now then and what is this nonsense all about. Do you know?" Using a key of "1234567890123456" The objective-c code to encrypt is the following: NOTE: it is a NSData category so assume that the method is called on an NSData object so 'self' contains the byte data to encrypt. - (NSData *)AESEncryptWithKey:(NSString *)key { char keyPtr[kCCKeySizeAES128+1]; // room for terminator (unused) bzero(keyPtr, sizeof(keyPtr)); // fill with zeroes (for padding) // fetch key data [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding]; NSUInteger dataLength = [self length]; //See the doc: For block ciphers, the output size will always be less than or //equal to the input size plus the size of one block. //That's why we need to add the size of one block here size_t bufferSize = dataLength + kCCBlockSizeAES128; void *buffer = malloc(bufferSize); size_t numBytesEncrypted = 0; CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt, kCCAlgorithmAES128, kCCOptionPKCS7Padding, keyPtr, kCCKeySizeAES128, NULL /* initialization vector (optional) */, [self bytes], dataLength, /* input */ buffer, bufferSize, /* output */ &numBytesEncrypted); if (cryptStatus == kCCSuccess) { //the returned NSData takes ownership of the buffer and will free it on deallocation return [NSData dataWithBytesNoCopy:buffer length:numBytesEncrypted]; } free(buffer); //free the buffer; return nil; } And the java encryption code is... public byte[] encryptData(byte[] data, String key) { byte[] encrypted = null; Security.addProvider(new org.bouncycastle.jce.provider.BouncyCastleProvider()); byte[] keyBytes = key.getBytes(); SecretKeySpec keySpec = new SecretKeySpec(keyBytes, "AES"); try { Cipher cipher = Cipher.getInstance("AES/ECB/PKCS7Padding", "BC"); cipher.init(Cipher.ENCRYPT_MODE, keySpec); encrypted = new byte[cipher.getOutputSize(data.length)]; int ctLength = cipher.update(data, 0, data.length, encrypted, 0); ctLength += cipher.doFinal(encrypted, ctLength); } catch (Exception e) { logger.log(Level.SEVERE, e.getMessage()); } finally { return encrypted; } } The hex output of the objective-c code is - 7a68ea36 8288c73d f7c45d8d 22432577 9693920a 4fae38b2 2e4bdcef 9aeb8afe 69394f3e 1eb62fa7 74da2b5c 8d7b3c89 a295d306 f1f90349 6899ac34 63a6efa0 and the java output is - 7a68ea36 8288c73d f7c45d8d 22432577 e66b32f9 772b6679 d7c0cb69 037b8740 883f8211 748229f4 723984beb 50b5aea1 f17594c9 fad2d05e e0926805 572156d As you can see everything is fine up to - 7a68ea36 8288c73d f7c45d8d 22432577 I am guessing I have some of the settings different but can't work out what, I tried changing between ECB and CBC on the java side and it had no effect. Can anyone help!? please....

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  • Objective-C : Member variable is losing reference between method calls.

    - by Winston
    Hello, I've been having with an objective-c class which appears to be losing its pointer reference between methods of the same class. In the MyTableViewController.h file, I declare: @interface SettingsTableViewController : UITableViewController <UITextFieldDelegate>{ OCRAppDelegate *delegate; } MyTableViewController.m file - (id) init { self = [ super initWithStyle: UITableViewStyleGrouped ]; delegate = [(OCRAppDelegate *)[[UIApplication sharedApplication] delegate] retain]; } The problem is when the "MyTableViewController" view appears again and a different method is executed within that same class, the delegate pointer (which was assigned during the init method) is no longer there. I tried to retain, but to no avail. Would anyone know why this is, it seems like perhaps it is a fundamental Objective-C issue which I am missing. Appreciate your help. Thanks, Winston

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  • Is MonoTouch worth the cost or should I just learn Objective-C?

    - by jamesaharvey
    After sitting through a session today on Mono at a local .Net event, the use of MonoTouch was 'touched' upon as an alternative for iPhone development. Being very comfortable in C# and .Net, it seems like an appealing option, despite some of the quirkiness of the Mono stack. However, since MonoTouch costs $400, I'm somewhat torn on if this is the way to go for iPhone development. Anyone have an experience developing with MonoTouch and Objective-C, and if so is developing with MonoTouch that much simpler and quicker than learning Objective-C, and in turn worth the $400?

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  • Why are alloc and init called separately in Objective-C?

    - by André Hoffmann
    Note: I'm relatively new to Objective-C and am coming from Java and PHP. Could someone explain to me why I always have to first allocate and then initialize an instance? Couldn't this be done in the init methods like this: + (MyClass*)init { MyClass *instance = [MyClass alloc]; [instance setFoo:@"bla"]; return instance; } + (MyClass*)initWithString:(NSString*)text { MyClass *instance = [MyClass init]; [instance setFoo:text]; return instance; } ... Is this just a relict from the old C days or is there something that I'm not seeing? I know this isn't a problem as I could as well always call alloc and init, but since it's a bit tedious I'd like to at least know why I'm doing it. I'm liking the expressiveness of the language so far, but this is something that I want to fully understand in order to think the Objective-C way. Thank you!

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  • What exactly does "adopt a protocol" mean in the Objective-C / Cocoa documentation ?

    - by driis
    I am a C# developer getting started on Objective-C / Cocoa Touch programming. I think I might have gotten some terms wrong because I keep thinking about them "the C# way". Specifically, I have come around the term "protocol" in various documentation and tutorials. In Objective-C, what exactly is a protocol ? Can it be compared to a C# interface ? Is the following declaration the same as saying "The class is implementing the protocol UITextFieldDelegate" ? Or is UITextFieldDelegate to be compared with a generic type parameter in C# ? @interface MyViewController : UIViewController <UITextFieldDelegate> { }

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  • Is there a name for a pure-data Objective-C class?

    - by BrianEnigma
    This is less of a code-specific question and more of an Objective-C nomenclature question. In C you have struct for pure data. In Enterprise Java, you have "bean" classes that are purely member variables with getters and setters, but no business logic. In Adobe FLEX, you have "Value Objects". In Objective-C, is there a proper name for an object (descended from NSObject, of course) that simply has ivars and getters/setters (or @property/@synthesize, if you want to get fancy) and no real business logic? A more concrete example might be a simple class with getters and setters for filename, file size, description, and assorted other metadata. You could then take a bunch of these and easily throw them into a container (NSDictionary, NSArray) without the need for messy NSValue wrapping of a C struct. It is also a little more structure than putting, say, a bunch of loosely-typed child NSDictionaries into a parent container object.

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  • Why are Objective-C instance variables declared in an interface?

    - by Chase
    I'm just getting into Objective-C (Java is my primary OO language). Defining an object's instance variables in the interface instead of the class seems strange. I'm used to an interface being a public API definition with nothing besides method signatures (not counting constants here). Is there some reason that state is defined in an interface (even if it is private) and behaviour is defined in a class. It just seems odd that since objects are state+behavior that the definition would be split into two separate places. Is it a design benefit is some way? A pain in the rear issue that you are just forced to deal with in Objective-C? A non-issue, just different? Any background on why it's done this way? Or can you put object state in a class and I just haven't hit that part in my book yet?

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  • If I start learning C on Ubuntu will it give me an edge when I start learning Objective-C later this

    - by Anonymous
    I know Ruby right now, however I want to learn a new language. I am running Ubuntu 10.04 right now but I am going to get a Mac later this summer. Anyways I want something more for GUI development. I was wondering if I should learn C on Ubuntu right now, and then learn Objective-C when I get an iMac? Will learning C give me an edge? Or should I just learn Python on Ubuntu and then learn Objective-C when I get a new computer? Please give me your opinions! Thanks!

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  • Why does Apple use Objective-C for iPhone development? (App Store)

    - by Luca Matteis
    I'm interested to know your opinion on why Apple uses a language such as Objective-C for app development. Does Apple's app store allow apps written only in this language? Does apple even look at your source-code or does it just care of the binary output? I learned that most of their app rejection (in the app store) is based upon apps crashing (probably memory leaks in which Objective-c is not very efficient unless you use a GC). Why not let developers use a safer language, like a scripting language? I think these are important questions for a developer (I don't even use Apple's products) because it seems like Apple's app store is the MOST successful app sale place on the web.

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