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  • Using Objective-C blocks with old compiler

    - by H2CO3
    I'm using the opensource iPhone toolchain on Linux for developing for jailbroken iPhones. I'd like to take advantage of the new (4.0, 5.0) iOS SDK features, but I can't as my old build of GCC doesn't understand the ^ block syntax. I noticed that blocks are just of type id (struct objc_object *). I know this from two resources: first, class-dump reports them as id, second, Apple docs clarify that "blocks can be retained". My quiestion is, how can I take advantage of blocks using this knowledge? I thought of something like: // this is in SDK 4.x/5.x - (void) doSomethingWithBlock:((int)(^block)(int)); // and I modify it like: - (void) doSomethingWithBlock(id)block; the question is: HOW TO ACTUALLY CALL IT? How do I create blocks? I can, of course, create function pointers (IMPs in particular), but how to achieve the object-like memory layout?

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  • Double pointer as Objective-C block parameter

    - by George WS
    Is it possible (and if so, safe) to create/use a block which takes a double pointer as an argument? For instance: - (void)methodWithBlock:(void (^)(NSError **error))block; Additional context, research, and questions: I'm using ARC. When I declare the method above and attempt to call it, XCode autocompletes my method invocation as follows: [self methodWithBlock:^(NSError *__autoreleasing *error) {}]; What does __autoreleasing mean here and why is it being added? I presume it has something to do with ARC. If this is possible and safe, can the pointer still be dereferenced in the block as it would be anywhere else? In general, what are the important differences between doing what I'm describing, and simply passing a double pointer as a method parameter (e.g. - (void)methodWithDoublePointer:(NSError **)error;)? What special considerations, if any, should be taken into account (again assuming this is possible at all)?

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  • Mixing Objective-C and C++: Game Loop Parts

    - by Peteyslatts
    I'm trying to write all of my game in C++ except for drawing and game loop timing. Those parts are going to be in Objective-C for iOS. Right now, I have ViewController handling the update cycle, but I want to create a GameModel class that ViewController could update. I want GameModel to be in C++. I know how to integrate these two classes. My problem is how to have these two parts interact with the drawing and image loading. GameModel will keep track of a list of children of type GameObject. These GameObjects update every frame, and then need to pass position and visibility data to whatever class or method will handle drawing. I feel like I'm answering my own question now (talking it out helps) but would it be a good idea to put all of the visible game objects into an array at the end of the update method, return it, and use that to update graphics inside ViewController?

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  • Objective C style nil in java?

    - by Usman Ismail
    Objective C has a concept of a nil object which would accept any method call with any parameters without complaining and silently return another nil. I have used something similar in Java using easymock and mockito for testing. Is there something similar for main line code? Is it even a good idea to have something like this? One use-case where I am considering using it is with optional metrics. We have codahale metrics counters on which we call mark() every time an event is generated. This is surrounded by an If/then to check for metrics enabled flag. I could just use a nil object as counter and silently accept the mark call if metrics are not enabled.

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  • Simplifying the process of compiling and running objective-c apps in GNUstep

    - by Matthew
    I just installed GNUstep (following this post: http://www.jaysonjc.com/programming/objective-c-programming-in-windows-gnustep-projectcenter.html) It says to run this code: gcc -o helloworld helloworld.m -I /GNUstep/System/Library/Headers -L /GNUstep/System/Library/Libraries -lobjc -lgnustep-base -fconstant-string-class=NSConstantString every time I want to compile. It works just fine for me. However as I'm learning and will be compiling/running apps way often (making little changes and trying again), I'd like a simpler way to do this. Is there an easier way to compile and then run the app? Or am I just being lazy?

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  • Objective C and ios development training courses feedback

    - by Mutuelinvestor
    I'm thinking about taking an Objective C / iphone/ipad development training course. Pragmatic Studio and Big Nerd Ranch appear to be the key players. I'd love to hear any feed back from anyone who has completed training with Pragmatic, Big Nerd or others. I'd interested in quality of instruction, how much you learned, strengths, weaknesses and any other valuable insights. Its a pretty big financial commitment for me and I want to get the most bang for my buck. Thanks in advance for your input.

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  • Objective-C Lesson in Class Design

    - by Pota Onasys
    I have the following classes: Teacher Student Class (like a school class) They all extend from KObject that has the following code: - initWithKey - send - processKey Teacher, Student Class all use the functions processKey and initWithKey from KObject parent class. They implement their own version of send. The problem I have is that KObject should not be instantiated ever. It is more like an abstract class, but there is no abstract class concept in objective-c. It is only useful for allowing subclasses to have access to one property and two functions. What can I do so that KObject cannot be instantiated but still allow subclasses to have access to the functions and properties of KObject?

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  • Style: Dot notation vs. message notation in Objective-C 2.0

    - by groundhog
    In Objective-C 2.0 we got the "dot" notation for properties. I've seen various back and forths about the merits of dot notation vs. message notation. To keep the responses untainted I'm not going to respond either way in the question. What is your thought about dot notation vs. message notation for property accessing? Please try to keep it focused on Objective-C - my one bias I'll put forth is that Objective-C is Objective-C, so your preference that it be like Java or JavaScript aren't valid. Valid commentary is to do with technical issues (operation ordering, cast precedence, performance, etc), clarity (structure vs. object nature, both pro and con!), succinctness, etc. Note, I'm of the school of rigorous quality and readability in code having worked on huge projects where code convention and quality is paramount (the write once read a thousand times paradigm).

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  • Add an objective @property attribute in objective-c

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

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  • importing a VCard in the address book , objective C [migrated]

    - by user1044771
    I am designing a QR code reader, and it needs to detect and import contact cards in vCard format. is there a way to add the card data to the system Address Book directly, or do I need to parse the vCard myself and add each field individually? I will be getting the VCArd in a NSString format I tried the code below (from a different post) and didn't work -(IBAction)saveContacts{ NSString *vCardString = @"vCardDataHere"; CFDataRef vCardData = (__bridge_retained CFDataRef)[vCardString dataUsingEncoding:NSUTF8StringEncoding]; ABAddressBookRef book = ABAddressBookCreate(); ABRecordRef defaultSource = ABAddressBookCopyDefaultSource(book); CFArrayRef vCardPeople = ABPersonCreatePeopleInSourceWithVCardRepresentation(defaultSource, vCardData); for (CFIndex index = 0; index < CFArrayGetCount(vCardPeople); index++) { ABRecordRef person = CFArrayGetValueAtIndex(vCardPeople, index); ABAddressBookAddRecord(book, person, NULL); CFRelease(person); } CFRelease(vCardPeople); CFRelease(defaultSource); ABAddressBookSave(book, NULL); CFRelease(book); } I have searched a bit and fixed the code and here how it looks like it doesn t crash anymore but it doesn t save the VCard (NSString format) in the address book , any clues ?

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  • Objective-c Cocos2d moving a sprite

    - by marcg11
    I hope someone knows how to do the following with cocos2d: I want a sprite to move but not in a single line by using [cocosGuy runAction: [CCMoveTo actionWithDuration:1 position:location]]; What I want is the sprite to do some kind of movements that I preestablish. For example in some point i want the sprirte to move for instance up and then down but in a curve. Do I have to do this with flash like this documents says? http://www.cocos2d-iphone.org/wiki/doku.php/prog_guide:animation Does animation in this page means moving sprites or what? thanks

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  • Objective - Gestures while finger touches screen

    - by marcg11
    I'm creating a space cocos2d game with objetive-c. I have in the bottom left 2 arrows to move the sprite left or right. I also implemented a swipe gesture to change weapon, however it only happens when I'm not touching the screen. I would like the player to change weapons while he's moving the sprite and not have to lift the finger from the arrows and stop moving the sprite to change weapons. Is there any way I can detect Gestures while having a finger pressed un a buton in thes screen?

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  • Objective-C Moving UIView along a curved path

    - by PruitIgoe
    I'm not sure if I am approaching this the correct way. In my app, when a user touches the screen I capture the point and create an arc from a fixed point to that touch point. I then want to move a UIView along that arc. Here's my code: ViewController.m //method to "shoot" object - KIP_Projectile creates the arc, KIP_Character creates the object I want to move along the arc ... //get arc for trajectory KIP_Projectile* vThisProjectile = [[KIP_Projectile alloc] initWithFrame:CGRectMake(51.0, fatElvisCenterPoint-30.0, touchPoint.x, 60.0)]; vThisProjectile.backgroundColor = [UIColor clearColor]; [self.view addSubview:vThisProjectile]; ... KIP_Character* thisChar = [[KIP_Character alloc] initWithFrame:CGRectMake(51, objCenterPoint-5, imgThisChar.size.width, imgThisChar.size.height)]; thisChar.backgroundColor = [UIColor clearColor]; thisChar.charID = charID; thisChar.charType = 2; thisChar.strCharType = @"Projectile"; thisChar.imgMyImage = imgThisChar; thisChar.myArc = vThisProjectile; [thisChar buildImage]; [thisChar traceArc]; in KIP_Projectile I build the arc using this code: - (CGMutablePathRef) createArcPathFromBottomOfRect : (CGRect) rect : (CGFloat) arcHeight { CGRect arcRect = CGRectMake(rect.origin.x, rect.origin.y + rect.size.height - arcHeight, rect.size.width, arcHeight); CGFloat arcRadius = (arcRect.size.height/2) + (pow(arcRect.size.width, 2) / (8*arcRect.size.height)); CGPoint arcCenter = CGPointMake(arcRect.origin.x + arcRect.size.width/2, arcRect.origin.y + arcRadius); CGFloat angle = acos(arcRect.size.width / (2*arcRadius)); CGFloat startAngle = radians(180) + angle; CGFloat endAngle = radians(360) - angle; CGMutablePathRef path = CGPathCreateMutable(); CGPathAddArc(path, NULL, arcCenter.x, arcCenter.y, arcRadius, startAngle, endAngle, 0); return path; } - (void)drawRect:(CGRect)rect { CGContextRef currentContext = UIGraphicsGetCurrentContext(); _myArcPath = [self createArcPathFromBottomOfRect:self.bounds:30.0]; CGContextSetLineWidth(currentContext, 1); CGFloat red[4] = {1.0f, 0.0f, 0.0f, 1.0f}; CGContextSetStrokeColor(currentContext, red); CGContextAddPath(currentContext, _myArcPath); CGContextStrokePath(currentContext); } Works fine. The arc is displayed with a red stroke on the screen. In KIP_Character, which has been passed it's relevant arc, I am using this code but getting no results. - (void) traceArc { CGMutablePathRef myArc = _myArc.myArcPath; // Set up path movement CAKeyframeAnimation *pathAnimation = [CAKeyframeAnimation animationWithKeyPath:@"position"]; pathAnimation.calculationMode = kCAAnimationPaced; pathAnimation.fillMode = kCAFillModeForwards; pathAnimation.removedOnCompletion = NO; pathAnimation.path = myArc; CGPathRelease(myArc); [self.layer addAnimation:pathAnimation forKey:@"savingAnimation"]; } Any help here would be appreciated.

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  • Ongoing confusion about ivars and properties in objective C

    - by Earl Grey
    After almost 8 months being in ios programming, I am again confused about the right approach. Maybe it is not the language but some OOP principle I am confused about. I don't know.. I was trying C# a few years back. There were fields (private variables, private data in an object), there were getters and setters (methods which exposed something to the world) ,and properties which was THE exposed thing. I liked the elegance of the solution, for example there could be a class that would have a property called DailyRevenue...a float...but there was no private variable called dailyRevenue, there was only a field - an array of single transaction revenues...and the getter for DailyRevenue property calculated the revenue transparently. If somehow the internals of daily revenue calculation would change, it would not affect somebody who consumed my DailyRevenue property in any way, since he would be shielded from getter implementation. I understood that sometimes there was , and sometimes there wasn't a 1-1 relationship between fields and properties. depending on the requirements. It seemed ok in my opinion. And that properties are THE way to acces the data in object. I know the difference betweeen private, protected, and public keyword. Now lets get to objectiveC. On what factor should I base my decision about making someting only an ivar or making it as a property? Is the mental model the same as I describe above? I know that ivars are "protected" by default, not "private" asi in c#..But thats ok I think, no big deal for my presnet level of understanding the whole ios development. The point is ivars are not accesible from outside (given i don't make them public..but i won't). The thing that clouds my clear understanding is that I can have IBOutlets from ivars. Why am I seeing internal object data in the UI? *Why is it ok?* On the other hand, if I make an IBOutlet from property, and I do not make it readonly, anybody can change it. Is this ok too? Let's say I have a ParseManager object. This object would use a built in Foundation framework class called NSXMLParser. Obviously my ParseManager will utilize this nsxmlparser's capabilities but will also do some additional work. Now my question is, who should initialize this NSXMLParser object and in which way should I make a reference to it from the ParseManager object, when there is a need to parse something. A) the ParseManager -1) in its default init method (possible here ivar - or - ivar+ppty) -2) with lazyloading in getter (required a ppty here) B) Some other object - who will pass a reference to NSXMLParser object to the ParseManager object. -1) in some custom initializer (initWithParser:(NSXMLPArser *) parser) when creating the ParseManager object.. A1 - the problem is, we create a parser and waste memory while it is not yet needed. However, we can be sure that all methods that are part ot ParserManager object, can use the ivar safely, since it exists. A2 - the problem is, the nsxmlparser is exposed to outside world, although it could be read only. Would we want a parser to be exposed in some scenario? B1 - this could maybe be useful when we would want to use more types of parsers..i dont know... I understand that architectural requirements and and language is not the same. But clearly the two are in relation. How to get out of that mess of my? Please bear with me, I wasn't able to come up with a single ultimate question. And secondly, it's better to not scare me with some superadvanced newspeak that talks about some crazy internals (what the compiler does) and edge cases.

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  • Objective C - Aggro with Images

    - by Will
    I have three UIImageViews. enemy1, enemy1AggroBox and mainSprite. What I want to do is when mainSprite and enemy1AggroBox interect, I want enemy1 to start moving towards mainSprite. Basically creating aggro for a game. if(CGRectIntersectsRect(mainSprite.frame, enemy1AggroBox.frame)){ //Code here// } My plan would be to call this method in viewDidLoad. I'm not using any sort of framework like cocos2d or OpenGLES. If you need to see any more code just ask.

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  • C-Objective Function

    - by nimbus
    I'm unsure about how to make MWE with C-Obective, so if you need anything else let me know. I am trying running through a tutorial on building an iPhone app and have gotten stuck defining a function. I keep getting an error message saying "use of undeclared indentifer." However I believe I have initiated the function. In the view controller I have: if (scrollAmount > 0) { moveViewUp = YES; [scrollTheView:YES]; } else{ moveViewUp = NO; } with the function under it - (void)scrollTheView:(BOOL)movedUp { [UIView beginAnimations:nil context:NULL]; [UIView setAnimationDuration:0.3]; CGRect rect = self.view.frame; if (movedUp){ rect.origin.y -= scrollAmount; } else { rect.origin.y += scrollAmount; } self.view.frame = rect; [UIView commitAnimations]; } I have initiated the function in the header file (that I have imported). - (void)scrollTheView:(BOOL)movedUp; Any help would be appreciated, thank you in advanced

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  • Why was Objective-C popularity so sudden on TIOBE index?

    - by l46kok
    I'd like to ask a question that is pretty similar to the one being asked here, but for Objective-C. According to TIOBE rankings, the rise of popularity of Objective-C is unprecedented. This is obviously tied to the popularity of Apple products, but I feel like this might be a hasty conclusion to make since it doesn't really explain the stagnant growth of Java (1. There are way more Android O/S devices distributed worldwide, 2. Java is used in virtually every platform one can imagine) Now I haven't programmed in Objective-C at all, but I'd like to ask if there are any unique features or advantages about the language itself compared to other prevalent languages such as C++, Java, C#, Python etc. What are some other factors that contributed into the rise of Objective-C in this short span of time?

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  • Something similar to Objective-C categories in other languages?

    - by adig
    I understand Objective-C categories and how they become useful, but I always have a hard time explaining the concept to other programmers that are not familiar with Objective C. Maybe I'm just bad at explaining things, but I was thinking at another way to explain it by comparing to similar features offered by other (more popular) languages. (ex : I can explain the similarities between Objective C protocols and Java Interfaces) Any examples similar to Categories ?

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  • How can Swift be so much faster than Objective-C in these comparisons?

    - by Yellow
    Apple launched its new programming language Swift at WWDC14. In the presentation, they made some performance comparisons between Objective-C and Python. The following is a picture of one of their slides, of a comparison of those three languages performing some complex object sort: There was an even more incredible graph about a performance comparison using the RC4 encryption algorithm. Obviously this is a marketing talk, and they didn't go into detail on how this was implemented in each. I leaves me wondering though: How can a new programming language be so much faster? Are the Objective-C results caused by a bad compiler or is there something less efficient in Objective-C than Swift? How would you explain a 40% performance increase? I understand that garbage collection/automated reference control might produce some additional overhead, but this much?

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  • What guidelines do you suggest for using Objective-C Properties?

    - by adarsha
    Objective-C 2.0 introduced properties. While I personally think properties are nice addition to the language, I have seen a trend of making every instance variable as a property. Apple sample codes are no exceptions to this. I believe this is against the spirit of OOP, and since it exposes a lot more implementation details of a class to the client than they need to know. What guidelines do you suggest for the proper usage properties in Objective C?

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  • How to create a protocol at runtime in Objective-C?

    - by Jared P
    Hi, First of all, I want to be clear that I'm not talking about defining a protocol, and that I understand the concept of @protocol someprotocol - (void)method; @end I know that the Obj-C runtime allows creation of classes at RUNTIME, as well as its ivars and methods. Also available for creation are SEL-s. I think I'm just missing something, but does anyone know what function to call to create a protocol at runtime? The main reason for this is for conformsToProtocol: to work, so just adding the appropriate methods doesn't really cut it.

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  • Is This a Valid Way to Use Blocks in Objective-C?

    - by Carter
    I've been building a HTTP client that uses web services to synchronize information between the client and server. I've been using Blocks and NSURLConnection to achieve this on the client side, but I'm getting frequent EXC_BAD_ACCESS crashes in objc_msgSend(). From what I understand, this usually means that a stored block that has fallen off the stack has been called. I think I've coded things correctly to avoid this, but I'm still stuck. Here is conceptually what my code is doing. It starts by calling "synchronizeWithWebServer". That method invokes "listRootObjectsOnServerWithBlock:" which takes in a block to be called when the method returns. "listRootObjectsOnServersWithBlock:" initiates a NSURLConnection to the web server asynchronously. It to expects a block to be called when it returns. Inside that block I want to be able to execute the original Block (so aptly named 'block'). This is only a simplified version of my code. The real synchronization process is more complex but it's mostly more of the same as what you see below. Sometimes the code works perfectly, but about 80% of the time it crashes very early on in the routine. It seems to be more vulnerable to crashing when my data set gets larger. - (void)synchronizeWithWebServer { [self listRootObjectsOnServerWithBlock:^(NSArray *results, NSError *error) { //Iterate over result objects and perform some other similar routines. }]; } - (void)listRootObjectsOnServerWithBlock:(void (^)(NSArray *results, NSError *error))block { //Create NSURLRequest Here //Create connection asynchronously. block = [block copy]; [NSURLConnection sendAsynchronousRequest:urlRequest queue:[NSOperationQueue currentQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *error){ //Parse response from web server (stored in NSData *data) NSArray *results = ..... //Call 'block' block(results, error); [block release]; }]; }

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  • Singleton again, but with multi-thread and Objective-C

    - by Tonny Xu
    I know Singleton pattern has been discussed so much. But because I'm not fully understand the memory management mechanism in Objective-C, so when I combined Singleton implementation with multithreading, I got a big error and cost me a whole day to resolve it. I had a singleton object, let's call it ObjectX. I declared an object inside ObjectX that will detach a new thread, let's call that object objectWillSpawnNewThread, when I called [[ObjectX sharedInstance].objectWillSpawnNewThread startNewThread]; The new thread could not be executed correctly, and finally I found out that I should not declare the object objectWillSpawnNewThread inside the singleton class. Here are my questions: How does Objective-C allocate static object in the memory? Where does Objective-C allocate them(Main thread stack or somewhere else)? Why would it be failed if we spawn a new thread inside the singleton object? I had searched the Objective-C language [ObjC.pdf] and Objective-C memory management document, maybe I missed something, but I currently I could not find any helpful information.

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  • Extending Python and Objective-C

    - by chpwn
    I'm a fan of clean code. I like my languages to be able to express what I'm trying to do, but I like the syntax to mirror that too. For example, I work on a lot of programs in Objective-C for jailbroken iPhones, which patch other code using the method_setImplementation() function of the runtime. Or, in PyObjC, I have to use the syntax UIView.initWithFrame_(), which is also pretty awful and unreadable with the way the method names are structured. In both cases, the language does not support this in syntax. I've found three basic ways that this is done: Insane macros. Take a look at this "CaptainHook", it does what I'm looking for in a usable way, but it isn't quite clean and is a major hack. There's also "Logos", which implements a very nice syntax, but is written in Perl parsing my code with a ton of regular expressions. This scares me. I like the idea of adding a %hook ClassName, but not by using regular expressions to parse C or Objective-C. Finally, there is Cycript. This is an extension to JavaScript which interfaces with the Objective-C runtime and allows you to use Objective-C style code in your JavaScript, and inject that into other processes. This is likely the cleanest as it actually uses a parser for the JavaScript, but I'm not a huge fan of that language in general. Should, and how should, I create an extension to Python and Objective-C to allow me to do this? Is it worth writing a parser for my language to transform the syntax into something nicer, if it is only in a very specialized niche like this? Should I just live with the horrible syntax of the default Objective-C hooking or PyObjC?

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