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  • What does the Asterisk * mean in Objective-C?

    - by Thanks
    Is it true, that the Asterisk always means "Hey, that is a pointer!" And an Pointer always holds an memory adress? (Yes I know for the exception that a * is used for math operation) For Example: NSString* myString; or SomeClass* thatClass; or (*somePointerToAStruct).myStructComponent = 5; I feel that there is more I need to know about the Asterirsk (*) than that I use it when defining an Variable that is a pointer to a class. Because sometimes I already say in the declaration of an parameter that the Parameter variable is a pointer, and still I have to use the Asterisk in front of the Variable in order to access the value. That recently happened after I wanted to pass a pointer of an struct to a method in a way like [myObj myMethod:&myStruct], I could not access a component value from that structure even though my method declaration already said that there is a parameter (DemoStruct*)myVar which indeed should be already known as a pointer to that demostruct, still I had always to say: "Man, compiler. Listen! It IIISSS a pointer:" and write: (*myVar).myStructComponentX = 5; I really really really do not understand why I have to say that twice. And only in this case. When I use the Asterisk in context of an NSString* myString then I can just access myString however I like, without telling the compiler each time that it's a pointer. i.e. like using *myString = @"yep". It just makes no sense to me.

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  • Objective C convention: When to use For and when to use With

    - by Howard
    According to the Apple guideline , seems it is confusing, e.g. for method viewWithTag In Java, I would have a method called getViewByTag // Java version, equivalent to viewWithTag in Obj-C But I also found there are some method like objectForKey, so why not just use objectWithKey instead? getObjectByKey or just get // Java version, equivalent to objectForKey, // but why not objectWithKey? Or not viewForKey above?

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  • Objective C - creating concrete class instances from base class depending upon type

    - by indiantroy
    Just to give a real world example, say the base class is Vehicle and concrete classes are TwoWheeler and FourWheeler. Now the type of the vehicle - TwoWheeler or FourWheeler, is decided by the base class Vehicle. When I create an instance of TwoWheeler/FourWheeler using alloc-init method, it calls the super implementation like below to set the value of common properties defined in the Vehicle class and out of these properties one of them is type that actually decides if the type is TwoWheeler or FourWheeler. if (self = [super initWithDictionary:dict]){ [self setOtherAttributes:dict]; return self; } Now when I get a collection of vehicles some of them could be TwoWheeler and others will be FourWheeler. Hence I cannot directly create an instance of TwoWheeler or FourWheeler like this Vehicle *v = [[TwoWheeler alloc] initWithDictionary:dict]; Is there any way I can create an instance of base class and once I know the type, create an instance of child class depending upon type and return it. With the current implementation, it would result in infinite loop because I call super implementation from concrete class. What would be the perfect design to handle this scenario when I don't know which concrete class should be instantiated beforehand?

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  • I need objective syntax for calculating bmi

    - by Umaid
    Actually I am working on bmi calculator. Where I would like to calculate bmi for height in inches and weight in lbs and also in need of correct formula for height in cm and weight in kgs. I have tried but couldn't calculate actual value coming withing the range as below. It exceeds the range. BMI Categories: * Underweight = <18.5 * Normal weight = 18.5-24.9 * Overweight = 25-29.9 * Obesity = BMI of 30 or greater

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  • objective-c - calling one constructor from another

    - by synic
    Say you had the following two constructors: - (id)initWithTitle:(NSString *)title; - (id)initWithTitle:(NSString *)title page:(NSString *)page; The second constructor is no different from the first, except that it sets up the member variable "page". Since it basically has to do the same thing, is there a way to call the first one from the second one to reduce code duplication, or do you have to set up a third method to do the common tasks? I'm talking about something similar to this, though I doubt this will work: - (id)initWithTitle:(NSString *)_title { if(self = [super init]) { self.title = _title; } return self; } - (id)initWithTitle:(NSString *)_title page:(NSString *)_page { if(self = [self initWithTitle:_title]) { self.page = _page; } return self; }

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  • Objective-c when to release objects

    - by Chris
    -(IBAction)registerUpdate:(id)sender { HTTPRequest* request = [[HTTPRequest alloc] initWithUrl:@"http://www.yahoo.com" delegate:self]; [request doRequest]; } The HTTPRequest makes an asynchronous request and calls the onHTTPResponse method in the current class. My question is do I have to release request? My guess is that I'm supposed to make it an instance variable? [NSString stringWithFormat:@"Data received: %@", [[NSString alloc] initWithData:data encoding:NSASCIIStringEncoding]]; How would I release that string object, or should I assign it to a variable?

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  • Function to swap pointers in Objective-C

    - by Michael
    - (void) swapController:(MyViewController*)controller1 with:(MyViewController*)controller2 { MyViewController *swap = controller2; controller2 = controller1; controller1 = swap; } Looks like this doesn't work because I'm not passing references. How to do it anyway?

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  • Storing acceleration values in Objective-C/Cocoa?

    - by ASchlaep
    Hi all, I'm writing for the iPhone and I'm trying to measure the time between maximum accelerations. Imagine you've attached your iPhone to an oscillating spring. What I want to do is measure the frequency of the oscillation. The way I am going about doing this is storing a certain number acceleration values (updated 20 times per second) in an NSMutableArray and comparing the current acceleration value with previous acceleration values. How do I add each updated acceleration value to the NSMutableArray and at the same time delete values from the back of the array as I don't need them any more? Thanks in advance!

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  • Way of knowing who called a singleton - objective C

    - by Cyril
    Hello, I am designing a game with several levels. I have a CCLayer defined as a singleton (called MasterScene) where I handle the pause page, transition page, player's score banner,... all the things common to all levels. So in each level, when the user pushes the pause button, a call is made to the singleton to display the CClayer corresponding to the pause page. My problem is that I want to know who called the singleton (which level) t. Is there a way of doing that ? Thanks

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  • constructor in objective c

    - by zp26
    HI, I have create my iPhone apps but i have a problem. I have a classViewController where i have implemented my program. I must alloc 3 NSMutableArray but i don't want do it in a grapich methods. There isn't a constructor like java for my class? Thanks so much and sorry for my english XP // I want put it in a method like constructor java arrayPosizioni = [[NSMutableArray alloc]init]; nomePosizioneCorrente = [NSString stringWithFormat:@"noPosition"];

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  • Objective C : UIButton image with NSArray in a random order

    - by Sarah
    Brief Idea about the flow : I have say minimum 1 and maximum 18 records in my database with a text and an image from which I have to fetch images and place any 3 of the same randomly to 3 UIButtons among which one image should match with my question. i.e. 1 is the answer and other 2 are the distractors. For Example : Question is : where is Apple? Now among the bunch of images, I want to place any 3 images on the 3 UIButtons(1 answer i.e. An Apple and 2 distractors) in a random order and on selecting the UIButton it should prompt me if it's a right answer or not. I am implementing below code for placing the UIImages in a random order : -(void) placeImages { NSMutableArray *images = [NSMutableArray arrayWithArray:arrImg]; NSArray *buttons = [NSArray arrayWithObjects:btn1,btn2,btn3, nil]; for (UIButton *btn in buttons) { int randomIndex= random() % images.count; UIImage *img = [images objectAtIndex:randomIndex]; [btn setImage:img forState:UIControlStateNormal]; [images removeObjectAtIndex:randomIndex]; } } But I am stuck at a point that how should I get 1 UIButton image with an answer and other as distractors also that how should i maintain the index of the image from the NSArray? Kindly guide me. Thank you.

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  • Objective-C FontAwesome

    - by sdover102
    I'm Attempting to get FontAwesome up and running on an iOS app and could use a little assistance. I have the following code for iOS: UIBarButtonItem * viewDeckButton = [[UIBarButtonItem alloc] initWithTitle:@"\uf0c9" style:UIBarButtonItemStyleBordered target:self.viewDeckController action:@selector(toggleLeftView)]; NSDictionary * customTextAttrs = [NSDictionary dictionaryWithObjectsAndKeys: [UIFont fontWithName:@"FontAwesome" size:14.0], UITextAttributeFont, nil]; [viewDeckButton setTitleTextAttributes:customTextAttrs forState:UIControlStateNormal]; @"\uf0c9" corresponds to the css class, icon-reorder. The font appears to be installed on my system (see http://cl.ly/image/2F1x1z2H0i2N). I'm getting the standard box character, as if the font is not loaded (see http://madmonkdev.com/badchar.png). Any help would be appreciated.

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  • Are Objective-C function names stored in text?

    - by thyrgle
    I don't remember where I heard about it, (I think I was searching up on how selectors worked and it ended up not being exactly the same as a callback function) and I can't confirm it. But more importantly than that, is there a way I could get a list of the function names from another application?

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  • What does “@public” mean in Objective-C?

    - by Ty
    After reading a question on @private I understand how that works. However, since all variables default to @protected and you cannot really access a variable without defining an accessor, what exactly does @public do? When would you use it?

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  • Crashing Strings.... :( objective-c

    - by Ruiter
    I have in the .h file : NSString *dataHML; NSString *dataHML2; NSString *dataHML3; NSString *dataHML4; NSString *dataHML5; NSString *dataHML6; NSString *dataHMLtotal; in the .m file i merge them with : NSString *dataHtmlTotal = [NSString stringWithFormat:@"%@%@%@%@%@%@", dataHtml, dataHtml2, dataHtml3, dataHtml4,dataHtml5,dataHtml6]; But unfortunately it crashes at some point because of this. Could anyone give me a other solution and post it please, because i already tried nsuserdefault or a nsarray, but without i coudn't get it working :(

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  • Wrong class type in objective C

    - by Max Hui
    I have a parent class and a child class. GameObjectBase (parent) GameObjectPlayer(child). When I override a method in Child class and call it using [myPlayerClass showNextFrame] It is calling the parent class one. It turns out in the debugger, I see the myPlayerClass was indeed class type GameObjectBase (which is the parent class) How come? GameObjectBase.h #import <Foundation/Foundation.h> #import "cocos2d.h" @class GameLayer; @interface GameObjectBase : NSObject { /* CCSprite *gameObjectSprite; // Sprite representing this game object GameLayer *parentGameLayer; */ // Reference of the game layer this object // belongs to } @property (nonatomic, assign) CCSprite *gameObjectSprite; @property (nonatomic, assign) GameLayer *parentGameLayer; // Class method. Autorelease + (id) initWithGameLayer:(GameLayer *) gamelayer imageFileName:(NSString *) fileName; // "Virtual methods" that the derived class should implement. // If not implemented, this method will be called and Assert game - (void) update: (ccTime) dt; - (void) showNextFrame; @end GameObjectPlayer.h #import <Foundation/Foundation.h> #import "GameObjectBase.h" @interface GameObjectPlayer : GameObjectBase { int direction; } @property (nonatomic) int direction; @end GameLayer.h #import "cocos2d.h" #import "GameObjectPlayer.h" @interface GameLayer : CCLayer { } // returns a CCScene that contains the GameLayer as the only child +(CCScene *) scene; @property (nonatomic, strong) GameObjectPlayer *player; @end When I call examine in debugger what type "temp" is in this function inside GameLayer class, it's giving parent class GameObjectBase instead of subclass GameObjectPlayer - (void) update:(ccTime) dt { GameObjectPlayer *temp = _player; [temp showNextFrame]; }

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  • Downside to including headers in every source file (Objective-C)

    - by Michael Waterfall
    I'm currently including my AppDelegate.h and all of my category headers into every one of my source files using the MyApp_Prefix.pch prefix header, instead of manually #importing them only where they are used. The category methods and lots of compiler #define's in my app delegate are used in lots of places in my code. Is there any down side to this? Is it just that compilation will take longer?

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  • Problem with class methods in objective c

    - by Rajashekar
    Hi Guys i have a tableview controller like so, NSString *selectedindex; @interface ContactsController : UITableViewController { NSMutableArray *names; NSMutableArray *phonenumbers; NSMutableArray *contacts; DatabaseCRUD *sampledatabase; } +(NSString *) returnselectedindex; @end in the implementation file i have +(NSString *) returnselectedindex { return selectedindex; } when a row is selected in the tableview i put have the following code. selectedindex = [NSString stringWithFormat:@"%d", indexPath.row]; NSLog(@"selected row is %@",selectedindex); in a different class i am trying to access the selectedindex. like so selected = [ContactsController returnselectedindex]; NSLog(@"selected is %@",selected); it gives me a warning: 'ContactsController' may not respond to '+returnselectedindex' and crashes. i am not sure why. i have used class methods previously lot of times , and never had a problem. any help please. Thank You.

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  • Converting Java code block to Objective-C

    - by user1123688
    I am trying to convert my Android app to iOS. This will be my first iOS app. I can't seem to translate this code properly. If someone wouldn't mind showing me how its done, that would be greatly appreciated. //scrambBase20 is a Byte array String descramble(String input){ char[] ret; ret = input.toCharArray(); int offset = -scrambBase20.length; for(int i=0;i<input.length();i++){ if(i%scrambBase20.length==0) offset+=scrambBase20.length; ret[scrambBase20[i%scrambBase20.length]+offset]=(char) ((byte) (input.charAt(i))^0x45); } String realRet = ""; for (char x : ret){ realRet+=x; } realRet = realRet.trim(); return realRet; }

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  • @"%@ in Objective C?

    - by doo
    I was following a tut and found a line of code like @"%@ button pressed.". I'm pretty sure the relevant part is the %@, but is the first @ an escape sequence or what? Anyways, searching symbols doesn't go well in any search engine so I thought I'd ask. I think the %@ is like {0} in C#?

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  • escape % in objective c

    - by Saurabh
    Hello All, I want to make an sql statement - sqlStatement = [NSString stringWithFormat:@"SELECT * FROM movies where title like '%%@%'",searchKeyword]; But sqlStatement is becoming - "SELECT * FROM movies where title like '%@'" I want to make it "SELECT * FROM movies where title like '%searchKeyword%'" How can I escape the "%" character? Thanks

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  • Please recommend a patterns book for iOS development

    - by Brett Ryan
    I've read several books on iOS development and Objective-C, however what a lot of them teach is how to work with interfaces and all contain the model inside the view controller, i.e. a UITableViewController based view will simply have an NSArray as it's model. I'm interested in what the best practices are for designing the structure of an application. Specifically I'm interested in best practices for the following: How to separate a model from the view controller. I think I know how to do this by simply replacing the NSArray style example with a specific model object, however what I do not know how to do is alert the view when the model changes. For example in .NET I would solve this by conforming to INotifyPropertyChanged and databinding, and similarly with Java I would use PropertyChangeListener. How to create a service model for my domain objects. For example I want to learn the best way to create a service for a hypothetical Widget object to manage an internal DB and also services for communicating with remote endpoints. I need to learn the best ways to do this in a way that interface components can subscribe to events such as widgetUpdated. These services should be singleton classes and some how dependency injected into model/controller objects. Books I've read so far are: Programming in Objective-C (4th Edition) Beginning iOS 5 Development: Exploring the iOS SDK The iOS 5 Developer's Cookbook: Expanded Electronic Edition: Essentials and Advanced Recipes for iOS Programmers Learn Objective-C on the Mac: For OS X and iOS I've also purchased the following updated books but not yet read them. The Core iOS 6 Developer's Cookbook (4th edition Programming in Objective-C (5th Edition) I come from a Java and C# background with 15 years experience, I understand that many of the ways I would do things in these languages may not fit to the ObjC way of developing applications. Any guidance on the topic is very much appreciated.

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