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• Adding More Than 2 Delegates in iPhone App

  - by golfromeo

  This is a simple question that can be answered fast by someone who's more familiar with Objective-C than I am- how can one add more than 2 delegates to a Class? To clarify, I'm used to putting delegates in classes like this: @interface ViewController : UIViewController <UIWebViewDelegate> { ... When I try to put two delegates: @interface ViewController : UIViewController <UIWebViewDelegate> <UITextFieldDelegate> { ... ...the app gives many errors, none of which help with the situation. Is there a separator that I need to put between the delegates, or is it possible at all to have more than two? Thanks for any help in advance.

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• How to determine if an application is using the GPU

  - by Andrew

  I'm looking for a way to determine how to know whether an application is using the GPU with Objective-C. I want to be able to determine if any applications currently running on the system have work going on on the GPU (ie: a reason why the latest MacBook Pros would switch to the discrete graphics over the Intel HD graphics). I've tried getting the information by crossing the list of active windows with the list of windows that have their backing location stored in video memory using Quartz Window Services, but all that does is return the Dock application and I have other applications open that I know are using the GPU (Photoshop CS5, Interface Builder), that and the Dock doesn't require the 330m.

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• NSString stringWithFormat: with C array?

  - by Chris Long

  Hi, I'm writing a program that calculates the Jacobi algorithm. It's written in Objective-C since it runs on a Mac, but the majority is written in standard C. I'm using a two-dimensional C array and an NSArray containing 5 NSTextField labels. The following code yields an EXC_BAD_ACCESS error: for ( int i = 0; i < 5; i++ ) { NSString *resultString = [NSString stringWithFormat:@"%g", matrix[i][i] ]; [[resultLabels objectAtIndex:i] setStringValue:resultString]; // error line } Any help?

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• Proper NSArray initialization for ivar data in a method

  - by Joost Schuur

  I'm new to Objective-C and iPhone development and have been using Apress' Beginning iPhone 3 Programming book as my main guide for a few weeks now. In a few cases as part of a viewDidLoad: method, ivars like a breadTypes NSArray are initialized like below, with an intermediate array defined and then ultimately set to the actual array like this: NSArray *breadArray = [[NSArray alloc] initWithObjects:@"White", @"Whole Weat", @"Rye", @"Sourdough", @"Seven Grain", nil]; self.breadTypes = breadArray; [breadArray release]; Why is it done this way, instead of simply like this: self.breadTypes = [[NSArray alloc] initWithObjects:@"White", @"Whole Weat", @"Rye", @"Sourdough", @"Seven Grain", nil]; Both seem to work when I compile and run it. Is the 2nd method above not doing proper memory management? I assume initWithObjects: returns an array with a retain count of 1 and I eventually release breadTypes again in the dealloc: method, so that wraps things up nicely. I'm guessing 'self.breadTypes = ...' copies the data to the new array, which is why the original array can be safely released, correct?

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• Argument passing regarding ivars

  - by StoneBreaker

  I am passing an iVar into a function. The iVar is a double. The value of the iVar inside the function is correct, but the value of the iVar outside the function is not changed. This must have something to do with the way that I am receiving the iVar into the function. How do I pass a double iVar in so that its value is changed in the object and not only in the function? I do the same thing with pointers and the results are as expected, so I think I am not understanding scalar argument passing in c/objective-c.

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• Optimising Database Calls

  - by Dwaine Bailey

  I have a database that is filled with information for films, which is (in turn) read in to the database from an XML file on a webserver. What happens is the following: Gather/Parse XML and store film info as objects Begin Statement For every film object we found: Check to see if record for film exists in database If no film record, write data for film Commit Statement Currently I just test for the existence of a film using (the very basic): SELECT film_title FROM film WHERE film_id = ? If that returns a row, then the film exists, if not then I need to add it... The only problem is, is that there are many many hundreds of records in the database (lots of films!) and because it has to check for the existence of a film in the database before it can write it, the whole process ends up taking quite a while (about 27 seconds for 210 films) Is there a more efficient method of doing this, or just any suggestions in general? Programming Language is Objective-C, database is in sqlite3 Thanks, Dwaine

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• Getting text from image on ios (image processing)

  - by Vikram.exe

  Hi, I am thinking of making an application that requires extracting TEXT from an image. I haven't done any thing similar and I don't want to implement the whole stuff on my own. Is there any known library or open source code (supported for ios, objective-C) which can help me in extracting the text from the image. A basic source code will also do (I will try to modify it as per my need). Kindly let me know if some one has any idea on this. Thanks, Vikram

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• Password authentication in sqlite3 for iphone

  - by user271753

  Hey Guys .. I am new to programming in Objective C . I checked many tutorials on reading data in sqlite3 , but almost all of them have show the data in UITableView . I have a page where the user types in the password, the password lets say 1234 is saved in the database ( I have created a table already ) . I have got the database into the project folder . I just want a statement like if(databasepassword == correct from the uitextfield ) { show next page } else { password is incorrect.text } I will figure out on how to show the next page and display the password is incorrect.text I just want a method to cross check with the password saved in the database . How can I do that ? Regards

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• How to use NSTableView's selectedRowIndexes?

  - by Jakub Lédl

  Hi guys, I'm just learning some basic programming in Objective C and Cocoa. I'm trying to get some data from NSTableView. Based on what I read in one tutorial, I wrote this: NSArray * items = [[itemsTableView selectedRowEnumerator] allObjects]; But then I learned that selectedRowEnumerator was deprecated already in 10.3 Panther and that I should use selectedRowIndexes. The problem is, I didn't find how to actually use the returned NSIndexSet to achieve the same result as with code written above. So, If anyone could give me a tip, I would be very grateful. Thanks.

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• Modifying all HTTP requests on iPhoneOS with MobileSubstrate?

  - by Yifan

  I want to write a MobileSubstrate (http://www.iphonedevwiki.net/index.php/MobileSubstrate) addon that takes every HTTP request and modifies the URL. (The reason is very complicated and would take a while to explain, so just trust me that there's not an alternative). Basically, I need to know what's the best Objective-C message or C function that I should overwrite to intercept any HTTP request, modify the URL, and send the request back to the original function (this shouldn't be just the first request sent by an application, but any redirects too). I think it may be in NSURL or CFNetwork, but am not sure where exactly. This function should, when replaced, work with any apps and the OS itself.

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• How can I efficiently select several unique random numbers from 1 to 50, excluding x?

  - by Cocorico

  I have 2 numbers which are between 0 and 49. Let's call them x and y. Now I want to get a couple of other numbers which are not x or y, but are also between 0 and 49 (I am using Objective C but this is more of a general theory question I think?). Method I thought of is: int a; int b; int c; do { a = arc4random() % 49; } while ((a == x) || (a == y)); do { b = arc4random() % 49; } while ((b == x) || (b == y) || (b == a)); do { c = arc4random() % 49; } while ((c == x) || (c == y) || (c == a) || (c == b)); But it seem kind of bad to me, I don't know, I am just trying to learn to be a better programmer, what would be the most elegant way to do this for best practices?

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• How do I get selected background color from SecondView to pass to FirstView?

  - by rob

  I am going insane! This is a simple app with two Views. FirstView is a text field with info button to flip to SecondView. In SecondView I have 6 buttons for background color choice. When button is pushed the color of background changes perfectly but cannot make it also change background color for FirstView. Any help would be GREAT! Thanks! I am using Objective C class working on a iPhone app. Sorry new at this. The SecondView acts almost like a settings page in the fact that when a button is pushed the background color changes to the button color. I need it so when I push the "back" button to go back to FirstView the background color has also changed to that color choice. Been thru sooooooooo many tutorials and codes that now I am totally lost......... Thanks again!

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• Detecting/Repairing NSConnection failure

  - by anthony

  I would like to use NSConnection/NSDistributedObject for interprocess communication. I would like the client to be able to handle the case where the server is only occasionally reachable. How can I determine if sending a message to the NSConnection will fail or has failed? Currently if my server (the process that has vended the remote object) dies, the client will crash if it sends a selector to the remote object. Ideally I'd like to have a wrapper for the remote object that can lazily instantiate (or reinstantiate) the connection, and return a default value in the case where the connection could not be instantiated, or the connection has failed. I don't really know the correct way to do this using objective c. Here's some pseudocode representing this logic: if myConnection is null: instantiate myConnection if MyConnection is null: return defaultValue try return [myConnection someMethod] catch myConnection = null return defaultValue

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• Initialize window code Mac OS X

  - by Jarle

  I'm currently reading "the red book" for learning OpenGL properly, and in one of the first examples, the author writes a line that says "InitializeAWindowPlease();" as a place holder for the code that will make a window to draw the OpenGL content in. Since I'm using Xcode for my programing, I know that I "get" a window to work with automatically (and that I have to make my own OpenGL view in interfacebuilder). How can I make this with pure code? I'm trying to learn programming, and I'm not to happy about taking "shortcuts" all the time. How can I make a window to draw my openGL stuff in? With Objective-C and C code I would love to see it. My goal is that I can make it without opening interface builder at all:)

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• Local variable assign versus direct assign; properties and memory.

  - by Typeoneerror

  In objective-c I see a lot of sample code where the author assigns a local variable, assigns it to a property, then releases the local variable. Is there a practical reason for doing this? I've been just assigning directly to the property for the most part. Would that cause a memory leak in any way? I guess I'd like to know if there's any difference between this: HomeScreenBtns *localHomeScreenBtns = [[HomeScreenBtns alloc] init]; self.homeScreenBtns = localHomeScreenBtns; [localHomeScreenBtns release]; and this: self.homeScreenBtns = [[HomeScreenBtns alloc] init]; Assuming that homeScreenBtns is a property like so: @property (nonatomic, retain) HomeScreenBtns *homeScreenBtns; I'm getting ready to submit my application to the app store so I'm in full optimize/QA mode.

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• Why check if your popoverController is nil? Doesn't Obj-C ignore messages to nil?

  - by Rob Fonseca-Ensor

  Pretty much everyone that writes about the UISplitView on the iPad uses the following code structure to dismiss a popover: if (popoverController != nil) { [popoverController dismissPopoverAnimated:YES]; } I though Objective-C was happy to ignore messages that are passed to nil? In fact, in the File New Project New Split View Application template, there's an example of this shortcut in the same code block (DetailsViewController.m): - (void)setDetailItem:(id)newDetailItem { if (detailItem != newDetailItem) { [detailItem release]; //might be nil detailItem = [newDetailItem retain]; // Update the view. [self configureView]; } if (popoverController != nil) { [popoverController dismissPopoverAnimated:YES]; //was checked for nil } } Why is that second if necessary?

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• How do I refer to a view controller in a subclass?

  - by thekevinscott

  Hey all, I'm currently teaching myself Objective C and I'm kind of stuck. I'm building a backgammon game and I have a subclass, "Piece", which is being initialized, repeatedly, in BackGammonViewController. In BackGammonViewController, if I do this: UIImage *myImage = [ UIImage imageNamed: @"white-piece.png" ]; UIImageView *myImageView = [ [ UIImageView alloc ] initWithImage: myImage ]; [self.view addSubview:myImageView]; [myImageView release]; The image appears. However, I want to do this within my "piece" class. How do I refer to the "self.view" from within the piece class? Do I need to pass a reference to the view, into the "piece class" ? Or is there a global reference I can call from within the "piece class" ? Thanks for your help.

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• Where should I put code that is supposed to fire AFTER the view has loaded?

  - by Timbo

  I’m writing an objective-c program that does some calculations based on time and will eventually updates UILabels each second. To explain the concept here’s some simplified code, which I’ve placed into the viewDidLoad of the class that handles the view. (void)viewDidLoad { [super viewDidLoad]; // how do i make this stuff happen AFTER the view has loaded?? int a = 1; while (a < 10) { NSLog(@"doing something"); a = a + 1; sleep(1); } } My problem is that the code halts the loading of the view until the loop is all complete (in this case 10 seconds). Where should I put code that I want to fire AFTER the view has finished loading? newbie question I know =/

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• Table View Page Control Code

  - by PerwyL

  Hi Everyone this is what i want to achieve 1) Have a page control that allows user to do a swipe to 6 different pages 2) each page is a table view controller 3) everything is done via code NOT IB The tutorials that are i find either use VIEW CONTROLLER or is done via IB. I am not very good with IB and prefer to have everything done via coding. I have a TableViewController.h and TableViewController.m When the user navigate to the TableViewController view, my application will display a table view (filled with some information), when the user swip to the next page, another page (table view) will appear with another set of information... I am very new to objective-c and iphone programing...can some one pls guide me on how to achieve the above or is there another way to doing things? oh yar....i have a tab bar controller as my root controller...and for one of the tab (tab A) i have a navigation controller and my TableViewControllers falls inside tab A. THANKS IN ADVANCE!!!

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• Return the name of the class instance with the highest 'someValue' instance variable

  - by Timbo

  I have a brand new Objective-C class called test. The test class has an instance variable called someValue, which contains an integer. I create 5 instances of the test class called aTest, bTest, cTest, dTest and eTest. The appropriate synthesize and property declarations for someValue are in place. Is there a clean way of returning the name of the class instance with the highest someValue value out of all the existing test class instances? The number of class instances may vary from the 5 in my example. Note I don't care what the value is, I just want to return the name of the class instance with the highest 'someValue' instance variable. I've tried a few NSMutable arrays however can only get the value not the name of the variable that contains it. Thanks in advance

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• How do you implement syntax highlighting?

  - by ML

  I am embarking on some learning and I want to write my own syntax highlighting for files in C++. Can anyone give me ideas on how to go about doing this? To me it seems that when a file is opened: It would need to be parsed and decided what type of source file it is. Trusting the extension might not be fool-proof A way to know what keywords/commands apply to what language A way to decide what color each keyword/command gets I want to do this on OS X, using C++ or Objective-C. Can anyone provide pointers on how I might get started with this?

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• Monotouch/C# version of "stringWithContentsOfUrl"

  - by Pselus

  I'm trying to convert a piece of Objective-C code into C# for use with Monotouch and I have no idea what to use to replace stringWithContentsOfUrl Should I use something like: HttpWebRequest request = (HttpWebRequest) WebRequest.Create("http://www.helephant.com"); HttpWebResponse response = (HttpWebResponse) request.GetResponse(); if (response.StatusCode == HttpStatusCode.OK && response.ContentLength > 0){ TextReader reader = new StreamReader(response.GetResponseStream()); string text = reader.ReadToEnd(); Console.Write(text); } Is that even safe to use in MonoTouch? Will it work for the iPhone?

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• Colors in Instruments when hunting down memory leaks

  - by Structurer

  Hi I'm currently hunting down a memory leak in my app for iPhone. I'm using Instruments to track down the code that is causing the leak (becoming more and more a friend of Instruments!). Now Instruments show two lines: one in dark blue (row 146) and one in a lighter blue (150). From some trial and error I get that they are connected somehow, but not good enough at Objective-C and Memory Management yet to really understand how. Does anyone know why different colors are used and what could be my problem? I have tried to release numberForArray but the the app crashes when showing the last line in a picker view. All ideas appreciated! (Posting this I also realize that line 139 is redundant! Se there, already an improvement ;-)

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• Class variable defined at @implementation rather than @interface?

  - by bitcruncher

  Hello. I'm new to Objective-C, but I am curious about something that I haven't really seen addressed anywhere else. Could anyone tell me what is the difference between a private variable that is declared at the @interface block versus a variable that is declared within the @implementation block outside of the class methods, i.e: @interface Someclass : NSObject { NSString *forExample; } @end vs. @implementation Someclass NSString *anotherExample; -(void)methodsAndSuch {} @end It seems both variables ( forExample, anotherExample ) are equally accessible throughout the class and I can't really find a difference in their behaviour. Is the second form also called an instance variable?

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• Get String Instead of Source - Xcode Cocoa

  - by Kevin

  Hello everyone, I have a program that will scan the contents of a website, and display it in a textbox. The problem is that it shows the html source. For example if my html code was: <html> <body> <p>Hello</p> </body> </html> instead of just showing hello, it'll show the code above... How can I get my objective c program to just read the hello, and not the html source.. I was assuming that it was the encoding when reading the website, but I might be possibly wrong.. I would greatly appreciate it if someone could give me a reasonable answer.. Best Regards, Kevin

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